docs/how-to-build.md: use proper markup for directory names

[unleashed/tickless.git] / kernel / net / tcp / tcp.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2011, Joyent Inc. All rights reserved.
 * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
 * Copyright (c) 2013,2014 by Delphix. All rights reserved.
 * Copyright 2014, OmniTI Computer Consulting, Inc. All rights reserved.
 */
/* Copyright (c) 1990 Mentat Inc. */

#include <sys/types.h>
#include <sys/stream.h>
#include <sys/strsun.h>
#include <sys/strsubr.h>
#include <sys/stropts.h>
#include <sys/strlog.h>
#define _SUN_TPI_VERSION 2
#include <sys/tihdr.h>
#include <sys/timod.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/suntpi.h>
#include <sys/xti_inet.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/sdt.h>
#include <sys/vtrace.h>
#include <sys/kmem.h>
#include <sys/ethernet.h>
#include <sys/cpuvar.h>
#include <sys/dlpi.h>
#include <sys/pattr.h>
#include <sys/policy.h>
#include <sys/priv.h>
#include <sys/zone.h>
#include <sys/sunldi.h>

#include <sys/errno.h>
#include <sys/signal.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sockio.h>
#include <sys/isa_defs.h>
#include <sys/md5.h>
#include <sys/random.h>
#include <sys/uio.h>
#include <sys/systm.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <net/if.h>
#include <net/route.h>
#include <inet/ipsec_impl.h>

#include <inet/common.h>
#include <inet/ip.h>
#include <inet/ip_impl.h>
#include <inet/ip6.h>
#include <inet/ip_ndp.h>
#include <inet/proto_set.h>
#include <inet/mib2.h>
#include <inet/optcom.h>
#include <inet/snmpcom.h>
#include <inet/kstatcom.h>
#include <inet/tcp.h>
#include <inet/tcp_impl.h>
#include <inet/udp_impl.h>
#include <net/pfkeyv2.h>
#include <inet/ipdrop.h>

#include <inet/ipclassifier.h>
#include <inet/ip_ire.h>
#include <inet/ip_ftable.h>
#include <inet/ip_if.h>
#include <inet/ipp_common.h>
#include <inet/ip_rts.h>
#include <inet/ip_netinfo.h>
#include <sys/squeue_impl.h>
#include <sys/squeue.h>
#include <rpc/pmap_prot.h>
#include <sys/callo.h>

/*
 * TCP Notes: aka FireEngine Phase I (PSARC 2002/433)
 *
 * (Read the detailed design doc in PSARC case directory)
 *
 * The entire tcp state is contained in tcp_t and conn_t structure
 * which are allocated in tandem using ipcl_conn_create() and passing
 * IPCL_TCPCONN as a flag. We use 'conn_ref' and 'conn_lock' to protect
 * the references on the tcp_t. The tcp_t structure is never compressed
 * and packets always land on the correct TCP perimeter from the time
 * eager is created till the time tcp_t dies (as such the old mentat
 * TCP global queue is not used for detached state and no IPSEC checking
 * is required). The global queue is still allocated to send out resets
 * for connection which have no listeners and IP directly calls
 * tcp_xmit_listeners_reset() which does any policy check.
 *
 * Protection and Synchronisation mechanism:
 *
 * The tcp data structure does not use any kind of lock for protecting
 * its state but instead uses 'squeues' for mutual exclusion from various
 * read and write side threads. To access a tcp member, the thread should
 * always be behind squeue (via squeue_enter with flags as SQ_FILL, SQ_PROCESS,
 * or SQ_NODRAIN). Since the squeues allow a direct function call, caller
 * can pass any tcp function having prototype of edesc_t as argument
 * (different from traditional STREAMs model where packets come in only
 * designated entry points). The list of functions that can be directly
 * called via squeue are listed before the usual function prototype.
 *
 * Referencing:
 *
 * TCP is MT-Hot and we use a reference based scheme to make sure that the
 * tcp structure doesn't disappear when its needed. When the application
 * creates an outgoing connection or accepts an incoming connection, we
 * start out with 2 references on 'conn_ref'. One for TCP and one for IP.
 * The IP reference is just a symbolic reference since ip_tcpclose()
 * looks at tcp structure after tcp_close_output() returns which could
 * have dropped the last TCP reference. So as long as the connection is
 * in attached state i.e. !TCP_IS_DETACHED, we have 2 references on the
 * conn_t. The classifier puts its own reference when the connection is
 * inserted in listen or connected hash. Anytime a thread needs to enter
 * the tcp connection perimeter, it retrieves the conn/tcp from q->ptr
 * on write side or by doing a classify on read side and then puts a
 * reference on the conn before doing squeue_enter/tryenter/fill. For
 * read side, the classifier itself puts the reference under fanout lock
 * to make sure that tcp can't disappear before it gets processed. The
 * squeue will drop this reference automatically so the called function
 * doesn't have to do a DEC_REF.
 *
 * Opening a new connection:
 *
 * The outgoing connection open is pretty simple. tcp_open() does the
 * work in creating the conn/tcp structure and initializing it. The
 * squeue assignment is done based on the CPU the application
 * is running on. So for outbound connections, processing is always done
 * on application CPU which might be different from the incoming CPU
 * being interrupted by the NIC. An optimal way would be to figure out
 * the NIC <-> CPU binding at listen time, and assign the outgoing
 * connection to the squeue attached to the CPU that will be interrupted
 * for incoming packets (we know the NIC based on the bind IP address).
 * This might seem like a problem if more data is going out but the
 * fact is that in most cases the transmit is ACK driven transmit where
 * the outgoing data normally sits on TCP's xmit queue waiting to be
 * transmitted.
 *
 * Accepting a connection:
 *
 * This is a more interesting case because of various races involved in
 * establishing a eager in its own perimeter. Read the meta comment on
 * top of tcp_input_listener(). But briefly, the squeue is picked by
 * ip_fanout based on the ring or the sender (if loopback).
 *
 * Closing a connection:
 *
 * The close is fairly straight forward. tcp_close() calls tcp_close_output()
 * via squeue to do the close and mark the tcp as detached if the connection
 * was in state TCPS_ESTABLISHED or greater. In the later case, TCP keep its
 * reference but tcp_close() drop IP's reference always. So if tcp was
 * not killed, it is sitting in time_wait list with 2 reference - 1 for TCP
 * and 1 because it is in classifier's connected hash. This is the condition
 * we use to determine that its OK to clean up the tcp outside of squeue
 * when time wait expires (check the ref under fanout and conn_lock and
 * if it is 2, remove it from fanout hash and kill it).
 *
 * Although close just drops the necessary references and marks the
 * tcp_detached state, tcp_close needs to know the tcp_detached has been
 * set (under squeue) before letting the STREAM go away (because a
 * inbound packet might attempt to go up the STREAM while the close
 * has happened and tcp_detached is not set). So a special lock and
 * flag is used along with a condition variable (tcp_closelock, tcp_closed,
 * and tcp_closecv) to signal tcp_close that tcp_close_out() has marked
 * tcp_detached.
 *
 * Special provisions and fast paths:
 *
 * We make special provisions for sockfs by marking tcp_issocket
 * whenever we have only sockfs on top of TCP. This allows us to skip
 * putting the tcp in acceptor hash since a sockfs listener can never
 * become acceptor and also avoid allocating a tcp_t for acceptor STREAM
 * since eager has already been allocated and the accept now happens
 * on acceptor STREAM. There is a big blob of comment on top of
 * tcp_input_listener explaining the new accept. When socket is POP'd,
 * sockfs sends us an ioctl to mark the fact and we go back to old
 * behaviour. Once tcp_issocket is unset, its never set for the
 * life of that connection.
 *
 * IPsec notes :
 *
 * Since a packet is always executed on the correct TCP perimeter
 * all IPsec processing is defered to IP including checking new
 * connections and setting IPSEC policies for new connection. The
 * only exception is tcp_xmit_listeners_reset() which is called
 * directly from IP and needs to policy check to see if TH_RST
 * can be sent out.
 */

/*
 * Values for squeue switch:
 * 1: SQ_NODRAIN
 * 2: SQ_PROCESS
 * 3: SQ_FILL
 */
int tcp_squeue_wput = 2;        /* /etc/systems */
int tcp_squeue_flag;

/*
 * To prevent memory hog, limit the number of entries in tcp_free_list
 * to 1% of available memory / number of cpus
 */
uint_t tcp_free_list_max_cnt = 0;

#define TIDUSZ  4096    /* transport interface data unit size */

/*
 * Size of acceptor hash list.  It has to be a power of 2 for hashing.
 */
#define TCP_ACCEPTOR_FANOUT_SIZE                512

#ifdef  _ILP32
#define TCP_ACCEPTOR_HASH(accid)                                        \
                (((uint_t)(accid) >> 8) & (TCP_ACCEPTOR_FANOUT_SIZE - 1))
#else
#define TCP_ACCEPTOR_HASH(accid)                                        \
                ((uint_t)(accid) & (TCP_ACCEPTOR_FANOUT_SIZE - 1))
#endif  /* _ILP32 */

/*
 * Minimum number of connections which can be created per listener.  Used
 * when the listener connection count is in effect.
 */
static uint32_t tcp_min_conn_listener = 2;

uint32_t tcp_early_abort = 30;

/* TCP Timer control structure */
typedef struct tcpt_s {
        pfv_t   tcpt_pfv;       /* The routine we are to call */
        tcp_t   *tcpt_tcp;      /* The parameter we are to pass in */
} tcpt_t;

/*
 * Functions called directly via squeue having a prototype of edesc_t.
 */
void            tcp_input_listener(void *arg, mblk_t *mp, void *arg2,
    ip_recv_attr_t *ira);
void            tcp_input_data(void *arg, mblk_t *mp, void *arg2,
    ip_recv_attr_t *ira);
static void     tcp_linger_interrupted(void *arg, mblk_t *mp, void *arg2,
    ip_recv_attr_t *dummy);


/* Prototype for TCP functions */
static int      tcp_connect_ipv4(tcp_t *tcp, ipaddr_t *dstaddrp,
                    in_port_t dstport, uint_t srcid);
static int      tcp_connect_ipv6(tcp_t *tcp, in6_addr_t *dstaddrp,
                    in_port_t dstport, uint32_t flowinfo,
                    uint_t srcid, uint32_t scope_id);
static void     tcp_iss_init(tcp_t *tcp);
static void     tcp_reinit(tcp_t *tcp);
static void     tcp_reinit_values(tcp_t *tcp);

static void     tcp_wsrv(queue_t *q);
static void     tcp_update_lso(tcp_t *tcp, ip_xmit_attr_t *ixa);
static void     tcp_update_zcopy(tcp_t *tcp);
static void     tcp_notify(void *, ip_xmit_attr_t *, ixa_notify_type_t,
    ixa_notify_arg_t);
static void     *tcp_stack_init(netstackid_t stackid, netstack_t *ns);
static void     tcp_stack_fini(netstackid_t stackid, void *arg);

static int      tcp_squeue_switch(int);

static int      tcp_open(queue_t *, dev_t *, int, int, cred_t *, boolean_t);
static int      tcp_openv4(queue_t *, dev_t *, int, int, cred_t *);
static int      tcp_openv6(queue_t *, dev_t *, int, int, cred_t *);

static void     tcp_squeue_add(squeue_t *);

struct module_info tcp_rinfo =  {
        TCP_MOD_ID, TCP_MOD_NAME, 0, INFPSZ, TCP_RECV_HIWATER, TCP_RECV_LOWATER
};

static struct module_info tcp_winfo =  {
        TCP_MOD_ID, TCP_MOD_NAME, 0, INFPSZ, 127, 16
};

/*
 * Entry points for TCP as a device. The normal case which supports
 * the TCP functionality.
 * We have separate open functions for the /dev/tcp and /dev/tcp6 devices.
 */
struct qinit tcp_rinitv4 = {
        NULL, (pfi_t)tcp_rsrv, tcp_openv4, tcp_tpi_close, NULL, &tcp_rinfo
};

struct qinit tcp_rinitv6 = {
        NULL, (pfi_t)tcp_rsrv, tcp_openv6, tcp_tpi_close, NULL, &tcp_rinfo
};

struct qinit tcp_winit = {
        (pfi_t)tcp_wput, (pfi_t)tcp_wsrv, NULL, NULL, NULL, &tcp_winfo
};

/* Initial entry point for TCP in socket mode. */
struct qinit tcp_sock_winit = {
        (pfi_t)tcp_wput_sock, (pfi_t)tcp_wsrv, NULL, NULL, NULL, &tcp_winfo
};

/* TCP entry point during fallback */
struct qinit tcp_fallback_sock_winit = {
        (pfi_t)tcp_wput_fallback, NULL, NULL, NULL, NULL, &tcp_winfo
};

/*
 * Entry points for TCP as a acceptor STREAM opened by sockfs when doing
 * an accept. Avoid allocating data structures since eager has already
 * been created.
 */
struct qinit tcp_acceptor_rinit = {
        NULL, (pfi_t)tcp_rsrv, NULL, tcp_tpi_close_accept, NULL, &tcp_winfo
};

struct qinit tcp_acceptor_winit = {
        (pfi_t)tcp_tpi_accept, NULL, NULL, NULL, NULL, &tcp_winfo
};

/* For AF_INET aka /dev/tcp */
struct streamtab tcpinfov4 = {
        &tcp_rinitv4, &tcp_winit
};

/* For AF_INET6 aka /dev/tcp6 */
struct streamtab tcpinfov6 = {
        &tcp_rinitv6, &tcp_winit
};

/*
 * Following assumes TPI alignment requirements stay along 32 bit
 * boundaries
 */
#define ROUNDUP32(x) \
        (((x) + (sizeof (int32_t) - 1)) & ~(sizeof (int32_t) - 1))

/* Template for response to info request. */
struct T_info_ack tcp_g_t_info_ack = {
        T_INFO_ACK,             /* PRIM_type */
        0,                      /* TSDU_size */
        T_INFINITE,             /* ETSDU_size */
        T_INVALID,              /* CDATA_size */
        T_INVALID,              /* DDATA_size */
        sizeof (sin_t),         /* ADDR_size */
        0,                      /* OPT_size - not initialized here */
        TIDUSZ,                 /* TIDU_size */
        T_COTS_ORD,             /* SERV_type */
        TCPS_IDLE,              /* CURRENT_state */
        (XPG4_1|EXPINLINE)      /* PROVIDER_flag */
};

struct T_info_ack tcp_g_t_info_ack_v6 = {
        T_INFO_ACK,             /* PRIM_type */
        0,                      /* TSDU_size */
        T_INFINITE,             /* ETSDU_size */
        T_INVALID,              /* CDATA_size */
        T_INVALID,              /* DDATA_size */
        sizeof (sin6_t),        /* ADDR_size */
        0,                      /* OPT_size - not initialized here */
        TIDUSZ,         /* TIDU_size */
        T_COTS_ORD,             /* SERV_type */
        TCPS_IDLE,              /* CURRENT_state */
        (XPG4_1|EXPINLINE)      /* PROVIDER_flag */
};

/*
 * TCP tunables related declarations. Definitions are in tcp_tunables.c
 */
extern mod_prop_info_t tcp_propinfo_tbl[];
extern int tcp_propinfo_count;

#define IS_VMLOANED_MBLK(mp) \
        (((mp)->b_datap->db_struioflag & STRUIO_ZC) != 0)

uint32_t do_tcpzcopy = 1;               /* 0: disable, 1: enable, 2: force */

/*
 * Forces all connections to obey the value of the tcps_maxpsz_multiplier
 * tunable settable via NDD.  Otherwise, the per-connection behavior is
 * determined dynamically during tcp_set_destination(), which is the default.
 */
boolean_t tcp_static_maxpsz = B_FALSE;

/*
 * If the receive buffer size is changed, this function is called to update
 * the upper socket layer on the new delayed receive wake up threshold.
 */
static void
tcp_set_recv_threshold(tcp_t *tcp, uint32_t new_rcvthresh)
{
        uint32_t default_threshold = SOCKET_RECVHIWATER >> 3;

        if (IPCL_IS_NONSTR(tcp->tcp_connp)) {
                conn_t *connp = tcp->tcp_connp;
                struct sock_proto_props sopp;

                /*
                 * only increase rcvthresh upto default_threshold
                 */
                if (new_rcvthresh > default_threshold)
                        new_rcvthresh = default_threshold;

                sopp.sopp_flags = SOCKOPT_RCVTHRESH;
                sopp.sopp_rcvthresh = new_rcvthresh;

                (*connp->conn_upcalls->su_set_proto_props)
                    (connp->conn_upper_handle, &sopp);
        }
}

/*
 * Figure out the value of window scale opton.  Note that the rwnd is
 * ASSUMED to be rounded up to the nearest MSS before the calculation.
 * We cannot find the scale value and then do a round up of tcp_rwnd
 * because the scale value may not be correct after that.
 *
 * Set the compiler flag to make this function inline.
 */
void
tcp_set_ws_value(tcp_t *tcp)
{
        int i;
        uint32_t rwnd = tcp->tcp_rwnd;

        for (i = 0; rwnd > TCP_MAXWIN && i < TCP_MAX_WINSHIFT;
            i++, rwnd >>= 1)
                ;
        tcp->tcp_rcv_ws = i;
}

/*
 * Remove cached/latched IPsec references.
 */
void
tcp_ipsec_cleanup(tcp_t *tcp)
{
        conn_t          *connp = tcp->tcp_connp;

        ASSERT(connp->conn_flags & IPCL_TCPCONN);

        if (connp->conn_latch != NULL) {
                IPLATCH_REFRELE(connp->conn_latch);
                connp->conn_latch = NULL;
        }
        if (connp->conn_latch_in_policy != NULL) {
                IPPOL_REFRELE(connp->conn_latch_in_policy);
                connp->conn_latch_in_policy = NULL;
        }
        if (connp->conn_latch_in_action != NULL) {
                IPACT_REFRELE(connp->conn_latch_in_action);
                connp->conn_latch_in_action = NULL;
        }
        if (connp->conn_policy != NULL) {
                IPPH_REFRELE(connp->conn_policy, connp->conn_netstack);
                connp->conn_policy = NULL;
        }
}

/*
 * Cleaup before placing on free list.
 * Disassociate from the netstack/tcp_stack_t since the freelist
 * is per squeue and not per netstack.
 */
void
tcp_cleanup(tcp_t *tcp)
{
        mblk_t          *mp;
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        netstack_t      *ns = tcps->tcps_netstack;
        mblk_t          *tcp_rsrv_mp;

        tcp_bind_hash_remove(tcp);

        /* Cleanup that which needs the netstack first */
        tcp_ipsec_cleanup(tcp);
        ixa_cleanup(connp->conn_ixa);

        if (connp->conn_ht_iphc != NULL) {
                kmem_free(connp->conn_ht_iphc, connp->conn_ht_iphc_allocated);
                connp->conn_ht_iphc = NULL;
                connp->conn_ht_iphc_allocated = 0;
                connp->conn_ht_iphc_len = 0;
                connp->conn_ht_ulp = NULL;
                connp->conn_ht_ulp_len = 0;
                tcp->tcp_ipha = NULL;
                tcp->tcp_ip6h = NULL;
                tcp->tcp_tcpha = NULL;
        }

        /* We clear any IP_OPTIONS and extension headers */
        ip_pkt_free(&connp->conn_xmit_ipp);

        tcp_free(tcp);

        /*
         * Since we will bzero the entire structure, we need to
         * remove it and reinsert it in global hash list. We
         * know the walkers can't get to this conn because we
         * had set CONDEMNED flag earlier and checked reference
         * under conn_lock so walker won't pick it and when we
         * go the ipcl_globalhash_remove() below, no walker
         * can get to it.
         */
        ipcl_globalhash_remove(connp);

        /* Save some state */
        mp = tcp->tcp_timercache;

        tcp_rsrv_mp = tcp->tcp_rsrv_mp;

        if (connp->conn_cred != NULL) {
                crfree(connp->conn_cred);
                connp->conn_cred = NULL;
        }
        ipcl_conn_cleanup(connp);
        connp->conn_flags = IPCL_TCPCONN;

        /*
         * Now it is safe to decrement the reference counts.
         * This might be the last reference on the netstack
         * in which case it will cause the freeing of the IP Instance.
         */
        connp->conn_netstack = NULL;
        connp->conn_ixa->ixa_ipst = NULL;
        netstack_rele(ns);
        ASSERT(tcps != NULL);
        tcp->tcp_tcps = NULL;

        bzero(tcp, sizeof (tcp_t));

        /* restore the state */
        tcp->tcp_timercache = mp;

        tcp->tcp_rsrv_mp = tcp_rsrv_mp;

        tcp->tcp_connp = connp;

        ASSERT(connp->conn_tcp == tcp);
        ASSERT(connp->conn_flags & IPCL_TCPCONN);
        connp->conn_state_flags = CONN_INCIPIENT;
        ASSERT(connp->conn_proto == IPPROTO_TCP);
        ASSERT(connp->conn_ref == 1);
}

/*
 * Adapt to the information, such as rtt and rtt_sd, provided from the
 * DCE and IRE maintained by IP.
 *
 * Checks for multicast and broadcast destination address.
 * Returns zero if ok; an errno on failure.
 *
 * Note that the MSS calculation here is based on the info given in
 * the DCE and IRE.  We do not do any calculation based on TCP options.  They
 * will be handled in tcp_input_data() when TCP knows which options to use.
 *
 * Note on how TCP gets its parameters for a connection.
 *
 * When a tcp_t structure is allocated, it gets all the default parameters.
 * In tcp_set_destination(), it gets those metric parameters, like rtt, rtt_sd,
 * spipe, rpipe, ... from the route metrics.  Route metric overrides the
 * default.
 *
 * An incoming SYN with a multicast or broadcast destination address is dropped
 * in ip_fanout_v4/v6.
 *
 * An incoming SYN with a multicast or broadcast source address is always
 * dropped in tcp_set_destination, since IPDF_ALLOW_MCBC is not set in
 * conn_connect.
 * The same logic in tcp_set_destination also serves to
 * reject an attempt to connect to a broadcast or multicast (destination)
 * address.
 */
int
tcp_set_destination(tcp_t *tcp)
{
        uint32_t        mss_max;
        uint32_t        mss;
        boolean_t       tcp_detached = TCP_IS_DETACHED(tcp);
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        iulp_t          uinfo;
        int             error;
        uint32_t        flags;

        flags = IPDF_LSO | IPDF_ZCOPY;
        /*
         * Make sure we have a dce for the destination to avoid dce_ident
         * contention for connected sockets.
         */
        flags |= IPDF_UNIQUE_DCE;

        if (!tcps->tcps_ignore_path_mtu)
                connp->conn_ixa->ixa_flags |= IXAF_PMTU_DISCOVERY;

        /* Use conn_lock to satify ASSERT; tcp is already serialized */
        mutex_enter(&connp->conn_lock);
        error = conn_connect(connp, &uinfo, flags);
        mutex_exit(&connp->conn_lock);
        if (error != 0)
                return (error);

        error = tcp_build_hdrs(tcp);
        if (error != 0)
                return (error);

        tcp->tcp_localnet = uinfo.iulp_localnet;

        if (uinfo.iulp_rtt != 0) {
                clock_t rto;

                tcp->tcp_rtt_sa = uinfo.iulp_rtt;
                tcp->tcp_rtt_sd = uinfo.iulp_rtt_sd;
                rto = (tcp->tcp_rtt_sa >> 3) + tcp->tcp_rtt_sd +
                    tcps->tcps_rexmit_interval_extra +
                    (tcp->tcp_rtt_sa >> 5);

                TCP_SET_RTO(tcp, rto);
        }
        if (uinfo.iulp_ssthresh != 0)
                tcp->tcp_cwnd_ssthresh = uinfo.iulp_ssthresh;
        else
                tcp->tcp_cwnd_ssthresh = TCP_MAX_LARGEWIN;
        if (uinfo.iulp_spipe > 0) {
                connp->conn_sndbuf = MIN(uinfo.iulp_spipe,
                    tcps->tcps_max_buf);
                if (tcps->tcps_snd_lowat_fraction != 0) {
                        connp->conn_sndlowat = connp->conn_sndbuf /
                            tcps->tcps_snd_lowat_fraction;
                }
                (void) tcp_maxpsz_set(tcp, B_TRUE);
        }
        /*
         * Note that up till now, acceptor always inherits receive
         * window from the listener.  But if there is a metrics
         * associated with a host, we should use that instead of
         * inheriting it from listener. Thus we need to pass this
         * info back to the caller.
         */
        if (uinfo.iulp_rpipe > 0) {
                tcp->tcp_rwnd = MIN(uinfo.iulp_rpipe,
                    tcps->tcps_max_buf);
        }

        if (uinfo.iulp_rtomax > 0) {
                tcp->tcp_second_timer_threshold =
                    uinfo.iulp_rtomax;
        }

        /*
         * Use the metric option settings, iulp_tstamp_ok and
         * iulp_wscale_ok, only for active open. What this means
         * is that if the other side uses timestamp or window
         * scale option, TCP will also use those options. That
         * is for passive open.  If the application sets a
         * large window, window scale is enabled regardless of
         * the value in iulp_wscale_ok.  This is the behavior
         * since 2.6.  So we keep it.
         * The only case left in passive open processing is the
         * check for SACK.
         * For ECN, it should probably be like SACK.  But the
         * current value is binary, so we treat it like the other
         * cases.  The metric only controls active open.For passive
         * open, the ndd param, tcp_ecn_permitted, controls the
         * behavior.
         */
        if (!tcp_detached) {
                /*
                 * The if check means that the following can only
                 * be turned on by the metrics only IRE, but not off.
                 */
                if (uinfo.iulp_tstamp_ok)
                        tcp->tcp_snd_ts_ok = B_TRUE;
                if (uinfo.iulp_wscale_ok)
                        tcp->tcp_snd_ws_ok = B_TRUE;
                if (uinfo.iulp_sack == 2)
                        tcp->tcp_snd_sack_ok = B_TRUE;
                if (uinfo.iulp_ecn_ok)
                        tcp->tcp_ecn_ok = B_TRUE;
        } else {
                /*
                 * Passive open.
                 *
                 * As above, the if check means that SACK can only be
                 * turned on by the metric only IRE.
                 */
                if (uinfo.iulp_sack > 0) {
                        tcp->tcp_snd_sack_ok = B_TRUE;
                }
        }

        /*
         * XXX Note that currently, iulp_mtu can be as small as 68
         * because of PMTUd.  So tcp_mss may go to negative if combined
         * length of all those options exceeds 28 bytes.  But because
         * of the tcp_mss_min check below, we may not have a problem if
         * tcp_mss_min is of a reasonable value.  The default is 1 so
         * the negative problem still exists.  And the check defeats PMTUd.
         * In fact, if PMTUd finds that the MSS should be smaller than
         * tcp_mss_min, TCP should turn off PMUTd and use the tcp_mss_min
         * value.
         *
         * We do not deal with that now.  All those problems related to
         * PMTUd will be fixed later.
         */
        ASSERT(uinfo.iulp_mtu != 0);
        mss = tcp->tcp_initial_pmtu = uinfo.iulp_mtu;

        /* Sanity check for MSS value. */
        if (connp->conn_ipversion == IPV4_VERSION)
                mss_max = tcps->tcps_mss_max_ipv4;
        else
                mss_max = tcps->tcps_mss_max_ipv6;

        if (tcp->tcp_ipsec_overhead == 0)
                tcp->tcp_ipsec_overhead = conn_ipsec_length(connp);

        mss -= tcp->tcp_ipsec_overhead;

        if (mss < tcps->tcps_mss_min)
                mss = tcps->tcps_mss_min;
        if (mss > mss_max)
                mss = mss_max;

        /* Note that this is the maximum MSS, excluding all options. */
        tcp->tcp_mss = mss;

        /*
         * Update the tcp connection with LSO capability.
         */
        tcp_update_lso(tcp, connp->conn_ixa);

        /*
         * Initialize the ISS here now that we have the full connection ID.
         * The RFC 1948 method of initial sequence number generation requires
         * knowledge of the full connection ID before setting the ISS.
         */
        tcp_iss_init(tcp);

        tcp->tcp_loopback = (uinfo.iulp_loopback | uinfo.iulp_local);

        /*
         * Make sure that conn is not marked incipient
         * for incoming connections. A blind
         * removal of incipient flag is cheaper than
         * check and removal.
         */
        mutex_enter(&connp->conn_lock);
        connp->conn_state_flags &= ~CONN_INCIPIENT;
        mutex_exit(&connp->conn_lock);
        return (0);
}

/*
 * tcp_clean_death / tcp_close_detached must not be called more than once
 * on a tcp. Thus every function that potentially calls tcp_clean_death
 * must check for the tcp state before calling tcp_clean_death.
 * Eg. tcp_input_data, tcp_eager_kill, tcp_clean_death_wrapper,
 * tcp_timer_handler, all check for the tcp state.
 */
/* ARGSUSED */
void
tcp_clean_death_wrapper(void *arg, mblk_t *mp, void *arg2,
    ip_recv_attr_t *dummy)
{
        tcp_t   *tcp = ((conn_t *)arg)->conn_tcp;

        freemsg(mp);
        if (tcp->tcp_state > TCPS_BOUND)
                (void) tcp_clean_death(((conn_t *)arg)->conn_tcp, ETIMEDOUT);
}

/*
 * We are dying for some reason.  Try to do it gracefully.  (May be called
 * as writer.)
 *
 * Return -1 if the structure was not cleaned up (if the cleanup had to be
 * done by a service procedure).
 * TBD - Should the return value distinguish between the tcp_t being
 * freed and it being reinitialized?
 */
int
tcp_clean_death(tcp_t *tcp, int err)
{
        mblk_t  *mp;
        queue_t *q;
        conn_t  *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;

        if (tcp->tcp_fused)
                tcp_unfuse(tcp);

        if (tcp->tcp_linger_tid != 0 &&
            TCP_TIMER_CANCEL(tcp, tcp->tcp_linger_tid) >= 0) {
                tcp_stop_lingering(tcp);
        }

        ASSERT(tcp != NULL);
        ASSERT((connp->conn_family == AF_INET &&
            connp->conn_ipversion == IPV4_VERSION) ||
            (connp->conn_family == AF_INET6 &&
            (connp->conn_ipversion == IPV4_VERSION ||
            connp->conn_ipversion == IPV6_VERSION)));

        if (TCP_IS_DETACHED(tcp)) {
                if (tcp->tcp_hard_binding) {
                        /*
                         * Its an eager that we are dealing with. We close the
                         * eager but in case a conn_ind has already gone to the
                         * listener, let tcp_accept_finish() send a discon_ind
                         * to the listener and drop the last reference. If the
                         * listener doesn't even know about the eager i.e. the
                         * conn_ind hasn't gone up, blow away the eager and drop
                         * the last reference as well. If the conn_ind has gone
                         * up, state should be BOUND. tcp_accept_finish
                         * will figure out that the connection has received a
                         * RST and will send a DISCON_IND to the application.
                         */
                        tcp_closei_local(tcp);
                        if (!tcp->tcp_tconnind_started) {
                                CONN_DEC_REF(connp);
                        } else {
                                tcp->tcp_state = TCPS_BOUND;
                                DTRACE_TCP6(state__change, void, NULL,
                                    ip_xmit_attr_t *, connp->conn_ixa,
                                    void, NULL, tcp_t *, tcp, void, NULL,
                                    int32_t, TCPS_CLOSED);
                        }
                } else {
                        tcp_close_detached(tcp);
                }
                return (0);
        }

        TCP_STAT(tcps, tcp_clean_death_nondetached);

        /*
         * The connection is dead.  Decrement listener connection counter if
         * necessary.
         */
        if (tcp->tcp_listen_cnt != NULL)
                TCP_DECR_LISTEN_CNT(tcp);

        /*
         * When a connection is moved to TIME_WAIT state, the connection
         * counter is already decremented.  So no need to decrement here
         * again.  See SET_TIME_WAIT() macro.
         */
        if (tcp->tcp_state >= TCPS_ESTABLISHED &&
            tcp->tcp_state < TCPS_TIME_WAIT) {
                TCPS_CONN_DEC(tcps);
        }

        q = connp->conn_rq;

        /* Trash all inbound data */
        if (!IPCL_IS_NONSTR(connp)) {
                ASSERT(q != NULL);
                flushq(q, FLUSHALL);
        }

        /*
         * If we are at least part way open and there is error
         * (err==0 implies no error)
         * notify our client by a T_DISCON_IND.
         */
        if ((tcp->tcp_state >= TCPS_SYN_SENT) && err) {
                if (tcp->tcp_state >= TCPS_ESTABLISHED &&
                    !TCP_IS_SOCKET(tcp)) {
                        /*
                         * Send M_FLUSH according to TPI. Because sockets will
                         * (and must) ignore FLUSHR we do that only for TPI
                         * endpoints and sockets in STREAMS mode.
                         */
                        (void) putnextctl1(q, M_FLUSH, FLUSHR);
                }
                if (connp->conn_debug) {
                        (void) strlog(TCP_MOD_ID, 0, 1, SL_TRACE|SL_ERROR,
                            "tcp_clean_death: discon err %d", err);
                }
                if (IPCL_IS_NONSTR(connp)) {
                        /* Direct socket, use upcall */
                        (*connp->conn_upcalls->su_disconnected)(
                            connp->conn_upper_handle, tcp->tcp_connid, err);
                } else {
                        mp = mi_tpi_discon_ind(NULL, err, 0);
                        if (mp != NULL) {
                                putnext(q, mp);
                        } else {
                                if (connp->conn_debug) {
                                        (void) strlog(TCP_MOD_ID, 0, 1,
                                            SL_ERROR|SL_TRACE,
                                            "tcp_clean_death, sending M_ERROR");
                                }
                                (void) putnextctl1(q, M_ERROR, EPROTO);
                        }
                }
                if (tcp->tcp_state <= TCPS_SYN_RCVD) {
                        /* SYN_SENT or SYN_RCVD */
                        TCPS_BUMP_MIB(tcps, tcpAttemptFails);
                } else if (tcp->tcp_state <= TCPS_CLOSE_WAIT) {
                        /* ESTABLISHED or CLOSE_WAIT */
                        TCPS_BUMP_MIB(tcps, tcpEstabResets);
                }
        }

        /*
         * ESTABLISHED non-STREAMS eagers are not 'detached' because
         * an upper handle is obtained when the SYN-ACK comes in. So it
         * should receive the 'disconnected' upcall, but tcp_reinit should
         * not be called since this is an eager.
         */
        if (tcp->tcp_listener != NULL && IPCL_IS_NONSTR(connp)) {
                tcp_closei_local(tcp);
                tcp->tcp_state = TCPS_BOUND;
                DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
                    connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
                    int32_t, TCPS_CLOSED);
                return (0);
        }

        tcp_reinit(tcp);
        if (IPCL_IS_NONSTR(connp))
                (void) tcp_do_unbind(connp);

        return (-1);
}

/*
 * In case tcp is in the "lingering state" and waits for the SO_LINGER timeout
 * to expire, stop the wait and finish the close.
 */
void
tcp_stop_lingering(tcp_t *tcp)
{
        clock_t delta = 0;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;

        tcp->tcp_linger_tid = 0;
        if (tcp->tcp_state > TCPS_LISTEN) {
                tcp_acceptor_hash_remove(tcp);
                mutex_enter(&tcp->tcp_non_sq_lock);
                if (tcp->tcp_flow_stopped) {
                        tcp_clrqfull(tcp);
                }
                mutex_exit(&tcp->tcp_non_sq_lock);

                if (tcp->tcp_timer_tid != 0) {
                        delta = TCP_TIMER_CANCEL(tcp, tcp->tcp_timer_tid);
                        tcp->tcp_timer_tid = 0;
                }
                /*
                 * Need to cancel those timers which will not be used when
                 * TCP is detached.  This has to be done before the conn_wq
                 * is cleared.
                 */
                tcp_timers_stop(tcp);

                tcp->tcp_detached = B_TRUE;
                connp->conn_rq = NULL;
                connp->conn_wq = NULL;

                if (tcp->tcp_state == TCPS_TIME_WAIT) {
                        tcp_time_wait_append(tcp);
                        TCP_DBGSTAT(tcps, tcp_detach_time_wait);
                        goto finish;
                }

                /*
                 * If delta is zero the timer event wasn't executed and was
                 * successfully canceled. In this case we need to restart it
                 * with the minimal delta possible.
                 */
                if (delta >= 0) {
                        tcp->tcp_timer_tid = TCP_TIMER(tcp, tcp_timer,
                            delta ? delta : 1);
                }
        } else {
                tcp_closei_local(tcp);
                CONN_DEC_REF(connp);
        }
finish:
        tcp->tcp_detached = B_TRUE;
        connp->conn_rq = NULL;
        connp->conn_wq = NULL;

        /* Signal closing thread that it can complete close */
        mutex_enter(&tcp->tcp_closelock);
        tcp->tcp_closed = 1;
        cv_signal(&tcp->tcp_closecv);
        mutex_exit(&tcp->tcp_closelock);

        /* If we have an upper handle (socket), release it */
        if (IPCL_IS_NONSTR(connp)) {
                ASSERT(connp->conn_upper_handle != NULL);
                (*connp->conn_upcalls->su_closed)(connp->conn_upper_handle);
                connp->conn_upper_handle = NULL;
                connp->conn_upcalls = NULL;
        }
}

void
tcp_close_common(conn_t *connp, int flags)
{
        tcp_t           *tcp = connp->conn_tcp;
        mblk_t          *mp = &tcp->tcp_closemp;
        boolean_t       conn_ioctl_cleanup_reqd = B_FALSE;
        mblk_t          *bp;

        ASSERT(connp->conn_ref >= 2);

        /*
         * Mark the conn as closing. ipsq_pending_mp_add will not
         * add any mp to the pending mp list, after this conn has
         * started closing.
         */
        mutex_enter(&connp->conn_lock);
        connp->conn_state_flags |= CONN_CLOSING;
        if (connp->conn_oper_pending_ill != NULL)
                conn_ioctl_cleanup_reqd = B_TRUE;
        CONN_INC_REF_LOCKED(connp);
        mutex_exit(&connp->conn_lock);
        tcp->tcp_closeflags = (uint8_t)flags;
        ASSERT(connp->conn_ref >= 3);

        /*
         * tcp_closemp_used is used below without any protection of a lock
         * as we don't expect any one else to use it concurrently at this
         * point otherwise it would be a major defect.
         */

        if (mp->b_prev == NULL)
                tcp->tcp_closemp_used = B_TRUE;
        else
                cmn_err(CE_PANIC, "tcp_close: concurrent use of tcp_closemp: "
                    "connp %p tcp %p\n", (void *)connp, (void *)tcp);

        TCP_DEBUG_GETPCSTACK(tcp->tcmp_stk, 15);

        /*
         * Cleanup any queued ioctls here. This must be done before the wq/rq
         * are re-written by tcp_close_output().
         */
        if (conn_ioctl_cleanup_reqd)
                conn_ioctl_cleanup(connp);

        /*
         * As CONN_CLOSING is set, no further ioctls should be passed down to
         * IP for this conn (see the guards in tcp_ioctl, tcp_wput_ioctl and
         * tcp_wput_iocdata). If the ioctl was queued on an ipsq,
         * conn_ioctl_cleanup should have found it and removed it. If the ioctl
         * was still in flight at the time, we wait for it here. See comments
         * for CONN_INC_IOCTLREF in ip.h for details.
         */
        mutex_enter(&connp->conn_lock);
        while (connp->conn_ioctlref > 0)
                cv_wait(&connp->conn_cv, &connp->conn_lock);
        ASSERT(connp->conn_ioctlref == 0);
        ASSERT(connp->conn_oper_pending_ill == NULL);
        mutex_exit(&connp->conn_lock);

        SQUEUE_ENTER_ONE(connp->conn_sqp, mp, tcp_close_output, connp,
            NULL, tcp_squeue_flag, SQTAG_IP_TCP_CLOSE);

        /*
         * For non-STREAMS sockets, the normal case is that the conn makes
         * an upcall when it's finally closed, so there is no need to wait
         * in the protocol. But in case of SO_LINGER the thread sleeps here
         * so it can properly deal with the thread being interrupted.
         */
        if (IPCL_IS_NONSTR(connp) && connp->conn_linger == 0)
                goto nowait;

        mutex_enter(&tcp->tcp_closelock);
        while (!tcp->tcp_closed) {
                if (!cv_wait_sig(&tcp->tcp_closecv, &tcp->tcp_closelock)) {
                        /*
                         * The cv_wait_sig() was interrupted. We now do the
                         * following:
                         *
                         * 1) If the endpoint was lingering, we allow this
                         * to be interrupted by cancelling the linger timeout
                         * and closing normally.
                         *
                         * 2) Revert to calling cv_wait()
                         *
                         * We revert to using cv_wait() to avoid an
                         * infinite loop which can occur if the calling
                         * thread is higher priority than the squeue worker
                         * thread and is bound to the same cpu.
                         */
                        if (connp->conn_linger && connp->conn_lingertime > 0) {
                                mutex_exit(&tcp->tcp_closelock);
                                /* Entering squeue, bump ref count. */
                                CONN_INC_REF(connp);
                                bp = allocb_wait(0, BPRI_HI, STR_NOSIG, NULL);
                                SQUEUE_ENTER_ONE(connp->conn_sqp, bp,
                                    tcp_linger_interrupted, connp, NULL,
                                    tcp_squeue_flag, SQTAG_IP_TCP_CLOSE);
                                mutex_enter(&tcp->tcp_closelock);
                        }
                        break;
                }
        }
        while (!tcp->tcp_closed)
                cv_wait(&tcp->tcp_closecv, &tcp->tcp_closelock);
        mutex_exit(&tcp->tcp_closelock);

        /*
         * In the case of listener streams that have eagers in the q or q0
         * we wait for the eagers to drop their reference to us. conn_rq and
         * conn_wq of the eagers point to our queues. By waiting for the
         * refcnt to drop to 1, we are sure that the eagers have cleaned
         * up their queue pointers and also dropped their references to us.
         *
         * For non-STREAMS sockets we do not have to wait here; the
         * listener will instead make a su_closed upcall when the last
         * reference is dropped.
         */
        if (tcp->tcp_wait_for_eagers && !IPCL_IS_NONSTR(connp)) {
                mutex_enter(&connp->conn_lock);
                while (connp->conn_ref != 1) {
                        cv_wait(&connp->conn_cv, &connp->conn_lock);
                }
                mutex_exit(&connp->conn_lock);
        }

nowait:
        connp->conn_cpid = NOPID;
}

/*
 * Called by tcp_close() routine via squeue when lingering is
 * interrupted by a signal.
 */

/* ARGSUSED */
static void
tcp_linger_interrupted(void *arg, mblk_t *mp, void *arg2, ip_recv_attr_t *dummy)
{
        conn_t  *connp = (conn_t *)arg;
        tcp_t   *tcp = connp->conn_tcp;

        freeb(mp);
        if (tcp->tcp_linger_tid != 0 &&
            TCP_TIMER_CANCEL(tcp, tcp->tcp_linger_tid) >= 0) {
                tcp_stop_lingering(tcp);
                tcp->tcp_client_errno = EINTR;
        }
}

/*
 * Clean up the b_next and b_prev fields of every mblk pointed at by *mpp.
 * Some stream heads get upset if they see these later on as anything but NULL.
 */
void
tcp_close_mpp(mblk_t **mpp)
{
        mblk_t  *mp;

        if ((mp = *mpp) != NULL) {
                do {
                        mp->b_next = NULL;
                        mp->b_prev = NULL;
                } while ((mp = mp->b_cont) != NULL);

                mp = *mpp;
                *mpp = NULL;
                freemsg(mp);
        }
}

/* Do detached close. */
void
tcp_close_detached(tcp_t *tcp)
{
        if (tcp->tcp_fused)
                tcp_unfuse(tcp);

        tcp_closei_local(tcp);
        CONN_DEC_REF(tcp->tcp_connp);
}

/*
 * The tcp_t is going away. Remove it from all lists and set it
 * to TCPS_CLOSED. The freeing up of memory is deferred until
 * tcp_inactive. This is needed since a thread in tcp_rput might have
 * done a CONN_INC_REF on this structure before it was removed from the
 * hashes.
 */
void
tcp_closei_local(tcp_t *tcp)
{
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        int32_t         oldstate;

        if (!TCP_IS_SOCKET(tcp))
                tcp_acceptor_hash_remove(tcp);

        TCPS_UPDATE_MIB(tcps, tcpHCInSegs, tcp->tcp_ibsegs);
        tcp->tcp_ibsegs = 0;
        TCPS_UPDATE_MIB(tcps, tcpHCOutSegs, tcp->tcp_obsegs);
        tcp->tcp_obsegs = 0;

        /*
         * This can be called via tcp_time_wait_processing() if TCP gets a
         * SYN with sequence number outside the TIME-WAIT connection's
         * window.  So we need to check for TIME-WAIT state here as the
         * connection counter is already decremented.  See SET_TIME_WAIT()
         * macro
         */
        if (tcp->tcp_state >= TCPS_ESTABLISHED &&
            tcp->tcp_state < TCPS_TIME_WAIT) {
                TCPS_CONN_DEC(tcps);
        }

        /*
         * If we are an eager connection hanging off a listener that
         * hasn't formally accepted the connection yet, get off its
         * list and blow off any data that we have accumulated.
         */
        if (tcp->tcp_listener != NULL) {
                tcp_t   *listener = tcp->tcp_listener;
                mutex_enter(&listener->tcp_eager_lock);
                /*
                 * tcp_tconnind_started == B_TRUE means that the
                 * conn_ind has already gone to listener. At
                 * this point, eager will be closed but we
                 * leave it in listeners eager list so that
                 * if listener decides to close without doing
                 * accept, we can clean this up. In tcp_tli_accept
                 * we take care of the case of accept on closed
                 * eager.
                 */
                if (!tcp->tcp_tconnind_started) {
                        tcp_eager_unlink(tcp);
                        mutex_exit(&listener->tcp_eager_lock);
                        /*
                         * We don't want to have any pointers to the
                         * listener queue, after we have released our
                         * reference on the listener
                         */
                        ASSERT(tcp->tcp_detached);
                        connp->conn_rq = NULL;
                        connp->conn_wq = NULL;
                        CONN_DEC_REF(listener->tcp_connp);
                } else {
                        mutex_exit(&listener->tcp_eager_lock);
                }
        }

        /* Stop all the timers */
        tcp_timers_stop(tcp);

        if (tcp->tcp_state == TCPS_LISTEN) {
                if (tcp->tcp_ip_addr_cache) {
                        kmem_free((void *)tcp->tcp_ip_addr_cache,
                            IP_ADDR_CACHE_SIZE * sizeof (ipaddr_t));
                        tcp->tcp_ip_addr_cache = NULL;
                }
        }

        /* Decrement listerner connection counter if necessary. */
        if (tcp->tcp_listen_cnt != NULL)
                TCP_DECR_LISTEN_CNT(tcp);

        mutex_enter(&tcp->tcp_non_sq_lock);
        if (tcp->tcp_flow_stopped)
                tcp_clrqfull(tcp);
        mutex_exit(&tcp->tcp_non_sq_lock);

        tcp_bind_hash_remove(tcp);
        /*
         * If the tcp_time_wait_collector (which runs outside the squeue)
         * is trying to remove this tcp from the time wait list, we will
         * block in tcp_time_wait_remove while trying to acquire the
         * tcp_time_wait_lock. The logic in tcp_time_wait_collector also
         * requires the ipcl_hash_remove to be ordered after the
         * tcp_time_wait_remove for the refcnt checks to work correctly.
         */
        if (tcp->tcp_state == TCPS_TIME_WAIT)
                (void) tcp_time_wait_remove(tcp, NULL);
        ipcl_hash_remove(connp);
        oldstate = tcp->tcp_state;
        tcp->tcp_state = TCPS_CLOSED;
        /* Need to probe before ixa_cleanup() is called */
        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
            connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
            int32_t, oldstate);
        ixa_cleanup(connp->conn_ixa);

        /*
         * Mark the conn as CONDEMNED
         */
        mutex_enter(&connp->conn_lock);
        connp->conn_state_flags |= CONN_CONDEMNED;
        mutex_exit(&connp->conn_lock);

        ASSERT(tcp->tcp_time_wait_next == NULL);
        ASSERT(tcp->tcp_time_wait_prev == NULL);
        ASSERT(tcp->tcp_time_wait_expire == 0);

        tcp_ipsec_cleanup(tcp);
}

/*
 * tcp is dying (called from ipcl_conn_destroy and error cases).
 * Free the tcp_t in either case.
 */
void
tcp_free(tcp_t *tcp)
{
        mblk_t          *mp;
        conn_t          *connp = tcp->tcp_connp;

        ASSERT(tcp != NULL);
        ASSERT(tcp->tcp_ptpahn == NULL && tcp->tcp_acceptor_hash == NULL);

        connp->conn_rq = NULL;
        connp->conn_wq = NULL;

        tcp_close_mpp(&tcp->tcp_xmit_head);
        tcp_close_mpp(&tcp->tcp_reass_head);
        if (tcp->tcp_rcv_list != NULL) {
                /* Free b_next chain */
                tcp_close_mpp(&tcp->tcp_rcv_list);
        }
        if ((mp = tcp->tcp_urp_mp) != NULL) {
                freemsg(mp);
        }
        if ((mp = tcp->tcp_urp_mark_mp) != NULL) {
                freemsg(mp);
        }

        if (tcp->tcp_fused_sigurg_mp != NULL) {
                ASSERT(!IPCL_IS_NONSTR(tcp->tcp_connp));
                freeb(tcp->tcp_fused_sigurg_mp);
                tcp->tcp_fused_sigurg_mp = NULL;
        }

        if (tcp->tcp_ordrel_mp != NULL) {
                ASSERT(!IPCL_IS_NONSTR(tcp->tcp_connp));
                freeb(tcp->tcp_ordrel_mp);
                tcp->tcp_ordrel_mp = NULL;
        }

        TCP_NOTSACK_REMOVE_ALL(tcp->tcp_notsack_list, tcp);
        bzero(&tcp->tcp_sack_info, sizeof (tcp_sack_info_t));

        if (tcp->tcp_hopopts != NULL) {
                mi_free(tcp->tcp_hopopts);
                tcp->tcp_hopopts = NULL;
                tcp->tcp_hopoptslen = 0;
        }
        ASSERT(tcp->tcp_hopoptslen == 0);
        if (tcp->tcp_dstopts != NULL) {
                mi_free(tcp->tcp_dstopts);
                tcp->tcp_dstopts = NULL;
                tcp->tcp_dstoptslen = 0;
        }
        ASSERT(tcp->tcp_dstoptslen == 0);
        if (tcp->tcp_rthdrdstopts != NULL) {
                mi_free(tcp->tcp_rthdrdstopts);
                tcp->tcp_rthdrdstopts = NULL;
                tcp->tcp_rthdrdstoptslen = 0;
        }
        ASSERT(tcp->tcp_rthdrdstoptslen == 0);
        if (tcp->tcp_rthdr != NULL) {
                mi_free(tcp->tcp_rthdr);
                tcp->tcp_rthdr = NULL;
                tcp->tcp_rthdrlen = 0;
        }
        ASSERT(tcp->tcp_rthdrlen == 0);

        /*
         * Following is really a blowing away a union.
         * It happens to have exactly two members of identical size
         * the following code is enough.
         */
        tcp_close_mpp(&tcp->tcp_conn.tcp_eager_conn_ind);

        /*
         * If this is a non-STREAM socket still holding on to an upper
         * handle, release it. As a result of fallback we might also see
         * STREAMS based conns with upper handles, in which case there is
         * nothing to do other than clearing the field.
         */
        if (connp->conn_upper_handle != NULL) {
                if (IPCL_IS_NONSTR(connp)) {
                        (*connp->conn_upcalls->su_closed)(
                            connp->conn_upper_handle);
                        tcp->tcp_detached = B_TRUE;
                }
                connp->conn_upper_handle = NULL;
                connp->conn_upcalls = NULL;
        }
}

/*
 * tcp_get_conn/tcp_free_conn
 *
 * tcp_get_conn is used to get a clean tcp connection structure.
 * It tries to reuse the connections put on the freelist by the
 * time_wait_collector failing which it goes to kmem_cache. This
 * way has two benefits compared to just allocating from and
 * freeing to kmem_cache.
 * 1) The time_wait_collector can free (which includes the cleanup)
 * outside the squeue. So when the interrupt comes, we have a clean
 * connection sitting in the freelist. Obviously, this buys us
 * performance.
 *
 * 2) Defence against DOS attack. Allocating a tcp/conn in tcp_input_listener
 * has multiple disadvantages - tying up the squeue during alloc.
 * But allocating the conn/tcp in IP land is also not the best since
 * we can't check the 'q' and 'q0' which are protected by squeue and
 * blindly allocate memory which might have to be freed here if we are
 * not allowed to accept the connection. By using the freelist and
 * putting the conn/tcp back in freelist, we don't pay a penalty for
 * allocating memory without checking 'q/q0' and freeing it if we can't
 * accept the connection.
 *
 * Care should be taken to put the conn back in the same squeue's freelist
 * from which it was allocated. Best results are obtained if conn is
 * allocated from listener's squeue and freed to the same. Time wait
 * collector will free up the freelist is the connection ends up sitting
 * there for too long.
 */
void *
tcp_get_conn(void *arg, tcp_stack_t *tcps)
{
        tcp_t                   *tcp = NULL;
        conn_t                  *connp = NULL;
        squeue_t                *sqp = (squeue_t *)arg;
        tcp_squeue_priv_t       *tcp_time_wait;
        netstack_t              *ns;
        mblk_t                  *tcp_rsrv_mp = NULL;

        tcp_time_wait =
            *((tcp_squeue_priv_t **)squeue_getprivate(sqp, SQPRIVATE_TCP));

        mutex_enter(&tcp_time_wait->tcp_time_wait_lock);
        tcp = tcp_time_wait->tcp_free_list;
        ASSERT((tcp != NULL) ^ (tcp_time_wait->tcp_free_list_cnt == 0));
        if (tcp != NULL) {
                tcp_time_wait->tcp_free_list = tcp->tcp_time_wait_next;
                tcp_time_wait->tcp_free_list_cnt--;
                mutex_exit(&tcp_time_wait->tcp_time_wait_lock);
                tcp->tcp_time_wait_next = NULL;
                connp = tcp->tcp_connp;
                connp->conn_flags |= IPCL_REUSED;

                ASSERT(tcp->tcp_tcps == NULL);
                ASSERT(connp->conn_netstack == NULL);
                ASSERT(tcp->tcp_rsrv_mp != NULL);
                ns = tcps->tcps_netstack;
                netstack_hold(ns);
                connp->conn_netstack = ns;
                connp->conn_ixa->ixa_ipst = ns->netstack_ip;
                tcp->tcp_tcps = tcps;
                ipcl_globalhash_insert(connp);

                connp->conn_ixa->ixa_notify_cookie = tcp;
                ASSERT(connp->conn_ixa->ixa_notify == tcp_notify);
                connp->conn_recv = tcp_input_data;
                ASSERT(connp->conn_recvicmp == tcp_icmp_input);
                ASSERT(connp->conn_verifyicmp == tcp_verifyicmp);
                return ((void *)connp);
        }
        mutex_exit(&tcp_time_wait->tcp_time_wait_lock);
        /*
         * Pre-allocate the tcp_rsrv_mp. This mblk will not be freed until
         * this conn_t/tcp_t is freed at ipcl_conn_destroy().
         */
        tcp_rsrv_mp = allocb(0, BPRI_HI);
        if (tcp_rsrv_mp == NULL)
                return (NULL);

        if ((connp = ipcl_conn_create(IPCL_TCPCONN, KM_NOSLEEP,
            tcps->tcps_netstack)) == NULL) {
                freeb(tcp_rsrv_mp);
                return (NULL);
        }

        tcp = connp->conn_tcp;
        tcp->tcp_rsrv_mp = tcp_rsrv_mp;
        mutex_init(&tcp->tcp_rsrv_mp_lock, NULL, MUTEX_DEFAULT, NULL);

        tcp->tcp_tcps = tcps;

        connp->conn_recv = tcp_input_data;
        connp->conn_recvicmp = tcp_icmp_input;
        connp->conn_verifyicmp = tcp_verifyicmp;

        /*
         * Register tcp_notify to listen to capability changes detected by IP.
         * This upcall is made in the context of the call to conn_ip_output
         * thus it is inside the squeue.
         */
        connp->conn_ixa->ixa_notify = tcp_notify;
        connp->conn_ixa->ixa_notify_cookie = tcp;

        return ((void *)connp);
}

/*
 * Handle connect to IPv4 destinations, including connections for AF_INET6
 * sockets connecting to IPv4 mapped IPv6 destinations.
 * Returns zero if OK, a positive errno, or a negative TLI error.
 */
static int
tcp_connect_ipv4(tcp_t *tcp, ipaddr_t *dstaddrp, in_port_t dstport,
    uint_t srcid)
{
        ipaddr_t        dstaddr = *dstaddrp;
        uint16_t        lport;
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        int             error;

        ASSERT(connp->conn_ipversion == IPV4_VERSION);

        /* Check for attempt to connect to INADDR_ANY */
        if (dstaddr == INADDR_ANY)  {
                /*
                 * SunOS 4.x and 4.3 BSD allow an application
                 * to connect a TCP socket to INADDR_ANY.
                 * When they do this, the kernel picks the
                 * address of one interface and uses it
                 * instead.  The kernel usually ends up
                 * picking the address of the loopback
                 * interface.  This is an undocumented feature.
                 * However, we provide the same thing here
                 * in order to have source and binary
                 * compatibility with SunOS 4.x.
                 * Update the T_CONN_REQ (sin/sin6) since it is used to
                 * generate the T_CONN_CON.
                 */
                dstaddr = htonl(INADDR_LOOPBACK);
                *dstaddrp = dstaddr;
        }

        /* Handle __sin6_src_id if socket not bound to an IP address */
        if (srcid != 0 && connp->conn_laddr_v4 == INADDR_ANY) {
                if (!ip_srcid_find_id(srcid, &connp->conn_laddr_v6,
                    IPCL_ZONEID(connp), B_TRUE, tcps->tcps_netstack)) {
                        /* Mismatch - conn_laddr_v6 would be v6 address. */
                        return (EADDRNOTAVAIL);
                }
                connp->conn_saddr_v6 = connp->conn_laddr_v6;
        }

        IN6_IPADDR_TO_V4MAPPED(dstaddr, &connp->conn_faddr_v6);
        connp->conn_fport = dstport;

        /*
         * At this point the remote destination address and remote port fields
         * in the tcp-four-tuple have been filled in the tcp structure. Now we
         * have to see which state tcp was in so we can take appropriate action.
         */
        if (tcp->tcp_state == TCPS_IDLE) {
                /*
                 * We support a quick connect capability here, allowing
                 * clients to transition directly from IDLE to SYN_SENT
                 * tcp_bindi will pick an unused port, insert the connection
                 * in the bind hash and transition to BOUND state.
                 */
                lport = tcp_update_next_port(tcps->tcps_next_port_to_try,
                    tcp, B_TRUE);
                lport = tcp_bindi(tcp, lport, &connp->conn_laddr_v6, 0, B_TRUE,
                    B_FALSE, B_FALSE);
                if (lport == 0)
                        return (-TNOADDR);
        }

        /*
         * Lookup the route to determine a source address and the uinfo.
         * Setup TCP parameters based on the metrics/DCE.
         */
        error = tcp_set_destination(tcp);
        if (error != 0)
                return (error);

        /*
         * Don't let an endpoint connect to itself.
         */
        if (connp->conn_faddr_v4 == connp->conn_laddr_v4 &&
            connp->conn_fport == connp->conn_lport)
                return (-TBADADDR);

        tcp->tcp_state = TCPS_SYN_SENT;

        return (ipcl_conn_insert_v4(connp));
}

/*
 * Handle connect to IPv6 destinations.
 * Returns zero if OK, a positive errno, or a negative TLI error.
 */
static int
tcp_connect_ipv6(tcp_t *tcp, in6_addr_t *dstaddrp, in_port_t dstport,
    uint32_t flowinfo, uint_t srcid, uint32_t scope_id)
{
        uint16_t        lport;
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        int             error;

        ASSERT(connp->conn_family == AF_INET6);

        /*
         * If we're here, it means that the destination address is a native
         * IPv6 address.  Return an error if conn_ipversion is not IPv6.  A
         * reason why it might not be IPv6 is if the socket was bound to an
         * IPv4-mapped IPv6 address.
         */
        if (connp->conn_ipversion != IPV6_VERSION)
                return (-TBADADDR);

        /*
         * Interpret a zero destination to mean loopback.
         * Update the T_CONN_REQ (sin/sin6) since it is used to
         * generate the T_CONN_CON.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(dstaddrp))
                *dstaddrp = ipv6_loopback;

        /* Handle __sin6_src_id if socket not bound to an IP address */
        if (srcid != 0 && IN6_IS_ADDR_UNSPECIFIED(&connp->conn_laddr_v6)) {
                if (!ip_srcid_find_id(srcid, &connp->conn_laddr_v6,
                    IPCL_ZONEID(connp), B_FALSE, tcps->tcps_netstack)) {
                        /* Mismatch - conn_laddr_v6 would be v4-mapped. */
                        return (EADDRNOTAVAIL);
                }
                connp->conn_saddr_v6 = connp->conn_laddr_v6;
        }

        /*
         * Take care of the scope_id now.
         */
        if (scope_id != 0 && IN6_IS_ADDR_LINKSCOPE(dstaddrp)) {
                connp->conn_ixa->ixa_flags |= IXAF_SCOPEID_SET;
                connp->conn_ixa->ixa_scopeid = scope_id;
        } else {
                connp->conn_ixa->ixa_flags &= ~IXAF_SCOPEID_SET;
        }

        connp->conn_flowinfo = flowinfo;
        connp->conn_faddr_v6 = *dstaddrp;
        connp->conn_fport = dstport;

        /*
         * At this point the remote destination address and remote port fields
         * in the tcp-four-tuple have been filled in the tcp structure. Now we
         * have to see which state tcp was in so we can take appropriate action.
         */
        if (tcp->tcp_state == TCPS_IDLE) {
                /*
                 * We support a quick connect capability here, allowing
                 * clients to transition directly from IDLE to SYN_SENT
                 * tcp_bindi will pick an unused port, insert the connection
                 * in the bind hash and transition to BOUND state.
                 */
                lport = tcp_update_next_port(tcps->tcps_next_port_to_try,
                    tcp, B_TRUE);
                lport = tcp_bindi(tcp, lport, &connp->conn_laddr_v6, 0, B_TRUE,
                    B_FALSE, B_FALSE);
                if (lport == 0)
                        return (-TNOADDR);
        }

        /*
         * Lookup the route to determine a source address and the uinfo.
         * Setup TCP parameters based on the metrics/DCE.
         */
        error = tcp_set_destination(tcp);
        if (error != 0)
                return (error);

        /*
         * Don't let an endpoint connect to itself.
         */
        if (IN6_ARE_ADDR_EQUAL(&connp->conn_faddr_v6, &connp->conn_laddr_v6) &&
            connp->conn_fport == connp->conn_lport)
                return (-TBADADDR);

        tcp->tcp_state = TCPS_SYN_SENT;

        return (ipcl_conn_insert_v6(connp));
}

/*
 * Disconnect
 * Note that unlike other functions this returns a positive tli error
 * when it fails; it never returns an errno.
 */
static int
tcp_disconnect_common(tcp_t *tcp, t_scalar_t seqnum)
{
        conn_t          *lconnp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;

        /*
         * Right now, upper modules pass down a T_DISCON_REQ to TCP,
         * when the stream is in BOUND state. Do not send a reset,
         * since the destination IP address is not valid, and it can
         * be the initialized value of all zeros (broadcast address).
         */
        if (tcp->tcp_state <= TCPS_BOUND) {
                if (connp->conn_debug) {
                        (void) strlog(TCP_MOD_ID, 0, 1, SL_ERROR|SL_TRACE,
                            "tcp_disconnect: bad state, %d", tcp->tcp_state);
                }
                return (TOUTSTATE);
        } else if (tcp->tcp_state >= TCPS_ESTABLISHED) {
                TCPS_CONN_DEC(tcps);
        }

        if (seqnum == -1 || tcp->tcp_conn_req_max == 0) {

                /*
                 * According to TPI, for non-listeners, ignore seqnum
                 * and disconnect.
                 * Following interpretation of -1 seqnum is historical
                 * and implied TPI ? (TPI only states that for T_CONN_IND,
                 * a valid seqnum should not be -1).
                 *
                 *      -1 means disconnect everything
                 *      regardless even on a listener.
                 */

                int old_state = tcp->tcp_state;
                ip_stack_t *ipst = tcps->tcps_netstack->netstack_ip;

                /*
                 * The connection can't be on the tcp_time_wait_head list
                 * since it is not detached.
                 */
                ASSERT(tcp->tcp_time_wait_next == NULL);
                ASSERT(tcp->tcp_time_wait_prev == NULL);
                ASSERT(tcp->tcp_time_wait_expire == 0);
                /*
                 * If it used to be a listener, check to make sure no one else
                 * has taken the port before switching back to LISTEN state.
                 */
                if (connp->conn_ipversion == IPV4_VERSION) {
                        lconnp = ipcl_lookup_listener_v4(connp->conn_lport,
                            connp->conn_laddr_v4, IPCL_ZONEID(connp), ipst);
                } else {
                        uint_t ifindex = 0;

                        if (connp->conn_ixa->ixa_flags & IXAF_SCOPEID_SET)
                                ifindex = connp->conn_ixa->ixa_scopeid;

                        /* Allow conn_bound_if listeners? */
                        lconnp = ipcl_lookup_listener_v6(connp->conn_lport,
                            &connp->conn_laddr_v6, ifindex, IPCL_ZONEID(connp),
                            ipst);
                }
                if (tcp->tcp_conn_req_max && lconnp == NULL) {
                        tcp->tcp_state = TCPS_LISTEN;
                        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
                            connp->conn_ixa, void, NULL, tcp_t *, tcp, void,
                            NULL, int32_t, old_state);
                } else if (old_state > TCPS_BOUND) {
                        tcp->tcp_conn_req_max = 0;
                        tcp->tcp_state = TCPS_BOUND;
                        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
                            connp->conn_ixa, void, NULL, tcp_t *, tcp, void,
                            NULL, int32_t, old_state);

                        /*
                         * If this end point is not going to become a listener,
                         * decrement the listener connection count if
                         * necessary.  Note that we do not do this if it is
                         * going to be a listner (the above if case) since
                         * then it may remove the counter struct.
                         */
                        if (tcp->tcp_listen_cnt != NULL)
                                TCP_DECR_LISTEN_CNT(tcp);
                }
                if (lconnp != NULL)
                        CONN_DEC_REF(lconnp);
                switch (old_state) {
                case TCPS_SYN_SENT:
                case TCPS_SYN_RCVD:
                        TCPS_BUMP_MIB(tcps, tcpAttemptFails);
                        break;
                case TCPS_ESTABLISHED:
                case TCPS_CLOSE_WAIT:
                        TCPS_BUMP_MIB(tcps, tcpEstabResets);
                        break;
                }

                if (tcp->tcp_fused)
                        tcp_unfuse(tcp);

                mutex_enter(&tcp->tcp_eager_lock);
                if ((tcp->tcp_conn_req_cnt_q0 != 0) ||
                    (tcp->tcp_conn_req_cnt_q != 0)) {
                        tcp_eager_cleanup(tcp, 0);
                }
                mutex_exit(&tcp->tcp_eager_lock);

                tcp_xmit_ctl("tcp_disconnect", tcp, tcp->tcp_snxt,
                    tcp->tcp_rnxt, TH_RST | TH_ACK);

                tcp_reinit(tcp);

                return (0);
        } else if (!tcp_eager_blowoff(tcp, seqnum)) {
                return (TBADSEQ);
        }
        return (0);
}

/*
 * Our client hereby directs us to reject the connection request
 * that tcp_input_listener() marked with 'seqnum'.  Rejection consists
 * of sending the appropriate RST, not an ICMP error.
 */
void
tcp_disconnect(tcp_t *tcp, mblk_t *mp)
{
        t_scalar_t seqnum;
        int     error;
        conn_t  *connp = tcp->tcp_connp;

        ASSERT((uintptr_t)(mp->b_wptr - mp->b_rptr) <= (uintptr_t)INT_MAX);
        if ((mp->b_wptr - mp->b_rptr) < sizeof (struct T_discon_req)) {
                tcp_err_ack(tcp, mp, TPROTO, 0);
                return;
        }
        seqnum = ((struct T_discon_req *)mp->b_rptr)->SEQ_number;
        error = tcp_disconnect_common(tcp, seqnum);
        if (error != 0)
                tcp_err_ack(tcp, mp, error, 0);
        else {
                if (tcp->tcp_state >= TCPS_ESTABLISHED) {
                        /* Send M_FLUSH according to TPI */
                        (void) putnextctl1(connp->conn_rq, M_FLUSH, FLUSHRW);
                }
                mp = mi_tpi_ok_ack_alloc(mp);
                if (mp != NULL)
                        putnext(connp->conn_rq, mp);
        }
}

/*
 * Handle reinitialization of a tcp structure.
 * Maintain "binding state" resetting the state to BOUND, LISTEN, or IDLE.
 */
static void
tcp_reinit(tcp_t *tcp)
{
        mblk_t          *mp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp  = tcp->tcp_connp;
        int32_t         oldstate;

        /* tcp_reinit should never be called for detached tcp_t's */
        ASSERT(tcp->tcp_listener == NULL);
        ASSERT((connp->conn_family == AF_INET &&
            connp->conn_ipversion == IPV4_VERSION) ||
            (connp->conn_family == AF_INET6 &&
            (connp->conn_ipversion == IPV4_VERSION ||
            connp->conn_ipversion == IPV6_VERSION)));

        /* Cancel outstanding timers */
        tcp_timers_stop(tcp);

        /*
         * Reset everything in the state vector, after updating global
         * MIB data from instance counters.
         */
        TCPS_UPDATE_MIB(tcps, tcpHCInSegs, tcp->tcp_ibsegs);
        tcp->tcp_ibsegs = 0;
        TCPS_UPDATE_MIB(tcps, tcpHCOutSegs, tcp->tcp_obsegs);
        tcp->tcp_obsegs = 0;

        tcp_close_mpp(&tcp->tcp_xmit_head);
        if (tcp->tcp_snd_zcopy_aware)
                tcp_zcopy_notify(tcp);
        tcp->tcp_xmit_last = tcp->tcp_xmit_tail = NULL;
        tcp->tcp_unsent = tcp->tcp_xmit_tail_unsent = 0;
        mutex_enter(&tcp->tcp_non_sq_lock);
        if (tcp->tcp_flow_stopped &&
            TCP_UNSENT_BYTES(tcp) <= connp->conn_sndlowat) {
                tcp_clrqfull(tcp);
        }
        mutex_exit(&tcp->tcp_non_sq_lock);
        tcp_close_mpp(&tcp->tcp_reass_head);
        tcp->tcp_reass_tail = NULL;
        if (tcp->tcp_rcv_list != NULL) {
                /* Free b_next chain */
                tcp_close_mpp(&tcp->tcp_rcv_list);
                tcp->tcp_rcv_last_head = NULL;
                tcp->tcp_rcv_last_tail = NULL;
                tcp->tcp_rcv_cnt = 0;
        }
        tcp->tcp_rcv_last_tail = NULL;

        if ((mp = tcp->tcp_urp_mp) != NULL) {
                freemsg(mp);
                tcp->tcp_urp_mp = NULL;
        }
        if ((mp = tcp->tcp_urp_mark_mp) != NULL) {
                freemsg(mp);
                tcp->tcp_urp_mark_mp = NULL;
        }
        if (tcp->tcp_fused_sigurg_mp != NULL) {
                ASSERT(!IPCL_IS_NONSTR(tcp->tcp_connp));
                freeb(tcp->tcp_fused_sigurg_mp);
                tcp->tcp_fused_sigurg_mp = NULL;
        }
        if (tcp->tcp_ordrel_mp != NULL) {
                ASSERT(!IPCL_IS_NONSTR(tcp->tcp_connp));
                freeb(tcp->tcp_ordrel_mp);
                tcp->tcp_ordrel_mp = NULL;
        }

        /*
         * Following is a union with two members which are
         * identical types and size so the following cleanup
         * is enough.
         */
        tcp_close_mpp(&tcp->tcp_conn.tcp_eager_conn_ind);

        /*
         * The connection can't be on the tcp_time_wait_head list
         * since it is not detached.
         */
        ASSERT(tcp->tcp_time_wait_next == NULL);
        ASSERT(tcp->tcp_time_wait_prev == NULL);
        ASSERT(tcp->tcp_time_wait_expire == 0);

        /*
         * Reset/preserve other values
         */
        tcp_reinit_values(tcp);
        ipcl_hash_remove(connp);
        /* Note that ixa_cred gets cleared in ixa_cleanup */
        ixa_cleanup(connp->conn_ixa);
        tcp_ipsec_cleanup(tcp);

        connp->conn_laddr_v6 = connp->conn_bound_addr_v6;
        connp->conn_saddr_v6 = connp->conn_bound_addr_v6;
        oldstate = tcp->tcp_state;

        if (tcp->tcp_conn_req_max != 0) {
                /*
                 * This is the case when a TLI program uses the same
                 * transport end point to accept a connection.  This
                 * makes the TCP both a listener and acceptor.  When
                 * this connection is closed, we need to set the state
                 * back to TCPS_LISTEN.  Make sure that the eager list
                 * is reinitialized.
                 *
                 * Note that this stream is still bound to the four
                 * tuples of the previous connection in IP.  If a new
                 * SYN with different foreign address comes in, IP will
                 * not find it and will send it to the global queue.  In
                 * the global queue, TCP will do a tcp_lookup_listener()
                 * to find this stream.  This works because this stream
                 * is only removed from connected hash.
                 *
                 */
                tcp->tcp_state = TCPS_LISTEN;
                tcp->tcp_eager_next_q0 = tcp->tcp_eager_prev_q0 = tcp;
                tcp->tcp_eager_next_drop_q0 = tcp;
                tcp->tcp_eager_prev_drop_q0 = tcp;
                /*
                 * Initially set conn_recv to tcp_input_listener_unbound to try
                 * to pick a good squeue for the listener when the first SYN
                 * arrives. tcp_input_listener_unbound sets it to
                 * tcp_input_listener on that first SYN.
                 */
                connp->conn_recv = tcp_input_listener_unbound;

                connp->conn_proto = IPPROTO_TCP;
                connp->conn_faddr_v6 = ipv6_all_zeros;
                connp->conn_fport = 0;

                (void) ipcl_bind_insert(connp);
        } else {
                tcp->tcp_state = TCPS_BOUND;
        }

        /*
         * Initialize to default values
         */
        tcp_init_values(tcp, NULL);

        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
            connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
            int32_t, oldstate);

        ASSERT(tcp->tcp_ptpbhn != NULL);
        tcp->tcp_rwnd = connp->conn_rcvbuf;
        tcp->tcp_mss = connp->conn_ipversion != IPV4_VERSION ?
            tcps->tcps_mss_def_ipv6 : tcps->tcps_mss_def_ipv4;
}

/*
 * Force values to zero that need be zero.
 * Do not touch values asociated with the BOUND or LISTEN state
 * since the connection will end up in that state after the reinit.
 * NOTE: tcp_reinit_values MUST have a line for each field in the tcp_t
 * structure!
 */
static void
tcp_reinit_values(tcp)
        tcp_t *tcp;
{
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;

#ifndef lint
#define DONTCARE(x)
#define PRESERVE(x)
#else
#define DONTCARE(x)     ((x) = (x))
#define PRESERVE(x)     ((x) = (x))
#endif  /* lint */

        PRESERVE(tcp->tcp_bind_hash_port);
        PRESERVE(tcp->tcp_bind_hash);
        PRESERVE(tcp->tcp_ptpbhn);
        PRESERVE(tcp->tcp_acceptor_hash);
        PRESERVE(tcp->tcp_ptpahn);

        /* Should be ASSERT NULL on these with new code! */
        ASSERT(tcp->tcp_time_wait_next == NULL);
        ASSERT(tcp->tcp_time_wait_prev == NULL);
        ASSERT(tcp->tcp_time_wait_expire == 0);
        PRESERVE(tcp->tcp_state);
        PRESERVE(connp->conn_rq);
        PRESERVE(connp->conn_wq);

        ASSERT(tcp->tcp_xmit_head == NULL);
        ASSERT(tcp->tcp_xmit_last == NULL);
        ASSERT(tcp->tcp_unsent == 0);
        ASSERT(tcp->tcp_xmit_tail == NULL);
        ASSERT(tcp->tcp_xmit_tail_unsent == 0);

        tcp->tcp_snxt = 0;                      /* Displayed in mib */
        tcp->tcp_suna = 0;                      /* Displayed in mib */
        tcp->tcp_swnd = 0;
        DONTCARE(tcp->tcp_cwnd);        /* Init in tcp_process_options */

        ASSERT(tcp->tcp_ibsegs == 0);
        ASSERT(tcp->tcp_obsegs == 0);

        if (connp->conn_ht_iphc != NULL) {
                kmem_free(connp->conn_ht_iphc, connp->conn_ht_iphc_allocated);
                connp->conn_ht_iphc = NULL;
                connp->conn_ht_iphc_allocated = 0;
                connp->conn_ht_iphc_len = 0;
                connp->conn_ht_ulp = NULL;
                connp->conn_ht_ulp_len = 0;
                tcp->tcp_ipha = NULL;
                tcp->tcp_ip6h = NULL;
                tcp->tcp_tcpha = NULL;
        }

        /* We clear any IP_OPTIONS and extension headers */
        ip_pkt_free(&connp->conn_xmit_ipp);

        DONTCARE(tcp->tcp_naglim);              /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_ipha);
        DONTCARE(tcp->tcp_ip6h);
        DONTCARE(tcp->tcp_tcpha);
        tcp->tcp_valid_bits = 0;

        DONTCARE(tcp->tcp_timer_backoff);       /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_last_recv_time);      /* Init in tcp_init_values */
        tcp->tcp_last_rcv_lbolt = 0;

        tcp->tcp_init_cwnd = 0;

        tcp->tcp_urp_last_valid = 0;
        tcp->tcp_hard_binding = 0;

        tcp->tcp_fin_acked = 0;
        tcp->tcp_fin_rcvd = 0;
        tcp->tcp_fin_sent = 0;
        tcp->tcp_ordrel_done = 0;

        tcp->tcp_detached = 0;

        tcp->tcp_snd_ws_ok = B_FALSE;
        tcp->tcp_snd_ts_ok = B_FALSE;
        tcp->tcp_zero_win_probe = 0;

        tcp->tcp_loopback = 0;
        tcp->tcp_localnet = 0;
        tcp->tcp_syn_defense = 0;
        tcp->tcp_set_timer = 0;

        tcp->tcp_active_open = 0;
        tcp->tcp_rexmit = B_FALSE;
        tcp->tcp_xmit_zc_clean = B_FALSE;

        tcp->tcp_snd_sack_ok = B_FALSE;
        tcp->tcp_hwcksum = B_FALSE;

        DONTCARE(tcp->tcp_maxpsz_multiplier);   /* Init in tcp_init_values */

        tcp->tcp_conn_def_q0 = 0;
        tcp->tcp_ip_forward_progress = B_FALSE;
        tcp->tcp_ecn_ok = B_FALSE;

        tcp->tcp_cwr = B_FALSE;
        tcp->tcp_ecn_echo_on = B_FALSE;
        tcp->tcp_is_wnd_shrnk = B_FALSE;

        TCP_NOTSACK_REMOVE_ALL(tcp->tcp_notsack_list, tcp);
        bzero(&tcp->tcp_sack_info, sizeof (tcp_sack_info_t));

        tcp->tcp_rcv_ws = 0;
        tcp->tcp_snd_ws = 0;
        tcp->tcp_ts_recent = 0;
        tcp->tcp_rnxt = 0;                      /* Displayed in mib */
        DONTCARE(tcp->tcp_rwnd);                /* Set in tcp_reinit() */
        tcp->tcp_initial_pmtu = 0;

        ASSERT(tcp->tcp_reass_head == NULL);
        ASSERT(tcp->tcp_reass_tail == NULL);

        tcp->tcp_cwnd_cnt = 0;

        ASSERT(tcp->tcp_rcv_list == NULL);
        ASSERT(tcp->tcp_rcv_last_head == NULL);
        ASSERT(tcp->tcp_rcv_last_tail == NULL);
        ASSERT(tcp->tcp_rcv_cnt == 0);

        DONTCARE(tcp->tcp_cwnd_ssthresh); /* Init in tcp_set_destination */
        DONTCARE(tcp->tcp_cwnd_max);            /* Init in tcp_init_values */
        tcp->tcp_csuna = 0;

        tcp->tcp_rto = 0;                       /* Displayed in MIB */
        DONTCARE(tcp->tcp_rtt_sa);              /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_rtt_sd);              /* Init in tcp_init_values */
        tcp->tcp_rtt_update = 0;

        DONTCARE(tcp->tcp_swl1); /* Init in case TCPS_LISTEN/TCPS_SYN_SENT */
        DONTCARE(tcp->tcp_swl2); /* Init in case TCPS_LISTEN/TCPS_SYN_SENT */

        tcp->tcp_rack = 0;                      /* Displayed in mib */
        tcp->tcp_rack_cnt = 0;
        tcp->tcp_rack_cur_max = 0;
        tcp->tcp_rack_abs_max = 0;

        tcp->tcp_max_swnd = 0;

        ASSERT(tcp->tcp_listener == NULL);

        DONTCARE(tcp->tcp_irs);                 /* tcp_valid_bits cleared */
        DONTCARE(tcp->tcp_iss);                 /* tcp_valid_bits cleared */
        DONTCARE(tcp->tcp_fss);                 /* tcp_valid_bits cleared */
        DONTCARE(tcp->tcp_urg);                 /* tcp_valid_bits cleared */

        ASSERT(tcp->tcp_conn_req_cnt_q == 0);
        ASSERT(tcp->tcp_conn_req_cnt_q0 == 0);
        PRESERVE(tcp->tcp_conn_req_max);
        PRESERVE(tcp->tcp_conn_req_seqnum);

        DONTCARE(tcp->tcp_first_timer_threshold); /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_second_timer_threshold); /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_first_ctimer_threshold); /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_second_ctimer_threshold); /* in tcp_init_values */

        DONTCARE(tcp->tcp_urp_last);    /* tcp_urp_last_valid is cleared */
        ASSERT(tcp->tcp_urp_mp == NULL);
        ASSERT(tcp->tcp_urp_mark_mp == NULL);
        ASSERT(tcp->tcp_fused_sigurg_mp == NULL);

        ASSERT(tcp->tcp_eager_next_q == NULL);
        ASSERT(tcp->tcp_eager_last_q == NULL);
        ASSERT((tcp->tcp_eager_next_q0 == NULL &&
            tcp->tcp_eager_prev_q0 == NULL) ||
            tcp->tcp_eager_next_q0 == tcp->tcp_eager_prev_q0);
        ASSERT(tcp->tcp_conn.tcp_eager_conn_ind == NULL);

        ASSERT((tcp->tcp_eager_next_drop_q0 == NULL &&
            tcp->tcp_eager_prev_drop_q0 == NULL) ||
            tcp->tcp_eager_next_drop_q0 == tcp->tcp_eager_prev_drop_q0);

        DONTCARE(tcp->tcp_ka_rinterval);        /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_ka_abort_thres);      /* Init in tcp_init_values */
        DONTCARE(tcp->tcp_ka_cnt);              /* Init in tcp_init_values */

        tcp->tcp_client_errno = 0;

        DONTCARE(connp->conn_sum);              /* Init in tcp_init_values */

        connp->conn_faddr_v6 = ipv6_all_zeros;  /* Displayed in MIB */

        PRESERVE(connp->conn_bound_addr_v6);
        tcp->tcp_last_sent_len = 0;
        tcp->tcp_dupack_cnt = 0;

        connp->conn_fport = 0;                  /* Displayed in MIB */
        PRESERVE(connp->conn_lport);

        PRESERVE(tcp->tcp_acceptor_lockp);

        ASSERT(tcp->tcp_ordrel_mp == NULL);
        PRESERVE(tcp->tcp_acceptor_id);
        DONTCARE(tcp->tcp_ipsec_overhead);

        PRESERVE(connp->conn_family);
        /* Remove any remnants of mapped address binding */
        if (connp->conn_family == AF_INET6) {
                connp->conn_ipversion = IPV6_VERSION;
                tcp->tcp_mss = tcps->tcps_mss_def_ipv6;
        } else {
                connp->conn_ipversion = IPV4_VERSION;
                tcp->tcp_mss = tcps->tcps_mss_def_ipv4;
        }

        connp->conn_bound_if = 0;
        connp->conn_recv_ancillary.crb_all = 0;
        tcp->tcp_recvifindex = 0;
        tcp->tcp_recvhops = 0;
        tcp->tcp_closed = 0;
        if (tcp->tcp_hopopts != NULL) {
                mi_free(tcp->tcp_hopopts);
                tcp->tcp_hopopts = NULL;
                tcp->tcp_hopoptslen = 0;
        }
        ASSERT(tcp->tcp_hopoptslen == 0);
        if (tcp->tcp_dstopts != NULL) {
                mi_free(tcp->tcp_dstopts);
                tcp->tcp_dstopts = NULL;
                tcp->tcp_dstoptslen = 0;
        }
        ASSERT(tcp->tcp_dstoptslen == 0);
        if (tcp->tcp_rthdrdstopts != NULL) {
                mi_free(tcp->tcp_rthdrdstopts);
                tcp->tcp_rthdrdstopts = NULL;
                tcp->tcp_rthdrdstoptslen = 0;
        }
        ASSERT(tcp->tcp_rthdrdstoptslen == 0);
        if (tcp->tcp_rthdr != NULL) {
                mi_free(tcp->tcp_rthdr);
                tcp->tcp_rthdr = NULL;
                tcp->tcp_rthdrlen = 0;
        }
        ASSERT(tcp->tcp_rthdrlen == 0);

        /* Reset fusion-related fields */
        tcp->tcp_fused = B_FALSE;
        tcp->tcp_unfusable = B_FALSE;
        tcp->tcp_fused_sigurg = B_FALSE;
        tcp->tcp_loopback_peer = NULL;

        tcp->tcp_lso = B_FALSE;

        tcp->tcp_in_ack_unsent = 0;
        tcp->tcp_cork = B_FALSE;
        tcp->tcp_tconnind_started = B_FALSE;

        PRESERVE(tcp->tcp_squeue_bytes);

        tcp->tcp_closemp_used = B_FALSE;

        PRESERVE(tcp->tcp_rsrv_mp);
        PRESERVE(tcp->tcp_rsrv_mp_lock);

#ifdef DEBUG
        DONTCARE(tcp->tcmp_stk[0]);
#endif

        PRESERVE(tcp->tcp_connid);

        ASSERT(tcp->tcp_listen_cnt == NULL);
        ASSERT(tcp->tcp_reass_tid == 0);

#undef  DONTCARE
#undef  PRESERVE
}

/*
 * Initialize the various fields in tcp_t.  If parent (the listener) is non
 * NULL, certain values will be inheritted from it.
 */
void
tcp_init_values(tcp_t *tcp, tcp_t *parent)
{
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;
        clock_t         rto;

        ASSERT((connp->conn_family == AF_INET &&
            connp->conn_ipversion == IPV4_VERSION) ||
            (connp->conn_family == AF_INET6 &&
            (connp->conn_ipversion == IPV4_VERSION ||
            connp->conn_ipversion == IPV6_VERSION)));

        if (parent == NULL) {
                tcp->tcp_naglim = tcps->tcps_naglim_def;

                tcp->tcp_rto_initial = tcps->tcps_rexmit_interval_initial;
                tcp->tcp_rto_min = tcps->tcps_rexmit_interval_min;
                tcp->tcp_rto_max = tcps->tcps_rexmit_interval_max;

                tcp->tcp_first_ctimer_threshold =
                    tcps->tcps_ip_notify_cinterval;
                tcp->tcp_second_ctimer_threshold =
                    tcps->tcps_ip_abort_cinterval;
                tcp->tcp_first_timer_threshold = tcps->tcps_ip_notify_interval;
                tcp->tcp_second_timer_threshold = tcps->tcps_ip_abort_interval;

                tcp->tcp_fin_wait_2_flush_interval =
                    tcps->tcps_fin_wait_2_flush_interval;

                tcp->tcp_ka_interval = tcps->tcps_keepalive_interval;
                tcp->tcp_ka_abort_thres = tcps->tcps_keepalive_abort_interval;
                tcp->tcp_ka_cnt = 0;
                tcp->tcp_ka_rinterval = 0;

                /*
                 * Default value of tcp_init_cwnd is 0, so no need to set here
                 * if parent is NULL.  But we need to inherit it from parent.
                 */
        } else {
                /* Inherit various TCP parameters from the parent. */
                tcp->tcp_naglim = parent->tcp_naglim;

                tcp->tcp_rto_initial = parent->tcp_rto_initial;
                tcp->tcp_rto_min = parent->tcp_rto_min;
                tcp->tcp_rto_max = parent->tcp_rto_max;

                tcp->tcp_first_ctimer_threshold =
                    parent->tcp_first_ctimer_threshold;
                tcp->tcp_second_ctimer_threshold =
                    parent->tcp_second_ctimer_threshold;
                tcp->tcp_first_timer_threshold =
                    parent->tcp_first_timer_threshold;
                tcp->tcp_second_timer_threshold =
                    parent->tcp_second_timer_threshold;

                tcp->tcp_fin_wait_2_flush_interval =
                    parent->tcp_fin_wait_2_flush_interval;

                tcp->tcp_ka_interval = parent->tcp_ka_interval;
                tcp->tcp_ka_abort_thres = parent->tcp_ka_abort_thres;
                tcp->tcp_ka_cnt = parent->tcp_ka_cnt;
                tcp->tcp_ka_rinterval = parent->tcp_ka_rinterval;

                tcp->tcp_init_cwnd = parent->tcp_init_cwnd;
        }

        /*
         * Initialize tcp_rtt_sa and tcp_rtt_sd so that the calculated RTO
         * will be close to tcp_rexmit_interval_initial.  By doing this, we
         * allow the algorithm to adjust slowly to large fluctuations of RTT
         * during first few transmissions of a connection as seen in slow
         * links.
         */
        tcp->tcp_rtt_sa = tcp->tcp_rto_initial << 2;
        tcp->tcp_rtt_sd = tcp->tcp_rto_initial >> 1;
        rto = (tcp->tcp_rtt_sa >> 3) + tcp->tcp_rtt_sd +
            tcps->tcps_rexmit_interval_extra + (tcp->tcp_rtt_sa >> 5) +
            tcps->tcps_conn_grace_period;
        TCP_SET_RTO(tcp, rto);

        tcp->tcp_timer_backoff = 0;
        tcp->tcp_ms_we_have_waited = 0;
        tcp->tcp_last_recv_time = ddi_get_lbolt();
        tcp->tcp_cwnd_max = tcps->tcps_cwnd_max_;
        tcp->tcp_cwnd_ssthresh = TCP_MAX_LARGEWIN;

        tcp->tcp_maxpsz_multiplier = tcps->tcps_maxpsz_multiplier;

        /* NOTE:  ISS is now set in tcp_set_destination(). */

        /* Reset fusion-related fields */
        tcp->tcp_fused = B_FALSE;
        tcp->tcp_unfusable = B_FALSE;
        tcp->tcp_fused_sigurg = B_FALSE;
        tcp->tcp_loopback_peer = NULL;

        /* We rebuild the header template on the next connect/conn_request */

        /*
         * Init the window scale to the max so tcp_rwnd_set() won't pare
         * down tcp_rwnd. tcp_set_destination() will set the right value later.
         */
        tcp->tcp_rcv_ws = TCP_MAX_WINSHIFT;
        tcp->tcp_rwnd = connp->conn_rcvbuf;

        tcp->tcp_cork = B_FALSE;
        /*
         * Init the tcp_debug option if it wasn't already set.  This value
         * determines whether TCP
         * calls strlog() to print out debug messages.  Doing this
         * initialization here means that this value is not inherited thru
         * tcp_reinit().
         */
        if (!connp->conn_debug)
                connp->conn_debug = tcps->tcps_dbg;
}

/*
 * Update the TCP connection according to change of PMTU.
 *
 * Path MTU might have changed by either increase or decrease, so need to
 * adjust the MSS based on the value of ixa_pmtu. No need to handle tiny
 * or negative MSS, since tcp_mss_set() will do it.
 */
void
tcp_update_pmtu(tcp_t *tcp, boolean_t decrease_only)
{
        uint32_t        pmtu;
        int32_t         mss;
        conn_t          *connp = tcp->tcp_connp;
        ip_xmit_attr_t  *ixa = connp->conn_ixa;
        iaflags_t       ixaflags;

        if (tcp->tcp_tcps->tcps_ignore_path_mtu)
                return;

        if (tcp->tcp_state < TCPS_ESTABLISHED)
                return;

        /*
         * Always call ip_get_pmtu() to make sure that IP has updated
         * ixa_flags properly.
         */
        pmtu = ip_get_pmtu(ixa);
        ixaflags = ixa->ixa_flags;

        /*
         * Calculate the MSS by decreasing the PMTU by conn_ht_iphc_len and
         * IPsec overhead if applied. Make sure to use the most recent
         * IPsec information.
         */
        mss = pmtu - connp->conn_ht_iphc_len - conn_ipsec_length(connp);

        /*
         * Nothing to change, so just return.
         */
        if (mss == tcp->tcp_mss)
                return;

        /*
         * Currently, for ICMP errors, only PMTU decrease is handled.
         */
        if (mss > tcp->tcp_mss && decrease_only)
                return;

        DTRACE_PROBE2(tcp_update_pmtu, int32_t, tcp->tcp_mss, uint32_t, mss);

        /*
         * Update ixa_fragsize and ixa_pmtu.
         */
        ixa->ixa_fragsize = ixa->ixa_pmtu = pmtu;

        /*
         * Adjust MSS and all relevant variables.
         */
        tcp_mss_set(tcp, mss);

        /*
         * If the PMTU is below the min size maintained by IP, then ip_get_pmtu
         * has set IXAF_PMTU_TOO_SMALL and cleared IXAF_PMTU_IPV4_DF. Since TCP
         * has a (potentially different) min size we do the same. Make sure to
         * clear IXAF_DONTFRAG, which is used by IP to decide whether to
         * fragment the packet.
         *
         * LSO over IPv6 can not be fragmented. So need to disable LSO
         * when IPv6 fragmentation is needed.
         */
        if (mss < tcp->tcp_tcps->tcps_mss_min)
                ixaflags |= IXAF_PMTU_TOO_SMALL;

        if (ixaflags & IXAF_PMTU_TOO_SMALL)
                ixaflags &= ~(IXAF_DONTFRAG | IXAF_PMTU_IPV4_DF);

        if ((connp->conn_ipversion == IPV4_VERSION) &&
            !(ixaflags & IXAF_PMTU_IPV4_DF)) {
                tcp->tcp_ipha->ipha_fragment_offset_and_flags = 0;
        }
        ixa->ixa_flags = ixaflags;
}

int
tcp_maxpsz_set(tcp_t *tcp, boolean_t set_maxblk)
{
        conn_t  *connp = tcp->tcp_connp;
        queue_t *q = connp->conn_rq;
        int32_t mss = tcp->tcp_mss;
        int     maxpsz;

        if (TCP_IS_DETACHED(tcp))
                return (mss);
        if (tcp->tcp_fused) {
                maxpsz = tcp_fuse_maxpsz(tcp);
                mss = INFPSZ;
        } else if (tcp->tcp_maxpsz_multiplier == 0) {
                /*
                 * Set the sd_qn_maxpsz according to the socket send buffer
                 * size, and sd_maxblk to INFPSZ (-1).  This will essentially
                 * instruct the stream head to copyin user data into contiguous
                 * kernel-allocated buffers without breaking it up into smaller
                 * chunks.  We round up the buffer size to the nearest SMSS.
                 */
                maxpsz = MSS_ROUNDUP(connp->conn_sndbuf, mss);
                mss = INFPSZ;
        } else {
                /*
                 * Set sd_qn_maxpsz to approx half the (receivers) buffer
                 * (and a multiple of the mss).  This instructs the stream
                 * head to break down larger than SMSS writes into SMSS-
                 * size mblks, up to tcp_maxpsz_multiplier mblks at a time.
                 */
                maxpsz = tcp->tcp_maxpsz_multiplier * mss;
                if (maxpsz > connp->conn_sndbuf / 2) {
                        maxpsz = connp->conn_sndbuf / 2;
                        /* Round up to nearest mss */
                        maxpsz = MSS_ROUNDUP(maxpsz, mss);
                }
        }

        (void) proto_set_maxpsz(q, connp, maxpsz);
        if (!(IPCL_IS_NONSTR(connp)))
                connp->conn_wq->q_maxpsz = maxpsz;
        if (set_maxblk)
                (void) proto_set_tx_maxblk(q, connp, mss);
        return (mss);
}

/* For /dev/tcp aka AF_INET open */
static int
tcp_openv4(queue_t *q, dev_t *devp, int flag, int sflag, cred_t *credp)
{
        return (tcp_open(q, devp, flag, sflag, credp, B_FALSE));
}

/* For /dev/tcp6 aka AF_INET6 open */
static int
tcp_openv6(queue_t *q, dev_t *devp, int flag, int sflag, cred_t *credp)
{
        return (tcp_open(q, devp, flag, sflag, credp, B_TRUE));
}

conn_t *
tcp_create_common(cred_t *credp, boolean_t isv6, boolean_t issocket,
    int *errorp)
{
        tcp_t           *tcp = NULL;
        conn_t          *connp;
        zoneid_t        zoneid;
        tcp_stack_t     *tcps;
        squeue_t        *sqp;

        ASSERT(errorp != NULL);
        /*
         * Find the proper zoneid and netstack.
         */
        /*
         * Special case for install: miniroot needs to be able to
         * access files via NFS as though it were always in the
         * global zone.
         */
        if (credp == kcred && nfs_global_client_only != 0) {
                zoneid = GLOBAL_ZONEID;
                tcps = netstack_find_by_stackid(GLOBAL_NETSTACKID)->
                    netstack_tcp;
                ASSERT(tcps != NULL);
        } else {
                netstack_t *ns;
                int err;

                if ((err = secpolicy_basic_net_access(credp)) != 0) {
                        *errorp = err;
                        return (NULL);
                }

                ns = netstack_find_by_cred(credp);
                ASSERT(ns != NULL);
                tcps = ns->netstack_tcp;
                ASSERT(tcps != NULL);

                /*
                 * For exclusive stacks we set the zoneid to zero
                 * to make TCP operate as if in the global zone.
                 */
                if (tcps->tcps_netstack->netstack_stackid !=
                    GLOBAL_NETSTACKID)
                        zoneid = GLOBAL_ZONEID;
                else
                        zoneid = crgetzoneid(credp);
        }

        sqp = IP_SQUEUE_GET((uint_t)gethrtime());
        connp = (conn_t *)tcp_get_conn(sqp, tcps);
        /*
         * Both tcp_get_conn and netstack_find_by_cred incremented refcnt,
         * so we drop it by one.
         */
        netstack_rele(tcps->tcps_netstack);
        if (connp == NULL) {
                *errorp = ENOSR;
                return (NULL);
        }
        ASSERT(connp->conn_ixa->ixa_protocol == connp->conn_proto);

        connp->conn_sqp = sqp;
        connp->conn_initial_sqp = connp->conn_sqp;
        connp->conn_ixa->ixa_sqp = connp->conn_sqp;
        tcp = connp->conn_tcp;

        /*
         * Besides asking IP to set the checksum for us, have conn_ip_output
         * to do the following checks when necessary:
         *
         * IXAF_VERIFY_SOURCE: drop packets when our outer source goes invalid
         * IXAF_VERIFY_PMTU: verify PMTU changes
         * IXAF_VERIFY_LSO: verify LSO capability changes
         */
        connp->conn_ixa->ixa_flags |= IXAF_SET_ULP_CKSUM | IXAF_VERIFY_SOURCE |
            IXAF_VERIFY_PMTU | IXAF_VERIFY_LSO;

        if (!tcps->tcps_dev_flow_ctl)
                connp->conn_ixa->ixa_flags |= IXAF_NO_DEV_FLOW_CTL;

        if (isv6) {
                connp->conn_ixa->ixa_src_preferences = IPV6_PREFER_SRC_DEFAULT;
                connp->conn_ipversion = IPV6_VERSION;
                connp->conn_family = AF_INET6;
                tcp->tcp_mss = tcps->tcps_mss_def_ipv6;
                connp->conn_default_ttl = tcps->tcps_ipv6_hoplimit;
        } else {
                connp->conn_ipversion = IPV4_VERSION;
                connp->conn_family = AF_INET;
                tcp->tcp_mss = tcps->tcps_mss_def_ipv4;
                connp->conn_default_ttl = tcps->tcps_ipv4_ttl;
        }
        connp->conn_xmit_ipp.ipp_unicast_hops = connp->conn_default_ttl;

        crhold(credp);
        connp->conn_cred = credp;
        connp->conn_cpid = curproc->p_pid;
        connp->conn_open_time = ddi_get_lbolt64();

        /* Cache things in the ixa without any refhold */
        ASSERT(!(connp->conn_ixa->ixa_free_flags & IXA_FREE_CRED));
        connp->conn_ixa->ixa_cred = credp;
        connp->conn_ixa->ixa_cpid = connp->conn_cpid;

        connp->conn_zoneid = zoneid;
        /* conn_allzones can not be set this early, hence no IPCL_ZONEID */
        connp->conn_ixa->ixa_zoneid = zoneid;
        ASSERT(connp->conn_netstack == tcps->tcps_netstack);
        ASSERT(tcp->tcp_tcps == tcps);

        connp->conn_zone_is_global = (crgetzoneid(credp) == GLOBAL_ZONEID);

        if (issocket) {
                tcp->tcp_issocket = 1;
        }

        connp->conn_rcvbuf = tcps->tcps_recv_hiwat;
        connp->conn_sndbuf = tcps->tcps_xmit_hiwat;
        if (tcps->tcps_snd_lowat_fraction != 0) {
                connp->conn_sndlowat = connp->conn_sndbuf /
                    tcps->tcps_snd_lowat_fraction;
        } else {
                connp->conn_sndlowat = tcps->tcps_xmit_lowat;
        }
        connp->conn_so_type = SOCK_STREAM;
        connp->conn_wroff = connp->conn_ht_iphc_allocated +
            tcps->tcps_wroff_xtra;

        SOCK_CONNID_INIT(tcp->tcp_connid);
        /* DTrace ignores this - it isn't a tcp:::state-change */
        tcp->tcp_state = TCPS_IDLE;
        tcp_init_values(tcp, NULL);
        return (connp);
}

static int
tcp_open(queue_t *q, dev_t *devp, int flag, int sflag, cred_t *credp,
    boolean_t isv6)
{
        tcp_t           *tcp = NULL;
        conn_t          *connp = NULL;
        int             err;
        vmem_t          *minor_arena = NULL;
        dev_t           conn_dev;
        boolean_t       issocket;

        if (q->q_ptr != NULL)
                return (0);

        if (sflag == MODOPEN)
                return (EINVAL);

        if ((ip_minor_arena_la != NULL) && (flag & SO_SOCKSTR) &&
            ((conn_dev = inet_minor_alloc(ip_minor_arena_la)) != 0)) {
                minor_arena = ip_minor_arena_la;
        } else {
                /*
                 * Either minor numbers in the large arena were exhausted
                 * or a non socket application is doing the open.
                 * Try to allocate from the small arena.
                 */
                if ((conn_dev = inet_minor_alloc(ip_minor_arena_sa)) == 0) {
                        return (EBUSY);
                }
                minor_arena = ip_minor_arena_sa;
        }

        ASSERT(minor_arena != NULL);

        *devp = makedevice(getmajor(*devp), (minor_t)conn_dev);

        if (flag & SO_FALLBACK) {
                /*
                 * Non streams socket needs a stream to fallback to
                 */
                RD(q)->q_ptr = (void *)conn_dev;
                WR(q)->q_qinfo = &tcp_fallback_sock_winit;
                WR(q)->q_ptr = (void *)minor_arena;
                qprocson(q);
                return (0);
        } else if (flag & SO_ACCEPTOR) {
                q->q_qinfo = &tcp_acceptor_rinit;
                /*
                 * the conn_dev and minor_arena will be subsequently used by
                 * tcp_tli_accept() and tcp_tpi_close_accept() to figure out
                 * the minor device number for this connection from the q_ptr.
                 */
                RD(q)->q_ptr = (void *)conn_dev;
                WR(q)->q_qinfo = &tcp_acceptor_winit;
                WR(q)->q_ptr = (void *)minor_arena;
                qprocson(q);
                return (0);
        }

        issocket = flag & SO_SOCKSTR;
        connp = tcp_create_common(credp, isv6, issocket, &err);

        if (connp == NULL) {
                inet_minor_free(minor_arena, conn_dev);
                q->q_ptr = WR(q)->q_ptr = NULL;
                return (err);
        }

        connp->conn_rq = q;
        connp->conn_wq = WR(q);
        q->q_ptr = WR(q)->q_ptr = connp;

        connp->conn_dev = conn_dev;
        connp->conn_minor_arena = minor_arena;

        ASSERT(q->q_qinfo == &tcp_rinitv4 || q->q_qinfo == &tcp_rinitv6);
        ASSERT(WR(q)->q_qinfo == &tcp_winit);

        tcp = connp->conn_tcp;

        if (issocket) {
                WR(q)->q_qinfo = &tcp_sock_winit;
        } else {
#ifdef  _ILP32
                tcp->tcp_acceptor_id = (t_uscalar_t)RD(q);
#else
                tcp->tcp_acceptor_id = conn_dev;
#endif  /* _ILP32 */
                tcp_acceptor_hash_insert(tcp->tcp_acceptor_id, tcp);
        }

        /*
         * Put the ref for TCP. Ref for IP was already put
         * by ipcl_conn_create. Also Make the conn_t globally
         * visible to walkers
         */
        mutex_enter(&connp->conn_lock);
        CONN_INC_REF_LOCKED(connp);
        ASSERT(connp->conn_ref == 2);
        connp->conn_state_flags &= ~CONN_INCIPIENT;
        mutex_exit(&connp->conn_lock);

        qprocson(q);
        return (0);
}

/*
 * Build/update the tcp header template (in conn_ht_iphc) based on
 * conn_xmit_ipp. The headers include ip6_t, any extension
 * headers, and the maximum size tcp header (to avoid reallocation
 * on the fly for additional tcp options).
 *
 * Assumes the caller has already set conn_{faddr,laddr,fport,lport,flowinfo}.
 * Returns failure if can't allocate memory.
 */
int
tcp_build_hdrs(tcp_t *tcp)
{
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;
        char            buf[TCP_MAX_HDR_LENGTH];
        uint_t          buflen;
        uint_t          ulplen = TCP_MIN_HEADER_LENGTH;
        uint_t          extralen = TCP_MAX_TCP_OPTIONS_LENGTH;
        tcpha_t         *tcpha;
        uint32_t        cksum;
        int             error;

        /*
         * We might be called after the connection is set up, and we might
         * have TS options already in the TCP header. Thus we  save any
         * existing tcp header.
         */
        buflen = connp->conn_ht_ulp_len;
        if (buflen != 0) {
                bcopy(connp->conn_ht_ulp, buf, buflen);
                extralen -= buflen - ulplen;
                ulplen = buflen;
        }

        /* Grab lock to satisfy ASSERT; TCP is serialized using squeue */
        mutex_enter(&connp->conn_lock);
        error = conn_build_hdr_template(connp, ulplen, extralen,
            &connp->conn_laddr_v6, &connp->conn_faddr_v6, connp->conn_flowinfo);
        mutex_exit(&connp->conn_lock);
        if (error != 0)
                return (error);

        /*
         * Any routing header/option has been massaged. The checksum difference
         * is stored in conn_sum for later use.
         */
        tcpha = (tcpha_t *)connp->conn_ht_ulp;
        tcp->tcp_tcpha = tcpha;

        /* restore any old tcp header */
        if (buflen != 0) {
                bcopy(buf, connp->conn_ht_ulp, buflen);
        } else {
                tcpha->tha_sum = 0;
                tcpha->tha_urp = 0;
                tcpha->tha_ack = 0;
                tcpha->tha_offset_and_reserved = (5 << 4);
                tcpha->tha_lport = connp->conn_lport;
                tcpha->tha_fport = connp->conn_fport;
        }

        /*
         * IP wants our header length in the checksum field to
         * allow it to perform a single pseudo-header+checksum
         * calculation on behalf of TCP.
         * Include the adjustment for a source route once IP_OPTIONS is set.
         */
        cksum = sizeof (tcpha_t) + connp->conn_sum;
        cksum = (cksum >> 16) + (cksum & 0xFFFF);
        ASSERT(cksum < 0x10000);
        tcpha->tha_sum = htons(cksum);

        if (connp->conn_ipversion == IPV4_VERSION)
                tcp->tcp_ipha = (ipha_t *)connp->conn_ht_iphc;
        else
                tcp->tcp_ip6h = (ip6_t *)connp->conn_ht_iphc;

        if (connp->conn_ht_iphc_allocated + tcps->tcps_wroff_xtra >
            connp->conn_wroff) {
                connp->conn_wroff = connp->conn_ht_iphc_allocated +
                    tcps->tcps_wroff_xtra;
                (void) proto_set_tx_wroff(connp->conn_rq, connp,
                    connp->conn_wroff);
        }
        return (0);
}

/*
 * tcp_rwnd_set() is called to adjust the receive window to a desired value.
 * We do not allow the receive window to shrink.  After setting rwnd,
 * set the flow control hiwat of the stream.
 *
 * This function is called in 2 cases:
 *
 * 1) Before data transfer begins, in tcp_input_listener() for accepting a
 *    connection (passive open) and in tcp_input_data() for active connect.
 *    This is called after tcp_mss_set() when the desired MSS value is known.
 *    This makes sure that our window size is a mutiple of the other side's
 *    MSS.
 * 2) Handling SO_RCVBUF option.
 *
 * It is ASSUMED that the requested size is a multiple of the current MSS.
 *
 * XXX - Should allow a lower rwnd than tcp_recv_hiwat_minmss * mss if the
 * user requests so.
 */
int
tcp_rwnd_set(tcp_t *tcp, uint32_t rwnd)
{
        uint32_t        mss = tcp->tcp_mss;
        uint32_t        old_max_rwnd;
        uint32_t        max_transmittable_rwnd;
        boolean_t       tcp_detached = TCP_IS_DETACHED(tcp);
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;

        /*
         * Insist on a receive window that is at least
         * tcp_recv_hiwat_minmss * MSS (default 4 * MSS) to avoid
         * funny TCP interactions of Nagle algorithm, SWS avoidance
         * and delayed acknowledgement.
         */
        rwnd = MAX(rwnd, tcps->tcps_recv_hiwat_minmss * mss);

        if (tcp->tcp_fused) {
                size_t sth_hiwat;
                tcp_t *peer_tcp = tcp->tcp_loopback_peer;

                ASSERT(peer_tcp != NULL);
                sth_hiwat = tcp_fuse_set_rcv_hiwat(tcp, rwnd);
                if (!tcp_detached) {
                        (void) proto_set_rx_hiwat(connp->conn_rq, connp,
                            sth_hiwat);
                        tcp_set_recv_threshold(tcp, sth_hiwat >> 3);
                }

                /* Caller could have changed tcp_rwnd; update tha_win */
                if (tcp->tcp_tcpha != NULL) {
                        tcp->tcp_tcpha->tha_win =
                            htons(tcp->tcp_rwnd >> tcp->tcp_rcv_ws);
                }
                if ((tcp->tcp_rcv_ws > 0) && rwnd > tcp->tcp_cwnd_max)
                        tcp->tcp_cwnd_max = rwnd;

                /*
                 * In the fusion case, the maxpsz stream head value of
                 * our peer is set according to its send buffer size
                 * and our receive buffer size; since the latter may
                 * have changed we need to update the peer's maxpsz.
                 */
                (void) tcp_maxpsz_set(peer_tcp, B_TRUE);
                return (sth_hiwat);
        }

        if (tcp_detached)
                old_max_rwnd = tcp->tcp_rwnd;
        else
                old_max_rwnd = connp->conn_rcvbuf;


        /*
         * If window size info has already been exchanged, TCP should not
         * shrink the window.  Shrinking window is doable if done carefully.
         * We may add that support later.  But so far there is not a real
         * need to do that.
         */
        if (rwnd < old_max_rwnd && tcp->tcp_state > TCPS_SYN_SENT) {
                /* MSS may have changed, do a round up again. */
                rwnd = MSS_ROUNDUP(old_max_rwnd, mss);
        }

        /*
         * tcp_rcv_ws starts with TCP_MAX_WINSHIFT so the following check
         * can be applied even before the window scale option is decided.
         */
        max_transmittable_rwnd = TCP_MAXWIN << tcp->tcp_rcv_ws;
        if (rwnd > max_transmittable_rwnd) {
                rwnd = max_transmittable_rwnd -
                    (max_transmittable_rwnd % mss);
                if (rwnd < mss)
                        rwnd = max_transmittable_rwnd;
                /*
                 * If we're over the limit we may have to back down tcp_rwnd.
                 * The increment below won't work for us. So we set all three
                 * here and the increment below will have no effect.
                 */
                tcp->tcp_rwnd = old_max_rwnd = rwnd;
        }
        if (tcp->tcp_localnet) {
                tcp->tcp_rack_abs_max =
                    MIN(tcps->tcps_local_dacks_max, rwnd / mss / 2);
        } else {
                /*
                 * For a remote host on a different subnet (through a router),
                 * we ack every other packet to be conforming to RFC1122.
                 * tcp_deferred_acks_max is default to 2.
                 */
                tcp->tcp_rack_abs_max =
                    MIN(tcps->tcps_deferred_acks_max, rwnd / mss / 2);
        }
        if (tcp->tcp_rack_cur_max > tcp->tcp_rack_abs_max)
                tcp->tcp_rack_cur_max = tcp->tcp_rack_abs_max;
        else
                tcp->tcp_rack_cur_max = 0;
        /*
         * Increment the current rwnd by the amount the maximum grew (we
         * can not overwrite it since we might be in the middle of a
         * connection.)
         */
        tcp->tcp_rwnd += rwnd - old_max_rwnd;
        connp->conn_rcvbuf = rwnd;

        /* Are we already connected? */
        if (tcp->tcp_tcpha != NULL) {
                tcp->tcp_tcpha->tha_win =
                    htons(tcp->tcp_rwnd >> tcp->tcp_rcv_ws);
        }

        if ((tcp->tcp_rcv_ws > 0) && rwnd > tcp->tcp_cwnd_max)
                tcp->tcp_cwnd_max = rwnd;

        if (tcp_detached)
                return (rwnd);

        tcp_set_recv_threshold(tcp, rwnd >> 3);

        (void) proto_set_rx_hiwat(connp->conn_rq, connp, rwnd);
        return (rwnd);
}

int
tcp_do_unbind(conn_t *connp)
{
        tcp_t *tcp = connp->conn_tcp;
        int32_t oldstate;

        switch (tcp->tcp_state) {
        case TCPS_BOUND:
        case TCPS_LISTEN:
                break;
        default:
                return (-TOUTSTATE);
        }

        /*
         * Need to clean up all the eagers since after the unbind, segments
         * will no longer be delivered to this listener stream.
         */
        mutex_enter(&tcp->tcp_eager_lock);
        if (tcp->tcp_conn_req_cnt_q0 != 0 || tcp->tcp_conn_req_cnt_q != 0) {
                tcp_eager_cleanup(tcp, 0);
        }
        mutex_exit(&tcp->tcp_eager_lock);

        /* Clean up the listener connection counter if necessary. */
        if (tcp->tcp_listen_cnt != NULL)
                TCP_DECR_LISTEN_CNT(tcp);
        connp->conn_laddr_v6 = ipv6_all_zeros;
        connp->conn_saddr_v6 = ipv6_all_zeros;
        tcp_bind_hash_remove(tcp);
        oldstate = tcp->tcp_state;
        tcp->tcp_state = TCPS_IDLE;
        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
            connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
            int32_t, oldstate);

        ip_unbind(connp);
        bzero(&connp->conn_ports, sizeof (connp->conn_ports));

        return (0);
}

/*
 * Collect protocol properties to send to the upper handle.
 */
void
tcp_get_proto_props(tcp_t *tcp, struct sock_proto_props *sopp)
{
        conn_t *connp = tcp->tcp_connp;

        sopp->sopp_flags = SOCKOPT_RCVHIWAT | SOCKOPT_MAXBLK | SOCKOPT_WROFF;
        sopp->sopp_maxblk = tcp_maxpsz_set(tcp, B_FALSE);

        sopp->sopp_rxhiwat = tcp->tcp_fused ?
            tcp_fuse_set_rcv_hiwat(tcp, connp->conn_rcvbuf) :
            connp->conn_rcvbuf;
        /*
         * Determine what write offset value to use depending on SACK and
         * whether the endpoint is fused or not.
         */
        if (tcp->tcp_fused) {
                ASSERT(tcp->tcp_loopback);
                ASSERT(tcp->tcp_loopback_peer != NULL);
                /*
                 * For fused tcp loopback, set the stream head's write
                 * offset value to zero since we won't be needing any room
                 * for TCP/IP headers.  This would also improve performance
                 * since it would reduce the amount of work done by kmem.
                 * Non-fused tcp loopback case is handled separately below.
                 */
                sopp->sopp_wroff = 0;
                /*
                 * Update the peer's transmit parameters according to
                 * our recently calculated high water mark value.
                 */
                (void) tcp_maxpsz_set(tcp->tcp_loopback_peer, B_TRUE);
        } else if (tcp->tcp_snd_sack_ok) {
                sopp->sopp_wroff = connp->conn_ht_iphc_allocated +
                    (tcp->tcp_loopback ? 0 : tcp->tcp_tcps->tcps_wroff_xtra);
        } else {
                sopp->sopp_wroff = connp->conn_ht_iphc_len +
                    (tcp->tcp_loopback ? 0 : tcp->tcp_tcps->tcps_wroff_xtra);
        }

        if (tcp->tcp_loopback) {
                sopp->sopp_flags |= SOCKOPT_LOOPBACK;
                sopp->sopp_loopback = B_TRUE;
        }
}

/*
 * Check the usability of ZEROCOPY. It's instead checking the flag set by IP.
 */
boolean_t
tcp_zcopy_check(tcp_t *tcp)
{
        conn_t          *connp = tcp->tcp_connp;
        ip_xmit_attr_t  *ixa = connp->conn_ixa;
        boolean_t       zc_enabled = B_FALSE;
        tcp_stack_t     *tcps = tcp->tcp_tcps;

        if (do_tcpzcopy == 2)
                zc_enabled = B_TRUE;
        else if ((do_tcpzcopy == 1) && (ixa->ixa_flags & IXAF_ZCOPY_CAPAB))
                zc_enabled = B_TRUE;

        tcp->tcp_snd_zcopy_on = zc_enabled;
        if (!TCP_IS_DETACHED(tcp)) {
                if (zc_enabled) {
                        ixa->ixa_flags |= IXAF_VERIFY_ZCOPY;
                        (void) proto_set_tx_copyopt(connp->conn_rq, connp,
                            ZCVMSAFE);
                        TCP_STAT(tcps, tcp_zcopy_on);
                } else {
                        ixa->ixa_flags &= ~IXAF_VERIFY_ZCOPY;
                        (void) proto_set_tx_copyopt(connp->conn_rq, connp,
                            ZCVMUNSAFE);
                        TCP_STAT(tcps, tcp_zcopy_off);
                }
        }
        return (zc_enabled);
}

/*
 * Backoff from a zero-copy message by copying data to a new allocated
 * message and freeing the original desballoca'ed segmapped message.
 *
 * This function is called by following two callers:
 * 1. tcp_timer: fix_xmitlist is set to B_TRUE, because it's safe to free
 *    the origial desballoca'ed message and notify sockfs. This is in re-
 *    transmit state.
 * 2. tcp_output: fix_xmitlist is set to B_FALSE. Flag STRUIO_ZCNOTIFY need
 *    to be copied to new message.
 */
mblk_t *
tcp_zcopy_backoff(tcp_t *tcp, mblk_t *bp, boolean_t fix_xmitlist)
{
        mblk_t          *nbp;
        mblk_t          *head = NULL;
        mblk_t          *tail = NULL;
        tcp_stack_t     *tcps = tcp->tcp_tcps;

        ASSERT(bp != NULL);
        while (bp != NULL) {
                if (IS_VMLOANED_MBLK(bp)) {
                        TCP_STAT(tcps, tcp_zcopy_backoff);
                        if ((nbp = copyb(bp)) == NULL) {
                                tcp->tcp_xmit_zc_clean = B_FALSE;
                                if (tail != NULL)
                                        tail->b_cont = bp;
                                return ((head == NULL) ? bp : head);
                        }

                        if (bp->b_datap->db_struioflag & STRUIO_ZCNOTIFY) {
                                if (fix_xmitlist)
                                        tcp_zcopy_notify(tcp);
                                else
                                        nbp->b_datap->db_struioflag |=
                                            STRUIO_ZCNOTIFY;
                        }
                        nbp->b_cont = bp->b_cont;

                        /*
                         * Copy saved information and adjust tcp_xmit_tail
                         * if needed.
                         */
                        if (fix_xmitlist) {
                                nbp->b_prev = bp->b_prev;
                                nbp->b_next = bp->b_next;

                                if (tcp->tcp_xmit_tail == bp)
                                        tcp->tcp_xmit_tail = nbp;
                        }

                        /* Free the original message. */
                        bp->b_prev = NULL;
                        bp->b_next = NULL;
                        freeb(bp);

                        bp = nbp;
                }

                if (head == NULL) {
                        head = bp;
                }
                if (tail == NULL) {
                        tail = bp;
                } else {
                        tail->b_cont = bp;
                        tail = bp;
                }

                /* Move forward. */
                bp = bp->b_cont;
        }

        if (fix_xmitlist) {
                tcp->tcp_xmit_last = tail;
                tcp->tcp_xmit_zc_clean = B_TRUE;
        }

        return (head);
}

void
tcp_zcopy_notify(tcp_t *tcp)
{
        struct stdata   *stp;
        conn_t          *connp;

        if (tcp->tcp_detached)
                return;
        connp = tcp->tcp_connp;
        if (IPCL_IS_NONSTR(connp)) {
                (*connp->conn_upcalls->su_zcopy_notify)
                    (connp->conn_upper_handle);
                return;
        }
        stp = STREAM(connp->conn_rq);
        mutex_enter(&stp->sd_lock);
        stp->sd_flag |= STZCNOTIFY;
        cv_broadcast(&stp->sd_zcopy_wait);
        mutex_exit(&stp->sd_lock);
}

/*
 * Update the TCP connection according to change of LSO capability.
 */
static void
tcp_update_lso(tcp_t *tcp, ip_xmit_attr_t *ixa)
{
        /*
         * We check against IPv4 header length to preserve the old behavior
         * of only enabling LSO when there are no IP options.
         * But this restriction might not be necessary at all. Before removing
         * it, need to verify how LSO is handled for source routing case, with
         * which IP does software checksum.
         *
         * For IPv6, whenever any extension header is needed, LSO is supressed.
         */
        if (ixa->ixa_ip_hdr_length != ((ixa->ixa_flags & IXAF_IS_IPV4) ?
            IP_SIMPLE_HDR_LENGTH : IPV6_HDR_LEN))
                return;

        /*
         * Either the LSO capability newly became usable, or it has changed.
         */
        if (ixa->ixa_flags & IXAF_LSO_CAPAB) {
                ill_lso_capab_t *lsoc = &ixa->ixa_lso_capab;

                ASSERT(lsoc->ill_lso_max > 0);
                tcp->tcp_lso_max = MIN(TCP_MAX_LSO_LENGTH, lsoc->ill_lso_max);

                DTRACE_PROBE3(tcp_update_lso, boolean_t, tcp->tcp_lso,
                    boolean_t, B_TRUE, uint32_t, tcp->tcp_lso_max);

                /*
                 * If LSO to be enabled, notify the STREAM header with larger
                 * data block.
                 */
                if (!tcp->tcp_lso)
                        tcp->tcp_maxpsz_multiplier = 0;

                tcp->tcp_lso = B_TRUE;
                TCP_STAT(tcp->tcp_tcps, tcp_lso_enabled);
        } else { /* LSO capability is not usable any more. */
                DTRACE_PROBE3(tcp_update_lso, boolean_t, tcp->tcp_lso,
                    boolean_t, B_FALSE, uint32_t, tcp->tcp_lso_max);

                /*
                 * If LSO to be disabled, notify the STREAM header with smaller
                 * data block. And need to restore fragsize to PMTU.
                 */
                if (tcp->tcp_lso) {
                        tcp->tcp_maxpsz_multiplier =
                            tcp->tcp_tcps->tcps_maxpsz_multiplier;
                        ixa->ixa_fragsize = ixa->ixa_pmtu;
                        tcp->tcp_lso = B_FALSE;
                        TCP_STAT(tcp->tcp_tcps, tcp_lso_disabled);
                }
        }

        (void) tcp_maxpsz_set(tcp, B_TRUE);
}

/*
 * Update the TCP connection according to change of ZEROCOPY capability.
 */
static void
tcp_update_zcopy(tcp_t *tcp)
{
        conn_t          *connp = tcp->tcp_connp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;

        if (tcp->tcp_snd_zcopy_on) {
                tcp->tcp_snd_zcopy_on = B_FALSE;
                if (!TCP_IS_DETACHED(tcp)) {
                        (void) proto_set_tx_copyopt(connp->conn_rq, connp,
                            ZCVMUNSAFE);
                        TCP_STAT(tcps, tcp_zcopy_off);
                }
        } else {
                tcp->tcp_snd_zcopy_on = B_TRUE;
                if (!TCP_IS_DETACHED(tcp)) {
                        (void) proto_set_tx_copyopt(connp->conn_rq, connp,
                            ZCVMSAFE);
                        TCP_STAT(tcps, tcp_zcopy_on);
                }
        }
}

/*
 * Notify function registered with ip_xmit_attr_t. It's called in the squeue
 * so it's safe to update the TCP connection.
 */
/* ARGSUSED1 */
static void
tcp_notify(void *arg, ip_xmit_attr_t *ixa, ixa_notify_type_t ntype,
    ixa_notify_arg_t narg)
{
        tcp_t           *tcp = (tcp_t *)arg;
        conn_t          *connp = tcp->tcp_connp;

        switch (ntype) {
        case IXAN_LSO:
                tcp_update_lso(tcp, connp->conn_ixa);
                break;
        case IXAN_PMTU:
                tcp_update_pmtu(tcp, B_FALSE);
                break;
        case IXAN_ZCOPY:
                tcp_update_zcopy(tcp);
                break;
        default:
                break;
        }
}

/*
 * The TCP write service routine should never be called...
 */
/* ARGSUSED */
static void
tcp_wsrv(queue_t *q)
{
        tcp_stack_t     *tcps = Q_TO_TCP(q)->tcp_tcps;

        TCP_STAT(tcps, tcp_wsrv_called);
}

/*
 * Hash list lookup routine for tcp_t structures.
 * Returns with a CONN_INC_REF tcp structure. Caller must do a CONN_DEC_REF.
 */
tcp_t *
tcp_acceptor_hash_lookup(t_uscalar_t id, tcp_stack_t *tcps)
{
        tf_t    *tf;
        tcp_t   *tcp;

        tf = &tcps->tcps_acceptor_fanout[TCP_ACCEPTOR_HASH(id)];
        mutex_enter(&tf->tf_lock);
        for (tcp = tf->tf_tcp; tcp != NULL;
            tcp = tcp->tcp_acceptor_hash) {
                if (tcp->tcp_acceptor_id == id) {
                        CONN_INC_REF(tcp->tcp_connp);
                        mutex_exit(&tf->tf_lock);
                        return (tcp);
                }
        }
        mutex_exit(&tf->tf_lock);
        return (NULL);
}

/*
 * Hash list insertion routine for tcp_t structures.
 */
void
tcp_acceptor_hash_insert(t_uscalar_t id, tcp_t *tcp)
{
        tf_t    *tf;
        tcp_t   **tcpp;
        tcp_t   *tcpnext;
        tcp_stack_t     *tcps = tcp->tcp_tcps;

        tf = &tcps->tcps_acceptor_fanout[TCP_ACCEPTOR_HASH(id)];

        if (tcp->tcp_ptpahn != NULL)
                tcp_acceptor_hash_remove(tcp);
        tcpp = &tf->tf_tcp;
        mutex_enter(&tf->tf_lock);
        tcpnext = tcpp[0];
        if (tcpnext)
                tcpnext->tcp_ptpahn = &tcp->tcp_acceptor_hash;
        tcp->tcp_acceptor_hash = tcpnext;
        tcp->tcp_ptpahn = tcpp;
        tcpp[0] = tcp;
        tcp->tcp_acceptor_lockp = &tf->tf_lock; /* For tcp_*_hash_remove */
        mutex_exit(&tf->tf_lock);
}

/*
 * Hash list removal routine for tcp_t structures.
 */
void
tcp_acceptor_hash_remove(tcp_t *tcp)
{
        tcp_t   *tcpnext;
        kmutex_t *lockp;

        /*
         * Extract the lock pointer in case there are concurrent
         * hash_remove's for this instance.
         */
        lockp = tcp->tcp_acceptor_lockp;

        if (tcp->tcp_ptpahn == NULL)
                return;

        ASSERT(lockp != NULL);
        mutex_enter(lockp);
        if (tcp->tcp_ptpahn) {
                tcpnext = tcp->tcp_acceptor_hash;
                if (tcpnext) {
                        tcpnext->tcp_ptpahn = tcp->tcp_ptpahn;
                        tcp->tcp_acceptor_hash = NULL;
                }
                *tcp->tcp_ptpahn = tcpnext;
                tcp->tcp_ptpahn = NULL;
        }
        mutex_exit(lockp);
        tcp->tcp_acceptor_lockp = NULL;
}

/*
 * Type three generator adapted from the random() function in 4.4 BSD:
 */

/*
 * Copyright (c) 1983, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Called by IP when IP is loaded into the kernel
 */
void
tcp_ddi_g_init(void)
{
        tcp_timercache = kmem_cache_create("tcp_timercache",
            sizeof (tcp_timer_t) + sizeof (mblk_t), 0,
            NULL, NULL, NULL, NULL, NULL, 0);

        tcp_notsack_blk_cache = kmem_cache_create("tcp_notsack_blk_cache",
            sizeof (notsack_blk_t), 0, NULL, NULL, NULL, NULL, NULL, 0);

        /* A single callback independently of how many netstacks we have */
        ip_squeue_init(tcp_squeue_add);

        tcp_g_kstat = tcp_g_kstat_init(&tcp_g_statistics);

        tcp_squeue_flag = tcp_squeue_switch(tcp_squeue_wput);

        /*
         * We want to be informed each time a stack is created or
         * destroyed in the kernel, so we can maintain the
         * set of tcp_stack_t's.
         */
        netstack_register(NS_TCP, tcp_stack_init, NULL, tcp_stack_fini);
}


#define INET_NAME       "ip"

/*
 * Initialize the TCP stack instance.
 */
static void *
tcp_stack_init(netstackid_t stackid, netstack_t *ns)
{
        tcp_stack_t     *tcps;
        int             i;
        int             error = 0;
        major_t         major;
        size_t          arrsz;
        uint8_t         secret[16];

        tcps = (tcp_stack_t *)kmem_zalloc(sizeof (*tcps), KM_SLEEP);
        tcps->tcps_netstack = ns;

        /* Initialize locks */
        mutex_init(&tcps->tcps_epriv_port_lock, NULL, MUTEX_DEFAULT, NULL);

        tcps->tcps_g_num_epriv_ports = TCP_NUM_EPRIV_PORTS;
        tcps->tcps_g_epriv_ports[0] = ULP_DEF_EPRIV_PORT1;
        tcps->tcps_g_epriv_ports[1] = ULP_DEF_EPRIV_PORT2;
        tcps->tcps_min_anonpriv_port = 512;

        tcps->tcps_bind_fanout = kmem_zalloc(sizeof (tf_t) *
            TCP_BIND_FANOUT_SIZE, KM_SLEEP);
        tcps->tcps_acceptor_fanout = kmem_zalloc(sizeof (tf_t) *
            TCP_ACCEPTOR_FANOUT_SIZE, KM_SLEEP);

        for (i = 0; i < TCP_BIND_FANOUT_SIZE; i++) {
                mutex_init(&tcps->tcps_bind_fanout[i].tf_lock, NULL,
                    MUTEX_DEFAULT, NULL);
        }

        for (i = 0; i < TCP_ACCEPTOR_FANOUT_SIZE; i++) {
                mutex_init(&tcps->tcps_acceptor_fanout[i].tf_lock, NULL,
                    MUTEX_DEFAULT, NULL);
        }

        /* TCP's IPsec code calls the packet dropper. */
        ip_drop_register(&tcps->tcps_dropper, "TCP IPsec policy enforcement");

        arrsz = tcp_propinfo_count * sizeof (mod_prop_info_t);
        tcps->tcps_propinfo_tbl = (mod_prop_info_t *)kmem_alloc(arrsz,
            KM_SLEEP);
        bcopy(tcp_propinfo_tbl, tcps->tcps_propinfo_tbl, arrsz);

        /*
         * Note: To really walk the device tree you need the devinfo
         * pointer to your device which is only available after probe/attach.
         * The following is safe only because it uses ddi_root_node()
         */
        tcp_max_optsize = optcom_max_optsize(tcp_opt_obj.odb_opt_des_arr,
            tcp_opt_obj.odb_opt_arr_cnt);

        /* Initialize the RFC 6528 ISS. */
        random_get_pseudo_bytes(secret, sizeof(secret));
        MD5Init(&tcps->tcps_iss_key);
        MD5Update(&tcps->tcps_iss_key, secret, sizeof(secret));

        tcps->tcps_kstat = tcp_kstat2_init(stackid);
        tcps->tcps_mibkp = tcp_kstat_init(stackid);

        major = mod_name_to_major(INET_NAME);
        error = ldi_ident_from_major(major, &tcps->tcps_ldi_ident);
        ASSERT(error == 0);
        tcps->tcps_ixa_cleanup_mp = allocb_wait(0, BPRI_MED, STR_NOSIG, NULL);
        ASSERT(tcps->tcps_ixa_cleanup_mp != NULL);
        cv_init(&tcps->tcps_ixa_cleanup_ready_cv, NULL, CV_DEFAULT, NULL);
        cv_init(&tcps->tcps_ixa_cleanup_done_cv, NULL, CV_DEFAULT, NULL);
        mutex_init(&tcps->tcps_ixa_cleanup_lock, NULL, MUTEX_DEFAULT, NULL);

        mutex_init(&tcps->tcps_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
        tcps->tcps_reclaim = B_FALSE;
        tcps->tcps_reclaim_tid = 0;
        tcps->tcps_reclaim_period = tcps->tcps_rexmit_interval_max;

        /*
         * ncpus is the current number of CPUs, which can be bigger than
         * boot_ncpus.  But we don't want to use ncpus to allocate all the
         * tcp_stats_cpu_t at system boot up time since it will be 1.  While
         * we handle adding CPU in tcp_cpu_update(), it will be slow if
         * there are many CPUs as we will be adding them 1 by 1.
         *
         * Note that tcps_sc_cnt never decreases and the tcps_sc[x] pointers
         * are not freed until the stack is going away.  So there is no need
         * to grab a lock to access the per CPU tcps_sc[x] pointer.
         */
        mutex_enter(&cpu_lock);
        tcps->tcps_sc_cnt = MAX(ncpus, boot_ncpus);
        mutex_exit(&cpu_lock);
        tcps->tcps_sc = kmem_zalloc(max_ncpus  * sizeof (tcp_stats_cpu_t *),
            KM_SLEEP);
        for (i = 0; i < tcps->tcps_sc_cnt; i++) {
                tcps->tcps_sc[i] = kmem_zalloc(sizeof (tcp_stats_cpu_t),
                    KM_SLEEP);
        }

        mutex_init(&tcps->tcps_listener_conf_lock, NULL, MUTEX_DEFAULT, NULL);
        list_create(&tcps->tcps_listener_conf, sizeof (tcp_listener_t),
            offsetof(tcp_listener_t, tl_link));

        return (tcps);
}

/*
 * Called when the IP module is about to be unloaded.
 */
void
tcp_ddi_g_destroy(void)
{
        tcp_g_kstat_fini(tcp_g_kstat);
        tcp_g_kstat = NULL;
        bzero(&tcp_g_statistics, sizeof (tcp_g_statistics));

        kmem_cache_destroy(tcp_timercache);
        kmem_cache_destroy(tcp_notsack_blk_cache);

        netstack_unregister(NS_TCP);
}

/*
 * Free the TCP stack instance.
 */
static void
tcp_stack_fini(netstackid_t stackid, void *arg)
{
        tcp_stack_t *tcps = (tcp_stack_t *)arg;
        int i;

        freeb(tcps->tcps_ixa_cleanup_mp);
        tcps->tcps_ixa_cleanup_mp = NULL;
        cv_destroy(&tcps->tcps_ixa_cleanup_ready_cv);
        cv_destroy(&tcps->tcps_ixa_cleanup_done_cv);
        mutex_destroy(&tcps->tcps_ixa_cleanup_lock);

        /*
         * Set tcps_reclaim to false tells tcp_reclaim_timer() not to restart
         * the timer.
         */
        mutex_enter(&tcps->tcps_reclaim_lock);
        tcps->tcps_reclaim = B_FALSE;
        mutex_exit(&tcps->tcps_reclaim_lock);
        if (tcps->tcps_reclaim_tid != 0)
                (void) untimeout(tcps->tcps_reclaim_tid);
        mutex_destroy(&tcps->tcps_reclaim_lock);

        tcp_listener_conf_cleanup(tcps);

        for (i = 0; i < tcps->tcps_sc_cnt; i++)
                kmem_free(tcps->tcps_sc[i], sizeof (tcp_stats_cpu_t));
        kmem_free(tcps->tcps_sc, max_ncpus * sizeof (tcp_stats_cpu_t *));

        kmem_free(tcps->tcps_propinfo_tbl,
            tcp_propinfo_count * sizeof (mod_prop_info_t));
        tcps->tcps_propinfo_tbl = NULL;

        for (i = 0; i < TCP_BIND_FANOUT_SIZE; i++) {
                ASSERT(tcps->tcps_bind_fanout[i].tf_tcp == NULL);
                mutex_destroy(&tcps->tcps_bind_fanout[i].tf_lock);
        }

        for (i = 0; i < TCP_ACCEPTOR_FANOUT_SIZE; i++) {
                ASSERT(tcps->tcps_acceptor_fanout[i].tf_tcp == NULL);
                mutex_destroy(&tcps->tcps_acceptor_fanout[i].tf_lock);
        }

        kmem_free(tcps->tcps_bind_fanout, sizeof (tf_t) * TCP_BIND_FANOUT_SIZE);
        tcps->tcps_bind_fanout = NULL;

        kmem_free(tcps->tcps_acceptor_fanout, sizeof (tf_t) *
            TCP_ACCEPTOR_FANOUT_SIZE);
        tcps->tcps_acceptor_fanout = NULL;

        mutex_destroy(&tcps->tcps_epriv_port_lock);

        ip_drop_unregister(&tcps->tcps_dropper);

        tcp_kstat2_fini(stackid, tcps->tcps_kstat);
        tcps->tcps_kstat = NULL;

        tcp_kstat_fini(stackid, tcps->tcps_mibkp);
        tcps->tcps_mibkp = NULL;

        ldi_ident_release(tcps->tcps_ldi_ident);
        kmem_free(tcps, sizeof (*tcps));
}

static void
tcp_iss_init(tcp_t *tcp)
{
        MD5_CTX context;
        struct { uint32_t ports; in6_addr_t src; in6_addr_t dst; } arg;
        uint32_t answer[4];
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t          *connp = tcp->tcp_connp;

        /* tcp_iss may already have been set in tcp_input_listener */
        if (!tcp->tcp_iss) {
                tcp->tcp_iss = gethrtime() >> ISS_NSEC_SHT;
                context = tcps->tcps_iss_key;
                arg.ports = connp->conn_ports;
                arg.src = connp->conn_laddr_v6;
                arg.dst = connp->conn_faddr_v6;
                MD5Update(&context, (uchar_t *)&arg, sizeof (arg));
                MD5Final((uchar_t *)answer, &context);
                tcp->tcp_iss += answer[0] ^ answer[1] ^ answer[2] ^ answer[3];
        }
        tcp->tcp_valid_bits = TCP_ISS_VALID;
        tcp->tcp_fss = tcp->tcp_iss - 1;
        tcp->tcp_suna = tcp->tcp_iss;
        tcp->tcp_snxt = tcp->tcp_iss + 1;
        tcp->tcp_rexmit_nxt = tcp->tcp_snxt;
        tcp->tcp_csuna = tcp->tcp_snxt;
}

/*
 * tcp_{set,clr}qfull() functions are used to either set or clear QFULL
 * on the specified backing STREAMS q. Note, the caller may make the
 * decision to call based on the tcp_t.tcp_flow_stopped value which
 * when check outside the q's lock is only an advisory check ...
 */
void
tcp_setqfull(tcp_t *tcp)
{
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        conn_t  *connp = tcp->tcp_connp;

        if (tcp->tcp_closed)
                return;

        conn_setqfull(connp, &tcp->tcp_flow_stopped);
        if (tcp->tcp_flow_stopped)
                TCP_STAT(tcps, tcp_flwctl_on);
}

void
tcp_clrqfull(tcp_t *tcp)
{
        conn_t  *connp = tcp->tcp_connp;

        if (tcp->tcp_closed)
                return;
        conn_clrqfull(connp, &tcp->tcp_flow_stopped);
}

static int
tcp_squeue_switch(int val)
{
        int rval = SQ_FILL;

        switch (val) {
        case 1:
                rval = SQ_NODRAIN;
                break;
        case 2:
                rval = SQ_PROCESS;
                break;
        default:
                break;
        }
        return (rval);
}

/*
 * This is called once for each squeue - globally for all stack
 * instances.
 */
static void
tcp_squeue_add(squeue_t *sqp)
{
        tcp_squeue_priv_t *tcp_time_wait = kmem_zalloc(
            sizeof (tcp_squeue_priv_t), KM_SLEEP);

        *squeue_getprivate(sqp, SQPRIVATE_TCP) = (intptr_t)tcp_time_wait;
        if (tcp_free_list_max_cnt == 0) {
                int tcp_ncpus = ((boot_max_ncpus == -1) ?
                    max_ncpus : boot_max_ncpus);

                /*
                 * Limit number of entries to 1% of availble memory / tcp_ncpus
                 */
                tcp_free_list_max_cnt = (freemem * PAGESIZE) /
                    (tcp_ncpus * sizeof (tcp_t) * 100);
        }
        tcp_time_wait->tcp_free_list_cnt = 0;
}
/*
 * Return unix error is tli error is TSYSERR, otherwise return a negative
 * tli error.
 */
int
tcp_do_bind(conn_t *connp, struct sockaddr *sa, socklen_t len, cred_t *cr,
    boolean_t bind_to_req_port_only)
{
        int error;
        tcp_t *tcp = connp->conn_tcp;

        if (tcp->tcp_state >= TCPS_BOUND) {
                if (connp->conn_debug) {
                        (void) strlog(TCP_MOD_ID, 0, 1, SL_ERROR|SL_TRACE,
                            "tcp_bind: bad state, %d", tcp->tcp_state);
                }
                return (-TOUTSTATE);
        }

        error = tcp_bind_check(connp, sa, len, cr, bind_to_req_port_only);
        if (error != 0)
                return (error);

        ASSERT(tcp->tcp_state == TCPS_BOUND);
        tcp->tcp_conn_req_max = 0;
        return (0);
}

/*
 * If the return value from this function is positive, it's a UNIX error.
 * Otherwise, if it's negative, then the absolute value is a TLI error.
 * the TPI routine tcp_tpi_connect() is a wrapper function for this.
 */
int
tcp_do_connect(conn_t *connp, const struct sockaddr *sa, socklen_t len,
    cred_t *cr, pid_t pid)
{
        tcp_t           *tcp = connp->conn_tcp;
        sin_t           *sin = (sin_t *)sa;
        sin6_t          *sin6 = (sin6_t *)sa;
        ipaddr_t        *dstaddrp;
        in_port_t       dstport;
        uint_t          srcid;
        int             error;
        uint32_t        mss;
        mblk_t          *syn_mp;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        int32_t         oldstate;
        ip_xmit_attr_t  *ixa = connp->conn_ixa;

        oldstate = tcp->tcp_state;

        switch (len) {
        default:
                /*
                 * Should never happen
                 */
                return (EINVAL);

        case sizeof (sin_t):
                sin = (sin_t *)sa;
                if (sin->sin_port == 0) {
                        return (-TBADADDR);
                }
                if (connp->conn_ipv6_v6only) {
                        return (EAFNOSUPPORT);
                }
                break;

        case sizeof (sin6_t):
                sin6 = (sin6_t *)sa;
                if (sin6->sin6_port == 0) {
                        return (-TBADADDR);
                }
                break;
        }
        /*
         * If we're connecting to an IPv4-mapped IPv6 address, we need to
         * make sure that the conn_ipversion is IPV4_VERSION.  We
         * need to this before we call tcp_bindi() so that the port lookup
         * code will look for ports in the correct port space (IPv4 and
         * IPv6 have separate port spaces).
         */
        if (connp->conn_family == AF_INET6 &&
            connp->conn_ipversion == IPV6_VERSION &&
            IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr)) {
                if (connp->conn_ipv6_v6only)
                        return (EADDRNOTAVAIL);

                connp->conn_ipversion = IPV4_VERSION;
        }

        switch (tcp->tcp_state) {
        case TCPS_LISTEN:
                /*
                 * Listening sockets are not allowed to issue connect().
                 */
                if (IPCL_IS_NONSTR(connp))
                        return (EOPNOTSUPP);
                /* FALLTHRU */
        case TCPS_IDLE:
                /*
                 * We support quick connect, refer to comments in
                 * tcp_connect_*()
                 */
                /* FALLTHRU */
        case TCPS_BOUND:
                break;
        default:
                return (-TOUTSTATE);
        }

        /*
         * We update our cred/cpid based on the caller of connect
         */
        if (connp->conn_cred != cr) {
                crhold(cr);
                crfree(connp->conn_cred);
                connp->conn_cred = cr;
        }
        connp->conn_cpid = pid;

        /* Cache things in the ixa without any refhold */
        ASSERT(!(ixa->ixa_free_flags & IXA_FREE_CRED));
        ixa->ixa_cred = cr;
        ixa->ixa_cpid = pid;

        if (connp->conn_family == AF_INET6) {
                if (!IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr)) {
                        error = tcp_connect_ipv6(tcp, &sin6->sin6_addr,
                            sin6->sin6_port, sin6->sin6_flowinfo,
                            sin6->__sin6_src_id, sin6->sin6_scope_id);
                } else {
                        /*
                         * Destination adress is mapped IPv6 address.
                         * Source bound address should be unspecified or
                         * IPv6 mapped address as well.
                         */
                        if (!IN6_IS_ADDR_UNSPECIFIED(
                            &connp->conn_bound_addr_v6) &&
                            !IN6_IS_ADDR_V4MAPPED(&connp->conn_bound_addr_v6)) {
                                return (EADDRNOTAVAIL);
                        }
                        dstaddrp = &V4_PART_OF_V6((sin6->sin6_addr));
                        dstport = sin6->sin6_port;
                        srcid = sin6->__sin6_src_id;
                        error = tcp_connect_ipv4(tcp, dstaddrp, dstport,
                            srcid);
                }
        } else {
                dstaddrp = &sin->sin_addr.s_addr;
                dstport = sin->sin_port;
                srcid = 0;
                error = tcp_connect_ipv4(tcp, dstaddrp, dstport, srcid);
        }

        if (error != 0)
                goto connect_failed;

        /* connect succeeded */
        TCPS_BUMP_MIB(tcps, tcpActiveOpens);
        tcp->tcp_active_open = 1;

        /*
         * tcp_set_destination() does not adjust for TCP/IP header length.
         */
        mss = tcp->tcp_mss - connp->conn_ht_iphc_len;

        /*
         * Just make sure our rwnd is at least rcvbuf * MSS large, and round up
         * to the nearest MSS.
         *
         * We do the round up here because we need to get the interface MTU
         * first before we can do the round up.
         */
        tcp->tcp_rwnd = connp->conn_rcvbuf;
        tcp->tcp_rwnd = MAX(MSS_ROUNDUP(tcp->tcp_rwnd, mss),
            tcps->tcps_recv_hiwat_minmss * mss);
        connp->conn_rcvbuf = tcp->tcp_rwnd;
        tcp_set_ws_value(tcp);
        tcp->tcp_tcpha->tha_win = htons(tcp->tcp_rwnd >> tcp->tcp_rcv_ws);
        if (tcp->tcp_rcv_ws > 0 || tcps->tcps_wscale_always)
                tcp->tcp_snd_ws_ok = B_TRUE;

        /*
         * Set tcp_snd_ts_ok to true
         * so that tcp_xmit_mp will
         * include the timestamp
         * option in the SYN segment.
         */
        if (tcps->tcps_tstamp_always ||
            (tcp->tcp_rcv_ws && tcps->tcps_tstamp_if_wscale)) {
                tcp->tcp_snd_ts_ok = B_TRUE;
        }

        /*
         * Note that tcp_snd_sack_ok can be set in tcp_set_destination() if
         * the SACK metric is set.  So here we just check the per stack SACK
         * permitted param.
         */
        if (tcps->tcps_sack_permitted == 2) {
                ASSERT(tcp->tcp_num_sack_blk == 0);
                ASSERT(tcp->tcp_notsack_list == NULL);
                tcp->tcp_snd_sack_ok = B_TRUE;
        }

        /*
         * Should we use ECN?  Note that the current
         * default value (SunOS 5.9) of tcp_ecn_permitted
         * is 1.  The reason for doing this is that there
         * are equipments out there that will drop ECN
         * enabled IP packets.  Setting it to 1 avoids
         * compatibility problems.
         */
        if (tcps->tcps_ecn_permitted == 2)
                tcp->tcp_ecn_ok = B_TRUE;

        /* Trace change from BOUND -> SYN_SENT here */
        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
            connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
            int32_t, TCPS_BOUND);

        TCP_TIMER_RESTART(tcp, tcp->tcp_rto);
        syn_mp = tcp_xmit_mp(tcp, NULL, 0, NULL, NULL,
            tcp->tcp_iss, B_FALSE, NULL, B_FALSE);
        if (syn_mp != NULL) {
                /*
                 * We must bump the generation before sending the syn
                 * to ensure that we use the right generation in case
                 * this thread issues a "connected" up call.
                 */
                SOCK_CONNID_BUMP(tcp->tcp_connid);
                /*
                 * DTrace sending the first SYN as a
                 * tcp:::connect-request event.
                 */
                DTRACE_TCP5(connect__request, mblk_t *, NULL,
                    ip_xmit_attr_t *, connp->conn_ixa,
                    void_ip_t *, syn_mp->b_rptr, tcp_t *, tcp,
                    tcph_t *,
                    &syn_mp->b_rptr[connp->conn_ixa->ixa_ip_hdr_length]);
                tcp_send_data(tcp, syn_mp);
        }

        if (tcp->tcp_conn.tcp_opts_conn_req != NULL)
                tcp_close_mpp(&tcp->tcp_conn.tcp_opts_conn_req);
        return (0);

connect_failed:
        connp->conn_faddr_v6 = ipv6_all_zeros;
        connp->conn_fport = 0;
        tcp->tcp_state = oldstate;
        if (tcp->tcp_conn.tcp_opts_conn_req != NULL)
                tcp_close_mpp(&tcp->tcp_conn.tcp_opts_conn_req);
        return (error);
}

int
tcp_do_listen(conn_t *connp, struct sockaddr *sa, socklen_t len,
    int backlog, cred_t *cr, boolean_t bind_to_req_port_only)
{
        tcp_t           *tcp = connp->conn_tcp;
        int             error = 0;
        tcp_stack_t     *tcps = tcp->tcp_tcps;
        int32_t         oldstate;

        /* All Solaris components should pass a cred for this operation. */
        ASSERT(cr != NULL);

        if (tcp->tcp_state >= TCPS_BOUND) {
                if ((tcp->tcp_state == TCPS_BOUND ||
                    tcp->tcp_state == TCPS_LISTEN) && backlog > 0) {
                        /*
                         * Handle listen() increasing backlog.
                         * This is more "liberal" then what the TPI spec
                         * requires but is needed to avoid a t_unbind
                         * when handling listen() since the port number
                         * might be "stolen" between the unbind and bind.
                         */
                        goto do_listen;
                }
                if (connp->conn_debug) {
                        (void) strlog(TCP_MOD_ID, 0, 1, SL_ERROR|SL_TRACE,
                            "tcp_listen: bad state, %d", tcp->tcp_state);
                }
                return (-TOUTSTATE);
        } else {
                if (sa == NULL) {
                        sin6_t  addr;
                        sin_t *sin;
                        sin6_t *sin6;

                        ASSERT(IPCL_IS_NONSTR(connp));
                        /* Do an implicit bind: Request for a generic port. */
                        if (connp->conn_family == AF_INET) {
                                len = sizeof (sin_t);
                                sin = (sin_t *)&addr;
                                *sin = sin_null;
                                sin->sin_family = AF_INET;
                        } else {
                                ASSERT(connp->conn_family == AF_INET6);
                                len = sizeof (sin6_t);
                                sin6 = (sin6_t *)&addr;
                                *sin6 = sin6_null;
                                sin6->sin6_family = AF_INET6;
                        }
                        sa = (struct sockaddr *)&addr;
                }

                error = tcp_bind_check(connp, sa, len, cr,
                    bind_to_req_port_only);
                if (error)
                        return (error);
                /* Fall through and do the fanout insertion */
        }

do_listen:
        ASSERT(tcp->tcp_state == TCPS_BOUND || tcp->tcp_state == TCPS_LISTEN);
        tcp->tcp_conn_req_max = backlog;
        if (tcp->tcp_conn_req_max) {
                if (tcp->tcp_conn_req_max < tcps->tcps_conn_req_min)
                        tcp->tcp_conn_req_max = tcps->tcps_conn_req_min;
                if (tcp->tcp_conn_req_max > tcps->tcps_conn_req_max_q)
                        tcp->tcp_conn_req_max = tcps->tcps_conn_req_max_q;
                /*
                 * If this is a listener, do not reset the eager list
                 * and other stuffs.  Note that we don't check if the
                 * existing eager list meets the new tcp_conn_req_max
                 * requirement.
                 */
                if (tcp->tcp_state != TCPS_LISTEN) {
                        tcp->tcp_state = TCPS_LISTEN;
                        DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
                            connp->conn_ixa, void, NULL, tcp_t *, tcp,
                            void, NULL, int32_t, TCPS_BOUND);
                        /* Initialize the chain. Don't need the eager_lock */
                        tcp->tcp_eager_next_q0 = tcp->tcp_eager_prev_q0 = tcp;
                        tcp->tcp_eager_next_drop_q0 = tcp;
                        tcp->tcp_eager_prev_drop_q0 = tcp;
                        tcp->tcp_second_ctimer_threshold =
                            tcps->tcps_ip_abort_linterval;
                }
        }

        /*
         * We need to make sure that the conn_recv is set to a non-null
         * value before we insert the conn into the classifier table.
         * This is to avoid a race with an incoming packet which does an
         * ipcl_classify().
         * We initially set it to tcp_input_listener_unbound to try to
         * pick a good squeue for the listener when the first SYN arrives.
         * tcp_input_listener_unbound sets it to tcp_input_listener on that
         * first SYN.
         */
        connp->conn_recv = tcp_input_listener_unbound;

        /* Insert the listener in the classifier table */
        error = ip_laddr_fanout_insert(connp);
        if (error != 0) {
                /* Undo the bind - release the port number */
                oldstate = tcp->tcp_state;
                tcp->tcp_state = TCPS_IDLE;
                DTRACE_TCP6(state__change, void, NULL, ip_xmit_attr_t *,
                    connp->conn_ixa, void, NULL, tcp_t *, tcp, void, NULL,
                    int32_t, oldstate);
                connp->conn_bound_addr_v6 = ipv6_all_zeros;

                connp->conn_laddr_v6 = ipv6_all_zeros;
                connp->conn_saddr_v6 = ipv6_all_zeros;
                connp->conn_ports = 0;

                tcp_bind_hash_remove(tcp);
                return (error);
        } else {
                /*
                 * If there is a connection limit, allocate and initialize
                 * the counter struct.  Note that since listen can be called
                 * multiple times, the struct may have been allready allocated.
                 */
                if (!list_is_empty(&tcps->tcps_listener_conf) &&
                    tcp->tcp_listen_cnt == NULL) {
                        tcp_listen_cnt_t *tlc;
                        uint32_t ratio;

                        ratio = tcp_find_listener_conf(tcps,
                            ntohs(connp->conn_lport));
                        if (ratio != 0) {
                                uint32_t mem_ratio, tot_buf;

                                tlc = kmem_alloc(sizeof (tcp_listen_cnt_t),
                                    KM_SLEEP);
                                /*
                                 * Calculate the connection limit based on
                                 * the configured ratio and maxusers.  Maxusers
                                 * are calculated based on memory size,
                                 * ~ 1 user per MB.  Note that the conn_rcvbuf
                                 * and conn_sndbuf may change after a
                                 * connection is accepted.  So what we have
                                 * is only an approximation.
                                 */
                                if ((tot_buf = connp->conn_rcvbuf +
                                    connp->conn_sndbuf) < MB) {
                                        mem_ratio = MB / tot_buf;
                                        tlc->tlc_max = maxusers / ratio *
                                            mem_ratio;
                                } else {
                                        mem_ratio = tot_buf / MB;
                                        tlc->tlc_max = maxusers / ratio /
                                            mem_ratio;
                                }
                                /* At least we should allow two connections! */
                                if (tlc->tlc_max <= tcp_min_conn_listener)
                                        tlc->tlc_max = tcp_min_conn_listener;
                                tlc->tlc_cnt = 1;
                                tlc->tlc_drop = 0;
                                tcp->tcp_listen_cnt = tlc;
                        }
                }
        }
        return (error);
}