8322 nl: misleading-indentation

[unleashed/tickless.git] / usr / src / cmd / cmd-inet / sbin / dhcpagent / packet.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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <string.h>
#include <sys/types.h>
#include <stdlib.h>
#include <dhcpmsg.h>
#include <stddef.h>
#include <assert.h>
#include <search.h>
#include <alloca.h>
#include <limits.h>
#include <stropts.h>
#include <netinet/dhcp6.h>
#include <arpa/inet.h>
#include <sys/sysmacros.h>
#include <sys/sockio.h>
#include <inet/ip6_asp.h>

#include "states.h"
#include "interface.h"
#include "agent.h"
#include "packet.h"
#include "util.h"

int v6_sock_fd = -1;
int v4_sock_fd = -1;

const in6_addr_t ipv6_all_dhcp_relay_and_servers = {
        0xff, 0x02, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00,
        0x00, 0x01, 0x00, 0x02
};

/*
 * We have our own version of this constant because dhcpagent is compiled with
 * -lxnet.
 */
const in6_addr_t my_in6addr_any = IN6ADDR_ANY_INIT;

static void     retransmit(iu_tq_t *, void *);
static void     next_retransmission(dhcp_smach_t *, boolean_t, boolean_t);
static boolean_t send_pkt_internal(dhcp_smach_t *);

/*
 * pkt_send_type(): returns an integer representing the packet's type; only
 *                  for use with outbound packets.
 *
 *   input: dhcp_pkt_t *: the packet to examine
 *  output: uchar_t: the packet type (0 if unknown)
 */

static uchar_t
pkt_send_type(const dhcp_pkt_t *dpkt)
{
        const uchar_t *option;

        if (dpkt->pkt_isv6)
                return (((const dhcpv6_message_t *)dpkt->pkt)->d6m_msg_type);

        /*
         * this is a little dirty but it should get the job done.
         * assumes that the type is in the statically allocated part
         * of the options field.
         */

        option = dpkt->pkt->options;
        for (;;) {
                if (*option == CD_PAD) {
                        option++;
                        continue;
                }
                if (*option == CD_END ||
                    option + 2 - dpkt->pkt->options >=
                    sizeof (dpkt->pkt->options))
                        return (0);
                if (*option == CD_DHCP_TYPE)
                        break;
                option++;
                option += *option + 1;
        }

        return (option[2]);
}

/*
 * pkt_recv_type(): returns an integer representing the packet's type; only
 *                  for use with inbound packets.
 *
 *   input: dhcp_pkt_t *: the packet to examine
 *  output: uchar_t: the packet type (0 if unknown)
 */

uchar_t
pkt_recv_type(const PKT_LIST *plp)
{
        if (plp->isv6)
                return (((const dhcpv6_message_t *)plp->pkt)->d6m_msg_type);
        else if (plp->opts[CD_DHCP_TYPE] != NULL)
                return (plp->opts[CD_DHCP_TYPE]->value[0]);
        else
                return (0);
}

/*
 * pkt_get_xid(): returns transaction ID from a DHCP packet.
 *
 *   input: const PKT *: the packet to examine
 *  output: uint_t: the transaction ID (0 if unknown)
 */

uint_t
pkt_get_xid(const PKT *pkt, boolean_t isv6)
{
        if (pkt == NULL)
                return (0);
        if (isv6)
                return (DHCPV6_GET_TRANSID((const dhcpv6_message_t *)pkt));
        else
                return (pkt->xid);
}

/*
 * init_pkt(): initializes and returns a packet of a given type
 *
 *   input: dhcp_smach_t *: the state machine that will send the packet
 *          uchar_t: the packet type (DHCP message type)
 *  output: dhcp_pkt_t *: a pointer to the initialized packet; may be NULL
 */

dhcp_pkt_t *
init_pkt(dhcp_smach_t *dsmp, uchar_t type)
{
        dhcp_pkt_t      *dpkt = &dsmp->dsm_send_pkt;
        dhcp_lif_t      *lif = dsmp->dsm_lif;
        dhcp_pif_t      *pif = lif->lif_pif;
        uint_t          mtu = lif->lif_max;
        uint32_t        xid;
        boolean_t       isv6;

        dpkt->pkt_isv6 = isv6 = pif->pif_isv6;

        /*
         * Since multiple dhcp leases may be maintained over the same pif
         * (e.g. "hme0" and "hme0:1"), make sure the xid is unique.
         *
         * Note that transaction ID zero is intentionally never assigned.
         * That's used to represent "no ID."  Also note that transaction IDs
         * are only 24 bits long in DHCPv6.
         */

        do {
                xid = mrand48();
                if (isv6)
                        xid &= 0xFFFFFF;
        } while (xid == 0 ||
            lookup_smach_by_xid(xid, NULL, dpkt->pkt_isv6) != NULL);

        if (isv6) {
                dhcpv6_message_t *v6;

                if (mtu != dpkt->pkt_max_len &&
                    (v6 = realloc(dpkt->pkt, mtu)) != NULL) {
                        /* LINTED: alignment known to be correct */
                        dpkt->pkt = (PKT *)v6;
                        dpkt->pkt_max_len = mtu;
                }

                if (sizeof (*v6) > dpkt->pkt_max_len) {
                        dhcpmsg(MSG_ERR, "init_pkt: cannot allocate v6 pkt: %u",
                            mtu);
                        return (NULL);
                }

                v6 = (dhcpv6_message_t *)dpkt->pkt;
                dpkt->pkt_cur_len = sizeof (*v6);

                (void) memset(v6, 0, dpkt->pkt_max_len);

                v6->d6m_msg_type = type;
                DHCPV6_SET_TRANSID(v6, xid);

                if (dsmp->dsm_cidlen > 0 &&
                    add_pkt_opt(dpkt, DHCPV6_OPT_CLIENTID, dsmp->dsm_cid,
                    dsmp->dsm_cidlen) == NULL) {
                        dhcpmsg(MSG_WARNING,
                            "init_pkt: cannot insert client ID");
                        return (NULL);
                }

                /* For v6, time starts with the creation of a transaction */
                dsmp->dsm_neg_hrtime = gethrtime();
                dsmp->dsm_newstart_monosec = monosec();
        } else {
                static uint8_t bootmagic[] = BOOTMAGIC;
                PKT *v4;

                if (mtu != dpkt->pkt_max_len &&
                    (v4 = realloc(dpkt->pkt, mtu)) != NULL) {
                        dpkt->pkt = v4;
                        dpkt->pkt_max_len = mtu;
                }

                if (offsetof(PKT, options) > dpkt->pkt_max_len) {
                        dhcpmsg(MSG_ERR, "init_pkt: cannot allocate v4 pkt: %u",
                            mtu);
                        return (NULL);
                }

                v4 = dpkt->pkt;
                dpkt->pkt_cur_len = offsetof(PKT, options);

                (void) memset(v4, 0, dpkt->pkt_max_len);
                (void) memcpy(v4->cookie, bootmagic, sizeof (bootmagic));
                if (pif->pif_hwlen <= sizeof (v4->chaddr)) {
                        v4->hlen  = pif->pif_hwlen;
                        (void) memcpy(v4->chaddr, pif->pif_hwaddr,
                            pif->pif_hwlen);
                } else {
                        /*
                         * The mac address does not fit in the chaddr
                         * field, thus it can not be sent to the server,
                         * thus server can not unicast the reply. Per
                         * RFC 2131 4.4.1, client can set this bit in
                         * DISCOVER/REQUEST. If the client is already
                         * in a bound state, do not set this bit, as it
                         * can respond to unicast responses from server
                         * using the 'ciaddr' address.
                         */
                        if (type == DISCOVER || (type == REQUEST &&
                            !is_bound_state(dsmp->dsm_state)))
                                v4->flags = htons(BCAST_MASK);
                }

                v4->xid   = xid;
                v4->op    = BOOTREQUEST;
                v4->htype = pif->pif_hwtype;

                if (add_pkt_opt(dpkt, CD_DHCP_TYPE, &type, 1) == NULL) {
                        dhcpmsg(MSG_WARNING,
                            "init_pkt: cannot set DHCP packet type");
                        return (NULL);
                }

                if (dsmp->dsm_cidlen > 0 &&
                    add_pkt_opt(dpkt, CD_CLIENT_ID, dsmp->dsm_cid,
                    dsmp->dsm_cidlen) == NULL) {
                        dhcpmsg(MSG_WARNING,
                            "init_pkt: cannot insert client ID");
                        return (NULL);
                }
        }

        return (dpkt);
}

/*
 * remove_pkt_opt(): removes the first instance of an option from a dhcp_pkt_t
 *
 *   input: dhcp_pkt_t *: the packet to remove the option from
 *          uint_t: the type of option being added
 *  output: boolean_t: B_TRUE on success, B_FALSE on failure
 *    note: currently does not work with DHCPv6 suboptions, or to remove
 *          arbitrary option instances.
 */

boolean_t
remove_pkt_opt(dhcp_pkt_t *dpkt, uint_t opt_type)
{
        uchar_t         *raw_pkt, *raw_end, *next;
        uint_t          len;

        raw_pkt = (uchar_t *)dpkt->pkt;
        raw_end = raw_pkt + dpkt->pkt_cur_len;
        if (dpkt->pkt_isv6) {
                dhcpv6_option_t d6o;

                raw_pkt += sizeof (dhcpv6_message_t);

                opt_type = htons(opt_type);
                while (raw_pkt + sizeof (d6o) <= raw_end) {
                        (void) memcpy(&d6o, raw_pkt, sizeof (d6o));
                        len = ntohs(d6o.d6o_len) + sizeof (d6o);
                        if (len > raw_end - raw_pkt)
                                break;
                        next = raw_pkt + len;
                        if (d6o.d6o_code == opt_type) {
                                if (next < raw_end) {
                                        (void) memmove(raw_pkt, next,
                                            raw_end - next);
                                }
                                dpkt->pkt_cur_len -= len;
                                return (B_TRUE);
                        }
                        raw_pkt = next;
                }
        } else {
                uchar_t *pstart, *padrun;

                raw_pkt += offsetof(PKT, options);
                pstart = raw_pkt;

                if (opt_type == CD_END || opt_type == CD_PAD)
                        return (B_FALSE);

                padrun = NULL;
                while (raw_pkt + 1 <= raw_end) {
                        if (*raw_pkt == CD_END)
                                break;
                        if (*raw_pkt == CD_PAD) {
                                if (padrun == NULL)
                                        padrun = raw_pkt;
                                raw_pkt++;
                                continue;
                        }
                        if (raw_pkt + 2 > raw_end)
                                break;
                        len = raw_pkt[1];
                        if (len > raw_end - raw_pkt || len < 2)
                                break;
                        next = raw_pkt + len;
                        if (*raw_pkt == opt_type) {
                                if (next < raw_end) {
                                        int toadd = (4 + ((next-pstart)&3) -
                                            ((raw_pkt-pstart)&3)) & 3;
                                        int torem = 4 - toadd;

                                        if (torem != 4 && padrun != NULL &&
                                            (raw_pkt - padrun) >= torem) {
                                                raw_pkt -= torem;
                                                dpkt->pkt_cur_len -= torem;
                                        } else if (toadd > 0) {
                                                (void) memset(raw_pkt, CD_PAD,
                                                    toadd);
                                                raw_pkt += toadd;
                                                /* max is not an issue here */
                                                dpkt->pkt_cur_len += toadd;
                                        }
                                        if (raw_pkt != next) {
                                                (void) memmove(raw_pkt, next,
                                                    raw_end - next);
                                        }
                                }
                                dpkt->pkt_cur_len -= len;
                                return (B_TRUE);
                        }
                        padrun = NULL;
                        raw_pkt = next;
                }
        }
        return (B_FALSE);
}

/*
 * update_v6opt_len(): updates the length field of a DHCPv6 option.
 *
 *   input: dhcpv6_option_t *: option to be updated
 *          int: number of octets to add or subtract
 *  output: boolean_t: B_TRUE on success, B_FALSE on failure
 */

boolean_t
update_v6opt_len(dhcpv6_option_t *opt, int adjust)
{
        dhcpv6_option_t optval;

        (void) memcpy(&optval, opt, sizeof (optval));
        adjust += ntohs(optval.d6o_len);
        if (adjust < 0 || adjust > UINT16_MAX) {
                return (B_FALSE);
        } else {
                optval.d6o_len = htons(adjust);
                (void) memcpy(opt, &optval, sizeof (optval));
                return (B_TRUE);
        }
}

/*
 * add_pkt_opt(): adds an option to a dhcp_pkt_t
 *
 *   input: dhcp_pkt_t *: the packet to add the option to
 *          uint_t: the type of option being added
 *          const void *: the value of that option
 *          uint_t: the length of the value of the option
 *  output: void *: pointer to the option that was added, or NULL on failure.
 */

void *
add_pkt_opt(dhcp_pkt_t *dpkt, uint_t opt_type, const void *opt_val,
    uint_t opt_len)
{
        uchar_t         *raw_pkt;
        int             req_len;
        void            *optr;

        raw_pkt = (uchar_t *)dpkt->pkt;
        optr = raw_pkt + dpkt->pkt_cur_len;
        if (dpkt->pkt_isv6) {
                dhcpv6_option_t d6o;

                req_len = opt_len + sizeof (d6o);

                if (dpkt->pkt_cur_len + req_len > dpkt->pkt_max_len) {
                        dhcpmsg(MSG_WARNING,
                            "add_pkt_opt: not enough room for v6 option %u in "
                            "packet (%u + %u > %u)", opt_type,
                            dpkt->pkt_cur_len, req_len, dpkt->pkt_max_len);
                        return (NULL);
                }
                d6o.d6o_code = htons(opt_type);
                d6o.d6o_len = htons(opt_len);
                (void) memcpy(&raw_pkt[dpkt->pkt_cur_len], &d6o, sizeof (d6o));
                dpkt->pkt_cur_len += sizeof (d6o);
                if (opt_len > 0) {
                        (void) memcpy(&raw_pkt[dpkt->pkt_cur_len], opt_val,
                            opt_len);
                        dpkt->pkt_cur_len += opt_len;
                }
        } else {
                req_len = opt_len + 2; /* + 2 for code & length bytes */

                /* CD_END and CD_PAD options don't have a length field */
                if (opt_type == CD_END || opt_type == CD_PAD) {
                        req_len = 1;
                } else if (opt_val == NULL) {
                        dhcpmsg(MSG_ERROR, "add_pkt_opt: option type %d is "
                            "missing required value", opt_type);
                        return (NULL);
                }

                if ((dpkt->pkt_cur_len + req_len) > dpkt->pkt_max_len) {
                        dhcpmsg(MSG_WARNING,
                            "add_pkt_opt: not enough room for v4 option %u in "
                            "packet", opt_type);
                        return (NULL);
                }

                raw_pkt[dpkt->pkt_cur_len++] = opt_type;

                if (req_len > 1) {
                        raw_pkt[dpkt->pkt_cur_len++] = opt_len;
                        if (opt_len > 0) {
                                (void) memcpy(&raw_pkt[dpkt->pkt_cur_len],
                                    opt_val, opt_len);
                                dpkt->pkt_cur_len += opt_len;
                        }
                }
        }
        return (optr);
}

/*
 * add_pkt_subopt(): adds an option to a dhcp_pkt_t option.  DHCPv6-specific,
 *                   but could be extended to IPv4 DHCP if necessary.  Assumes
 *                   that if the parent isn't a top-level option, the caller
 *                   will adjust any upper-level options recursively using
 *                   update_v6opt_len.
 *
 *   input: dhcp_pkt_t *: the packet to add the suboption to
 *          dhcpv6_option_t *: the start of the option to that should contain
 *                             it (parent)
 *          uint_t: the type of suboption being added
 *          const void *: the value of that option
 *          uint_t: the length of the value of the option
 *  output: void *: pointer to the suboption that was added, or NULL on
 *                  failure.
 */

void *
add_pkt_subopt(dhcp_pkt_t *dpkt, dhcpv6_option_t *parentopt, uint_t opt_type,
    const void *opt_val, uint_t opt_len)
{
        uchar_t         *raw_pkt;
        int             req_len;
        void            *optr;
        dhcpv6_option_t d6o;
        uchar_t         *optend;
        int             olen;

        if (!dpkt->pkt_isv6)
                return (NULL);

        raw_pkt = (uchar_t *)dpkt->pkt;
        req_len = opt_len + sizeof (d6o);

        if (dpkt->pkt_cur_len + req_len > dpkt->pkt_max_len) {
                dhcpmsg(MSG_WARNING,
                    "add_pkt_subopt: not enough room for v6 suboption %u in "
                    "packet (%u + %u > %u)", opt_type,
                    dpkt->pkt_cur_len, req_len, dpkt->pkt_max_len);
                return (NULL);
        }

        /*
         * Update the parent option to include room for this option,
         * and compute the insertion point.
         */
        (void) memcpy(&d6o, parentopt, sizeof (d6o));
        olen = ntohs(d6o.d6o_len);
        optend = (uchar_t *)(parentopt + 1) + olen;
        olen += req_len;
        d6o.d6o_len = htons(olen);
        (void) memcpy(parentopt, &d6o, sizeof (d6o));

        /*
         * If there's anything at the end to move, then move it.  Also bump up
         * the packet size.
         */
        if (optend < raw_pkt + dpkt->pkt_cur_len) {
                (void) memmove(optend + req_len, optend,
                    (raw_pkt + dpkt->pkt_cur_len) - optend);
        }
        dpkt->pkt_cur_len += req_len;

        /*
         * Now format the suboption and add it in.
         */
        optr = optend;
        d6o.d6o_code = htons(opt_type);
        d6o.d6o_len = htons(opt_len);
        (void) memcpy(optend, &d6o, sizeof (d6o));
        if (opt_len > 0)
                (void) memcpy(optend + sizeof (d6o), opt_val, opt_len);
        return (optr);
}

/*
 * add_pkt_opt16(): adds an option with a 16-bit value to a dhcp_pkt_t
 *
 *   input: dhcp_pkt_t *: the packet to add the option to
 *          uint_t: the type of option being added
 *          uint16_t: the value of that option
 *  output: void *: pointer to the option that was added, or NULL on failure.
 */

void *
add_pkt_opt16(dhcp_pkt_t *dpkt, uint_t opt_type, uint16_t opt_value)
{
        return (add_pkt_opt(dpkt, opt_type, &opt_value, 2));
}

/*
 * add_pkt_opt32(): adds an option with a 32-bit value to a dhcp_pkt_t
 *
 *   input: dhcp_pkt_t *: the packet to add the option to
 *          uint_t: the type of option being added
 *          uint32_t: the value of that option
 *  output: void *: pointer to the option that was added, or NULL on failure.
 */

void *
add_pkt_opt32(dhcp_pkt_t *dpkt, uint_t opt_type, uint32_t opt_value)
{
        return (add_pkt_opt(dpkt, opt_type, &opt_value, 4));
}

/*
 * add_pkt_prl(): adds the parameter request option to the packet
 *
 *   input: dhcp_pkt_t *: the packet to add the option to
 *          dhcp_smach_t *: state machine with request option
 *  output: void *: pointer to the option that was added, or NULL on failure.
 */

void *
add_pkt_prl(dhcp_pkt_t *dpkt, dhcp_smach_t *dsmp)
{
        uint_t len;

        if (dsmp->dsm_prllen == 0)
                return (0);

        if (dpkt->pkt_isv6) {
                uint16_t *prl;

                /*
                 * RFC 3315 requires that we include the option, even if we
                 * have nothing to request.
                 */
                if (dsmp->dsm_prllen == 0)
                        prl = NULL;
                else
                        prl = alloca(dsmp->dsm_prllen * sizeof (uint16_t));

                for (len = 0; len < dsmp->dsm_prllen; len++)
                        prl[len] = htons(dsmp->dsm_prl[len]);
                return (add_pkt_opt(dpkt, DHCPV6_OPT_ORO, prl,
                    len * sizeof (uint16_t)));
        } else {
                uint8_t *prl = alloca(dsmp->dsm_prllen);

                for (len = 0; len < dsmp->dsm_prllen; len++)
                        prl[len] = dsmp->dsm_prl[len];
                return (add_pkt_opt(dpkt, CD_REQUEST_LIST, prl, len));
        }
}

/*
 * add_pkt_lif(): Adds CD_REQUESTED_IP_ADDR (IPv4 DHCP) or IA_NA and IAADDR
 *                (DHCPv6) options to the packet to represent the given LIF.
 *
 *   input: dhcp_pkt_t *: the packet to add the options to
 *          dhcp_lif_t *: the logical interface to represent
 *          int: status code (unused for IPv4 DHCP)
 *          const char *: message to include with status option, or NULL
 *  output: boolean_t: B_TRUE on success, B_FALSE on failure
 */

boolean_t
add_pkt_lif(dhcp_pkt_t *dpkt, dhcp_lif_t *lif, int status, const char *msg)
{
        if (lif->lif_pif->pif_isv6) {
                dhcp_smach_t *dsmp;
                dhcpv6_message_t *d6m;
                dhcpv6_ia_na_t d6in;
                dhcpv6_iaaddr_t d6ia;
                uint32_t iaid;
                uint16_t *statusopt;
                dhcpv6_option_t *d6o, *d6so;
                uint_t olen;

                /*
                 * Currently, we support just one IAID related to the primary
                 * LIF on the state machine.
                 */
                dsmp = lif->lif_lease->dl_smach;
                iaid = dsmp->dsm_lif->lif_iaid;
                iaid = htonl(iaid);

                d6m = (dhcpv6_message_t *)dpkt->pkt;

                /*
                 * Find or create the IA_NA needed for this LIF.  If we
                 * supported IA_TA, we'd check the IFF_TEMPORARY bit here.
                 */
                d6o = NULL;
                while ((d6o = dhcpv6_find_option(d6m + 1,
                    dpkt->pkt_cur_len - sizeof (*d6m), d6o, DHCPV6_OPT_IA_NA,
                    &olen)) != NULL) {
                        if (olen < sizeof (d6in))
                                continue;
                        (void) memcpy(&d6in, d6o, sizeof (d6in));
                        if (d6in.d6in_iaid == iaid)
                                break;
                }
                if (d6o == NULL) {
                        d6in.d6in_iaid = iaid;
                        d6in.d6in_t1 = 0;
                        d6in.d6in_t2 = 0;
                        d6o = add_pkt_opt(dpkt, DHCPV6_OPT_IA_NA,
                            (dhcpv6_option_t *)&d6in + 1,
                            sizeof (d6in) - sizeof (*d6o));
                        if (d6o == NULL)
                                return (B_FALSE);
                }

                /*
                 * Now add the IAADDR suboption for this LIF.  No need to
                 * search here, as we know that this is unique.
                 */
                d6ia.d6ia_addr = lif->lif_v6addr;

                /*
                 * For Release and Decline, we zero out the lifetime.  For
                 * Renew and Rebind, we report the original time as the
                 * preferred and valid lifetimes.
                 */
                if (d6m->d6m_msg_type == DHCPV6_MSG_RELEASE ||
                    d6m->d6m_msg_type == DHCPV6_MSG_DECLINE) {
                        d6ia.d6ia_preflife = 0;
                        d6ia.d6ia_vallife = 0;
                } else {
                        d6ia.d6ia_preflife = htonl(lif->lif_preferred.dt_start);
                        d6ia.d6ia_vallife = htonl(lif->lif_expire.dt_start);
                }
                d6so = add_pkt_subopt(dpkt, d6o, DHCPV6_OPT_IAADDR,
                    (dhcpv6_option_t *)&d6ia + 1,
                    sizeof (d6ia) - sizeof (*d6o));
                if (d6so == NULL)
                        return (B_FALSE);

                /*
                 * Add a status code suboption to the IAADDR to tell the server
                 * why we're declining the address.  Note that we must manually
                 * update the enclosing IA_NA, as add_pkt_subopt doesn't know
                 * how to do that.
                 */
                if (status != DHCPV6_STAT_SUCCESS || msg != NULL) {
                        olen = sizeof (*statusopt) +
                            (msg == NULL ? 0 : strlen(msg));
                        statusopt = alloca(olen);
                        *statusopt = htons(status);
                        if (msg != NULL) {
                                (void) memcpy((char *)(statusopt + 1), msg,
                                    olen - sizeof (*statusopt));
                        }
                        d6so = add_pkt_subopt(dpkt, d6so,
                            DHCPV6_OPT_STATUS_CODE, statusopt, olen);
                        if (d6so != NULL) {
                                /*
                                 * Update for length of suboption header and
                                 * suboption contents.
                                 */
                                (void) update_v6opt_len(d6o, sizeof (*d6so) +
                                    olen);
                        }
                }
        } else {
                /*
                 * For DECLINE, we need to add the CD_REQUESTED_IP_ADDR option.
                 * In all other cases (RELEASE and REQUEST), we need to set
                 * ciadr.
                 */
                if (pkt_send_type(dpkt) == DECLINE) {
                        if (!add_pkt_opt32(dpkt, CD_REQUESTED_IP_ADDR,
                            lif->lif_addr))
                                return (B_FALSE);
                } else {
                        dpkt->pkt->ciaddr.s_addr = lif->lif_addr;
                }

                /*
                 * It's not too worrisome if the message fails to fit in the
                 * packet.  The result will still be valid.
                 */
                if (msg != NULL)
                        (void) add_pkt_opt(dpkt, CD_MESSAGE, msg,
                            strlen(msg) + 1);
        }
        return (B_TRUE);
}

/*
 * free_pkt_entry(): frees a packet list list entry
 *
 *   input: PKT_LIST *: the packet list entry to free
 *  output: void
 */
void
free_pkt_entry(PKT_LIST *plp)
{
        if (plp != NULL) {
                free(plp->pkt);
                free(plp);
        }
}

/*
 * free_pkt_list(): frees an entire packet list
 *
 *   input: PKT_LIST **: the packet list to free
 *  output: void
 */

void
free_pkt_list(PKT_LIST **head)
{
        PKT_LIST *plp;

        while ((plp = *head) != NULL) {
                remque(plp);
                free_pkt_entry(plp);
        }
}

/*
 * send_pkt_internal(): sends a packet out on an interface
 *
 *   input: dhcp_smach_t *: the state machine with a packet to send
 *  output: boolean_t: B_TRUE if the packet is sent, B_FALSE otherwise
 */

static boolean_t
send_pkt_internal(dhcp_smach_t *dsmp)
{
        ssize_t         n_bytes;
        dhcp_lif_t      *lif = dsmp->dsm_lif;
        dhcp_pkt_t      *dpkt = &dsmp->dsm_send_pkt;
        uchar_t         ptype = pkt_send_type(dpkt);
        const char      *pkt_name;
        struct iovec    iov;
        struct msghdr   msg;
        struct cmsghdr  *cmsg;
        struct in6_pktinfo *ipi6;
        boolean_t       ismcast;
        int             msgtype;

        /*
         * Timer should not be running at the point we go to send a packet.
         */
        if (dsmp->dsm_retrans_timer != -1) {
                dhcpmsg(MSG_CRIT, "send_pkt_internal: unexpected retransmit "
                    "timer on %s", dsmp->dsm_name);
                stop_pkt_retransmission(dsmp);
        }

        pkt_name = pkt_type_to_string(ptype, dpkt->pkt_isv6);

        /*
         * if needed, schedule a retransmission timer, then attempt to
         * send the packet.  if we fail, then log the error.  our
         * return value should indicate whether or not we were
         * successful in sending the request, independent of whether
         * we could schedule a timer.
         */

        if (dsmp->dsm_send_timeout != 0) {
                if ((dsmp->dsm_retrans_timer = iu_schedule_timer_ms(tq,
                    dsmp->dsm_send_timeout, retransmit, dsmp)) == -1)
                        dhcpmsg(MSG_WARNING, "send_pkt_internal: cannot "
                            "schedule retransmit timer for %s packet",
                            pkt_name);
                else
                        hold_smach(dsmp);
        }

        if (dpkt->pkt_isv6) {
                hrtime_t delta;

                /*
                 * Convert current time into centiseconds since transaction
                 * started.  This is what DHCPv6 expects to see in the Elapsed
                 * Time option.
                 */
                delta = (gethrtime() - dsmp->dsm_neg_hrtime) /
                    (NANOSEC / 100);
                if (delta > DHCPV6_FOREVER)
                        delta = DHCPV6_FOREVER;
                (void) remove_pkt_opt(dpkt, DHCPV6_OPT_ELAPSED_TIME);
                (void) add_pkt_opt16(dpkt, DHCPV6_OPT_ELAPSED_TIME,
                    htons(delta));
        } else {
                /*
                 * set the `pkt->secs' field depending on the type of packet.
                 * it should be zero, except in the following cases:
                 *
                 * DISCOVER:    set to the number of seconds since we started
                 *              trying to obtain a lease.
                 *
                 * INFORM:      set to the number of seconds since we started
                 *              trying to get configuration parameters.
                 *
                 * REQUEST:     if in the REQUESTING state, then same value as
                 *              DISCOVER, otherwise the number of seconds
                 *              since we started trying to obtain a lease.
                 *
                 * we also set `dsm_newstart_monosec', to the time we sent a
                 * REQUEST or DISCOVER packet, so we know the lease start
                 * time (the DISCOVER case is for handling BOOTP servers).
                 */

                switch (ptype) {

                case DISCOVER:
                        dsmp->dsm_newstart_monosec = monosec();
                        dsmp->dsm_disc_secs = dsmp->dsm_newstart_monosec -
                            hrtime_to_monosec(dsmp->dsm_neg_hrtime);
                        dpkt->pkt->secs = htons(dsmp->dsm_disc_secs);
                        break;

                case INFORM:
                        dpkt->pkt->secs = htons(monosec() -
                            hrtime_to_monosec(dsmp->dsm_neg_hrtime));
                        break;

                case REQUEST:
                        dsmp->dsm_newstart_monosec = monosec();

                        if (dsmp->dsm_state == REQUESTING) {
                                dpkt->pkt->secs = htons(dsmp->dsm_disc_secs);
                                break;
                        }

                        dpkt->pkt->secs = htons(monosec() -
                            hrtime_to_monosec(dsmp->dsm_neg_hrtime));
                        break;

                default:
                        dpkt->pkt->secs = htons(0);
                        break;
                }
        }

        if (dpkt->pkt_isv6) {
                struct sockaddr_in6 sin6;

                (void) memset(&iov, 0, sizeof (iov));
                iov.iov_base = dpkt->pkt;
                iov.iov_len = dpkt->pkt_cur_len;

                (void) memset(&msg, 0, sizeof (msg));
                msg.msg_name = &dsmp->dsm_send_dest.v6;
                msg.msg_namelen = sizeof (struct sockaddr_in6);
                msg.msg_iov = &iov;
                msg.msg_iovlen = 1;

                /*
                 * If the address that's requested cannot be reached, then fall
                 * back to the multcast address.
                 */
                if (IN6_IS_ADDR_MULTICAST(&dsmp->dsm_send_dest.v6.sin6_addr)) {
                        ismcast = B_TRUE;
                } else {
                        struct dstinforeq dinfo;
                        struct strioctl str;

                        ismcast = B_FALSE;
                        (void) memset(&dinfo, 0, sizeof (dinfo));
                        dinfo.dir_daddr = dsmp->dsm_send_dest.v6.sin6_addr;
                        str.ic_cmd = SIOCGDSTINFO;
                        str.ic_timout = 0;
                        str.ic_len = sizeof (dinfo);
                        str.ic_dp = (char *)&dinfo;
                        if (ioctl(v6_sock_fd, I_STR, &str) == -1) {
                                dhcpmsg(MSG_ERR,
                                    "send_pkt_internal: ioctl SIOCGDSTINFO");
                        } else if (!dinfo.dir_dreachable) {
                                char abuf[INET6_ADDRSTRLEN];

                                dhcpmsg(MSG_DEBUG, "send_pkt_internal: %s is "
                                    "not reachable; using multicast instead",
                                    inet_ntop(AF_INET6, &dinfo.dir_daddr, abuf,
                                    sizeof (abuf)));
                                sin6 = dsmp->dsm_send_dest.v6;
                                sin6.sin6_addr =
                                    ipv6_all_dhcp_relay_and_servers;
                                msg.msg_name = &sin6;
                                ismcast = B_TRUE;
                        }
                }

                /*
                 * Make room for our ancillary data option as well as a dummy
                 * option used by CMSG_NXTHDR.
                 */
                msg.msg_controllen = sizeof (*cmsg) + _MAX_ALIGNMENT +
                    sizeof (*ipi6) + _MAX_ALIGNMENT + sizeof (*cmsg);
                msg.msg_control = alloca(msg.msg_controllen);
                cmsg = CMSG_FIRSTHDR(&msg);
                cmsg->cmsg_level = IPPROTO_IPV6;
                cmsg->cmsg_type = IPV6_PKTINFO;
                /* LINTED: alignment */
                ipi6 = (struct in6_pktinfo *)CMSG_DATA(cmsg);
                if (ismcast)
                        ipi6->ipi6_addr = lif->lif_v6addr;
                else
                        ipi6->ipi6_addr = my_in6addr_any;
                if (lif->lif_pif->pif_under_ipmp)
                        ipi6->ipi6_ifindex = lif->lif_pif->pif_grindex;
                else
                        ipi6->ipi6_ifindex = lif->lif_pif->pif_index;
                cmsg->cmsg_len = (char *)(ipi6 + 1) - (char *)cmsg;

                /*
                 * Now correct the control message length.
                 */
                cmsg = CMSG_NXTHDR(&msg, cmsg);
                msg.msg_controllen = (char *)cmsg - (char *)msg.msg_control;

                n_bytes = sendmsg(v6_sock_fd, &msg, 0);
        } else {
                n_bytes = sendto(lif->lif_sock_ip_fd, dpkt->pkt,
                    dpkt->pkt_cur_len, 0,
                    (struct sockaddr *)&dsmp->dsm_send_dest.v4,
                    sizeof (struct sockaddr_in));
        }

        if (n_bytes != dpkt->pkt_cur_len) {
                msgtype = (n_bytes == -1) ? MSG_ERR : MSG_WARNING;
                if (dsmp->dsm_retrans_timer == -1)
                        dhcpmsg(msgtype, "send_pkt_internal: cannot send "
                            "%s packet to server", pkt_name);
                else
                        dhcpmsg(msgtype, "send_pkt_internal: cannot send "
                            "%s packet to server (will retry in %u seconds)",
                            pkt_name, dsmp->dsm_send_timeout / MILLISEC);
                return (B_FALSE);
        }

        dhcpmsg(MSG_VERBOSE, "sent %s xid %x packet out %s", pkt_name,
            pkt_get_xid(dpkt->pkt, dpkt->pkt_isv6), dsmp->dsm_name);

        dsmp->dsm_packet_sent++;
        dsmp->dsm_sent++;
        return (B_TRUE);
}

/*
 * send_pkt(): sends a packet out
 *
 *   input: dhcp_smach_t *: the state machine sending the packet
 *          dhcp_pkt_t *: the packet to send out
 *          in_addr_t: the destination IP address for the packet
 *          stop_func_t *: a pointer to function to indicate when to stop
 *                         retransmitting the packet (if NULL, packet is
 *                         not retransmitted)
 *  output: boolean_t: B_TRUE if the packet was sent, B_FALSE otherwise
 */

boolean_t
send_pkt(dhcp_smach_t *dsmp, dhcp_pkt_t *dpkt, in_addr_t dest,
    stop_func_t *stop)
{
        /*
         * packets must be at least sizeof (PKT) or they may be dropped
         * by routers.  pad out the packet in this case.
         */

        dpkt->pkt_cur_len = MAX(dpkt->pkt_cur_len, sizeof (PKT));

        dsmp->dsm_packet_sent = 0;

        (void) memset(&dsmp->dsm_send_dest.v4, 0,
            sizeof (dsmp->dsm_send_dest.v4));
        dsmp->dsm_send_dest.v4.sin_addr.s_addr  = dest;
        dsmp->dsm_send_dest.v4.sin_family       = AF_INET;
        dsmp->dsm_send_dest.v4.sin_port         = htons(IPPORT_BOOTPS);
        dsmp->dsm_send_stop_func                = stop;

        /*
         * TODO: dispose of this gruesome assumption (there's no real
         * technical gain from doing so, but it would be cleaner)
         */

        assert(dpkt == &dsmp->dsm_send_pkt);

        /*
         * clear out any packets which had been previously received
         * but not pulled off of the recv_packet queue.
         */

        free_pkt_list(&dsmp->dsm_recv_pkt_list);

        if (stop == NULL)
                dsmp->dsm_send_timeout = 0;     /* prevents retransmissions */
        else
                next_retransmission(dsmp, B_TRUE, B_FALSE);

        return (send_pkt_internal(dsmp));
}

/*
 * send_pkt_v6(): sends a DHCPv6 packet out
 *
 *   input: dhcp_smach_t *: the state machine sending the packet
 *          dhcp_pkt_t *: the packet to send out
 *          in6_addr_t: the destination IPv6 address for the packet
 *          stop_func_t *: a pointer to function to indicate when to stop
 *                         retransmitting the packet (if NULL, packet is
 *                         not retransmitted)
 *          uint_t: Initial Retransmit Timer value
 *          uint_t: Maximum Retransmit Timer value, zero if none
 *  output: boolean_t: B_TRUE if the packet was sent, B_FALSE otherwise
 */

boolean_t
send_pkt_v6(dhcp_smach_t *dsmp, dhcp_pkt_t *dpkt, in6_addr_t dest,
    stop_func_t *stop, uint_t irt, uint_t mrt)
{
        dsmp->dsm_packet_sent = 0;

        (void) memset(&dsmp->dsm_send_dest.v6, 0,
            sizeof (dsmp->dsm_send_dest.v6));
        dsmp->dsm_send_dest.v6.sin6_addr        = dest;
        dsmp->dsm_send_dest.v6.sin6_family      = AF_INET6;
        dsmp->dsm_send_dest.v6.sin6_port        = htons(IPPORT_DHCPV6S);
        dsmp->dsm_send_stop_func                = stop;

        /*
         * TODO: dispose of this gruesome assumption (there's no real
         * technical gain from doing so, but it would be cleaner)
         */

        assert(dpkt == &dsmp->dsm_send_pkt);

        /*
         * clear out any packets which had been previously received
         * but not pulled off of the recv_packet queue.
         */

        free_pkt_list(&dsmp->dsm_recv_pkt_list);

        if (stop == NULL) {
                dsmp->dsm_send_timeout = 0;     /* prevents retransmissions */
        } else {
                dsmp->dsm_send_timeout = irt;
                dsmp->dsm_send_tcenter = mrt;
                /*
                 * This is quite ugly, but RFC 3315 section 17.1.2 requires
                 * that the RAND value for the very first retransmission of a
                 * Solicit message is strictly greater than zero.
                 */
                next_retransmission(dsmp, B_TRUE,
                    pkt_send_type(dpkt) == DHCPV6_MSG_SOLICIT);
        }

        return (send_pkt_internal(dsmp));
}

/*
 * retransmit(): retransmits the current packet on an interface
 *
 *   input: iu_tq_t *: unused
 *          void *: the dhcp_smach_t * (state machine) sending a packet
 *  output: void
 */

/* ARGSUSED */
static void
retransmit(iu_tq_t *tqp, void *arg)
{
        dhcp_smach_t    *dsmp = arg;

        dsmp->dsm_retrans_timer = -1;

        if (!verify_smach(dsmp))
                return;

        /*
         * Check the callback to see if we should keep sending retransmissions.
         * Compute the next retransmission time first, so that the callback can
         * cap the value if need be.  (Required for DHCPv6 Confirm messages.)
         *
         * Hold the state machine across the callback so that the called
         * function can remove the state machine from the system without
         * disturbing the string used subsequently for verbose logging.  The
         * Release function destroys the state machine when the retry count
         * expires.
         */

        next_retransmission(dsmp, B_FALSE, B_FALSE);
        hold_smach(dsmp);
        if (dsmp->dsm_send_stop_func(dsmp, dsmp->dsm_packet_sent)) {
                dhcpmsg(MSG_VERBOSE, "retransmit: time to stop on %s",
                    dsmp->dsm_name);
        } else {
                dhcpmsg(MSG_VERBOSE, "retransmit: sending another on %s",
                    dsmp->dsm_name);
                (void) send_pkt_internal(dsmp);
        }
        release_smach(dsmp);
}

/*
 * stop_pkt_retransmission(): stops retransmission of last sent packet
 *
 *   input: dhcp_smach_t *: the state machine to stop retransmission on
 *  output: void
 */

void
stop_pkt_retransmission(dhcp_smach_t *dsmp)
{
        if (dsmp->dsm_retrans_timer != -1 &&
            iu_cancel_timer(tq, dsmp->dsm_retrans_timer, NULL) == 1) {
                dhcpmsg(MSG_VERBOSE, "stop_pkt_retransmission: stopped on %s",
                    dsmp->dsm_name);
                dsmp->dsm_retrans_timer = -1;
                release_smach(dsmp);
        }
}

/*
 * retransmit_now(): force a packet retransmission right now.  Used only with
 *                   the DHCPv6 UseMulticast status code.  Use with caution;
 *                   triggered retransmissions can cause packet storms.
 *
 *   input: dhcp_smach_t *: the state machine to force retransmission on
 *  output: void
 */

void
retransmit_now(dhcp_smach_t *dsmp)
{
        stop_pkt_retransmission(dsmp);
        (void) send_pkt_internal(dsmp);
}

/*
 * alloc_pkt_entry(): Allocates a packet list entry with a given data area
 *                    size.
 *
 *   input: size_t: size of data area for packet
 *          boolean_t: B_TRUE for IPv6
 *  output: PKT_LIST *: allocated packet list entry
 */

PKT_LIST *
alloc_pkt_entry(size_t psize, boolean_t isv6)
{
        PKT_LIST        *plp;

        if ((plp = calloc(1, sizeof (*plp))) == NULL ||
            (plp->pkt = malloc(psize)) == NULL) {
                free(plp);
                plp = NULL;
        } else {
                plp->len = psize;
                plp->isv6 = isv6;
        }

        return (plp);
}

/*
 * sock_recvpkt(): read from the given socket into an allocated buffer and
 *                 handles any ancillary data options.
 *
 *   input: int: file descriptor to read
 *          PKT_LIST *: allocated buffer
 *  output: ssize_t: number of bytes read, or -1 on error
 */

static ssize_t
sock_recvpkt(int fd, PKT_LIST *plp)
{
        struct iovec iov;
        struct msghdr msg;
        int64_t ctrl[8192 / sizeof (int64_t)];
        ssize_t msglen;

        (void) memset(&iov, 0, sizeof (iov));
        iov.iov_base = (caddr_t)plp->pkt;
        iov.iov_len = plp->len;

        (void) memset(&msg, 0, sizeof (msg));
        msg.msg_name = &plp->pktfrom;
        msg.msg_namelen = sizeof (plp->pktfrom);
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        msg.msg_control = ctrl;
        msg.msg_controllen = sizeof (ctrl);

        if ((msglen = recvmsg(fd, &msg, 0)) != -1) {
                struct cmsghdr *cmsg;

                for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
                    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
                        struct sockaddr_in *sinp;
                        struct sockaddr_in6 *sin6;
                        struct in6_pktinfo *ipi6;

                        switch (cmsg->cmsg_level) {
                        case IPPROTO_IP:
                                switch (cmsg->cmsg_type) {
                                case IP_RECVDSTADDR:
                                        sinp = (struct sockaddr_in *)
                                            &plp->pktto;
                                        sinp->sin_family = AF_INET;
                                        (void) memcpy(&sinp->sin_addr.s_addr,
                                            CMSG_DATA(cmsg),
                                            sizeof (ipaddr_t));
                                        break;

                                case IP_RECVIF:
                                        (void) memcpy(&plp->ifindex,
                                            CMSG_DATA(cmsg), sizeof (uint_t));
                                        break;
                                }
                                break;

                        case IPPROTO_IPV6:
                                switch (cmsg->cmsg_type) {
                                case IPV6_PKTINFO:
                                        /* LINTED: alignment */
                                        ipi6 = (struct in6_pktinfo *)
                                            CMSG_DATA(cmsg);
                                        sin6 = (struct sockaddr_in6 *)
                                            &plp->pktto;
                                        sin6->sin6_family = AF_INET6;
                                        (void) memcpy(&sin6->sin6_addr,
                                            &ipi6->ipi6_addr,
                                            sizeof (ipi6->ipi6_addr));
                                        (void) memcpy(&plp->ifindex,
                                            &ipi6->ipi6_ifindex,
                                            sizeof (uint_t));
                                        break;
                                }
                        }
                }
        }
        return (msglen);
}

/*
 * recv_pkt(): receives a single DHCP packet on a given file descriptor.
 *
 *   input: int: the file descriptor to receive the packet from
 *          int: the maximum packet size to allow
 *          boolean_t: B_TRUE for IPv6
 *  output: PKT_LIST *: the received packet
 */

PKT_LIST *
recv_pkt(int fd, int mtu, boolean_t isv6)
{
        PKT_LIST        *plp;
        ssize_t         retval;

        if ((plp = alloc_pkt_entry(mtu, isv6)) == NULL) {
                dhcpmsg(MSG_ERROR,
                    "recv_pkt: allocation failure; dropped packet");
                return (NULL);
        }

        retval = sock_recvpkt(fd, plp);
        if (retval == -1) {
                dhcpmsg(MSG_ERR, "recv_pkt: recvfrom v%d failed, dropped",
                    isv6 ? 6 : 4);
                goto failure;
        }

        plp->len = retval;

        if (isv6) {
                if (retval < sizeof (dhcpv6_message_t)) {
                        dhcpmsg(MSG_WARNING, "recv_pkt: runt message");
                        goto failure;
                }
        } else {
                switch (dhcp_options_scan(plp, B_TRUE)) {

                case DHCP_WRONG_MSG_TYPE:
                        dhcpmsg(MSG_WARNING,
                            "recv_pkt: unexpected DHCP message");
                        goto failure;

                case DHCP_GARBLED_MSG_TYPE:
                        dhcpmsg(MSG_WARNING,
                            "recv_pkt: garbled DHCP message type");
                        goto failure;

                case DHCP_BAD_OPT_OVLD:
                        dhcpmsg(MSG_WARNING, "recv_pkt: bad option overload");
                        goto failure;

                case 0:
                        break;

                default:
                        dhcpmsg(MSG_WARNING,
                            "recv_pkt: packet corrupted, dropped");
                        goto failure;
                }
        }
        return (plp);

failure:
        free_pkt_entry(plp);
        return (NULL);
}

/*
 * pkt_v4_match(): check if a given DHCPv4 message type is in a given set
 *
 *   input: uchar_t: packet type
 *          dhcp_message_type_t: bit-wise OR of DHCP_P* values.
 *  output: boolean_t: B_TRUE if packet type is in the set
 */

boolean_t
pkt_v4_match(uchar_t type, dhcp_message_type_t match_type)
{
        /*
         * note: the ordering here allows direct indexing of the table
         *       based on the RFC2131 packet type value passed in.
         */

        static dhcp_message_type_t type_map[] = {
                DHCP_PUNTYPED, DHCP_PDISCOVER, DHCP_POFFER, DHCP_PREQUEST,
                DHCP_PDECLINE, DHCP_PACK, DHCP_PNAK, DHCP_PRELEASE,
                DHCP_PINFORM
        };

        if (type < (sizeof (type_map) / sizeof (*type_map)))
                return ((type_map[type] & match_type) ? B_TRUE : B_FALSE);
        else
                return (B_FALSE);
}

/*
 * pkt_smach_enqueue(): enqueue a packet on a given state machine
 *
 *   input: dhcp_smach_t: state machine
 *          PKT_LIST *: packet to enqueue
 *  output: none
 */

void
pkt_smach_enqueue(dhcp_smach_t *dsmp, PKT_LIST *plp)
{
        dhcpmsg(MSG_VERBOSE, "pkt_smach_enqueue: received %s %s packet on %s",
            pkt_type_to_string(pkt_recv_type(plp), dsmp->dsm_isv6),
            dsmp->dsm_isv6 ? "v6" : "v4", dsmp->dsm_name);

        /* add to front of list */
        insque(plp, &dsmp->dsm_recv_pkt_list);
}

/*
 * next_retransmission(): computes the number of seconds until the next
 *                        retransmission, based on the algorithms in RFCs 2131
 *                        3315.
 *
 *   input: dhcp_smach_t *: state machine that needs a new timer
 *          boolean_t: B_TRUE if this is the first time sending the message
 *          boolean_t: B_TRUE for positive RAND values only (RFC 3315 17.1.2)
 *  output: none
 */

static void
next_retransmission(dhcp_smach_t *dsmp, boolean_t first_send,
    boolean_t positive_only)
{
        uint32_t timeout_ms;

        if (dsmp->dsm_isv6) {
                double randval;

                /*
                 * The RFC specifies 0 to 10% jitter for the initial
                 * solicitation, and plus or minus 10% jitter for all others.
                 * This works out to 100 milliseconds on the shortest timer we
                 * use.
                 */
                if (positive_only)
                        randval = drand48() / 10.0;
                else
                        randval = (drand48() - 0.5) / 5.0;

                /* The RFC specifies doubling *after* the first transmission */
                timeout_ms = dsmp->dsm_send_timeout;
                if (!first_send)
                        timeout_ms *= 2;
                timeout_ms += (int)(randval * dsmp->dsm_send_timeout);

                /* This checks the MRT (maximum retransmission time) */
                if (dsmp->dsm_send_tcenter != 0 &&
                    timeout_ms > dsmp->dsm_send_tcenter) {
                        timeout_ms = dsmp->dsm_send_tcenter +
                            (uint_t)(randval * dsmp->dsm_send_tcenter);
                }

                dsmp->dsm_send_timeout = timeout_ms;
        } else {
                if (dsmp->dsm_state == RENEWING ||
                    dsmp->dsm_state == REBINDING) {
                        monosec_t mono;

                        timeout_ms = dsmp->dsm_state == RENEWING ?
                            dsmp->dsm_leases->dl_t2.dt_start :
                            dsmp->dsm_leases->dl_lifs->lif_expire.dt_start;
                        timeout_ms += dsmp->dsm_curstart_monosec;
                        mono = monosec();
                        if (mono > timeout_ms)
                                timeout_ms = 0;
                        else
                                timeout_ms -= mono;
                        timeout_ms *= MILLISEC / 2;
                } else {
                        /*
                         * Start at 4, and increase by a factor of 2 up to 64.
                         */
                        if (first_send) {
                                timeout_ms = 4 * MILLISEC;
                        } else {
                                timeout_ms = MIN(dsmp->dsm_send_tcenter << 1,
                                    64 * MILLISEC);
                        }
                }

                dsmp->dsm_send_tcenter = timeout_ms;

                /*
                 * At each iteration, jitter the timeout by some fraction of a
                 * second.
                 */
                dsmp->dsm_send_timeout = timeout_ms +
                    ((lrand48() % (2 * MILLISEC)) - MILLISEC);
        }
}

/*
 * dhcp_ip_default(): open and bind the default IP sockets used for I/O and
 *                    interface control.
 *
 *   input: none
 *  output: B_TRUE on success
 */

boolean_t
dhcp_ip_default(void)
{
        int on = 1;

        if ((v4_sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
                dhcpmsg(MSG_ERR,
                    "dhcp_ip_default: unable to create IPv4 socket");
                return (B_FALSE);
        }

        if (setsockopt(v4_sock_fd, IPPROTO_IP, IP_RECVDSTADDR, &on,
            sizeof (on)) == -1) {
                dhcpmsg(MSG_ERR,
                    "dhcp_ip_default: unable to enable IP_RECVDSTADDR");
                return (B_FALSE);
        }

        if (setsockopt(v4_sock_fd, IPPROTO_IP, IP_RECVIF, &on, sizeof (on)) ==
            -1) {
                dhcpmsg(MSG_ERR,
                    "dhcp_ip_default: unable to enable IP_RECVIF");
                return (B_FALSE);
        }

        if (!bind_sock(v4_sock_fd, IPPORT_BOOTPC, INADDR_ANY)) {
                dhcpmsg(MSG_ERROR,
                    "dhcp_ip_default: unable to bind IPv4 socket to port %d",
                    IPPORT_BOOTPC);
                return (B_FALSE);
        }

        if (iu_register_event(eh, v4_sock_fd, POLLIN, dhcp_acknak_global,
            NULL) == -1) {
                dhcpmsg(MSG_WARNING, "dhcp_ip_default: cannot register to "
                    "receive IPv4 broadcasts");
                return (B_FALSE);
        }

        if ((v6_sock_fd = socket(AF_INET6, SOCK_DGRAM, 0)) == -1) {
                dhcpmsg(MSG_ERR,
                    "dhcp_ip_default: unable to create IPv6 socket");
                return (B_FALSE);
        }

        if (setsockopt(v6_sock_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on,
            sizeof (on)) == -1) {
                dhcpmsg(MSG_ERR,
                    "dhcp_ip_default: unable to enable IPV6_RECVPKTINFO");
                return (B_FALSE);
        }

        if (!bind_sock_v6(v6_sock_fd, IPPORT_DHCPV6C, NULL)) {
                dhcpmsg(MSG_ERROR,
                    "dhcp_ip_default: unable to bind IPv6 socket to port %d",
                    IPPORT_DHCPV6C);
                return (B_FALSE);
        }

        if (iu_register_event(eh, v6_sock_fd, POLLIN, dhcp_acknak_global,
            NULL) == -1) {
                dhcpmsg(MSG_WARNING, "dhcp_ip_default: cannot register to "
                    "receive IPv6 packets");
                return (B_FALSE);
        }

        return (B_TRUE);
}