/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "defs.h"
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
/* router advertisement ICMP packet */
struct icmp_ad {
        u_int8_t    icmp_type;          /* type of message */
        u_int8_t    icmp_code;          /* type sub code */
        u_int16_t   icmp_cksum;         /* ones complement cksum of struct */
        u_int8_t    icmp_ad_num;        /* # of following router addresses */
        u_int8_t    icmp_ad_asize;      /* 2--words in each advertisement */
        u_int16_t   icmp_ad_life;       /* seconds of validity */
        struct icmp_ad_info {
            n_long  icmp_ad_addr;
            n_long  icmp_ad_pref;
        } icmp_ad_info[1];
};

/* router solicitation ICMP packet */
struct icmp_so {
        u_int8_t    icmp_type;          /* type of message */
        u_int8_t    icmp_code;          /* type sub code */
        u_int16_t   icmp_cksum;         /* ones complement cksum of struct */
        n_long      icmp_so_rsvd;
};

union ad_u {
        struct icmp icmp;
        struct icmp_ad ad;
        struct icmp_so so;
};


int     rdisc_sock = -1;                /* router-discovery raw socket */
static const struct interface *rdisc_sock_mcast; /* current multicast interface */

struct timeval rdisc_timer;
int rdisc_ok;                           /* using solicited route */


#define MAX_ADS 16                      /* at least one per interface */
struct dr {                             /* accumulated advertisements */
    struct interface *dr_ifp;
    naddr   dr_gate;                    /* gateway */
    time_t  dr_ts;                      /* when received */
    time_t  dr_life;                    /* lifetime in host byte order */
    n_long  dr_recv_pref;               /* received but biased preference */
    n_long  dr_pref;                    /* preference adjusted by metric */
};
static const struct dr *cur_drp;
static struct dr drs[MAX_ADS];

/* convert between signed, balanced around zero,
 * and unsigned zero-based preferences */
#define SIGN_PREF(p) ((p) ^ MIN_PreferenceLevel)
#define UNSIGN_PREF(p) SIGN_PREF(p)
/* adjust unsigned preference by interface metric,
 * without driving it to infinity */
#define PREF(p, ifp) ((int)(p) <= ((ifp)->int_metric+(ifp)->int_adj_outmetric)\
                      ? ((p) != 0 ? 1 : 0)                                  \
                      : (p) - ((ifp)->int_metric+(ifp)->int_adj_outmetric))

static void rdisc_sort(void);


/* dump an ICMP Router Discovery Advertisement Message
 */
static void
trace_rdisc(const char  *act,
            naddr       from,
            naddr       to,
            struct interface *ifp,
            union ad_u  *p,
            u_int       len)
{
        int i;
        n_long *wp, *lim;


        if (!TRACEPACKETS || ftrace == NULL)
                return;

        lastlog();

        if (p->icmp.icmp_type == ICMP_ROUTERADVERT) {
                (void)fprintf(ftrace, "%s Router Ad"
                              " from %s to %s via %s life=%d\n",
                              act, naddr_ntoa(from), naddr_ntoa(to),
                              ifp ? ifp->int_name : "?",
                              ntohs(p->ad.icmp_ad_life));
                if (!TRACECONTENTS)
                        return;

                wp = &p->ad.icmp_ad_info[0].icmp_ad_addr;
                lim = &wp[(len - sizeof(p->ad)) / sizeof(*wp)];
                for (i = 0; i < p->ad.icmp_ad_num && wp <= lim; i++) {
                        (void)fprintf(ftrace, "\t%s preference=%d",
                                      naddr_ntoa(wp[0]), (int)ntohl(wp[1]));
                        wp += p->ad.icmp_ad_asize;
                }
                (void)fputc('\n',ftrace);

        } else {
                trace_act("%s Router Solic. from %s to %s via %s value=%#x",
                          act, naddr_ntoa(from), naddr_ntoa(to),
                          ifp ? ifp->int_name : "?",
                          (int)ntohl(p->so.icmp_so_rsvd));
        }
}

/* prepare Router Discovery socket.
 */
static void
get_rdisc_sock(void)
{
        if (rdisc_sock < 0) {
                rdisc_sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
                if (rdisc_sock < 0)
                        BADERR(1,"rdisc_sock = socket()");
                fix_sock(rdisc_sock,"rdisc_sock");
                fix_select();
        }
}


/* Pick multicast group for router-discovery socket
 */
void
set_rdisc_mg(struct interface *ifp,
             int on)                    /* 0=turn it off */
{
        struct group_req gr;
        struct sockaddr_in *sin;

        assert(ifp != NULL);

        if (rdisc_sock < 0) {
                /* Create the raw socket so that we can hear at least
                 * broadcast router discovery packets.
                 */
                if ((ifp->int_state & IS_NO_RDISC) == IS_NO_RDISC
                    || !on)
                        return;
                get_rdisc_sock();
        }

        if (!(ifp->int_if_flags & IFF_MULTICAST)) {
                ifp->int_state &= ~(IS_ALL_HOSTS | IS_ALL_ROUTERS);
                return;
        }

        memset(&gr, 0, sizeof(gr));
        gr.gr_interface = ifp->int_index;
        sin = (struct sockaddr_in *)&gr.gr_group;
        sin->sin_family = AF_INET;
#ifdef _HAVE_SIN_LEN
        sin->sin_len = sizeof(struct sockaddr_in);
#endif

        if (supplier
            || (ifp->int_state & IS_NO_ADV_IN)
            || !on) {
                /* stop listening to advertisements
                 */
                if (ifp->int_state & IS_ALL_HOSTS) {
                        sin->sin_addr.s_addr = htonl(INADDR_ALLHOSTS_GROUP);
                        if (setsockopt(rdisc_sock, IPPROTO_IP,
                                       MCAST_LEAVE_GROUP,
                                       &gr, sizeof(gr)) < 0)
                                LOGERR("MCAST_LEAVE_GROUP ALLHOSTS");
                        ifp->int_state &= ~IS_ALL_HOSTS;
                }

        } else if (!(ifp->int_state & IS_ALL_HOSTS)) {
                /* start listening to advertisements
                 */
                sin->sin_addr.s_addr = htonl(INADDR_ALLHOSTS_GROUP);
                if (setsockopt(rdisc_sock, IPPROTO_IP, MCAST_JOIN_GROUP,
                               &gr, sizeof(gr)) < 0) {
                        LOGERR("MCAST_JOIN_GROUP ALLHOSTS");
                } else {
                        ifp->int_state |= IS_ALL_HOSTS;
                }
        }

        if (!supplier
            || (ifp->int_state & IS_NO_ADV_OUT)
            || !on) {
                /* stop listening to solicitations
                 */
                if (ifp->int_state & IS_ALL_ROUTERS) {
                        sin->sin_addr.s_addr = htonl(INADDR_ALLROUTERS_GROUP);
                        if (setsockopt(rdisc_sock, IPPROTO_IP,
                                       MCAST_LEAVE_GROUP,
                                       &gr, sizeof(gr)) < 0)
                                LOGERR("MCAST_LEAVE_GROUP ALLROUTERS");
                        ifp->int_state &= ~IS_ALL_ROUTERS;
                }

        } else if (!(ifp->int_state & IS_ALL_ROUTERS)) {
                /* start hearing solicitations
                 */
                sin->sin_addr.s_addr = htonl(INADDR_ALLROUTERS_GROUP);
                if (setsockopt(rdisc_sock, IPPROTO_IP, MCAST_JOIN_GROUP,
                               &gr, sizeof(gr)) < 0) {
                        LOGERR("MCAST_JOIN_GROUP ALLROUTERS");
                } else {
                        ifp->int_state |= IS_ALL_ROUTERS;
                }
        }
}


/* start supplying routes
 */
void
set_supplier(void)
{
        struct interface *ifp;
        struct dr *drp;

        if (supplier_set)
                return;

        trace_act("start supplying routes");

        /* Forget discovered routes.
         */
        for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
                drp->dr_recv_pref = 0;
                drp->dr_life = 0;
        }
        rdisc_age(0);

        supplier_set = 1;
        supplier = 1;

        /* Do not start advertising until we have heard some RIP routes */
        LIM_SEC(rdisc_timer, now.tv_sec+MIN_WAITTIME);

        /* Switch router discovery multicast groups from soliciting
         * to advertising.
         */
        LIST_FOREACH(ifp, &ifnet, int_list) {
                if (ifp->int_state & IS_BROKE)
                        continue;
                ifp->int_rdisc_cnt = 0;
                ifp->int_rdisc_timer.tv_usec = rdisc_timer.tv_usec;
                ifp->int_rdisc_timer.tv_sec = now.tv_sec+MIN_WAITTIME;
                set_rdisc_mg(ifp, 1);
        }

        /* get rid of any redirects */
        del_redirects(0,0);
}


/* age discovered routes and find the best one
 */
void
rdisc_age(naddr bad_gate)
{
        time_t sec;
        struct dr *drp;


        /* If only advertising, then do only that. */
        if (supplier) {
                /* If switching from client to server, get rid of old
                 * default routes.
                 */
                if (cur_drp != NULL)
                        rdisc_sort();
                rdisc_adv();
                return;
        }

        /* If we are being told about a bad router,
         * then age the discovered default route, and if there is
         * no alternative, solicit a replacement.
         */
        if (bad_gate != 0) {
                /* Look for the bad discovered default route.
                 * Age it and note its interface.
                 */
                for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
                        if (drp->dr_ts == 0)
                                continue;

                        /* When we find the bad router, then age the route
                         * to at most SUPPLY_INTERVAL.
                         * This is contrary to RFC 1256, but defends against
                         * black holes.
                         */
                        if (drp->dr_gate == bad_gate) {
                                sec = (now.tv_sec - drp->dr_life
                                       + SUPPLY_INTERVAL);
                                if (drp->dr_ts > sec) {
                                        trace_act("age 0.0.0.0 --> %s via %s",
                                                  naddr_ntoa(drp->dr_gate),
                                                  drp->dr_ifp->int_name);
                                        drp->dr_ts = sec;
                                }
                                break;
                        }
                }
        }

        rdisc_sol();
        rdisc_sort();

        /* Delete old redirected routes to keep the kernel table small,
         * and to prevent black holes.  Check that the kernel table
         * matches the daemon table (i.e. has the default route).
         * But only if RIP is not running and we are not dealing with
         * a bad gateway, since otherwise age() will be called.
         */
        if (rip_sock < 0 && bad_gate == 0)
                age(0);
}


/* Zap all routes discovered via an interface that has gone bad
 *      This should only be called when !(ifp->int_state & IS_ALIAS)
 */
void
if_bad_rdisc(struct interface *ifp)
{
        struct dr *drp;

        for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
                if (drp->dr_ifp != ifp)
                        continue;
                drp->dr_recv_pref = 0;
                drp->dr_ts = 0;
                drp->dr_life = 0;
        }

        /* make a note to re-solicit, turn RIP on or off, etc. */
        rdisc_timer.tv_sec = 0;
}


/* mark an interface ok for router discovering.
 */
void
if_ok_rdisc(struct interface *ifp)
{
        set_rdisc_mg(ifp, 1);

        ifp->int_rdisc_cnt = 0;
        ifp->int_rdisc_timer.tv_sec = now.tv_sec + (supplier
                                                    ? MIN_WAITTIME
                                                    : MAX_SOLICITATION_DELAY);
        if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
                rdisc_timer = ifp->int_rdisc_timer;
}


/* get rid of a dead discovered router
 */
static void
del_rdisc(struct dr *drp)
{
        struct interface *ifp;
        naddr gate;
        int i;


        del_redirects(gate = drp->dr_gate, 0);
        drp->dr_ts = 0;
        drp->dr_life = 0;


        /* Count the other discovered routes on the interface.
         */
        i = 0;
        ifp = drp->dr_ifp;
        for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
                if (drp->dr_ts != 0
                    && drp->dr_ifp == ifp)
                        i++;
        }

        /* If that was the last good discovered router on the interface,
         * then solicit a new one.
         * This is contrary to RFC 1256, but defends against black holes.
         */
        if (i != 0) {
                trace_act("discovered router %s via %s"
                          " is bad--have %d remaining",
                          naddr_ntoa(gate), ifp->int_name, i);
        } else if (ifp->int_rdisc_cnt >= MAX_SOLICITATIONS) {
                trace_act("last discovered router %s via %s"
                          " is bad--re-solicit",
                          naddr_ntoa(gate), ifp->int_name);
                ifp->int_rdisc_cnt = 0;
                ifp->int_rdisc_timer.tv_sec = 0;
                rdisc_sol();
        } else {
                trace_act("last discovered router %s via %s"
                          " is bad--wait to solicit",
                          naddr_ntoa(gate), ifp->int_name);
        }
}


/* Find the best discovered route,
 * and discard stale routers.
 */
static void
rdisc_sort(void)
{
        struct dr *drp, *new_drp;
        struct rt_entry *rt;
        struct rt_spare new;
        struct interface *ifp;
        u_int new_st = 0;
        n_long new_pref = 0;


        /* Find the best discovered route.
         */
        new_drp = NULL;
        for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
                if (drp->dr_ts == 0)
                        continue;
                ifp = drp->dr_ifp;

                /* Get rid of expired discovered routers.
                 */
                if (drp->dr_ts + drp->dr_life <= now.tv_sec) {
                        del_rdisc(drp);
                        continue;
                }

                LIM_SEC(rdisc_timer, drp->dr_ts+drp->dr_life+1);

                /* Update preference with possibly changed interface
                 * metric.
                 */
                drp->dr_pref = PREF(drp->dr_recv_pref, ifp);

                /* Prefer the current route to prevent thrashing.
                 * Prefer shorter lifetimes to speed the detection of
                 * bad routers.
                 * Avoid sick interfaces.
                 */
                if (new_drp == NULL
                    || (!((new_st ^ drp->dr_ifp->int_state) & IS_SICK)
                        && (new_pref < drp->dr_pref
                            || (new_pref == drp->dr_pref
                                && (drp == cur_drp
                                    || (new_drp != cur_drp
                                        && new_drp->dr_life > drp->dr_life)))))
                    || ((new_st & IS_SICK)
                        && !(drp->dr_ifp->int_state & IS_SICK))) {
                            new_drp = drp;
                            new_st = drp->dr_ifp->int_state;
                            new_pref = drp->dr_pref;
                }
        }

        /* switch to a better default route
         */
        if (new_drp != cur_drp) {
                rt = rtget(RIP_DEFAULT, 0);

                /* Stop using discovered routes if they are all bad
                 */
                if (new_drp == NULL) {
                        trace_act("turn off Router Discovery client");
                        rdisc_ok = 0;

                        if (rt != NULL
                            && (rt->rt_state & RS_RDISC)) {
                                new = rt->rt_spares[0];
                                new.rts_metric = HOPCNT_INFINITY;
                                new.rts_time = now.tv_sec - GARBAGE_TIME;
                                rtchange(rt, rt->rt_state & ~RS_RDISC,
                                         &new, 0);
                                rtswitch(rt, 0);
                        }

                } else {
                        if (cur_drp == NULL) {
                                trace_act("turn on Router Discovery client"
                                          " using %s via %s",
                                          naddr_ntoa(new_drp->dr_gate),
                                          new_drp->dr_ifp->int_name);
                                rdisc_ok = 1;

                        } else {
                                trace_act("switch Router Discovery from"
                                          " %s via %s to %s via %s",
                                          naddr_ntoa(cur_drp->dr_gate),
                                          cur_drp->dr_ifp->int_name,
                                          naddr_ntoa(new_drp->dr_gate),
                                          new_drp->dr_ifp->int_name);
                        }

                        memset(&new, 0, sizeof(new));
                        new.rts_ifp = new_drp->dr_ifp;
                        new.rts_gate = new_drp->dr_gate;
                        new.rts_router = new_drp->dr_gate;
                        new.rts_metric = HOPCNT_INFINITY-1;
                        new.rts_time = now.tv_sec;
                        if (rt != NULL) {
                                rtchange(rt, rt->rt_state | RS_RDISC, &new, 0);
                        } else {
                                rtadd(RIP_DEFAULT, 0, RS_RDISC, &new);
                        }
                }

                cur_drp = new_drp;
        }

        /* turn RIP on or off */
        if (!rdisc_ok || rip_interfaces > 1) {
                rip_on(0);
        } else {
                rip_off();
        }
}


/* handle a single address in an advertisement
 */
static void
parse_ad(naddr from,
         naddr gate,
         n_long pref,                   /* signed and in network order */
         u_short life,                  /* in host byte order */
         struct interface *ifp)
{
        static struct msg_limit bad_gate;
        struct dr *drp, *new_drp;


        if (gate == RIP_DEFAULT
            || !check_dst(gate)) {
                msglim(&bad_gate, from,"router %s advertising bad gateway %s",
                       naddr_ntoa(from),
                       naddr_ntoa(gate));
                return;
        }

        /* ignore pointers to ourself and routes via unreachable networks
         */
        if (ifwithaddr(gate, 1, 0) != NULL) {
                trace_pkt("    discard Router Discovery Ad pointing at us");
                return;
        }
        if (!on_net(gate, ifp->int_net, ifp->int_mask)) {
                trace_pkt("    discard Router Discovery Ad"
                          " toward unreachable net");
                return;
        }

        /* Convert preference to an unsigned value
         * and later bias it by the metric of the interface.
         */
        pref = UNSIGN_PREF(ntohl(pref));

        if (pref == 0 || life < MinMaxAdvertiseInterval) {
                pref = 0;
                life = 0;
        }

        for (new_drp = NULL, drp = drs; drp < &drs[MAX_ADS]; drp++) {
                /* accept new info for a familiar entry
                 */
                if (drp->dr_gate == gate) {
                        new_drp = drp;
                        break;
                }

                if (life == 0)
                        continue;       /* do not worry about dead ads */

                if (drp->dr_ts == 0) {
                        new_drp = drp;  /* use unused entry */

                } else if (new_drp == NULL) {
                        /* look for an entry worse than the new one to
                         * reuse.
                         */
                        if ((!(ifp->int_state & IS_SICK)
                             && (drp->dr_ifp->int_state & IS_SICK))
                            || (pref > drp->dr_pref
                                && !((ifp->int_state ^ drp->dr_ifp->int_state)
                                     & IS_SICK)))
                                new_drp = drp;

                } else if (new_drp->dr_ts != 0) {
                        /* look for the least valuable entry to reuse
                         */
                        if ((!(new_drp->dr_ifp->int_state & IS_SICK)
                             && (drp->dr_ifp->int_state & IS_SICK))
                            || (new_drp->dr_pref > drp->dr_pref
                                && !((new_drp->dr_ifp->int_state
                                      ^ drp->dr_ifp->int_state)
                                     & IS_SICK)))
                                new_drp = drp;
                }
        }

        /* forget it if all of the current entries are better */
        if (new_drp == NULL)
                return;

        new_drp->dr_ifp = ifp;
        new_drp->dr_gate = gate;
        new_drp->dr_ts = now.tv_sec;
        new_drp->dr_life = life;
        new_drp->dr_recv_pref = pref;
        /* bias functional preference by metric of the interface */
        new_drp->dr_pref = PREF(pref,ifp);

        /* after hearing a good advertisement, stop asking
         */
        if (!(ifp->int_state & IS_SICK))
                ifp->int_rdisc_cnt = MAX_SOLICITATIONS;
}


/* Compute the IP checksum
 *      This assumes the packet is less than 32K long.
 */
static u_short
in_cksum(u_short *p,
         u_int len)
{
        u_int sum = 0;
        int nwords = len >> 1;

        while (nwords-- != 0)
                sum += *p++;

        if (len & 1)
                sum += *(u_char *)p;

        /* end-around-carry */
        sum = (sum >> 16) + (sum & 0xffff);
        sum += (sum >> 16);
        return (~sum);
}


/* Send a router discovery advertisement or solicitation ICMP packet.
 */
static void
send_rdisc(union ad_u *p,
           int p_size,
           struct interface *ifp,
           naddr dst,                   /* 0 or unicast destination */
           int  type)                   /* 0=unicast, 1=bcast, 2=mcast */
{
        struct sockaddr_in rsin;
        int flags;
        const char *msg;


        memset(&rsin, 0, sizeof(rsin));
        rsin.sin_addr.s_addr = dst;
        rsin.sin_family = AF_INET;
#ifdef _HAVE_SIN_LEN
        rsin.sin_len = sizeof(rsin);
#endif
        flags = MSG_DONTROUTE;

        switch (type) {
        case 0:                         /* unicast */
        default:
                msg = "Send";
                break;

        case 1:                         /* broadcast */
                if (ifp->int_if_flags & IFF_POINTOPOINT) {
                        msg = "Send pt-to-pt";
                        rsin.sin_addr.s_addr = ifp->int_dstaddr;
                } else {
                        msg = "Send broadcast";
                        rsin.sin_addr.s_addr = ifp->int_brdaddr;
                }
                break;

        case 2:                         /* multicast */
                msg = "Send multicast";
                if (ifp->int_state & IS_DUP) {
                        trace_act("abort multicast output via %s"
                                  " with duplicate address",
                                  ifp->int_name);
                        return;
                }
                if (rdisc_sock_mcast != ifp) {
                        /* select the right interface. */
                        struct ip_mreqn mreqn;

                        memset(&mreqn, 0, sizeof(struct ip_mreqn));
                        mreqn.imr_ifindex = ifp->int_index;
                        if (0 > setsockopt(rdisc_sock,
                                           IPPROTO_IP, IP_MULTICAST_IF,
                                           &mreqn,
                                           sizeof(mreqn))) {
                                LOGERR("setsockopt(rdisc_sock,"
                                       "IP_MULTICAST_IF)");
                                rdisc_sock_mcast = NULL;
                                return;
                        }
                        rdisc_sock_mcast = ifp;
                }
                flags = 0;
                break;
        }

        if (rdisc_sock < 0)
                get_rdisc_sock();

        trace_rdisc(msg, (ifp ? ifp->int_addr : 0), rsin.sin_addr.s_addr, ifp,
                    p, p_size);

        if (0 > sendto(rdisc_sock, p, p_size, flags,
                       (struct sockaddr *)&rsin, sizeof(rsin))) {
                if (ifp == NULL || !(ifp->int_state & IS_BROKE))
                        msglog("sendto(%s%s%s): %s",
                               ifp != NULL ? ifp->int_name : "",
                               ifp != NULL ? ", " : "",
                               inet_ntoa(rsin.sin_addr),
                               strerror(errno));
                if (ifp != NULL)
                        if_sick(ifp);
        }
}


/* Send an advertisement
 */
static void
send_adv(struct interface *ifp,
         naddr  dst,                    /* 0 or unicast destination */
         int    type)                   /* 0=unicast, 1=bcast, 2=mcast */
{
        union ad_u u;
        n_long pref;


        memset(&u, 0, sizeof(u.ad));

        u.ad.icmp_type = ICMP_ROUTERADVERT;
        u.ad.icmp_ad_num = 1;
        u.ad.icmp_ad_asize = sizeof(u.ad.icmp_ad_info[0])/4;

        u.ad.icmp_ad_life = stopint ? 0 : htons(ifp->int_rdisc_int*3);

        /* Convert the configured preference to an unsigned value,
         * bias it by the interface metric, and then send it as a
         * signed, network byte order value.
         */
        pref = UNSIGN_PREF(ifp->int_rdisc_pref);
        u.ad.icmp_ad_info[0].icmp_ad_pref = htonl(SIGN_PREF(PREF(pref, ifp)));

        u.ad.icmp_ad_info[0].icmp_ad_addr = ifp->int_addr;

        u.ad.icmp_cksum = in_cksum((u_short*)&u.ad, sizeof(u.ad));

        send_rdisc(&u, sizeof(u.ad), ifp, dst, type);
}


/* Advertise for Router Discovery
 */
void
rdisc_adv(void)
{
        struct interface *ifp;

        if (!supplier)
                return;

        rdisc_timer.tv_sec = now.tv_sec + NEVER;

        LIST_FOREACH(ifp, &ifnet, int_list) {
                if (0 != (ifp->int_state & (IS_NO_ADV_OUT | IS_BROKE)))
                        continue;

                if (!timercmp(&ifp->int_rdisc_timer, &now, >)
                    || stopint) {
                        send_adv(ifp, htonl(INADDR_ALLHOSTS_GROUP),
                                 (ifp->int_state&IS_BCAST_RDISC) ? 1 : 2);
                        ifp->int_rdisc_cnt++;

                        intvl_random(&ifp->int_rdisc_timer,
                                     (ifp->int_rdisc_int*3)/4,
                                     ifp->int_rdisc_int);
                        if (ifp->int_rdisc_cnt < MAX_INITIAL_ADVERTS
                            && (ifp->int_rdisc_timer.tv_sec
                                > MAX_INITIAL_ADVERT_INTERVAL)) {
                                ifp->int_rdisc_timer.tv_sec
                                = MAX_INITIAL_ADVERT_INTERVAL;
                        }
                        timevaladd(&ifp->int_rdisc_timer, &now);
                }

                if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
                        rdisc_timer = ifp->int_rdisc_timer;
        }
}


/* Solicit for Router Discovery
 */
void
rdisc_sol(void)
{
        struct interface *ifp;
        union ad_u u;


        if (supplier)
                return;

        rdisc_timer.tv_sec = now.tv_sec + NEVER;

        LIST_FOREACH(ifp, &ifnet, int_list) {
                if (0 != (ifp->int_state & (IS_NO_SOL_OUT | IS_BROKE))
                    || ifp->int_rdisc_cnt >= MAX_SOLICITATIONS)
                        continue;

                if (!timercmp(&ifp->int_rdisc_timer, &now, >)) {
                        memset(&u, 0, sizeof(u.so));
                        u.so.icmp_type = ICMP_ROUTERSOLICIT;
                        u.so.icmp_cksum = in_cksum((u_short*)&u.so,
                                                   sizeof(u.so));
                        send_rdisc(&u, sizeof(u.so), ifp,
                                   htonl(INADDR_ALLROUTERS_GROUP),
                                   ((ifp->int_state&IS_BCAST_RDISC) ? 1 : 2));

                        if (++ifp->int_rdisc_cnt >= MAX_SOLICITATIONS)
                                continue;

                        ifp->int_rdisc_timer.tv_sec = SOLICITATION_INTERVAL;
                        ifp->int_rdisc_timer.tv_usec = 0;
                        timevaladd(&ifp->int_rdisc_timer, &now);
                }

                if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
                        rdisc_timer = ifp->int_rdisc_timer;
        }
}


/* check the IP header of a possible Router Discovery ICMP packet */
static struct interface *               /* 0 if bad */
ck_icmp(const char *act,
        naddr   from,
        struct interface *ifp,
        naddr   to,
        union ad_u *p,
        u_int   len)
{
        const char *type;


        if (p->icmp.icmp_type == ICMP_ROUTERADVERT) {
                type = "advertisement";
        } else if (p->icmp.icmp_type == ICMP_ROUTERSOLICIT) {
                type = "solicitation";
        } else {
                return 0;
        }

        if (p->icmp.icmp_code != 0) {
                trace_pkt("unrecognized ICMP Router %s code=%d from %s to %s",
                          type, p->icmp.icmp_code,
                          naddr_ntoa(from), naddr_ntoa(to));
                return 0;
        }

        trace_rdisc(act, from, to, ifp, p, len);

        if (ifp == NULL)
                trace_pkt("unknown interface for router-discovery %s"
                          " from %s to %s",
                          type, naddr_ntoa(from), naddr_ntoa(to));

        return ifp;
}


/* read packets from the router discovery socket
 */
void
read_d(void)
{
        static struct msg_limit bad_asize, bad_len;
#ifdef USE_PASSIFNAME
        static struct msg_limit  bad_name;
#endif
        struct sockaddr_in from;
        int n, fromlen, cc, hlen;
        struct {
#ifdef USE_PASSIFNAME
                char    ifname[IFNAMSIZ];
#endif
                union {
                        struct ip ip;
                        u_char  b[512];
                } pkt;
        } buf;
        union ad_u *p;
        n_long *wp;
        struct interface *ifp;


        for (;;) {
                fromlen = sizeof(from);
                cc = recvfrom(rdisc_sock, &buf, sizeof(buf), 0,
                              (struct sockaddr*)&from,
                              &fromlen);
                if (cc <= 0) {
                        if (cc < 0 && errno != EWOULDBLOCK)
                                LOGERR("recvfrom(rdisc_sock)");
                        break;
                }
                if (fromlen != sizeof(struct sockaddr_in))
                        logbad(1,"impossible recvfrom(rdisc_sock) fromlen=%d",
                               fromlen);
#ifdef USE_PASSIFNAME
                if ((cc -= sizeof(buf.ifname)) < 0)
                        logbad(0,"missing USE_PASSIFNAME; only %d bytes",
                               cc+sizeof(buf.ifname));
#endif

                hlen = buf.pkt.ip.ip_hl << 2;
                if (cc < hlen + ICMP_MINLEN)
                        continue;
                p = (union ad_u *)&buf.pkt.b[hlen];
                cc -= hlen;

#ifdef USE_PASSIFNAME
                ifp = ifwithname(buf.ifname, 0);
                if (ifp == NULL)
                        msglim(&bad_name, from.sin_addr.s_addr,
                               "impossible rdisc if_ name %.*s",
                               IFNAMSIZ, buf.ifname);
#else
                /* If we could tell the interface on which a packet from
                 * address 0 arrived, we could deal with such solicitations.
                 */
                ifp = ((from.sin_addr.s_addr == 0)
                       ? 0 : iflookup(from.sin_addr.s_addr));
#endif
                ifp = ck_icmp("Recv", from.sin_addr.s_addr, ifp,
                              buf.pkt.ip.ip_dst.s_addr, p, cc);
                if (ifp == NULL)
                        continue;
                if (ifwithaddr(from.sin_addr.s_addr, 0, 0)) {
                        trace_pkt("    "
                                  "discard our own Router Discovery message");
                        continue;
                }

                switch (p->icmp.icmp_type) {
                case ICMP_ROUTERADVERT:
                        if (p->ad.icmp_ad_asize*4
                            < (int)sizeof(p->ad.icmp_ad_info[0])) {
                                msglim(&bad_asize, from.sin_addr.s_addr,
                                       "intolerable rdisc address size=%d",
                                       p->ad.icmp_ad_asize);
                                continue;
                        }
                        if (p->ad.icmp_ad_num == 0) {
                                trace_pkt("    empty?");
                                continue;
                        }
                        if (cc != (int)(sizeof(p->ad)
                                        - sizeof(p->ad.icmp_ad_info)
                                        + (p->ad.icmp_ad_num
                                           * sizeof(p->ad.icmp_ad_info[0])))) {
                                msglim(&bad_len, from.sin_addr.s_addr,
                                       "rdisc length %d does not match ad_num"
                                       " %d", cc, p->ad.icmp_ad_num);
                                continue;
                        }
                        if (supplier)
                                continue;
                        if (ifp->int_state & IS_NO_ADV_IN)
                                continue;

                        wp = &p->ad.icmp_ad_info[0].icmp_ad_addr;
                        for (n = 0; n < p->ad.icmp_ad_num; n++) {
                                parse_ad(from.sin_addr.s_addr,
                                         wp[0], wp[1],
                                         ntohs(p->ad.icmp_ad_life),
                                         ifp);
                                wp += p->ad.icmp_ad_asize;
                        }
                        break;


                case ICMP_ROUTERSOLICIT:
                        if (!supplier)
                                continue;
                        if (ifp->int_state & IS_NO_ADV_OUT)
                                continue;
                        if (stopint)
                                continue;

                        /* XXX
                         * We should handle messages from address 0.
                         */

                        /* Respond with a point-to-point advertisement */
                        send_adv(ifp, from.sin_addr.s_addr, 0);
                        break;
                }
        }

        rdisc_sort();
}