sbin/dhcpagent/request.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.
 *
 * REQUESTING state of the client state machine.
 */

#include <stdlib.h>
#include <string.h>
#include <search.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/dhcp.h>
#include <netinet/udp.h>
#include <netinet/ip_var.h>
#include <netinet/udp_var.h>
#include <arpa/inet.h>
#include <dhcp_hostconf.h>
#include <dhcpagent_util.h>
#include <dhcpmsg.h>

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

static PKT_LIST     *select_best(dhcp_smach_t *);
static void     request_failed(dhcp_smach_t *);
static stop_func_t  stop_requesting;

/*
 * send_v6_request(): sends a DHCPv6 Request message and switches to REQUESTING
 *            state.  This is a separate function because a NoBinding
 *            response can also cause us to do this.
 *
 *   input: dhcp_smach_t *: the state machine
 *  output: none
 */

void
send_v6_request(dhcp_smach_t *dsmp)
{
    dhcp_pkt_t *dpkt;
    dhcpv6_ia_na_t d6in;

    dpkt = init_pkt(dsmp, DHCPV6_MSG_REQUEST);
    (void) add_pkt_opt(dpkt, DHCPV6_OPT_SERVERID, dsmp->dsm_serverid,
        dsmp->dsm_serveridlen);

    /* Add an IA_NA option for our controlling LIF */
    d6in.d6in_iaid = htonl(dsmp->dsm_lif->lif_iaid);
    d6in.d6in_t1 = htonl(0);
    d6in.d6in_t2 = htonl(0);
    (void) add_pkt_opt(dpkt, DHCPV6_OPT_IA_NA,
        (dhcpv6_option_t *)&d6in + 1,
        sizeof (d6in) - sizeof (dhcpv6_option_t));

    /* Add required Option Request option */
    (void) add_pkt_prl(dpkt, dsmp);

    (void) send_pkt_v6(dsmp, dpkt, dsmp->dsm_server, stop_requesting,
        DHCPV6_REQ_TIMEOUT, DHCPV6_REQ_MAX_RT);

    /* For DHCPv6, state switch cannot fail */
    (void) set_smach_state(dsmp, REQUESTING);
}

/*
 * server_unicast_option(): determines the server address to use based on the
 *              DHCPv6 Server Unicast option present in the given
 *              packet.
 *
 *   input: dhcp_smach_t *: the state machine
 *      PKT_LIST *: received packet (Advertisement or Reply)
 *  output: none
 */

void
server_unicast_option(dhcp_smach_t *dsmp, PKT_LIST *plp)
{
    const dhcpv6_option_t *d6o;
    uint_t olen;

    d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_UNICAST, &olen);
    olen -= sizeof (*d6o);
    /* LINTED: no consequent */
    if (d6o == NULL) {
        /* No Server Unicast option specified */
    } else if (olen != sizeof (dsmp->dsm_server)) {
        dhcpmsg(MSG_WARNING, "server_unicast_option: %s has Server "
            "Unicast option with bad length",
            pkt_type_to_string(pkt_recv_type(plp), B_TRUE));
    } else {
        in6_addr_t addr;

        (void) memcpy(&addr, d6o + 1, olen);
        if (IN6_IS_ADDR_UNSPECIFIED(&addr)) {
            dhcpmsg(MSG_WARNING, "server_unicast_option: unicast "
                "to unspecified address ignored");
        } else if (IN6_IS_ADDR_MULTICAST(&addr)) {
            dhcpmsg(MSG_WARNING, "server_unicast_option: unicast "
                "to multicast address ignored");
        } else if (IN6_IS_ADDR_V4COMPAT(&addr) ||
            IN6_IS_ADDR_V4MAPPED(&addr)) {
            dhcpmsg(MSG_WARNING, "server_unicast_option: unicast "
                "to invalid address ignored");
        } else {
            dsmp->dsm_server = addr;
        }
    }
}

/*
 * dhcp_requesting(): checks if OFFER packets to come in from DHCP servers.
 *            if so, chooses the best one, sends a REQUEST to the
 *            server and registers an event handler to receive
 *            the ACK/NAK.  This may be called by the offer timer or
 *            by any function that wants to check for offers after
 *            canceling that timer.
 *
 *   input: iu_tq_t *: timer queue; non-NULL if this is a timer callback
 *      void *: the state machine receiving OFFER packets
 *  output: void
 */

void
dhcp_requesting(iu_tq_t *tqp, void *arg)
{
    dhcp_smach_t        *dsmp = arg;
    dhcp_pkt_t      *dpkt;
    PKT_LIST        *offer;
    lease_t         lease;
    boolean_t       isv6 = dsmp->dsm_isv6;

    /*
     * We assume here that if tqp is set, then this means we're being
     * called back by the offer wait timer.  If so, then drop our hold
     * on the state machine.  Otherwise, cancel the timer if it's running.
     */
    if (tqp != NULL) {
        dhcpmsg(MSG_VERBOSE,
            "dhcp_requesting: offer wait timer on v%d %s",
            isv6 ? 6 : 4, dsmp->dsm_name);
        dsmp->dsm_offer_timer = -1;
        if (!verify_smach(dsmp))
            return;
    } else {
        cancel_offer_timer(dsmp);
    }

    /*
     * select the best OFFER; all others pitched.
     */

    offer = select_best(dsmp);
    if (offer == NULL) {

        dhcpmsg(MSG_VERBOSE,
            "no OFFERs/Advertisements on %s, waiting...",
            dsmp->dsm_name);

        /*
         * no acceptable OFFERs have come in.  reschedule
         * ourself for callback.
         */

        if ((dsmp->dsm_offer_timer = iu_schedule_timer(tq,
            dsmp->dsm_offer_wait, dhcp_requesting, dsmp)) == -1) {

            /*
             * ugh.  the best we can do at this point is
             * revert back to INIT and wait for a user to
             * restart us.
             */

            dhcpmsg(MSG_WARNING, "dhcp_requesting: cannot "
                "reschedule callback, reverting to INIT state on "
                "%s", dsmp->dsm_name);

            stop_pkt_retransmission(dsmp);
            (void) set_smach_state(dsmp, INIT);
            dsmp->dsm_dflags |= DHCP_IF_FAILED;
            ipc_action_finish(dsmp, DHCP_IPC_E_MEMORY);
        } else {
            hold_smach(dsmp);
        }

        return;
    }

    /*
     * With IPv4, the DHCPREQUEST packet we're about to transmit implicitly
     * declines all other offers we've received.  We can no longer use any
     * cached offers, so we must discard them now.  With DHCPv6, though,
     * we're permitted to hang onto the advertisements (offers) and try
     * them if the preferred one doesn't pan out.
     */
    if (!isv6)
        free_pkt_list(&dsmp->dsm_recv_pkt_list);

    /* stop collecting packets. */

    stop_pkt_retransmission(dsmp);

    /*
     * For IPv4, check to see whether we got an OFFER or a BOOTP packet.
     * If we got a BOOTP packet, go to the BOUND state now.
     */
    if (!isv6 && offer->opts[CD_DHCP_TYPE] == NULL) {
        free_pkt_list(&dsmp->dsm_recv_pkt_list);

        if (!set_smach_state(dsmp, REQUESTING)) {
            dhcp_restart(dsmp);
            return;
        }

        if (!dhcp_bound(dsmp, offer)) {
            dhcpmsg(MSG_WARNING, "dhcp_requesting: dhcp_bound "
                "failed for %s", dsmp->dsm_name);
            dhcp_restart(dsmp);
            return;
        }

        return;
    }

    if (isv6) {
        const char *estr, *msg;
        const dhcpv6_option_t *d6o;
        uint_t olen, msglen;

        /* If there's a Status Code option, print the message */
        d6o = dhcpv6_pkt_option(offer, NULL, DHCPV6_OPT_STATUS_CODE,
            &olen);
        (void) dhcpv6_status_code(d6o, olen, &estr, &msg, &msglen);
        print_server_msg(dsmp, msg, msglen);

        /* Copy in the Server ID (guaranteed to be present now) */
        if (!save_server_id(dsmp, offer))
            goto failure;

        /*
         * Determine how to send this message.  If the Advertisement
         * (offer) has the unicast option, then use the address
         * specified in the option.  Otherwise, send via multicast.
         */
        server_unicast_option(dsmp, offer);

        send_v6_request(dsmp);
    } else {
        /* if we got a message from the server, display it. */
        if (offer->opts[CD_MESSAGE] != NULL) {
            print_server_msg(dsmp,
                (char *)offer->opts[CD_MESSAGE]->value,
                offer->opts[CD_MESSAGE]->len);
        }

        /*
         * assemble a DHCPREQUEST, with the ciaddr field set to 0,
         * since we got here from the INIT state.
         */

        dpkt = init_pkt(dsmp, REQUEST);

        /*
         * Grab the lease out of the OFFER; we know it's valid because
         * select_best() already checked.  The max dhcp message size
         * option is set to the interface max, minus the size of the
         * udp and ip headers.
         */

        (void) memcpy(&lease, offer->opts[CD_LEASE_TIME]->value,
            sizeof (lease_t));

        (void) add_pkt_opt32(dpkt, CD_LEASE_TIME, lease);
        (void) add_pkt_opt16(dpkt, CD_MAX_DHCP_SIZE,
            htons(dsmp->dsm_lif->lif_max - sizeof (struct udpiphdr)));
        (void) add_pkt_opt32(dpkt, CD_REQUESTED_IP_ADDR,
            offer->pkt->yiaddr.s_addr);
        (void) add_pkt_opt(dpkt, CD_SERVER_ID,
            offer->opts[CD_SERVER_ID]->value,
            offer->opts[CD_SERVER_ID]->len);

        if (class_id_len != 0) {
            (void) add_pkt_opt(dpkt, CD_CLASS_ID, class_id,
                class_id_len);
        }
        (void) add_pkt_prl(dpkt, dsmp);

        /*
         * dsm_reqhost was set for this state machine in
         * dhcp_selecting() if the DF_REQUEST_HOSTNAME option set and a
         * host name was found
         */
        if (dsmp->dsm_reqhost != NULL) {
            (void) add_pkt_opt(dpkt, CD_HOSTNAME, dsmp->dsm_reqhost,
                strlen(dsmp->dsm_reqhost));
        }
        (void) add_pkt_opt(dpkt, CD_END, NULL, 0);

        /*
         * send out the REQUEST, trying retransmissions.  either a NAK
         * or too many REQUEST attempts will revert us to SELECTING.
         */

        if (!set_smach_state(dsmp, REQUESTING)) {
            dhcpmsg(MSG_ERROR, "dhcp_requesting: cannot switch to "
                "REQUESTING state; reverting to INIT on %s",
                dsmp->dsm_name);
            goto failure;
        }

        (void) send_pkt(dsmp, dpkt, htonl(INADDR_BROADCAST),
            stop_requesting);
    }

    /* all done with the offer */
    free_pkt_entry(offer);

    return;

failure:
    dsmp->dsm_dflags |= DHCP_IF_FAILED;
    (void) set_smach_state(dsmp, INIT);
    ipc_action_finish(dsmp, DHCP_IPC_E_MEMORY);
    free_pkt_list(&dsmp->dsm_recv_pkt_list);
}

/*
 * compute_points_v6(): compute the number of "points" for a given v6
 *          advertisement.
 *
 *   input: const PKT_LIST *: packet to inspect
 *      const dhcp_smach_t *: state machine that received the packet
 *  output: int: -1 to discard, -2 to accept immediately, >=0 for preference.
 */

static int
compute_points_v6(const PKT_LIST *pkt, const dhcp_smach_t *dsmp)
{
    char abuf[INET6_ADDRSTRLEN];
    int points = 0;
    const dhcpv6_option_t *d6o, *d6so;
    uint_t olen, solen;
    int i;
    const char *estr, *msg;
    uint_t msglen;

    /*
     * Look through the packet contents.  Valid packets must have our
     * client ID and a server ID, which has already been checked by
     * dhcp_packet_lif.  Bonus points for each option.
     */

    /* One point for having a valid message. */
    points++;

    /*
     * Per RFC 3315, if the Advertise message says, "yes, we have no
     * bananas today," then ignore the entire message.  (Why it's just
     * _this_ error and no other is a bit of a mystery, but a standard is a
     * standard.)
     */
    d6o = dhcpv6_pkt_option(pkt, NULL, DHCPV6_OPT_STATUS_CODE, &olen);
    if (dhcpv6_status_code(d6o, olen, &estr, &msg, &msglen) ==
        DHCPV6_STAT_NOADDRS) {
        dhcpmsg(MSG_INFO,
            "discard advertisement from %s on %s: no address status",
            inet_ntop(AF_INET6,
            &((struct sockaddr_in6 *)&pkt->pktfrom)->sin6_addr,
            abuf, sizeof (abuf)), dsmp->dsm_name);
        return (-1);
    }

    /* Two points for each batch of offered IP addresses */
    d6o = NULL;
    while ((d6o = dhcpv6_pkt_option(pkt, d6o, DHCPV6_OPT_IA_NA,
        &olen)) != NULL) {

        /*
         * Note that it's possible to have "no bananas" on an
         * individual IA.  We must look for that here.
         *
         * RFC 3315 section 17.1.3 does not refer to the status code
         * embedded in the IA itself.  However, the TAHI test suite
         * checks for this specific case.  Because it's extremely
         * unlikely that any usable server is going to report that it
         * has no addresses on a network using DHCP for address
         * assignment, we allow such messages to be dropped.
         */
        d6so = dhcpv6_find_option(
            (const char *)d6o + sizeof (dhcpv6_ia_na_t),
            olen - sizeof (dhcpv6_ia_na_t), NULL,
            DHCPV6_OPT_STATUS_CODE, &solen);
        if (dhcpv6_status_code(d6so, solen, &estr, &msg, &msglen) ==
            DHCPV6_STAT_NOADDRS)
            return (-1);
        points += 2;
    }

    /*
     * Note that we drive on in the case where there are no addresses.  The
     * hope here is that we'll at least get some useful configuration
     * information.
     */

    /* One point for each requested option */
    for (i = 0; i < dsmp->dsm_prllen; i++) {
        if (dhcpv6_pkt_option(pkt, NULL, dsmp->dsm_prl[i], NULL) !=
            NULL)
            points++;
    }

    /*
     * Ten points for each point of "preference."  Note: the value 255 is
     * special.  It means "stop right now and select this server."
     */
    d6o = dhcpv6_pkt_option(pkt, NULL, DHCPV6_OPT_PREFERENCE, &olen);
    if (d6o != NULL && olen == sizeof (*d6o) + 1) {
        int pref = *(const uchar_t *)(d6o + 1);

        if (pref == 255)
            return (-2);
        points += 10 * pref;
    }

    return (points);
}

/*
 * compute_points_v4(): compute the number of "points" for a given v4 offer.
 *
 *   input: const PKT_LIST *: packet to inspect
 *      const dhcp_smach_t *: state machine that received the packet
 *  output: int: -1 to discard, >=0 for preference.
 */

static int
compute_points_v4(const PKT_LIST *pkt)
{
    int points = 0;

    if (pkt->opts[CD_DHCP_TYPE] == NULL) {
        dhcpmsg(MSG_VERBOSE, "compute_points_v4: valid BOOTP reply");
        goto valid_offer;
    }

    if (pkt->opts[CD_LEASE_TIME] == NULL) {
        dhcpmsg(MSG_WARNING, "compute_points_v4: OFFER without lease "
            "time");
        return (-1);
    }

    if (pkt->opts[CD_LEASE_TIME]->len != sizeof (lease_t)) {
        dhcpmsg(MSG_WARNING, "compute_points_v4: OFFER with garbled "
            "lease time");
        return (-1);
    }

    if (pkt->opts[CD_SERVER_ID] == NULL) {
        dhcpmsg(MSG_WARNING, "compute_points_v4: OFFER without server "
            "id");
        return (-1);
    }

    if (pkt->opts[CD_SERVER_ID]->len != sizeof (ipaddr_t)) {
        dhcpmsg(MSG_WARNING, "compute_points_v4: OFFER with garbled "
            "server id");
        return (-1);
    }

    /* valid DHCP OFFER.  see if we got our parameters. */
    dhcpmsg(MSG_VERBOSE, "compute_points_v4: valid OFFER packet");
    points += 30;

valid_offer:
    if (pkt->rfc1048)
        points += 5;

    /*
     * also could be faked, though more difficult because the encapsulation
     * is hard to encode on a BOOTP server; plus there's not as much real
     * estate in the packet for options, so it's likely this option would
     * get dropped.
     */

    if (pkt->opts[CD_VENDOR_SPEC] != NULL)
        points += 80;

    if (pkt->opts[CD_SUBNETMASK] != NULL)
        points++;

    if (pkt->opts[CD_ROUTER] != NULL)
        points++;

    if (pkt->opts[CD_HOSTNAME] != NULL)
        points += 5;

    return (points);
}

/*
 * select_best(): selects the best offer from a list of IPv4 OFFER packets or
 *        DHCPv6 Advertise packets.
 *
 *   input: dhcp_smach_t *: state machine with enqueued offers
 *  output: PKT_LIST *: the best packet, or NULL if none are acceptable
 */

static PKT_LIST *
select_best(dhcp_smach_t *dsmp)
{
    PKT_LIST    *current = dsmp->dsm_recv_pkt_list;
    PKT_LIST    *next, *best = NULL;
    int     points, best_points = -1;

    /*
     * pick out the best offer.  point system.
     * what's important for IPv4?
     *
     *  0) DHCP (30 points)
     *  1) no option overload
     *  2) encapsulated vendor option (80 points)
     *  3) non-null sname and siaddr fields
     *  4) non-null file field
     *  5) hostname (5 points)
     *  6) subnetmask (1 point)
     *  7) router (1 point)
     */

    for (; current != NULL; current = next) {
        next = current->next;

        points = current->isv6 ?
            compute_points_v6(current, dsmp) :
            compute_points_v4(current);

        /*
         * Just discard any unacceptable entries we encounter.
         */
        if (points == -1) {
            remque(current);
            free_pkt_entry(current);
            continue;
        }

        dhcpmsg(MSG_DEBUG, "select_best: OFFER had %d points", points);

        /* Special case: stop now and select */
        if (points == -2) {
            best = current;
            break;
        }

        if (points >= best_points) {
            best_points = points;
            best = current;
        }
    }

    if (best != NULL) {
        dhcpmsg(MSG_DEBUG, "select_best: most points: %d", best_points);
        remque(best);
    } else {
        dhcpmsg(MSG_DEBUG, "select_best: no valid OFFER/BOOTP reply");
    }

    return (best);
}

/*
 * accept_v4_acknak(): determine what to do with a DHCPv4 ACK/NAK based on the
 *             current state.  If we're renewing or rebinding, the ACK
 *             must be for the same address and must have a new lease
 *             time.  If it's a NAK, then our cache is garbage, and we
 *             must restart.  Finally, call dhcp_bound on accepted
 *             ACKs.
 *
 *   input: dhcp_smach_t *: the state machine to handle the ACK/NAK
 *      PKT_LIST *: the ACK/NAK message
 *  output: void
 */

static void
accept_v4_acknak(dhcp_smach_t *dsmp, PKT_LIST *plp)
{
    /* Account for received and processed messages */
    dsmp->dsm_received++;

    if (*plp->opts[CD_DHCP_TYPE]->value == ACK) {
        if (dsmp->dsm_state != INFORM_SENT &&
            dsmp->dsm_state != INFORMATION &&
            (plp->opts[CD_LEASE_TIME] == NULL ||
            plp->opts[CD_LEASE_TIME]->len != sizeof (lease_t))) {
            dhcpmsg(MSG_WARNING, "accept_v4_acknak: ACK packet on "
                "%s missing mandatory lease option, ignored",
                dsmp->dsm_name);
            dsmp->dsm_bad_offers++;
            free_pkt_entry(plp);
            return;
        }
        if ((dsmp->dsm_state == RENEWING ||
            dsmp->dsm_state == REBINDING) &&
            dsmp->dsm_leases->dl_lifs->lif_addr !=
            plp->pkt->yiaddr.s_addr) {
            dhcpmsg(MSG_WARNING, "accept_v4_acknak: renewal ACK "
                "packet has a different IP address (%s), ignored",
                inet_ntoa(plp->pkt->yiaddr));
            dsmp->dsm_bad_offers++;
            free_pkt_entry(plp);
            return;
        }
    }

    /*
     * looks good; cancel the retransmission timer and unregister
     * the acknak handler. ACK to BOUND, NAK back to SELECTING.
     */

    stop_pkt_retransmission(dsmp);

    if (*plp->opts[CD_DHCP_TYPE]->value == NAK) {
        dhcpmsg(MSG_WARNING, "accept_v4_acknak: NAK on interface %s",
            dsmp->dsm_name);
        dsmp->dsm_bad_offers++;
        free_pkt_entry(plp);
        dhcp_restart(dsmp);

        /*
         * remove any bogus cached configuration we might have
         * around (right now would only happen if we got here
         * from INIT_REBOOT).
         */

        (void) remove_hostconf(dsmp->dsm_name, dsmp->dsm_isv6);
        return;
    }

    if (plp->opts[CD_SERVER_ID] == NULL ||
        plp->opts[CD_SERVER_ID]->len != sizeof (ipaddr_t)) {
        dhcpmsg(MSG_ERROR, "accept_v4_acknak: ACK with no valid "
            "server id on %s", dsmp->dsm_name);
        dsmp->dsm_bad_offers++;
        free_pkt_entry(plp);
        dhcp_restart(dsmp);
        return;
    }

    if (plp->opts[CD_MESSAGE] != NULL) {
        print_server_msg(dsmp, (char *)plp->opts[CD_MESSAGE]->value,
            plp->opts[CD_MESSAGE]->len);
    }

    dhcpmsg(MSG_VERBOSE, "accept_v4_acknak: ACK on %s", dsmp->dsm_name);
    if (!dhcp_bound(dsmp, plp)) {
        dhcpmsg(MSG_WARNING, "accept_v4_acknak: dhcp_bound failed "
            "for %s", dsmp->dsm_name);
        dhcp_restart(dsmp);
    }
}

/*
 * accept_v6_message(): determine what to do with a DHCPv6 message based on the
 *          current state.
 *
 *   input: dhcp_smach_t *: the state machine to handle the message
 *      PKT_LIST *: the DHCPv6 message
 *      const char *: type of message (for logging)
 *      uchar_t: type of message (extracted from packet)
 *  output: void
 */

static void
accept_v6_message(dhcp_smach_t *dsmp, PKT_LIST *plp, const char *pname,
    uchar_t recv_type)
{
    const dhcpv6_option_t *d6o;
    uint_t olen;
    const char *estr, *msg;
    uint_t msglen;
    int status;

    /* Account for received and processed messages */
    dsmp->dsm_received++;

    /* We don't yet support Reconfigure at all. */
    if (recv_type == DHCPV6_MSG_RECONFIGURE) {
        dhcpmsg(MSG_VERBOSE, "accept_v6_message: ignored Reconfigure "
            "on %s", dsmp->dsm_name);
        free_pkt_entry(plp);
        return;
    }

    /*
     * All valid DHCPv6 messages must have our Client ID specified.
     */
    d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_CLIENTID, &olen);
    olen -= sizeof (*d6o);
    if (d6o == NULL || olen != dsmp->dsm_cidlen ||
        memcmp(d6o + 1, dsmp->dsm_cid, olen) != 0) {
        dhcpmsg(MSG_VERBOSE,
            "accept_v6_message: discarded %s on %s: %s Client ID",
            pname, dsmp->dsm_name, d6o == NULL ? "no" : "wrong");
        free_pkt_entry(plp);
        return;
    }

    /*
     * All valid DHCPv6 messages must have a Server ID specified.
     *
     * If this is a Reply and it's not in response to Solicit, Confirm,
     * Rebind, or Information-Request, then it must also match the Server
     * ID we're expecting.
     *
     * For Reply in the Solicit, Confirm, Rebind, and Information-Request
     * cases, the Server ID needs to be saved.  This is done inside of
     * dhcp_bound().
     */
    d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_SERVERID, &olen);
    if (d6o == NULL) {
        dhcpmsg(MSG_DEBUG,
            "accept_v6_message: discarded %s on %s: no Server ID",
            pname, dsmp->dsm_name);
        free_pkt_entry(plp);
        return;
    }
    if (recv_type == DHCPV6_MSG_REPLY && dsmp->dsm_state != SELECTING &&
        dsmp->dsm_state != INIT_REBOOT && dsmp->dsm_state != REBINDING &&
        dsmp->dsm_state != INFORM_SENT) {
        olen -= sizeof (*d6o);
        if (olen != dsmp->dsm_serveridlen ||
            memcmp(d6o + 1, dsmp->dsm_serverid, olen) != 0) {
            dhcpmsg(MSG_DEBUG, "accept_v6_message: discarded %s on "
                "%s: wrong Server ID", pname, dsmp->dsm_name);
            free_pkt_entry(plp);
            return;
        }
    }

    /*
     * Break out of the switch if the input message needs to be discarded.
     * Return from the function if the message has been enqueued or
     * consumed.
     */
    switch (dsmp->dsm_state) {
    case SELECTING:
        /* A Reply message signifies a Rapid-Commit. */
        if (recv_type == DHCPV6_MSG_REPLY) {
            if (dhcpv6_pkt_option(plp, NULL,
                DHCPV6_OPT_RAPID_COMMIT, &olen) == NULL) {
                dhcpmsg(MSG_DEBUG, "accept_v6_message: Reply "
                    "on %s lacks Rapid-Commit; ignoring",
                    dsmp->dsm_name);
                break;
            }
            dhcpmsg(MSG_VERBOSE,
                "accept_v6_message: rapid-commit Reply on %s",
                dsmp->dsm_name);
            cancel_offer_timer(dsmp);
            goto rapid_commit;
        }

        /* Otherwise, we're looking for Advertisements. */
        if (recv_type != DHCPV6_MSG_ADVERTISE)
            break;

        /*
         * Special case: if this advertisement has preference 255, then
         * we must stop right now and select this server.
         */
        d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_PREFERENCE,
            &olen);
        if (d6o != NULL && olen == sizeof (*d6o) + 1 &&
            *(const uchar_t *)(d6o + 1) == 255) {
            pkt_smach_enqueue(dsmp, plp);
            dhcpmsg(MSG_DEBUG, "accept_v6_message: preference 255;"
                " immediate Request on %s", dsmp->dsm_name);
            dhcp_requesting(NULL, dsmp);
        } else {
            pkt_smach_enqueue(dsmp, plp);
        }
        return;

    case PRE_BOUND:
    case BOUND:
        /*
         * Not looking for anything in these states.  (If we
         * implemented reconfigure, that might go here.)
         */
        break;

    case REQUESTING:
    case INIT_REBOOT:
    case RENEWING:
    case REBINDING:
    case INFORM_SENT:
        /*
         * We're looking for Reply messages.
         */
        if (recv_type != DHCPV6_MSG_REPLY)
            break;
        dhcpmsg(MSG_VERBOSE,
            "accept_v6_message: received Reply message on %s",
            dsmp->dsm_name);
    rapid_commit:
        /*
         * Extract the status code option.  If one is present and the
         * request failed, then try to go to another advertisement in
         * the list or restart the selection machinery.
         */
        d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_STATUS_CODE,
            &olen);
        status = dhcpv6_status_code(d6o, olen, &estr, &msg, &msglen);
        /*
         * Check for the UseMulticast status code.  If this is present,
         * and if we were actually using unicast, then drop back and
         * try again.  If we weren't using unicast, then just pretend
         * we never saw this message -- the peer is confused.  (TAHI
         * does this.)
         */
        if (status == DHCPV6_STAT_USEMCAST) {
            if (IN6_IS_ADDR_MULTICAST(
                &dsmp->dsm_send_dest.v6.sin6_addr)) {
                break;
            } else {
                free_pkt_entry(plp);
                dsmp->dsm_send_dest.v6.sin6_addr =
                    ipv6_all_dhcp_relay_and_servers;
                retransmit_now(dsmp);
                return;
            }
        }
        print_server_msg(dsmp, msg, msglen);
        /*
         * We treat NoBinding at the top level as "success."  Granted,
         * this doesn't make much sense, but the TAHI test suite does
         * this.  NoBinding really only makes sense in the context of a
         * specific IA, as it refers to the GUID:IAID binding, so
         * ignoring it at the top level is safe.
         */
        if (status == DHCPV6_STAT_SUCCESS ||
            status == DHCPV6_STAT_NOBINDING) {
            if (dhcp_bound(dsmp, plp)) {
                /*
                 * dhcp_bound will stop retransmission on
                 * success, if that's called for.
                 */
                server_unicast_option(dsmp, plp);
            } else {
                stop_pkt_retransmission(dsmp);
                dhcpmsg(MSG_WARNING, "accept_v6_message: "
                    "dhcp_bound failed for %s", dsmp->dsm_name);
                (void) remove_hostconf(dsmp->dsm_name,
                    dsmp->dsm_isv6);
                dhcp_restart(dsmp);
            }
        } else {
            dhcpmsg(MSG_WARNING, "accept_v6_message: Reply: %s",
                estr);
            stop_pkt_retransmission(dsmp);
            free_pkt_entry(plp);
            if (dsmp->dsm_state == INFORM_SENT) {
                (void) set_smach_state(dsmp, INIT);
                ipc_action_finish(dsmp, DHCP_IPC_E_SRVFAILED);
            } else {
                (void) remove_hostconf(dsmp->dsm_name,
                    dsmp->dsm_isv6);
                request_failed(dsmp);
            }
        }
        return;

    case DECLINING:
        /*
         * We're looking for Reply messages.
         */
        if (recv_type != DHCPV6_MSG_REPLY)
            break;
        stop_pkt_retransmission(dsmp);
        /*
         * Extract the status code option.  Note that it's not a
         * failure if the server reports an error.
         */
        d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_STATUS_CODE,
            &olen);
        if (dhcpv6_status_code(d6o, olen, &estr, &msg,
            &msglen) == DHCPV6_STAT_SUCCESS) {
            print_server_msg(dsmp, msg, msglen);
        } else {
            dhcpmsg(MSG_WARNING, "accept_v6_message: Reply: %s",
                estr);
        }
        free_pkt_entry(plp);
        if (dsmp->dsm_leases == NULL) {
            dhcpmsg(MSG_VERBOSE, "accept_v6_message: %s has no "
                "leases left", dsmp->dsm_name);
            dhcp_restart(dsmp);
        } else if (dsmp->dsm_lif_wait == 0) {
            (void) set_smach_state(dsmp, BOUND);
        } else {
            (void) set_smach_state(dsmp, PRE_BOUND);
        }
        return;

    case RELEASING:
        /*
         * We're looking for Reply messages.
         */
        if (recv_type != DHCPV6_MSG_REPLY)
            break;
        stop_pkt_retransmission(dsmp);
        /*
         * Extract the status code option.
         */
        d6o = dhcpv6_pkt_option(plp, NULL, DHCPV6_OPT_STATUS_CODE,
            &olen);
        if (dhcpv6_status_code(d6o, olen, &estr, &msg,
            &msglen) == DHCPV6_STAT_SUCCESS) {
            print_server_msg(dsmp, msg, msglen);
        } else {
            dhcpmsg(MSG_WARNING, "accept_v6_message: Reply: %s",
                estr);
        }
        free_pkt_entry(plp);
        finished_smach(dsmp, DHCP_IPC_SUCCESS);
        return;
    }

    /*
     * Break from above switch means that the message must be discarded.
     */
    dhcpmsg(MSG_VERBOSE,
        "accept_v6_message: discarded v6 %s on %s; state %s",
        pname, dsmp->dsm_name, dhcp_state_to_string(dsmp->dsm_state));
    free_pkt_entry(plp);
}

/*
 * dhcp_acknak_global(): Processes reception of an ACK or NAK packet on the
 *           global socket -- broadcast packets for IPv4, all
 *           packets for DHCPv6.
 *
 *   input: iu_eh_t *: unused
 *      int: the global file descriptor the ACK/NAK arrived on
 *      short: unused
 *      iu_event_id_t: unused
 *      void *: unused
 *  output: void
 */

/* ARGSUSED */
void
dhcp_acknak_global(iu_eh_t *ehp, int fd, short events, iu_event_id_t id,
    void *arg)
{
    PKT_LIST    *plp;
    dhcp_pif_t  *pif;
    uchar_t     recv_type;
    const char  *pname;
    uint_t      xid;
    dhcp_smach_t    *dsmp;
    boolean_t   isv6 = (fd == v6_sock_fd);
    struct sockaddr_in sin;
    const char  *reason;
    size_t      sinlen = sizeof (sin);
    int     sock;

    plp = recv_pkt(fd, get_max_mtu(isv6), isv6);
    if (plp == NULL)
        return;

    recv_type = pkt_recv_type(plp);
    pname = pkt_type_to_string(recv_type, isv6);

    /*
     * Find the corresponding state machine and pif.
     *
     * Note that DHCPv6 Reconfigure would be special: it's not the reply to
     * any transaction, and thus we would need to search on transaction ID
     * zero (all state machines) to find the match.  However, Reconfigure
     * is not yet supported.
     */
    xid = pkt_get_xid(plp->pkt, isv6);

    for (dsmp = lookup_smach_by_xid(xid, NULL, isv6); dsmp != NULL;
        dsmp = lookup_smach_by_xid(xid, dsmp, isv6)) {
        pif = dsmp->dsm_lif->lif_pif;
        if (pif->pif_index == plp->ifindex ||
            pif->pif_under_ipmp && pif->pif_grindex == plp->ifindex)
            break;
    }

    if (dsmp == NULL) {
        dhcpmsg(MSG_VERBOSE, "dhcp_acknak_global: ignored v%d %s packet"
            " on ifindex %d: unknown state machine", isv6 ? 6 : 4,
            pname, plp->ifindex);
        free_pkt_entry(plp);
        return;
    }

    if (!isv6 && !pkt_v4_match(recv_type, DHCP_PACK|DHCP_PNAK)) {
        reason = "not ACK or NAK";
        goto drop;
    }

    /*
     * For IPv4, most packets will be handled by dhcp_packet_lif().  The
     * only exceptions are broadcast packets sent when lif_sock_ip_fd has
     * bound to something other than INADDR_ANY.
     */
    if (!isv6) {
        sock = dsmp->dsm_lif->lif_sock_ip_fd;

        if (getsockname(sock, (struct sockaddr *)&sin, &sinlen) != -1 &&
            sin.sin_addr.s_addr == INADDR_ANY) {
            reason = "handled by lif_sock_ip_fd";
            goto drop;
        }
    }

    /*
     * We've got a packet; make sure it's acceptable and cancel the REQUEST
     * retransmissions.
     */
    if (isv6)
        accept_v6_message(dsmp, plp, pname, recv_type);
    else
        accept_v4_acknak(dsmp, plp);
    return;
drop:
    dhcpmsg(MSG_VERBOSE, "dhcp_acknak_global: ignored v%d %s packet for %s "
        "received on global socket: %s", isv6 ? 6 : 4, pname, pif->pif_name,
        reason);
    free_pkt_entry(plp);
}

/*
 * request_failed(): Attempt to request an address has failed.  Take an
 *           appropriate action.
 *
 *   input: dhcp_smach_t *: state machine that has failed
 *  output: void
 */

static void
request_failed(dhcp_smach_t *dsmp)
{
    PKT_LIST *offer;

    dsmp->dsm_server = ipv6_all_dhcp_relay_and_servers;
    if ((offer = select_best(dsmp)) != NULL) {
        insque(offer, &dsmp->dsm_recv_pkt_list);
        dhcp_requesting(NULL, dsmp);
    } else {
        dhcpmsg(MSG_INFO, "no offers left on %s; restarting",
            dsmp->dsm_name);
        dhcp_selecting(dsmp);
    }
}

/*
 * dhcp_packet_lif(): Processes reception of an ACK, NAK, or OFFER packet on
 *            a given logical interface for IPv4 (only).
 *
 *   input: iu_eh_t *: unused
 *      int: the file descriptor the packet arrived on
 *      short: unused
 *      iu_event_id_t: the id of this event callback with the handler
 *      void *: pointer to logical interface receiving message
 *  output: void
 */

/* ARGSUSED */
void
dhcp_packet_lif(iu_eh_t *ehp, int fd, short events, iu_event_id_t id,
    void *arg)
{
    dhcp_lif_t  *lif = arg;
    PKT_LIST    *plp;
    uchar_t     recv_type;
    const char  *pname;
    uint_t      xid;
    dhcp_smach_t    *dsmp;

    if ((plp = recv_pkt(fd, lif->lif_max, B_FALSE)) == NULL)
        return;

    recv_type = pkt_recv_type(plp);
    pname = pkt_type_to_string(recv_type, B_FALSE);

    if (!pkt_v4_match(recv_type,
        DHCP_PACK | DHCP_PNAK | DHCP_PUNTYPED | DHCP_POFFER)) {
        dhcpmsg(MSG_VERBOSE, "dhcp_packet_lif: ignored v4 %s packet "
            "received via LIF %s", pname, lif->lif_name);
        free_pkt_entry(plp);
        return;
    }

    /*
     * Find the corresponding state machine.
     */
    xid = pkt_get_xid(plp->pkt, B_FALSE);
    for (dsmp = lookup_smach_by_xid(xid, NULL, B_FALSE); dsmp != NULL;
        dsmp = lookup_smach_by_xid(xid, dsmp, B_FALSE)) {
        if (dsmp->dsm_lif == lif)
            break;
    }

    if (dsmp == NULL)
        goto drop;

    if (pkt_v4_match(recv_type, DHCP_PACK|DHCP_PNAK)) {
        /*
         * We've got an ACK/NAK; make sure it's acceptable and cancel
         * the REQUEST retransmissions.
         */
        accept_v4_acknak(dsmp, plp);
    } else {
        if (is_bound_state(dsmp->dsm_state))
            goto drop;
        /*
         * Must be an OFFER or a BOOTP message: enqueue it for later
         * processing by select_best().
         */
        pkt_smach_enqueue(dsmp, plp);
    }
    return;
drop:
    dhcpmsg(MSG_VERBOSE, "dhcp_packet_lif: ignored %s packet xid "
        "%x received via LIF %s; %s", pname, xid, lif->lif_name,
        dsmp == NULL ? "unknown state machine" : "bound");
    free_pkt_entry(plp);
}

/*
 * dhcp_restart(): restarts DHCP (from INIT) on a given state machine, but only
 *         if we're leasing addresses.  Doesn't restart for information-
 *         only interfaces.
 *
 *   input: dhcp_smach_t *: the state machine to restart DHCP on
 *  output: void
 */

void
dhcp_restart(dhcp_smach_t *dsmp)
{
    if (dsmp->dsm_state == INFORM_SENT || dsmp->dsm_state == INFORMATION)
        return;

    /*
     * As we're returning to INIT state, we need to discard any leases we
     * may have, and (for v4) canonize the LIF.  There's a bit of tension
     * between keeping around a possibly still working address, and obeying
     * the RFCs.  A more elaborate design would be to mark the addresses as
     * DEPRECATED, and then start a removal timer.  Such a design would
     * probably compromise testing.
     */
    deprecate_leases(dsmp);

    if (!set_start_timer(dsmp)) {
        dhcpmsg(MSG_ERROR, "dhcp_restart: cannot schedule dhcp_start, "
            "reverting to INIT state on %s", dsmp->dsm_name);

        (void) set_smach_state(dsmp, INIT);
        dsmp->dsm_dflags |= DHCP_IF_FAILED;
        ipc_action_finish(dsmp, DHCP_IPC_E_MEMORY);
    } else {
        dhcpmsg(MSG_DEBUG, "dhcp_restart: restarting DHCP on %s",
            dsmp->dsm_name);
    }
}

/*
 * stop_requesting(): decides when to stop retransmitting REQUESTs
 *
 *   input: dhcp_smach_t *: the state machine REQUESTs are being sent from
 *      unsigned int: the number of REQUESTs sent so far
 *  output: boolean_t: B_TRUE if retransmissions should stop
 */

static boolean_t
stop_requesting(dhcp_smach_t *dsmp, unsigned int n_requests)
{
    uint_t maxreq;

    maxreq = dsmp->dsm_isv6 ? DHCPV6_REQ_MAX_RC : DHCP_MAX_REQUESTS;
    if (n_requests >= maxreq) {

        dhcpmsg(MSG_INFO, "no ACK/NAK/Reply to REQUEST on %s",
            dsmp->dsm_name);

        request_failed(dsmp);
        return (B_TRUE);
    } else {
        return (B_FALSE);
    }
}