drm/connector: make mode_valid take a const struct drm_display_mode

[drm/drm-misc.git] / net / sunrpc / svcsock.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/net/sunrpc/svcsock.c
 *
 * These are the RPC server socket internals.
 *
 * The server scheduling algorithm does not always distribute the load
 * evenly when servicing a single client. May need to modify the
 * svc_xprt_enqueue procedure...
 *
 * TCP support is largely untested and may be a little slow. The problem
 * is that we currently do two separate recvfrom's, one for the 4-byte
 * record length, and the second for the actual record. This could possibly
 * be improved by always reading a minimum size of around 100 bytes and
 * tucking any superfluous bytes away in a temporary store. Still, that
 * leaves write requests out in the rain. An alternative may be to peek at
 * the first skb in the queue, and if it matches the next TCP sequence
 * number, to extract the record marker. Yuck.
 *
 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/freezer.h>
#include <linux/bvec.h>

#include <net/sock.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/tcp_states.h>
#include <net/tls_prot.h>
#include <net/handshake.h>
#include <linux/uaccess.h>
#include <linux/highmem.h>
#include <asm/ioctls.h>
#include <linux/key.h>

#include <linux/sunrpc/types.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/xdr.h>
#include <linux/sunrpc/msg_prot.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/xprt.h>

#include <trace/events/sock.h>
#include <trace/events/sunrpc.h>

#include "socklib.h"
#include "sunrpc.h"

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

/* To-do: to avoid tying up an nfsd thread while waiting for a
 * handshake request, the request could instead be deferred.
 */
enum {
        SVC_HANDSHAKE_TO        = 5U * HZ
};

static struct svc_sock *svc_setup_socket(struct svc_serv *, struct socket *,
                                         int flags);
static int              svc_udp_recvfrom(struct svc_rqst *);
static int              svc_udp_sendto(struct svc_rqst *);
static void             svc_sock_detach(struct svc_xprt *);
static void             svc_tcp_sock_detach(struct svc_xprt *);
static void             svc_sock_free(struct svc_xprt *);

static struct svc_xprt *svc_create_socket(struct svc_serv *, int,
                                          struct net *, struct sockaddr *,
                                          int, int);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key svc_key[2];
static struct lock_class_key svc_slock_key[2];

static void svc_reclassify_socket(struct socket *sock)
{
        struct sock *sk = sock->sk;

        if (WARN_ON_ONCE(!sock_allow_reclassification(sk)))
                return;

        switch (sk->sk_family) {
        case AF_INET:
                sock_lock_init_class_and_name(sk, "slock-AF_INET-NFSD",
                                              &svc_slock_key[0],
                                              "sk_xprt.xpt_lock-AF_INET-NFSD",
                                              &svc_key[0]);
                break;

        case AF_INET6:
                sock_lock_init_class_and_name(sk, "slock-AF_INET6-NFSD",
                                              &svc_slock_key[1],
                                              "sk_xprt.xpt_lock-AF_INET6-NFSD",
                                              &svc_key[1]);
                break;

        default:
                BUG();
        }
}
#else
static void svc_reclassify_socket(struct socket *sock)
{
}
#endif

/**
 * svc_tcp_release_ctxt - Release transport-related resources
 * @xprt: the transport which owned the context
 * @ctxt: the context from rqstp->rq_xprt_ctxt or dr->xprt_ctxt
 *
 */
static void svc_tcp_release_ctxt(struct svc_xprt *xprt, void *ctxt)
{
}

/**
 * svc_udp_release_ctxt - Release transport-related resources
 * @xprt: the transport which owned the context
 * @ctxt: the context from rqstp->rq_xprt_ctxt or dr->xprt_ctxt
 *
 */
static void svc_udp_release_ctxt(struct svc_xprt *xprt, void *ctxt)
{
        struct sk_buff *skb = ctxt;

        if (skb)
                consume_skb(skb);
}

union svc_pktinfo_u {
        struct in_pktinfo pkti;
        struct in6_pktinfo pkti6;
};
#define SVC_PKTINFO_SPACE \
        CMSG_SPACE(sizeof(union svc_pktinfo_u))

static void svc_set_cmsg_data(struct svc_rqst *rqstp, struct cmsghdr *cmh)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        switch (svsk->sk_sk->sk_family) {
        case AF_INET: {
                        struct in_pktinfo *pki = CMSG_DATA(cmh);

                        cmh->cmsg_level = SOL_IP;
                        cmh->cmsg_type = IP_PKTINFO;
                        pki->ipi_ifindex = 0;
                        pki->ipi_spec_dst.s_addr =
                                 svc_daddr_in(rqstp)->sin_addr.s_addr;
                        cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
                }
                break;

        case AF_INET6: {
                        struct in6_pktinfo *pki = CMSG_DATA(cmh);
                        struct sockaddr_in6 *daddr = svc_daddr_in6(rqstp);

                        cmh->cmsg_level = SOL_IPV6;
                        cmh->cmsg_type = IPV6_PKTINFO;
                        pki->ipi6_ifindex = daddr->sin6_scope_id;
                        pki->ipi6_addr = daddr->sin6_addr;
                        cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
                }
                break;
        }
}

static int svc_sock_result_payload(struct svc_rqst *rqstp, unsigned int offset,
                                   unsigned int length)
{
        return 0;
}

/*
 * Report socket names for nfsdfs
 */
static int svc_one_sock_name(struct svc_sock *svsk, char *buf, int remaining)
{
        const struct sock *sk = svsk->sk_sk;
        const char *proto_name = sk->sk_protocol == IPPROTO_UDP ?
                                                        "udp" : "tcp";
        int len;

        switch (sk->sk_family) {
        case PF_INET:
                len = snprintf(buf, remaining, "ipv4 %s %pI4 %d\n",
                                proto_name,
                                &inet_sk(sk)->inet_rcv_saddr,
                                inet_sk(sk)->inet_num);
                break;
#if IS_ENABLED(CONFIG_IPV6)
        case PF_INET6:
                len = snprintf(buf, remaining, "ipv6 %s %pI6 %d\n",
                                proto_name,
                                &sk->sk_v6_rcv_saddr,
                                inet_sk(sk)->inet_num);
                break;
#endif
        default:
                len = snprintf(buf, remaining, "*unknown-%d*\n",
                                sk->sk_family);
        }

        if (len >= remaining) {
                *buf = '\0';
                return -ENAMETOOLONG;
        }
        return len;
}

static int
svc_tcp_sock_process_cmsg(struct socket *sock, struct msghdr *msg,
                          struct cmsghdr *cmsg, int ret)
{
        u8 content_type = tls_get_record_type(sock->sk, cmsg);
        u8 level, description;

        switch (content_type) {
        case 0:
                break;
        case TLS_RECORD_TYPE_DATA:
                /* TLS sets EOR at the end of each application data
                 * record, even though there might be more frames
                 * waiting to be decrypted.
                 */
                msg->msg_flags &= ~MSG_EOR;
                break;
        case TLS_RECORD_TYPE_ALERT:
                tls_alert_recv(sock->sk, msg, &level, &description);
                ret = (level == TLS_ALERT_LEVEL_FATAL) ?
                        -ENOTCONN : -EAGAIN;
                break;
        default:
                /* discard this record type */
                ret = -EAGAIN;
        }
        return ret;
}

static int
svc_tcp_sock_recv_cmsg(struct svc_sock *svsk, struct msghdr *msg)
{
        union {
                struct cmsghdr  cmsg;
                u8              buf[CMSG_SPACE(sizeof(u8))];
        } u;
        struct socket *sock = svsk->sk_sock;
        int ret;

        msg->msg_control = &u;
        msg->msg_controllen = sizeof(u);
        ret = sock_recvmsg(sock, msg, MSG_DONTWAIT);
        if (unlikely(msg->msg_controllen != sizeof(u)))
                ret = svc_tcp_sock_process_cmsg(sock, msg, &u.cmsg, ret);
        return ret;
}

#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
static void svc_flush_bvec(const struct bio_vec *bvec, size_t size, size_t seek)
{
        struct bvec_iter bi = {
                .bi_size        = size + seek,
        };
        struct bio_vec bv;

        bvec_iter_advance(bvec, &bi, seek & PAGE_MASK);
        for_each_bvec(bv, bvec, bi, bi)
                flush_dcache_page(bv.bv_page);
}
#else
static inline void svc_flush_bvec(const struct bio_vec *bvec, size_t size,
                                  size_t seek)
{
}
#endif

/*
 * Read from @rqstp's transport socket. The incoming message fills whole
 * pages in @rqstp's rq_pages array until the last page of the message
 * has been received into a partial page.
 */
static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
                                size_t seek)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct bio_vec *bvec = rqstp->rq_bvec;
        struct msghdr msg = { NULL };
        unsigned int i;
        ssize_t len;
        size_t t;

        clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);

        for (i = 0, t = 0; t < buflen; i++, t += PAGE_SIZE)
                bvec_set_page(&bvec[i], rqstp->rq_pages[i], PAGE_SIZE, 0);
        rqstp->rq_respages = &rqstp->rq_pages[i];
        rqstp->rq_next_page = rqstp->rq_respages + 1;

        iov_iter_bvec(&msg.msg_iter, ITER_DEST, bvec, i, buflen);
        if (seek) {
                iov_iter_advance(&msg.msg_iter, seek);
                buflen -= seek;
        }
        len = svc_tcp_sock_recv_cmsg(svsk, &msg);
        if (len > 0)
                svc_flush_bvec(bvec, len, seek);

        /* If we read a full record, then assume there may be more
         * data to read (stream based sockets only!)
         */
        if (len == buflen)
                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);

        return len;
}

/*
 * Set socket snd and rcv buffer lengths
 */
static void svc_sock_setbufsize(struct svc_sock *svsk, unsigned int nreqs)
{
        unsigned int max_mesg = svsk->sk_xprt.xpt_server->sv_max_mesg;
        struct socket *sock = svsk->sk_sock;

        nreqs = min(nreqs, INT_MAX / 2 / max_mesg);

        lock_sock(sock->sk);
        sock->sk->sk_sndbuf = nreqs * max_mesg * 2;
        sock->sk->sk_rcvbuf = nreqs * max_mesg * 2;
        sock->sk->sk_write_space(sock->sk);
        release_sock(sock->sk);
}

static void svc_sock_secure_port(struct svc_rqst *rqstp)
{
        if (svc_port_is_privileged(svc_addr(rqstp)))
                set_bit(RQ_SECURE, &rqstp->rq_flags);
        else
                clear_bit(RQ_SECURE, &rqstp->rq_flags);
}

/*
 * INET callback when data has been received on the socket.
 */
static void svc_data_ready(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        trace_sk_data_ready(sk);

        if (svsk) {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_odata(sk);
                trace_svcsock_data_ready(&svsk->sk_xprt, 0);
                if (test_bit(XPT_HANDSHAKE, &svsk->sk_xprt.xpt_flags))
                        return;
                if (!test_and_set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags))
                        svc_xprt_enqueue(&svsk->sk_xprt);
        }
}

/*
 * INET callback when space is newly available on the socket.
 */
static void svc_write_space(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)(sk->sk_user_data);

        if (svsk) {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                trace_svcsock_write_space(&svsk->sk_xprt, 0);
                svsk->sk_owspace(sk);
                svc_xprt_enqueue(&svsk->sk_xprt);
        }
}

static int svc_tcp_has_wspace(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        if (test_bit(XPT_LISTENER, &xprt->xpt_flags))
                return 1;
        return !test_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
}

static void svc_tcp_kill_temp_xprt(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        sock_no_linger(svsk->sk_sock->sk);
}

/**
 * svc_tcp_handshake_done - Handshake completion handler
 * @data: address of xprt to wake
 * @status: status of handshake
 * @peerid: serial number of key containing the remote peer's identity
 *
 * If a security policy is specified as an export option, we don't
 * have a specific export here to check. So we set a "TLS session
 * is present" flag on the xprt and let an upper layer enforce local
 * security policy.
 */
static void svc_tcp_handshake_done(void *data, int status, key_serial_t peerid)
{
        struct svc_xprt *xprt = data;
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        if (!status) {
                if (peerid != TLS_NO_PEERID)
                        set_bit(XPT_PEER_AUTH, &xprt->xpt_flags);
                set_bit(XPT_TLS_SESSION, &xprt->xpt_flags);
        }
        clear_bit(XPT_HANDSHAKE, &xprt->xpt_flags);
        complete_all(&svsk->sk_handshake_done);
}

/**
 * svc_tcp_handshake - Perform a transport-layer security handshake
 * @xprt: connected transport endpoint
 *
 */
static void svc_tcp_handshake(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct sock *sk = svsk->sk_sock->sk;
        struct tls_handshake_args args = {
                .ta_sock        = svsk->sk_sock,
                .ta_done        = svc_tcp_handshake_done,
                .ta_data        = xprt,
        };
        int ret;

        trace_svc_tls_upcall(xprt);

        clear_bit(XPT_TLS_SESSION, &xprt->xpt_flags);
        init_completion(&svsk->sk_handshake_done);

        ret = tls_server_hello_x509(&args, GFP_KERNEL);
        if (ret) {
                trace_svc_tls_not_started(xprt);
                goto out_failed;
        }

        ret = wait_for_completion_interruptible_timeout(&svsk->sk_handshake_done,
                                                        SVC_HANDSHAKE_TO);
        if (ret <= 0) {
                if (tls_handshake_cancel(sk)) {
                        trace_svc_tls_timed_out(xprt);
                        goto out_close;
                }
        }

        if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags)) {
                trace_svc_tls_unavailable(xprt);
                goto out_close;
        }

        /* Mark the transport ready in case the remote sent RPC
         * traffic before the kernel received the handshake
         * completion downcall.
         */
        set_bit(XPT_DATA, &xprt->xpt_flags);
        svc_xprt_enqueue(xprt);
        return;

out_close:
        set_bit(XPT_CLOSE, &xprt->xpt_flags);
out_failed:
        clear_bit(XPT_HANDSHAKE, &xprt->xpt_flags);
        set_bit(XPT_DATA, &xprt->xpt_flags);
        svc_xprt_enqueue(xprt);
}

/*
 * See net/ipv6/ip_sockglue.c : ip_cmsg_recv_pktinfo
 */
static int svc_udp_get_dest_address4(struct svc_rqst *rqstp,
                                     struct cmsghdr *cmh)
{
        struct in_pktinfo *pki = CMSG_DATA(cmh);
        struct sockaddr_in *daddr = svc_daddr_in(rqstp);

        if (cmh->cmsg_type != IP_PKTINFO)
                return 0;

        daddr->sin_family = AF_INET;
        daddr->sin_addr.s_addr = pki->ipi_spec_dst.s_addr;
        return 1;
}

/*
 * See net/ipv6/datagram.c : ip6_datagram_recv_ctl
 */
static int svc_udp_get_dest_address6(struct svc_rqst *rqstp,
                                     struct cmsghdr *cmh)
{
        struct in6_pktinfo *pki = CMSG_DATA(cmh);
        struct sockaddr_in6 *daddr = svc_daddr_in6(rqstp);

        if (cmh->cmsg_type != IPV6_PKTINFO)
                return 0;

        daddr->sin6_family = AF_INET6;
        daddr->sin6_addr = pki->ipi6_addr;
        daddr->sin6_scope_id = pki->ipi6_ifindex;
        return 1;
}

/*
 * Copy the UDP datagram's destination address to the rqstp structure.
 * The 'destination' address in this case is the address to which the
 * peer sent the datagram, i.e. our local address. For multihomed
 * hosts, this can change from msg to msg. Note that only the IP
 * address changes, the port number should remain the same.
 */
static int svc_udp_get_dest_address(struct svc_rqst *rqstp,
                                    struct cmsghdr *cmh)
{
        switch (cmh->cmsg_level) {
        case SOL_IP:
                return svc_udp_get_dest_address4(rqstp, cmh);
        case SOL_IPV6:
                return svc_udp_get_dest_address6(rqstp, cmh);
        }

        return 0;
}

/**
 * svc_udp_recvfrom - Receive a datagram from a UDP socket.
 * @rqstp: request structure into which to receive an RPC Call
 *
 * Called in a loop when XPT_DATA has been set.
 *
 * Returns:
 *   On success, the number of bytes in a received RPC Call, or
 *   %0 if a complete RPC Call message was not ready to return
 */
static int svc_udp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        struct sk_buff  *skb;
        union {
                struct cmsghdr  hdr;
                long            all[SVC_PKTINFO_SPACE / sizeof(long)];
        } buffer;
        struct cmsghdr *cmh = &buffer.hdr;
        struct msghdr msg = {
                .msg_name = svc_addr(rqstp),
                .msg_control = cmh,
                .msg_controllen = sizeof(buffer),
                .msg_flags = MSG_DONTWAIT,
        };
        size_t len;
        int err;

        if (test_and_clear_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags))
            /* udp sockets need large rcvbuf as all pending
             * requests are still in that buffer.  sndbuf must
             * also be large enough that there is enough space
             * for one reply per thread.  We count all threads
             * rather than threads in a particular pool, which
             * provides an upper bound on the number of threads
             * which will access the socket.
             */
            svc_sock_setbufsize(svsk, serv->sv_nrthreads + 3);

        clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
                             0, 0, MSG_PEEK | MSG_DONTWAIT);
        if (err < 0)
                goto out_recv_err;
        skb = skb_recv_udp(svsk->sk_sk, MSG_DONTWAIT, &err);
        if (!skb)
                goto out_recv_err;

        len = svc_addr_len(svc_addr(rqstp));
        rqstp->rq_addrlen = len;
        if (skb->tstamp == 0) {
                skb->tstamp = ktime_get_real();
                /* Don't enable netstamp, sunrpc doesn't
                   need that much accuracy */
        }
        sock_write_timestamp(svsk->sk_sk, skb->tstamp);
        set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); /* there may be more data... */

        len = skb->len;
        rqstp->rq_arg.len = len;
        trace_svcsock_udp_recv(&svsk->sk_xprt, len);

        rqstp->rq_prot = IPPROTO_UDP;

        if (!svc_udp_get_dest_address(rqstp, cmh))
                goto out_cmsg_err;
        rqstp->rq_daddrlen = svc_addr_len(svc_daddr(rqstp));

        if (skb_is_nonlinear(skb)) {
                /* we have to copy */
                local_bh_disable();
                if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb))
                        goto out_bh_enable;
                local_bh_enable();
                consume_skb(skb);
        } else {
                /* we can use it in-place */
                rqstp->rq_arg.head[0].iov_base = skb->data;
                rqstp->rq_arg.head[0].iov_len = len;
                if (skb_checksum_complete(skb))
                        goto out_free;
                rqstp->rq_xprt_ctxt = skb;
        }

        rqstp->rq_arg.page_base = 0;
        if (len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = len;
                rqstp->rq_arg.page_len = 0;
                rqstp->rq_respages = rqstp->rq_pages+1;
        } else {
                rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
                rqstp->rq_respages = rqstp->rq_pages + 1 +
                        DIV_ROUND_UP(rqstp->rq_arg.page_len, PAGE_SIZE);
        }
        rqstp->rq_next_page = rqstp->rq_respages+1;

        if (serv->sv_stats)
                serv->sv_stats->netudpcnt++;

        svc_sock_secure_port(rqstp);
        svc_xprt_received(rqstp->rq_xprt);
        return len;

out_recv_err:
        if (err != -EAGAIN) {
                /* possibly an icmp error */
                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        }
        trace_svcsock_udp_recv_err(&svsk->sk_xprt, err);
        goto out_clear_busy;
out_cmsg_err:
        net_warn_ratelimited("svc: received unknown control message %d/%d; dropping RPC reply datagram\n",
                             cmh->cmsg_level, cmh->cmsg_type);
        goto out_free;
out_bh_enable:
        local_bh_enable();
out_free:
        kfree_skb(skb);
out_clear_busy:
        svc_xprt_received(rqstp->rq_xprt);
        return 0;
}

/**
 * svc_udp_sendto - Send out a reply on a UDP socket
 * @rqstp: completed svc_rqst
 *
 * xpt_mutex ensures @rqstp's whole message is written to the socket
 * without interruption.
 *
 * Returns the number of bytes sent, or a negative errno.
 */
static int svc_udp_sendto(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct xdr_buf *xdr = &rqstp->rq_res;
        union {
                struct cmsghdr  hdr;
                long            all[SVC_PKTINFO_SPACE / sizeof(long)];
        } buffer;
        struct cmsghdr *cmh = &buffer.hdr;
        struct msghdr msg = {
                .msg_name       = &rqstp->rq_addr,
                .msg_namelen    = rqstp->rq_addrlen,
                .msg_control    = cmh,
                .msg_flags      = MSG_SPLICE_PAGES,
                .msg_controllen = sizeof(buffer),
        };
        unsigned int count;
        int err;

        svc_udp_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
        rqstp->rq_xprt_ctxt = NULL;

        svc_set_cmsg_data(rqstp, cmh);

        mutex_lock(&xprt->xpt_mutex);

        if (svc_xprt_is_dead(xprt))
                goto out_notconn;

        count = xdr_buf_to_bvec(rqstp->rq_bvec,
                                ARRAY_SIZE(rqstp->rq_bvec), xdr);

        iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
                      count, rqstp->rq_res.len);
        err = sock_sendmsg(svsk->sk_sock, &msg);
        if (err == -ECONNREFUSED) {
                /* ICMP error on earlier request. */
                iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
                              count, rqstp->rq_res.len);
                err = sock_sendmsg(svsk->sk_sock, &msg);
        }

        trace_svcsock_udp_send(xprt, err);

        mutex_unlock(&xprt->xpt_mutex);
        return err;

out_notconn:
        mutex_unlock(&xprt->xpt_mutex);
        return -ENOTCONN;
}

static int svc_udp_has_wspace(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = xprt->xpt_server;
        unsigned long required;

        /*
         * Set the SOCK_NOSPACE flag before checking the available
         * sock space.
         */
        set_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
        required = atomic_read(&svsk->sk_xprt.xpt_reserved) + serv->sv_max_mesg;
        if (required*2 > sock_wspace(svsk->sk_sk))
                return 0;
        clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
        return 1;
}

static struct svc_xprt *svc_udp_accept(struct svc_xprt *xprt)
{
        BUG();
        return NULL;
}

static void svc_udp_kill_temp_xprt(struct svc_xprt *xprt)
{
}

static struct svc_xprt *svc_udp_create(struct svc_serv *serv,
                                       struct net *net,
                                       struct sockaddr *sa, int salen,
                                       int flags)
{
        return svc_create_socket(serv, IPPROTO_UDP, net, sa, salen, flags);
}

static const struct svc_xprt_ops svc_udp_ops = {
        .xpo_create = svc_udp_create,
        .xpo_recvfrom = svc_udp_recvfrom,
        .xpo_sendto = svc_udp_sendto,
        .xpo_result_payload = svc_sock_result_payload,
        .xpo_release_ctxt = svc_udp_release_ctxt,
        .xpo_detach = svc_sock_detach,
        .xpo_free = svc_sock_free,
        .xpo_has_wspace = svc_udp_has_wspace,
        .xpo_accept = svc_udp_accept,
        .xpo_kill_temp_xprt = svc_udp_kill_temp_xprt,
};

static struct svc_xprt_class svc_udp_class = {
        .xcl_name = "udp",
        .xcl_owner = THIS_MODULE,
        .xcl_ops = &svc_udp_ops,
        .xcl_max_payload = RPCSVC_MAXPAYLOAD_UDP,
        .xcl_ident = XPRT_TRANSPORT_UDP,
};

static void svc_udp_init(struct svc_sock *svsk, struct svc_serv *serv)
{
        svc_xprt_init(sock_net(svsk->sk_sock->sk), &svc_udp_class,
                      &svsk->sk_xprt, serv);
        clear_bit(XPT_CACHE_AUTH, &svsk->sk_xprt.xpt_flags);
        svsk->sk_sk->sk_data_ready = svc_data_ready;
        svsk->sk_sk->sk_write_space = svc_write_space;

        /* initialise setting must have enough space to
         * receive and respond to one request.
         * svc_udp_recvfrom will re-adjust if necessary
         */
        svc_sock_setbufsize(svsk, 3);

        /* data might have come in before data_ready set up */
        set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags);

        /* make sure we get destination address info */
        switch (svsk->sk_sk->sk_family) {
        case AF_INET:
                ip_sock_set_pktinfo(svsk->sk_sock->sk);
                break;
        case AF_INET6:
                ip6_sock_set_recvpktinfo(svsk->sk_sock->sk);
                break;
        default:
                BUG();
        }
}

/*
 * A data_ready event on a listening socket means there's a connection
 * pending. Do not use state_change as a substitute for it.
 */
static void svc_tcp_listen_data_ready(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        trace_sk_data_ready(sk);

        /*
         * This callback may called twice when a new connection
         * is established as a child socket inherits everything
         * from a parent LISTEN socket.
         * 1) data_ready method of the parent socket will be called
         *    when one of child sockets become ESTABLISHED.
         * 2) data_ready method of the child socket may be called
         *    when it receives data before the socket is accepted.
         * In case of 2, we should ignore it silently and DO NOT
         * dereference svsk.
         */
        if (sk->sk_state != TCP_LISTEN)
                return;

        if (svsk) {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_odata(sk);
                set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
                svc_xprt_enqueue(&svsk->sk_xprt);
        }
}

/*
 * A state change on a connected socket means it's dying or dead.
 */
static void svc_tcp_state_change(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        if (svsk) {
                /* Refer to svc_setup_socket() for details. */
                rmb();
                svsk->sk_ostate(sk);
                trace_svcsock_tcp_state(&svsk->sk_xprt, svsk->sk_sock);
                if (sk->sk_state != TCP_ESTABLISHED)
                        svc_xprt_deferred_close(&svsk->sk_xprt);
        }
}

/*
 * Accept a TCP connection
 */
static struct svc_xprt *svc_tcp_accept(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct sockaddr_storage addr;
        struct sockaddr *sin = (struct sockaddr *) &addr;
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        struct socket   *sock = svsk->sk_sock;
        struct socket   *newsock;
        struct svc_sock *newsvsk;
        int             err, slen;

        if (!sock)
                return NULL;

        clear_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
        err = kernel_accept(sock, &newsock, O_NONBLOCK);
        if (err < 0) {
                if (err != -EAGAIN)
                        trace_svcsock_accept_err(xprt, serv->sv_name, err);
                return NULL;
        }
        if (IS_ERR(sock_alloc_file(newsock, O_NONBLOCK, NULL)))
                return NULL;

        set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);

        err = kernel_getpeername(newsock, sin);
        if (err < 0) {
                trace_svcsock_getpeername_err(xprt, serv->sv_name, err);
                goto failed;            /* aborted connection or whatever */
        }
        slen = err;

        /* Reset the inherited callbacks before calling svc_setup_socket */
        newsock->sk->sk_state_change = svsk->sk_ostate;
        newsock->sk->sk_data_ready = svsk->sk_odata;
        newsock->sk->sk_write_space = svsk->sk_owspace;

        /* make sure that a write doesn't block forever when
         * low on memory
         */
        newsock->sk->sk_sndtimeo = HZ*30;

        newsvsk = svc_setup_socket(serv, newsock,
                                 (SVC_SOCK_ANONYMOUS | SVC_SOCK_TEMPORARY));
        if (IS_ERR(newsvsk))
                goto failed;
        svc_xprt_set_remote(&newsvsk->sk_xprt, sin, slen);
        err = kernel_getsockname(newsock, sin);
        slen = err;
        if (unlikely(err < 0))
                slen = offsetof(struct sockaddr, sa_data);
        svc_xprt_set_local(&newsvsk->sk_xprt, sin, slen);

        if (sock_is_loopback(newsock->sk))
                set_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
        else
                clear_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
        if (serv->sv_stats)
                serv->sv_stats->nettcpconn++;

        return &newsvsk->sk_xprt;

failed:
        sockfd_put(newsock);
        return NULL;
}

static size_t svc_tcp_restore_pages(struct svc_sock *svsk,
                                    struct svc_rqst *rqstp)
{
        size_t len = svsk->sk_datalen;
        unsigned int i, npages;

        if (!len)
                return 0;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                if (rqstp->rq_pages[i] != NULL)
                        put_page(rqstp->rq_pages[i]);
                BUG_ON(svsk->sk_pages[i] == NULL);
                rqstp->rq_pages[i] = svsk->sk_pages[i];
                svsk->sk_pages[i] = NULL;
        }
        rqstp->rq_arg.head[0].iov_base = page_address(rqstp->rq_pages[0]);
        return len;
}

static void svc_tcp_save_pages(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        unsigned int i, len, npages;

        if (svsk->sk_datalen == 0)
                return;
        len = svsk->sk_datalen;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                svsk->sk_pages[i] = rqstp->rq_pages[i];
                rqstp->rq_pages[i] = NULL;
        }
}

static void svc_tcp_clear_pages(struct svc_sock *svsk)
{
        unsigned int i, len, npages;

        if (svsk->sk_datalen == 0)
                goto out;
        len = svsk->sk_datalen;
        npages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        for (i = 0; i < npages; i++) {
                if (svsk->sk_pages[i] == NULL) {
                        WARN_ON_ONCE(1);
                        continue;
                }
                put_page(svsk->sk_pages[i]);
                svsk->sk_pages[i] = NULL;
        }
out:
        svsk->sk_tcplen = 0;
        svsk->sk_datalen = 0;
}

/*
 * Receive fragment record header into sk_marker.
 */
static ssize_t svc_tcp_read_marker(struct svc_sock *svsk,
                                   struct svc_rqst *rqstp)
{
        ssize_t want, len;

        /* If we haven't gotten the record length yet,
         * get the next four bytes.
         */
        if (svsk->sk_tcplen < sizeof(rpc_fraghdr)) {
                struct msghdr   msg = { NULL };
                struct kvec     iov;

                want = sizeof(rpc_fraghdr) - svsk->sk_tcplen;
                iov.iov_base = ((char *)&svsk->sk_marker) + svsk->sk_tcplen;
                iov.iov_len  = want;
                iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, want);
                len = svc_tcp_sock_recv_cmsg(svsk, &msg);
                if (len < 0)
                        return len;
                svsk->sk_tcplen += len;
                if (len < want) {
                        /* call again to read the remaining bytes */
                        goto err_short;
                }
                trace_svcsock_marker(&svsk->sk_xprt, svsk->sk_marker);
                if (svc_sock_reclen(svsk) + svsk->sk_datalen >
                    svsk->sk_xprt.xpt_server->sv_max_mesg)
                        goto err_too_large;
        }
        return svc_sock_reclen(svsk);

err_too_large:
        net_notice_ratelimited("svc: %s %s RPC fragment too large: %d\n",
                               __func__, svsk->sk_xprt.xpt_server->sv_name,
                               svc_sock_reclen(svsk));
        svc_xprt_deferred_close(&svsk->sk_xprt);
err_short:
        return -EAGAIN;
}

static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
{
        struct rpc_xprt *bc_xprt = svsk->sk_xprt.xpt_bc_xprt;
        struct rpc_rqst *req = NULL;
        struct kvec *src, *dst;
        __be32 *p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
        __be32 xid = *p;

        if (!bc_xprt)
                return -EAGAIN;
        spin_lock(&bc_xprt->queue_lock);
        req = xprt_lookup_rqst(bc_xprt, xid);
        if (!req)
                goto unlock_eagain;

        memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
        /*
         * XXX!: cheating for now!  Only copying HEAD.
         * But we know this is good enough for now (in fact, for any
         * callback reply in the forseeable future).
         */
        dst = &req->rq_private_buf.head[0];
        src = &rqstp->rq_arg.head[0];
        if (dst->iov_len < src->iov_len)
                goto unlock_eagain; /* whatever; just giving up. */
        memcpy(dst->iov_base, src->iov_base, src->iov_len);
        xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
        rqstp->rq_arg.len = 0;
        spin_unlock(&bc_xprt->queue_lock);
        return 0;
unlock_eagain:
        spin_unlock(&bc_xprt->queue_lock);
        return -EAGAIN;
}

static void svc_tcp_fragment_received(struct svc_sock *svsk)
{
        /* If we have more data, signal svc_xprt_enqueue() to try again */
        svsk->sk_tcplen = 0;
        svsk->sk_marker = xdr_zero;

        smp_wmb();
        tcp_set_rcvlowat(svsk->sk_sk, 1);
}

/**
 * svc_tcp_recvfrom - Receive data from a TCP socket
 * @rqstp: request structure into which to receive an RPC Call
 *
 * Called in a loop when XPT_DATA has been set.
 *
 * Read the 4-byte stream record marker, then use the record length
 * in that marker to set up exactly the resources needed to receive
 * the next RPC message into @rqstp.
 *
 * Returns:
 *   On success, the number of bytes in a received RPC Call, or
 *   %0 if a complete RPC Call message was not ready to return
 *
 * The zero return case handles partial receives and callback Replies.
 * The state of a partial receive is preserved in the svc_sock for
 * the next call to svc_tcp_recvfrom.
 */
static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk =
                container_of(rqstp->rq_xprt, struct svc_sock, sk_xprt);
        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
        size_t want, base;
        ssize_t len;
        __be32 *p;
        __be32 calldir;

        clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
        len = svc_tcp_read_marker(svsk, rqstp);
        if (len < 0)
                goto error;

        base = svc_tcp_restore_pages(svsk, rqstp);
        want = len - (svsk->sk_tcplen - sizeof(rpc_fraghdr));
        len = svc_tcp_read_msg(rqstp, base + want, base);
        if (len >= 0) {
                trace_svcsock_tcp_recv(&svsk->sk_xprt, len);
                svsk->sk_tcplen += len;
                svsk->sk_datalen += len;
        }
        if (len != want || !svc_sock_final_rec(svsk))
                goto err_incomplete;
        if (svsk->sk_datalen < 8)
                goto err_nuts;

        rqstp->rq_arg.len = svsk->sk_datalen;
        rqstp->rq_arg.page_base = 0;
        if (rqstp->rq_arg.len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = rqstp->rq_arg.len;
                rqstp->rq_arg.page_len = 0;
        } else
                rqstp->rq_arg.page_len = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;

        rqstp->rq_xprt_ctxt   = NULL;
        rqstp->rq_prot        = IPPROTO_TCP;
        if (test_bit(XPT_LOCAL, &svsk->sk_xprt.xpt_flags))
                set_bit(RQ_LOCAL, &rqstp->rq_flags);
        else
                clear_bit(RQ_LOCAL, &rqstp->rq_flags);

        p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
        calldir = p[1];
        if (calldir)
                len = receive_cb_reply(svsk, rqstp);

        /* Reset TCP read info */
        svsk->sk_datalen = 0;
        svc_tcp_fragment_received(svsk);

        if (len < 0)
                goto error;

        svc_xprt_copy_addrs(rqstp, &svsk->sk_xprt);
        if (serv->sv_stats)
                serv->sv_stats->nettcpcnt++;

        svc_sock_secure_port(rqstp);
        svc_xprt_received(rqstp->rq_xprt);
        return rqstp->rq_arg.len;

err_incomplete:
        svc_tcp_save_pages(svsk, rqstp);
        if (len < 0 && len != -EAGAIN)
                goto err_delete;
        if (len == want)
                svc_tcp_fragment_received(svsk);
        else {
                /* Avoid more ->sk_data_ready() calls until the rest
                 * of the message has arrived. This reduces service
                 * thread wake-ups on large incoming messages. */
                tcp_set_rcvlowat(svsk->sk_sk,
                                 svc_sock_reclen(svsk) - svsk->sk_tcplen);

                trace_svcsock_tcp_recv_short(&svsk->sk_xprt,
                                svc_sock_reclen(svsk),
                                svsk->sk_tcplen - sizeof(rpc_fraghdr));
        }
        goto err_noclose;
error:
        if (len != -EAGAIN)
                goto err_delete;
        trace_svcsock_tcp_recv_eagain(&svsk->sk_xprt, 0);
        goto err_noclose;
err_nuts:
        svsk->sk_datalen = 0;
err_delete:
        trace_svcsock_tcp_recv_err(&svsk->sk_xprt, len);
        svc_xprt_deferred_close(&svsk->sk_xprt);
err_noclose:
        svc_xprt_received(rqstp->rq_xprt);
        return 0;       /* record not complete */
}

/*
 * MSG_SPLICE_PAGES is used exclusively to reduce the number of
 * copy operations in this path. Therefore the caller must ensure
 * that the pages backing @xdr are unchanging.
 */
static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
                           rpc_fraghdr marker, unsigned int *sentp)
{
        struct msghdr msg = {
                .msg_flags      = MSG_SPLICE_PAGES,
        };
        unsigned int count;
        void *buf;
        int ret;

        *sentp = 0;

        /* The stream record marker is copied into a temporary page
         * fragment buffer so that it can be included in rq_bvec.
         */
        buf = page_frag_alloc(&svsk->sk_frag_cache, sizeof(marker),
                              GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        memcpy(buf, &marker, sizeof(marker));
        bvec_set_virt(rqstp->rq_bvec, buf, sizeof(marker));

        count = xdr_buf_to_bvec(rqstp->rq_bvec + 1,
                                ARRAY_SIZE(rqstp->rq_bvec) - 1, &rqstp->rq_res);

        iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
                      1 + count, sizeof(marker) + rqstp->rq_res.len);
        ret = sock_sendmsg(svsk->sk_sock, &msg);
        page_frag_free(buf);
        if (ret < 0)
                return ret;
        *sentp += ret;
        return 0;
}

/**
 * svc_tcp_sendto - Send out a reply on a TCP socket
 * @rqstp: completed svc_rqst
 *
 * xpt_mutex ensures @rqstp's whole message is written to the socket
 * without interruption.
 *
 * Returns the number of bytes sent, or a negative errno.
 */
static int svc_tcp_sendto(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct xdr_buf *xdr = &rqstp->rq_res;
        rpc_fraghdr marker = cpu_to_be32(RPC_LAST_STREAM_FRAGMENT |
                                         (u32)xdr->len);
        unsigned int sent;
        int err;

        svc_tcp_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
        rqstp->rq_xprt_ctxt = NULL;

        mutex_lock(&xprt->xpt_mutex);
        if (svc_xprt_is_dead(xprt))
                goto out_notconn;
        err = svc_tcp_sendmsg(svsk, rqstp, marker, &sent);
        trace_svcsock_tcp_send(xprt, err < 0 ? (long)err : sent);
        if (err < 0 || sent != (xdr->len + sizeof(marker)))
                goto out_close;
        mutex_unlock(&xprt->xpt_mutex);
        return sent;

out_notconn:
        mutex_unlock(&xprt->xpt_mutex);
        return -ENOTCONN;
out_close:
        pr_notice("rpc-srv/tcp: %s: %s %d when sending %d bytes - shutting down socket\n",
                  xprt->xpt_server->sv_name,
                  (err < 0) ? "got error" : "sent",
                  (err < 0) ? err : sent, xdr->len);
        svc_xprt_deferred_close(xprt);
        mutex_unlock(&xprt->xpt_mutex);
        return -EAGAIN;
}

static struct svc_xprt *svc_tcp_create(struct svc_serv *serv,
                                       struct net *net,
                                       struct sockaddr *sa, int salen,
                                       int flags)
{
        return svc_create_socket(serv, IPPROTO_TCP, net, sa, salen, flags);
}

static const struct svc_xprt_ops svc_tcp_ops = {
        .xpo_create = svc_tcp_create,
        .xpo_recvfrom = svc_tcp_recvfrom,
        .xpo_sendto = svc_tcp_sendto,
        .xpo_result_payload = svc_sock_result_payload,
        .xpo_release_ctxt = svc_tcp_release_ctxt,
        .xpo_detach = svc_tcp_sock_detach,
        .xpo_free = svc_sock_free,
        .xpo_has_wspace = svc_tcp_has_wspace,
        .xpo_accept = svc_tcp_accept,
        .xpo_kill_temp_xprt = svc_tcp_kill_temp_xprt,
        .xpo_handshake = svc_tcp_handshake,
};

static struct svc_xprt_class svc_tcp_class = {
        .xcl_name = "tcp",
        .xcl_owner = THIS_MODULE,
        .xcl_ops = &svc_tcp_ops,
        .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
        .xcl_ident = XPRT_TRANSPORT_TCP,
};

void svc_init_xprt_sock(void)
{
        svc_reg_xprt_class(&svc_tcp_class);
        svc_reg_xprt_class(&svc_udp_class);
}

void svc_cleanup_xprt_sock(void)
{
        svc_unreg_xprt_class(&svc_tcp_class);
        svc_unreg_xprt_class(&svc_udp_class);
}

static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv)
{
        struct sock     *sk = svsk->sk_sk;

        svc_xprt_init(sock_net(svsk->sk_sock->sk), &svc_tcp_class,
                      &svsk->sk_xprt, serv);
        set_bit(XPT_CACHE_AUTH, &svsk->sk_xprt.xpt_flags);
        set_bit(XPT_CONG_CTRL, &svsk->sk_xprt.xpt_flags);
        if (sk->sk_state == TCP_LISTEN) {
                strcpy(svsk->sk_xprt.xpt_remotebuf, "listener");
                set_bit(XPT_LISTENER, &svsk->sk_xprt.xpt_flags);
                sk->sk_data_ready = svc_tcp_listen_data_ready;
                set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
        } else {
                sk->sk_state_change = svc_tcp_state_change;
                sk->sk_data_ready = svc_data_ready;
                sk->sk_write_space = svc_write_space;

                svsk->sk_marker = xdr_zero;
                svsk->sk_tcplen = 0;
                svsk->sk_datalen = 0;
                memset(&svsk->sk_pages[0], 0, sizeof(svsk->sk_pages));

                tcp_sock_set_nodelay(sk);

                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
                switch (sk->sk_state) {
                case TCP_SYN_RECV:
                case TCP_ESTABLISHED:
                        break;
                default:
                        svc_xprt_deferred_close(&svsk->sk_xprt);
                }
        }
}

void svc_sock_update_bufs(struct svc_serv *serv)
{
        /*
         * The number of server threads has changed. Update
         * rcvbuf and sndbuf accordingly on all sockets
         */
        struct svc_sock *svsk;

        spin_lock_bh(&serv->sv_lock);
        list_for_each_entry(svsk, &serv->sv_permsocks, sk_xprt.xpt_list)
                set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags);
        spin_unlock_bh(&serv->sv_lock);
}

/*
 * Initialize socket for RPC use and create svc_sock struct
 */
static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
                                                struct socket *sock,
                                                int flags)
{
        struct svc_sock *svsk;
        struct sock     *inet;
        int             pmap_register = !(flags & SVC_SOCK_ANONYMOUS);

        svsk = kzalloc(sizeof(*svsk), GFP_KERNEL);
        if (!svsk)
                return ERR_PTR(-ENOMEM);

        inet = sock->sk;

        if (pmap_register) {
                int err;

                err = svc_register(serv, sock_net(sock->sk), inet->sk_family,
                                     inet->sk_protocol,
                                     ntohs(inet_sk(inet)->inet_sport));
                if (err < 0) {
                        kfree(svsk);
                        return ERR_PTR(err);
                }
        }

        svsk->sk_sock = sock;
        svsk->sk_sk = inet;
        svsk->sk_ostate = inet->sk_state_change;
        svsk->sk_odata = inet->sk_data_ready;
        svsk->sk_owspace = inet->sk_write_space;
        /*
         * This barrier is necessary in order to prevent race condition
         * with svc_data_ready(), svc_tcp_listen_data_ready(), and others
         * when calling callbacks above.
         */
        wmb();
        inet->sk_user_data = svsk;

        /* Initialize the socket */
        if (sock->type == SOCK_DGRAM)
                svc_udp_init(svsk, serv);
        else
                svc_tcp_init(svsk, serv);

        trace_svcsock_new(svsk, sock);
        return svsk;
}

/**
 * svc_addsock - add a listener socket to an RPC service
 * @serv: pointer to RPC service to which to add a new listener
 * @net: caller's network namespace
 * @fd: file descriptor of the new listener
 * @name_return: pointer to buffer to fill in with name of listener
 * @len: size of the buffer
 * @cred: credential
 *
 * Fills in socket name and returns positive length of name if successful.
 * Name is terminated with '\n'.  On error, returns a negative errno
 * value.
 */
int svc_addsock(struct svc_serv *serv, struct net *net, const int fd,
                char *name_return, const size_t len, const struct cred *cred)
{
        int err = 0;
        struct socket *so = sockfd_lookup(fd, &err);
        struct svc_sock *svsk = NULL;
        struct sockaddr_storage addr;
        struct sockaddr *sin = (struct sockaddr *)&addr;
        int salen;

        if (!so)
                return err;
        err = -EINVAL;
        if (sock_net(so->sk) != net)
                goto out;
        err = -EAFNOSUPPORT;
        if ((so->sk->sk_family != PF_INET) && (so->sk->sk_family != PF_INET6))
                goto out;
        err =  -EPROTONOSUPPORT;
        if (so->sk->sk_protocol != IPPROTO_TCP &&
            so->sk->sk_protocol != IPPROTO_UDP)
                goto out;
        err = -EISCONN;
        if (so->state > SS_UNCONNECTED)
                goto out;
        err = -ENOENT;
        if (!try_module_get(THIS_MODULE))
                goto out;
        svsk = svc_setup_socket(serv, so, SVC_SOCK_DEFAULTS);
        if (IS_ERR(svsk)) {
                module_put(THIS_MODULE);
                err = PTR_ERR(svsk);
                goto out;
        }
        salen = kernel_getsockname(svsk->sk_sock, sin);
        if (salen >= 0)
                svc_xprt_set_local(&svsk->sk_xprt, sin, salen);
        svsk->sk_xprt.xpt_cred = get_cred(cred);
        svc_add_new_perm_xprt(serv, &svsk->sk_xprt);
        return svc_one_sock_name(svsk, name_return, len);
out:
        sockfd_put(so);
        return err;
}
EXPORT_SYMBOL_GPL(svc_addsock);

/*
 * Create socket for RPC service.
 */
static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
                                          int protocol,
                                          struct net *net,
                                          struct sockaddr *sin, int len,
                                          int flags)
{
        struct svc_sock *svsk;
        struct socket   *sock;
        int             error;
        int             type;
        struct sockaddr_storage addr;
        struct sockaddr *newsin = (struct sockaddr *)&addr;
        int             newlen;
        int             family;

        if (protocol != IPPROTO_UDP && protocol != IPPROTO_TCP) {
                printk(KERN_WARNING "svc: only UDP and TCP "
                                "sockets supported\n");
                return ERR_PTR(-EINVAL);
        }

        type = (protocol == IPPROTO_UDP)? SOCK_DGRAM : SOCK_STREAM;
        switch (sin->sa_family) {
        case AF_INET6:
                family = PF_INET6;
                break;
        case AF_INET:
                family = PF_INET;
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        error = __sock_create(net, family, type, protocol, &sock, 1);
        if (error < 0)
                return ERR_PTR(error);

        svc_reclassify_socket(sock);

        /*
         * If this is an PF_INET6 listener, we want to avoid
         * getting requests from IPv4 remotes.  Those should
         * be shunted to a PF_INET listener via rpcbind.
         */
        if (family == PF_INET6)
                ip6_sock_set_v6only(sock->sk);
        if (type == SOCK_STREAM)
                sock->sk->sk_reuse = SK_CAN_REUSE; /* allow address reuse */
        error = kernel_bind(sock, sin, len);
        if (error < 0)
                goto bummer;

        error = kernel_getsockname(sock, newsin);
        if (error < 0)
                goto bummer;
        newlen = error;

        if (protocol == IPPROTO_TCP) {
                __netns_tracker_free(net, &sock->sk->ns_tracker, false);
                sock->sk->sk_net_refcnt = 1;
                get_net_track(net, &sock->sk->ns_tracker, GFP_KERNEL);
                sock_inuse_add(net, 1);
                if ((error = kernel_listen(sock, 64)) < 0)
                        goto bummer;
        }

        svsk = svc_setup_socket(serv, sock, flags);
        if (IS_ERR(svsk)) {
                error = PTR_ERR(svsk);
                goto bummer;
        }
        svc_xprt_set_local(&svsk->sk_xprt, newsin, newlen);
        return (struct svc_xprt *)svsk;
bummer:
        sock_release(sock);
        return ERR_PTR(error);
}

/*
 * Detach the svc_sock from the socket so that no
 * more callbacks occur.
 */
static void svc_sock_detach(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct sock *sk = svsk->sk_sk;

        /* put back the old socket callbacks */
        lock_sock(sk);
        sk->sk_state_change = svsk->sk_ostate;
        sk->sk_data_ready = svsk->sk_odata;
        sk->sk_write_space = svsk->sk_owspace;
        sk->sk_user_data = NULL;
        release_sock(sk);
}

/*
 * Disconnect the socket, and reset the callbacks
 */
static void svc_tcp_sock_detach(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);

        tls_handshake_close(svsk->sk_sock);

        svc_sock_detach(xprt);

        if (!test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
                svc_tcp_clear_pages(svsk);
                kernel_sock_shutdown(svsk->sk_sock, SHUT_RDWR);
        }
}

/*
 * Free the svc_sock's socket resources and the svc_sock itself.
 */
static void svc_sock_free(struct svc_xprt *xprt)
{
        struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
        struct socket *sock = svsk->sk_sock;

        trace_svcsock_free(svsk, sock);

        tls_handshake_cancel(sock->sk);
        if (sock->file)
                sockfd_put(sock);
        else
                sock_release(sock);

        page_frag_cache_drain(&svsk->sk_frag_cache);
        kfree(svsk);
}