top.1: Improve description of -m

[FreeBSD/FreeBSD.git] / sbin / routed / table.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1983, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. 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.
 *
 * $FreeBSD$
 */

#include "defs.h"

__RCSID("$FreeBSD$");

static struct rt_spare *rts_better(struct rt_entry *);
static struct rt_spare rts_empty = {0,0,0,HOPCNT_INFINITY,0,0,0};
static void  set_need_flash(void);
#ifdef _HAVE_SIN_LEN
static void masktrim(struct sockaddr_in *ap);
#else
static void masktrim(struct sockaddr_in_new *ap);
#endif
static void rtbad(struct rt_entry *);


struct radix_node_head *rhead;          /* root of the radix tree */

int     need_flash = 1;                 /* flash update needed
                                         * start =1 to suppress the 1st
                                         */

struct timeval age_timer;               /* next check of old routes */
struct timeval need_kern = {            /* need to update kernel table */
        EPOCH+MIN_WAITTIME-1, 0
};

int     stopint;

int     total_routes;

/* zap any old routes through this gateway */
static naddr age_bad_gate;


/* It is desirable to "aggregate" routes, to combine differing routes of
 * the same metric and next hop into a common route with a smaller netmask
 * or to suppress redundant routes, routes that add no information to
 * routes with smaller netmasks.
 *
 * A route is redundant if and only if any and all routes with smaller
 * but matching netmasks and nets are the same.  Since routes are
 * kept sorted in the radix tree, redundant routes always come second.
 *
 * There are two kinds of aggregations.  First, two routes of the same bit
 * mask and differing only in the least significant bit of the network
 * number can be combined into a single route with a coarser mask.
 *
 * Second, a route can be suppressed in favor of another route with a more
 * coarse mask provided no incompatible routes with intermediate masks
 * are present.  The second kind of aggregation involves suppressing routes.
 * A route must not be suppressed if an incompatible route exists with
 * an intermediate mask, since the suppressed route would be covered
 * by the intermediate.
 *
 * This code relies on the radix tree walk encountering routes
 * sorted first by address, with the smallest address first.
 */

static struct ag_info ag_slots[NUM_AG_SLOTS], *ag_avail, *ag_corsest, *ag_finest;

/* #define DEBUG_AG */
#ifdef DEBUG_AG
#define CHECK_AG() {int acnt = 0; struct ag_info *cag;          \
        for (cag = ag_avail; cag != NULL; cag = cag->ag_fine)   \
                acnt++;                                         \
        for (cag = ag_corsest; cag != NULL; cag = cag->ag_fine) \
                acnt++;                                         \
        if (acnt != NUM_AG_SLOTS) {                             \
                (void)fflush(stderr);                           \
                abort();                                        \
        }                                                       \
}
#else
#define CHECK_AG()
#endif


/* Output the contents of an aggregation table slot.
 *      This function must always be immediately followed with the deletion
 *      of the target slot.
 */
static void
ag_out(struct ag_info *ag,
         void (*out)(struct ag_info *))
{
        struct ag_info *ag_cors;
        naddr bit;


        /* Forget it if this route should not be output for split-horizon. */
        if (ag->ag_state & AGS_SPLIT_HZ)
                return;

        /* If we output both the even and odd twins, then the immediate parent,
         * if it is present, is redundant, unless the parent manages to
         * aggregate into something coarser.
         * On successive calls, this code detects the even and odd twins,
         * and marks the parent.
         *
         * Note that the order in which the radix tree code emits routes
         * ensures that the twins are seen before the parent is emitted.
         */
        ag_cors = ag->ag_cors;
        if (ag_cors != NULL
            && ag_cors->ag_mask == ag->ag_mask<<1
            && ag_cors->ag_dst_h == (ag->ag_dst_h & ag_cors->ag_mask)) {
                ag_cors->ag_state |= ((ag_cors->ag_dst_h == ag->ag_dst_h)
                                      ? AGS_REDUN0
                                      : AGS_REDUN1);
        }

        /* Skip it if this route is itself redundant.
         *
         * It is ok to change the contents of the slot here, since it is
         * always deleted next.
         */
        if (ag->ag_state & AGS_REDUN0) {
                if (ag->ag_state & AGS_REDUN1)
                        return;         /* quit if fully redundant */
                /* make it finer if it is half-redundant */
                bit = (-ag->ag_mask) >> 1;
                ag->ag_dst_h |= bit;
                ag->ag_mask |= bit;

        } else if (ag->ag_state & AGS_REDUN1) {
                /* make it finer if it is half-redundant */
                bit = (-ag->ag_mask) >> 1;
                ag->ag_mask |= bit;
        }
        out(ag);
}


static void
ag_del(struct ag_info *ag)
{
        CHECK_AG();

        if (ag->ag_cors == NULL)
                ag_corsest = ag->ag_fine;
        else
                ag->ag_cors->ag_fine = ag->ag_fine;

        if (ag->ag_fine == NULL)
                ag_finest = ag->ag_cors;
        else
                ag->ag_fine->ag_cors = ag->ag_cors;

        ag->ag_fine = ag_avail;
        ag_avail = ag;

        CHECK_AG();
}


/* Flush routes waiting for aggregation.
 *      This must not suppress a route unless it is known that among all
 *      routes with coarser masks that match it, the one with the longest
 *      mask is appropriate.  This is ensured by scanning the routes
 *      in lexical order, and with the most restrictive mask first
 *      among routes to the same destination.
 */
void
ag_flush(naddr lim_dst_h,               /* flush routes to here */
         naddr lim_mask,                /* matching this mask */
         void (*out)(struct ag_info *))
{
        struct ag_info *ag, *ag_cors;
        naddr dst_h;


        for (ag = ag_finest;
             ag != NULL && ag->ag_mask >= lim_mask;
             ag = ag_cors) {
                ag_cors = ag->ag_cors;

                /* work on only the specified routes */
                dst_h = ag->ag_dst_h;
                if ((dst_h & lim_mask) != lim_dst_h)
                        continue;

                if (!(ag->ag_state & AGS_SUPPRESS))
                        ag_out(ag, out);

                else for ( ; ; ag_cors = ag_cors->ag_cors) {
                        /* Look for a route that can suppress the
                         * current route */
                        if (ag_cors == NULL) {
                                /* failed, so output it and look for
                                 * another route to work on
                                 */
                                ag_out(ag, out);
                                break;
                        }

                        if ((dst_h & ag_cors->ag_mask) == ag_cors->ag_dst_h) {
                                /* We found a route with a coarser mask that
                                 * aggregates the current target.
                                 *
                                 * If it has a different next hop, it
                                 * cannot replace the target, so output
                                 * the target.
                                 */
                                if (ag->ag_gate != ag_cors->ag_gate
                                    && !(ag->ag_state & AGS_FINE_GATE)
                                    && !(ag_cors->ag_state & AGS_CORS_GATE)) {
                                        ag_out(ag, out);
                                        break;
                                }

                                /* If the coarse route has a good enough
                                 * metric, it suppresses the target.
                                 * If the suppressed target was redundant,
                                 * then mark the suppressor redundant.
                                 */
                                if (ag_cors->ag_pref <= ag->ag_pref) {
                                    if (AG_IS_REDUN(ag->ag_state)
                                        && ag_cors->ag_mask==ag->ag_mask<<1) {
                                        if (ag_cors->ag_dst_h == dst_h)
                                            ag_cors->ag_state |= AGS_REDUN0;
                                        else
                                            ag_cors->ag_state |= AGS_REDUN1;
                                    }
                                    if (ag->ag_tag != ag_cors->ag_tag)
                                            ag_cors->ag_tag = 0;
                                    if (ag->ag_nhop != ag_cors->ag_nhop)
                                            ag_cors->ag_nhop = 0;
                                    break;
                                }
                        }
                }

                /* That route has either been output or suppressed */
                ag_cors = ag->ag_cors;
                ag_del(ag);
        }

        CHECK_AG();
}


/* Try to aggregate a route with previous routes.
 */
void
ag_check(naddr  dst,
         naddr  mask,
         naddr  gate,
         naddr  nhop,
         char   metric,
         char   pref,
         u_int  new_seqno,
         u_short tag,
         u_short state,
         void (*out)(struct ag_info *)) /* output using this */
{
        struct ag_info *ag, *nag, *ag_cors;
        naddr xaddr;
        int x;

        dst = ntohl(dst);

        /* Punt non-contiguous subnet masks.
         *
         * (X & -X) contains a single bit if and only if X is a power of 2.
         * (X + (X & -X)) == 0 if and only if X is a power of 2.
         */
        if ((mask & -mask) + mask != 0) {
                struct ag_info nc_ag;

                nc_ag.ag_dst_h = dst;
                nc_ag.ag_mask = mask;
                nc_ag.ag_gate = gate;
                nc_ag.ag_nhop = nhop;
                nc_ag.ag_metric = metric;
                nc_ag.ag_pref = pref;
                nc_ag.ag_tag = tag;
                nc_ag.ag_state = state;
                nc_ag.ag_seqno = new_seqno;
                out(&nc_ag);
                return;
        }

        /* Search for the right slot in the aggregation table.
         */
        ag_cors = NULL;
        ag = ag_corsest;
        while (ag != NULL) {
                if (ag->ag_mask >= mask)
                        break;

                /* Suppress old routes (i.e. combine with compatible routes
                 * with coarser masks) as we look for the right slot in the
                 * aggregation table for the new route.
                 * A route to an address less than the current destination
                 * will not be affected by the current route or any route
                 * seen hereafter.  That means it is safe to suppress it.
                 * This check keeps poor routes (e.g. with large hop counts)
                 * from preventing suppression of finer routes.
                 */
                if (ag_cors != NULL
                    && ag->ag_dst_h < dst
                    && (ag->ag_state & AGS_SUPPRESS)
                    && ag_cors->ag_pref <= ag->ag_pref
                    && (ag->ag_dst_h & ag_cors->ag_mask) == ag_cors->ag_dst_h
                    && (ag_cors->ag_gate == ag->ag_gate
                        || (ag->ag_state & AGS_FINE_GATE)
                        || (ag_cors->ag_state & AGS_CORS_GATE))) {
                        /*  If the suppressed target was redundant,
                         * then mark the suppressor redundant.
                         */
                        if (AG_IS_REDUN(ag->ag_state)
                            && ag_cors->ag_mask == ag->ag_mask<<1) {
                                if (ag_cors->ag_dst_h == dst)
                                        ag_cors->ag_state |= AGS_REDUN0;
                                else
                                        ag_cors->ag_state |= AGS_REDUN1;
                        }
                        if (ag->ag_tag != ag_cors->ag_tag)
                                ag_cors->ag_tag = 0;
                        if (ag->ag_nhop != ag_cors->ag_nhop)
                                ag_cors->ag_nhop = 0;
                        ag_del(ag);
                        CHECK_AG();
                } else {
                        ag_cors = ag;
                }
                ag = ag_cors->ag_fine;
        }

        /* If we find the even/odd twin of the new route, and if the
         * masks and so forth are equal, we can aggregate them.
         * We can probably promote one of the pair.
         *
         * Since the routes are encountered in lexical order,
         * the new route must be odd.  However, the second or later
         * times around this loop, it could be the even twin promoted
         * from the even/odd pair of twins of the finer route.
         */
        while (ag != NULL
               && ag->ag_mask == mask
               && ((ag->ag_dst_h ^ dst) & (mask<<1)) == 0) {

                /* Here we know the target route and the route in the current
                 * slot have the same netmasks and differ by at most the
                 * last bit.  They are either for the same destination, or
                 * for an even/odd pair of destinations.
                 */
                if (ag->ag_dst_h == dst) {
                        /* We have two routes to the same destination.
                         * Routes are encountered in lexical order, so a
                         * route is never promoted until the parent route is
                         * already present.  So we know that the new route is
                         * a promoted (or aggregated) pair and the route
                         * already in the slot is the explicit route.
                         *
                         * Prefer the best route if their metrics differ,
                         * or the aggregated one if not, following a sort
                         * of longest-match rule.
                         */
                        if (pref <= ag->ag_pref) {
                                ag->ag_gate = gate;
                                ag->ag_nhop = nhop;
                                ag->ag_tag = tag;
                                ag->ag_metric = metric;
                                ag->ag_pref = pref;
                                if (ag->ag_seqno < new_seqno)
                                        ag->ag_seqno = new_seqno;
                                x = ag->ag_state;
                                ag->ag_state = state;
                                state = x;
                        }

                        /* Some bits are set if they are set on either route,
                         * except when the route is for an interface.
                         */
                        if (!(ag->ag_state & AGS_IF))
                                ag->ag_state |= (state & (AGS_AGGREGATE_EITHER
                                                        | AGS_REDUN0
                                                        | AGS_REDUN1));
                        return;
                }

                /* If one of the routes can be promoted and the other can
                 * be suppressed, it may be possible to combine them or
                 * worthwhile to promote one.
                 *
                 * Any route that can be promoted is always
                 * marked to be eligible to be suppressed.
                 */
                if (!((state & AGS_AGGREGATE)
                      && (ag->ag_state & AGS_SUPPRESS))
                    && !((ag->ag_state & AGS_AGGREGATE)
                         && (state & AGS_SUPPRESS)))
                        break;

                /* A pair of even/odd twin routes can be combined
                 * if either is redundant, or if they are via the
                 * same gateway and have the same metric.
                 */
                if (AG_IS_REDUN(ag->ag_state)
                    || AG_IS_REDUN(state)
                    || (ag->ag_gate == gate
                        && ag->ag_pref == pref
                        && (state & ag->ag_state & AGS_AGGREGATE) != 0)) {

                        /* We have both the even and odd pairs.
                         * Since the routes are encountered in order,
                         * the route in the slot must be the even twin.
                         *
                         * Combine and promote (aggregate) the pair of routes.
                         */
                        if (new_seqno < ag->ag_seqno)
                                new_seqno = ag->ag_seqno;
                        if (!AG_IS_REDUN(state))
                                state &= ~AGS_REDUN1;
                        if (AG_IS_REDUN(ag->ag_state))
                                state |= AGS_REDUN0;
                        else
                                state &= ~AGS_REDUN0;
                        state |= (ag->ag_state & AGS_AGGREGATE_EITHER);
                        if (ag->ag_tag != tag)
                                tag = 0;
                        if (ag->ag_nhop != nhop)
                                nhop = 0;

                        /* Get rid of the even twin that was already
                         * in the slot.
                         */
                        ag_del(ag);

                } else if (ag->ag_pref >= pref
                           && (ag->ag_state & AGS_AGGREGATE)) {
                        /* If we cannot combine the pair, maybe the route
                         * with the worse metric can be promoted.
                         *
                         * Promote the old, even twin, by giving its slot
                         * in the table to the new, odd twin.
                         */
                        ag->ag_dst_h = dst;

                        xaddr = ag->ag_gate;
                        ag->ag_gate = gate;
                        gate = xaddr;

                        xaddr = ag->ag_nhop;
                        ag->ag_nhop = nhop;
                        nhop = xaddr;

                        x = ag->ag_tag;
                        ag->ag_tag = tag;
                        tag = x;

                        /* The promoted route is even-redundant only if the
                         * even twin was fully redundant.  It is not
                         * odd-redundant because the odd-twin will still be
                         * in the table.
                         */
                        x = ag->ag_state;
                        if (!AG_IS_REDUN(x))
                                x &= ~AGS_REDUN0;
                        x &= ~AGS_REDUN1;
                        ag->ag_state = state;
                        state = x;

                        x = ag->ag_metric;
                        ag->ag_metric = metric;
                        metric = x;

                        x = ag->ag_pref;
                        ag->ag_pref = pref;
                        pref = x;

                        /* take the newest sequence number */
                        if (new_seqno <= ag->ag_seqno)
                                new_seqno = ag->ag_seqno;
                        else
                                ag->ag_seqno = new_seqno;

                } else {
                        if (!(state & AGS_AGGREGATE))
                                break;  /* cannot promote either twin */

                        /* Promote the new, odd twin by shaving its
                         * mask and address.
                         * The promoted route is odd-redundant only if the
                         * odd twin was fully redundant.  It is not
                         * even-redundant because the even twin is still in
                         * the table.
                         */
                        if (!AG_IS_REDUN(state))
                                state &= ~AGS_REDUN1;
                        state &= ~AGS_REDUN0;
                        if (new_seqno < ag->ag_seqno)
                                new_seqno = ag->ag_seqno;
                        else
                                ag->ag_seqno = new_seqno;
                }

                mask <<= 1;
                dst &= mask;

                if (ag_cors == NULL) {
                        ag = ag_corsest;
                        break;
                }
                ag = ag_cors;
                ag_cors = ag->ag_cors;
        }

        /* When we can no longer promote and combine routes,
         * flush the old route in the target slot.  Also flush
         * any finer routes that we know will never be aggregated by
         * the new route.
         *
         * In case we moved toward coarser masks,
         * get back where we belong
         */
        if (ag != NULL
            && ag->ag_mask < mask) {
                ag_cors = ag;
                ag = ag->ag_fine;
        }

        /* Empty the target slot
         */
        if (ag != NULL && ag->ag_mask == mask) {
                ag_flush(ag->ag_dst_h, ag->ag_mask, out);
                ag = (ag_cors == NULL) ? ag_corsest : ag_cors->ag_fine;
        }

#ifdef DEBUG_AG
        (void)fflush(stderr);
        if (ag == NULL && ag_cors != ag_finest)
                abort();
        if (ag_cors == NULL && ag != ag_corsest)
                abort();
        if (ag != NULL && ag->ag_cors != ag_cors)
                abort();
        if (ag_cors != NULL && ag_cors->ag_fine != ag)
                abort();
        CHECK_AG();
#endif

        /* Save the new route on the end of the table.
         */
        nag = ag_avail;
        ag_avail = nag->ag_fine;

        nag->ag_dst_h = dst;
        nag->ag_mask = mask;
        nag->ag_gate = gate;
        nag->ag_nhop = nhop;
        nag->ag_metric = metric;
        nag->ag_pref = pref;
        nag->ag_tag = tag;
        nag->ag_state = state;
        nag->ag_seqno = new_seqno;

        nag->ag_fine = ag;
        if (ag != NULL)
                ag->ag_cors = nag;
        else
                ag_finest = nag;
        nag->ag_cors = ag_cors;
        if (ag_cors == NULL)
                ag_corsest = nag;
        else
                ag_cors->ag_fine = nag;
        CHECK_AG();
}

static const char *
rtm_type_name(u_char type)
{
        static const char * const rtm_types[] = {
                "RTM_ADD",
                "RTM_DELETE",
                "RTM_CHANGE",
                "RTM_GET",
                "RTM_LOSING",
                "RTM_REDIRECT",
                "RTM_MISS",
                "RTM_LOCK",
                "RTM_OLDADD",
                "RTM_OLDDEL",
                "RTM_RESOLVE",
                "RTM_NEWADDR",
                "RTM_DELADDR",
#ifdef RTM_OIFINFO
                "RTM_OIFINFO",
#endif
                "RTM_IFINFO",
                "RTM_NEWMADDR",
                "RTM_DELMADDR"
        };
#define NEW_RTM_PAT "RTM type %#x"
        static char name0[sizeof(NEW_RTM_PAT)+2];


        if (type > sizeof(rtm_types)/sizeof(rtm_types[0])
            || type == 0) {
                snprintf(name0, sizeof(name0), NEW_RTM_PAT, type);
                return name0;
        } else {
                return rtm_types[type-1];
        }
#undef NEW_RTM_PAT
}


/* Trim a mask in a sockaddr
 *      Produce a length of 0 for an address of 0.
 *      Otherwise produce the index of the first zero byte.
 */
void
#ifdef _HAVE_SIN_LEN
masktrim(struct sockaddr_in *ap)
#else
masktrim(struct sockaddr_in_new *ap)
#endif
{
        char *cp;

        if (ap->sin_addr.s_addr == 0) {
                ap->sin_len = 0;
                return;
        }
        cp = (char *)(&ap->sin_addr.s_addr+1);
        while (*--cp == 0)
                continue;
        ap->sin_len = cp - (char*)ap + 1;
}


/* Tell the kernel to add, delete or change a route
 */
static void
rtioctl(int action,                     /* RTM_DELETE, etc */
        naddr dst,
        naddr gate,
        naddr mask,
        int metric,
        int flags)
{
        struct {
                struct rt_msghdr w_rtm;
                struct sockaddr_in w_dst;
                struct sockaddr_in w_gate;
#ifdef _HAVE_SA_LEN
                struct sockaddr_in w_mask;
#else
                struct sockaddr_in_new w_mask;
#endif
        } w;
        long cc;
#   define PAT " %-10s %s metric=%d flags=%#x"
#   define ARGS rtm_type_name(action), rtname(dst,mask,gate), metric, flags

again:
        memset(&w, 0, sizeof(w));
        w.w_rtm.rtm_msglen = sizeof(w);
        w.w_rtm.rtm_version = RTM_VERSION;
        w.w_rtm.rtm_type = action;
        w.w_rtm.rtm_flags = flags;
        w.w_rtm.rtm_seq = ++rt_sock_seqno;
        w.w_rtm.rtm_addrs = RTA_DST|RTA_GATEWAY;
        if (metric != 0 || action == RTM_CHANGE) {
                w.w_rtm.rtm_rmx.rmx_hopcount = metric;
                w.w_rtm.rtm_inits |= RTV_HOPCOUNT;
        }
        w.w_dst.sin_family = AF_INET;
        w.w_dst.sin_addr.s_addr = dst;
        w.w_gate.sin_family = AF_INET;
        w.w_gate.sin_addr.s_addr = gate;
#ifdef _HAVE_SA_LEN
        w.w_dst.sin_len = sizeof(w.w_dst);
        w.w_gate.sin_len = sizeof(w.w_gate);
#endif
        if (mask == HOST_MASK) {
                w.w_rtm.rtm_flags |= RTF_HOST;
                w.w_rtm.rtm_msglen -= sizeof(w.w_mask);
        } else {
                w.w_rtm.rtm_addrs |= RTA_NETMASK;
                w.w_mask.sin_addr.s_addr = htonl(mask);
#ifdef _HAVE_SA_LEN
                masktrim(&w.w_mask);
                if (w.w_mask.sin_len == 0)
                        w.w_mask.sin_len = sizeof(long);
                w.w_rtm.rtm_msglen -= (sizeof(w.w_mask) - w.w_mask.sin_len);
#endif
        }

#ifndef NO_INSTALL
        cc = write(rt_sock, &w, w.w_rtm.rtm_msglen);
        if (cc < 0) {
                if (errno == ESRCH
                    && (action == RTM_CHANGE || action == RTM_DELETE)) {
                        trace_act("route disappeared before" PAT, ARGS);
                        if (action == RTM_CHANGE) {
                                action = RTM_ADD;
                                goto again;
                        }
                        return;
                }
                msglog("write(rt_sock)" PAT ": %s", ARGS, strerror(errno));
                return;
        } else if (cc != w.w_rtm.rtm_msglen) {
                msglog("write(rt_sock) wrote %ld instead of %d for" PAT,
                       cc, w.w_rtm.rtm_msglen, ARGS);
                return;
        }
#endif
        if (TRACEKERNEL)
                trace_misc("write kernel" PAT, ARGS);
#undef PAT
#undef ARGS
}


#define KHASH_SIZE 71                   /* should be prime */
#define KHASH(a,m) khash_bins[((a) ^ (m)) % KHASH_SIZE]
static struct khash {
        struct khash *k_next;
        naddr   k_dst;
        naddr   k_mask;
        naddr   k_gate;
        short   k_metric;
        u_short k_state;
#define     KS_NEW      0x001
#define     KS_DELETE   0x002           /* need to delete the route */
#define     KS_ADD      0x004           /* add to the kernel */
#define     KS_CHANGE   0x008           /* tell kernel to change the route */
#define     KS_DEL_ADD  0x010           /* delete & add to change the kernel */
#define     KS_STATIC   0x020           /* Static flag in kernel */
#define     KS_GATEWAY  0x040           /* G flag in kernel */
#define     KS_DYNAMIC  0x080           /* result of redirect */
#define     KS_DELETED  0x100           /* already deleted from kernel */
#define     KS_CHECK    0x200
        time_t  k_keep;
#define     K_KEEP_LIM  30
        time_t  k_redirect_time;        /* when redirected route 1st seen */
} *khash_bins[KHASH_SIZE];


static struct khash*
kern_find(naddr dst, naddr mask, struct khash ***ppk)
{
        struct khash *k, **pk;

        for (pk = &KHASH(dst,mask); (k = *pk) != NULL; pk = &k->k_next) {
                if (k->k_dst == dst && k->k_mask == mask)
                        break;
        }
        if (ppk != NULL)
                *ppk = pk;
        return k;
}


static struct khash*
kern_add(naddr dst, naddr mask)
{
        struct khash *k, **pk;

        k = kern_find(dst, mask, &pk);
        if (k != NULL)
                return k;

        k = (struct khash *)rtmalloc(sizeof(*k), "kern_add");

        memset(k, 0, sizeof(*k));
        k->k_dst = dst;
        k->k_mask = mask;
        k->k_state = KS_NEW;
        k->k_keep = now.tv_sec;
        *pk = k;

        return k;
}


/* If a kernel route has a non-zero metric, check that it is still in the
 *      daemon table, and not deleted by interfaces coming and going.
 */
static void
kern_check_static(struct khash *k,
                  struct interface *ifp)
{
        struct rt_entry *rt;
        struct rt_spare new;

        if (k->k_metric == 0)
                return;

        memset(&new, 0, sizeof(new));
        new.rts_ifp = ifp;
        new.rts_gate = k->k_gate;
        new.rts_router = (ifp != NULL) ? ifp->int_addr : loopaddr;
        new.rts_metric = k->k_metric;
        new.rts_time = now.tv_sec;

        rt = rtget(k->k_dst, k->k_mask);
        if (rt != NULL) {
                if (!(rt->rt_state & RS_STATIC))
                        rtchange(rt, rt->rt_state | RS_STATIC, &new, 0);
        } else {
                rtadd(k->k_dst, k->k_mask, RS_STATIC, &new);
        }
}


/* operate on a kernel entry
 */
static void
kern_ioctl(struct khash *k,
           int action,                  /* RTM_DELETE, etc */
           int flags)

{
        switch (action) {
        case RTM_DELETE:
                k->k_state &= ~KS_DYNAMIC;
                if (k->k_state & KS_DELETED)
                        return;
                k->k_state |= KS_DELETED;
                break;
        case RTM_ADD:
                k->k_state &= ~KS_DELETED;
                break;
        case RTM_CHANGE:
                if (k->k_state & KS_DELETED) {
                        action = RTM_ADD;
                        k->k_state &= ~KS_DELETED;
                }
                break;
        }

        rtioctl(action, k->k_dst, k->k_gate, k->k_mask, k->k_metric, flags);
}


/* add a route the kernel told us
 */
static void
rtm_add(struct rt_msghdr *rtm,
        struct rt_addrinfo *info,
        time_t keep)
{
        struct khash *k;
        struct interface *ifp;
        naddr mask;


        if (rtm->rtm_flags & RTF_HOST) {
                mask = HOST_MASK;
        } else if (INFO_MASK(info) != 0) {
                mask = ntohl(S_ADDR(INFO_MASK(info)));
        } else {
                msglog("ignore %s without mask", rtm_type_name(rtm->rtm_type));
                return;
        }

        k = kern_add(S_ADDR(INFO_DST(info)), mask);
        if (k->k_state & KS_NEW)
                k->k_keep = now.tv_sec+keep;
        if (INFO_GATE(info) == 0) {
                trace_act("note %s without gateway",
                          rtm_type_name(rtm->rtm_type));
                k->k_metric = HOPCNT_INFINITY;
        } else if (INFO_GATE(info)->sa_family != AF_INET) {
                trace_act("note %s with gateway AF=%d",
                          rtm_type_name(rtm->rtm_type),
                          INFO_GATE(info)->sa_family);
                k->k_metric = HOPCNT_INFINITY;
        } else {
                k->k_gate = S_ADDR(INFO_GATE(info));
                k->k_metric = rtm->rtm_rmx.rmx_hopcount;
                if (k->k_metric < 0)
                        k->k_metric = 0;
                else if (k->k_metric > HOPCNT_INFINITY-1)
                        k->k_metric = HOPCNT_INFINITY-1;
        }
        k->k_state &= ~(KS_DELETE | KS_ADD | KS_CHANGE | KS_DEL_ADD
                        | KS_DELETED | KS_GATEWAY | KS_STATIC
                        | KS_NEW | KS_CHECK);
        if (rtm->rtm_flags & RTF_GATEWAY)
                k->k_state |= KS_GATEWAY;
        if (rtm->rtm_flags & RTF_STATIC)
                k->k_state |= KS_STATIC;

        if (0 != (rtm->rtm_flags & (RTF_DYNAMIC | RTF_MODIFIED))) {
                if (INFO_AUTHOR(info) != 0
                    && INFO_AUTHOR(info)->sa_family == AF_INET)
                        ifp = iflookup(S_ADDR(INFO_AUTHOR(info)));
                else
                        ifp = NULL;
                if (supplier
                    && (ifp == NULL || !(ifp->int_state & IS_REDIRECT_OK))) {
                        /* Routers are not supposed to listen to redirects,
                         * so delete it if it came via an unknown interface
                         * or the interface does not have special permission.
                         */
                        k->k_state &= ~KS_DYNAMIC;
                        k->k_state |= KS_DELETE;
                        LIM_SEC(need_kern, 0);
                        trace_act("mark for deletion redirected %s --> %s"
                                  " via %s",
                                  addrname(k->k_dst, k->k_mask, 0),
                                  naddr_ntoa(k->k_gate),
                                  ifp ? ifp->int_name : "unknown interface");
                } else {
                        k->k_state |= KS_DYNAMIC;
                        k->k_redirect_time = now.tv_sec;
                        trace_act("accept redirected %s --> %s via %s",
                                  addrname(k->k_dst, k->k_mask, 0),
                                  naddr_ntoa(k->k_gate),
                                  ifp ? ifp->int_name : "unknown interface");
                }
                return;
        }

        /* If it is not a static route, quit until the next comparison
         * between the kernel and daemon tables, when it will be deleted.
         */
        if (!(k->k_state & KS_STATIC)) {
                k->k_state |= KS_DELETE;
                LIM_SEC(need_kern, k->k_keep);
                return;
        }

        /* Put static routes with real metrics into the daemon table so
         * they can be advertised.
         *
         * Find the interface toward the gateway.
         */
        ifp = iflookup(k->k_gate);
        if (ifp == NULL)
                msglog("static route %s --> %s impossibly lacks ifp",
                       addrname(S_ADDR(INFO_DST(info)), mask, 0),
                       naddr_ntoa(k->k_gate));

        kern_check_static(k, ifp);
}


/* deal with packet loss
 */
static void
rtm_lose(struct rt_msghdr *rtm,
         struct rt_addrinfo *info)
{
        if (INFO_GATE(info) == 0
            || INFO_GATE(info)->sa_family != AF_INET) {
                trace_act("ignore %s without gateway",
                          rtm_type_name(rtm->rtm_type));
                return;
        }

        if (rdisc_ok)
                rdisc_age(S_ADDR(INFO_GATE(info)));
        age(S_ADDR(INFO_GATE(info)));
}


/* Make the gateway slot of an info structure point to something
 * useful.  If it is not already useful, but it specifies an interface,
 * then fill in the sockaddr_in provided and point it there.
 */
static int
get_info_gate(struct sockaddr **sap,
              struct sockaddr_in *rsin)
{
        struct sockaddr_dl *sdl = (struct sockaddr_dl *)*sap;
        struct interface *ifp;

        if (sdl == NULL)
                return 0;
        if ((sdl)->sdl_family == AF_INET)
                return 1;
        if ((sdl)->sdl_family != AF_LINK)
                return 0;

        ifp = ifwithindex(sdl->sdl_index, 1);
        if (ifp == NULL)
                return 0;

        rsin->sin_addr.s_addr = ifp->int_addr;
#ifdef _HAVE_SA_LEN
        rsin->sin_len = sizeof(*rsin);
#endif
        rsin->sin_family = AF_INET;
        *sap = (struct sockaddr*)rsin;

        return 1;
}


/* Clean the kernel table by copying it to the daemon image.
 * Eventually the daemon will delete any extra routes.
 */
void
flush_kern(void)
{
        static char *sysctl_buf;
        static size_t sysctl_buf_size = 0;
        size_t needed;
        int mib[6];
        char *next, *lim;
        struct rt_msghdr *rtm;
        struct sockaddr_in gate_sin;
        struct rt_addrinfo info;
        int i;
        struct khash *k;


        for (i = 0; i < KHASH_SIZE; i++) {
                for (k = khash_bins[i]; k != NULL; k = k->k_next) {
                        k->k_state |= KS_CHECK;
                }
        }

        mib[0] = CTL_NET;
        mib[1] = PF_ROUTE;
        mib[2] = 0;             /* protocol */
        mib[3] = 0;             /* wildcard address family */
        mib[4] = NET_RT_DUMP;
        mib[5] = 0;             /* no flags */
        for (;;) {
                if ((needed = sysctl_buf_size) != 0) {
                        if (sysctl(mib, 6, sysctl_buf,&needed, 0, 0) >= 0)
                                break;
                        if (errno != ENOMEM && errno != EFAULT)
                                BADERR(1,"flush_kern: sysctl(RT_DUMP)");
                        free(sysctl_buf);
                        needed = 0;
                }
                if (sysctl(mib, 6, 0, &needed, 0, 0) < 0)
                        BADERR(1,"flush_kern: sysctl(RT_DUMP) estimate");
                /* Kludge around the habit of some systems, such as
                 * BSD/OS 3.1, to not admit how many routes are in the
                 * kernel, or at least to be quite wrong.
                 */
                needed += 50*(sizeof(*rtm)+5*sizeof(struct sockaddr));
                sysctl_buf = rtmalloc(sysctl_buf_size = needed,
                                      "flush_kern sysctl(RT_DUMP)");
        }

        lim = sysctl_buf + needed;
        for (next = sysctl_buf; next < lim; next += rtm->rtm_msglen) {
                rtm = (struct rt_msghdr *)next;
                if (rtm->rtm_msglen == 0) {
                        msglog("zero length kernel route at "
                               " %#lx in buffer %#lx before %#lx",
                               (u_long)rtm, (u_long)sysctl_buf, (u_long)lim);
                        break;
                }

                rt_xaddrs(&info,
                          (struct sockaddr *)(rtm+1),
                          (struct sockaddr *)(next + rtm->rtm_msglen),
                          rtm->rtm_addrs);

                if (INFO_DST(&info) == 0
                    || INFO_DST(&info)->sa_family != AF_INET)
                        continue;

#if defined (RTF_LLINFO)                
                /* ignore ARP table entries on systems with a merged route
                 * and ARP table.
                 */
                if (rtm->rtm_flags & RTF_LLINFO)
                        continue;
#endif
#if defined(RTF_WASCLONED) && defined(__FreeBSD__)
                /* ignore cloned routes
                 */
                if (rtm->rtm_flags & RTF_WASCLONED)
                        continue;
#endif

                /* ignore multicast addresses
                 */
                if (IN_MULTICAST(ntohl(S_ADDR(INFO_DST(&info)))))
                        continue;

                if (!get_info_gate(&INFO_GATE(&info), &gate_sin))
                        continue;

                /* Note static routes and interface routes, and also
                 * preload the image of the kernel table so that
                 * we can later clean it, as well as avoid making
                 * unneeded changes.  Keep the old kernel routes for a
                 * few seconds to allow a RIP or router-discovery
                 * response to be heard.
                 */
                rtm_add(rtm,&info,MIN_WAITTIME);
        }

        for (i = 0; i < KHASH_SIZE; i++) {
                for (k = khash_bins[i]; k != NULL; k = k->k_next) {
                        if (k->k_state & KS_CHECK) {
                                msglog("%s --> %s disappeared from kernel",
                                       addrname(k->k_dst, k->k_mask, 0),
                                       naddr_ntoa(k->k_gate));
                                del_static(k->k_dst, k->k_mask, k->k_gate, 1);
                        }
                }
        }
}


/* Listen to announcements from the kernel
 */
void
read_rt(void)
{
        long cc;
        struct interface *ifp;
        struct sockaddr_in gate_sin;
        naddr mask, gate;
        union {
                struct {
                        struct rt_msghdr rtm;
                        struct sockaddr addrs[RTAX_MAX];
                } r;
                struct if_msghdr ifm;
        } m;
        char str[100], *strp;
        struct rt_addrinfo info;


        for (;;) {
                cc = read(rt_sock, &m, sizeof(m));
                if (cc <= 0) {
                        if (cc < 0 && errno != EWOULDBLOCK)
                                LOGERR("read(rt_sock)");
                        return;
                }

                if (m.r.rtm.rtm_version != RTM_VERSION) {
                        msglog("bogus routing message version %d",
                               m.r.rtm.rtm_version);
                        continue;
                }

                /* Ignore our own results.
                 */
                if (m.r.rtm.rtm_type <= RTM_CHANGE
                    && m.r.rtm.rtm_pid == mypid) {
                        static int complained = 0;
                        if (!complained) {
                                msglog("receiving our own change messages");
                                complained = 1;
                        }
                        continue;
                }

                if (m.r.rtm.rtm_type == RTM_IFINFO
                    || m.r.rtm.rtm_type == RTM_NEWADDR
                    || m.r.rtm.rtm_type == RTM_DELADDR) {
                        ifp = ifwithindex(m.ifm.ifm_index,
                                          m.r.rtm.rtm_type != RTM_DELADDR);
                        if (ifp == NULL)
                                trace_act("note %s with flags %#x"
                                          " for unknown interface index #%d",
                                          rtm_type_name(m.r.rtm.rtm_type),
                                          m.ifm.ifm_flags,
                                          m.ifm.ifm_index);
                        else
                                trace_act("note %s with flags %#x for %s",
                                          rtm_type_name(m.r.rtm.rtm_type),
                                          m.ifm.ifm_flags,
                                          ifp->int_name);

                        /* After being informed of a change to an interface,
                         * check them all now if the check would otherwise
                         * be a long time from now, if the interface is
                         * not known, or if the interface has been turned
                         * off or on.
                         */
                        if (ifinit_timer.tv_sec-now.tv_sec>=CHECK_BAD_INTERVAL
                            || ifp == NULL
                            || ((ifp->int_if_flags ^ m.ifm.ifm_flags)
                                & IFF_UP) != 0)
                                ifinit_timer.tv_sec = now.tv_sec;
                        continue;
                }
#ifdef RTM_OIFINFO
                if (m.r.rtm.rtm_type == RTM_OIFINFO)
                        continue;       /* ignore compat message */
#endif

                strlcpy(str, rtm_type_name(m.r.rtm.rtm_type), sizeof(str));
                strp = &str[strlen(str)];
                if (m.r.rtm.rtm_type <= RTM_CHANGE)
                        strp += sprintf(strp," from pid %d",m.r.rtm.rtm_pid);

                /*
                 * Only messages that use the struct rt_msghdr format are
                 * allowed beyond this point.
                 */
                if (m.r.rtm.rtm_type > RTM_RESOLVE) {
                        trace_act("ignore %s", str);
                        continue;
                }
                
                rt_xaddrs(&info, m.r.addrs, &m.r.addrs[RTAX_MAX],
                          m.r.rtm.rtm_addrs);

                if (INFO_DST(&info) == 0) {
                        trace_act("ignore %s without dst", str);
                        continue;
                }

                if (INFO_DST(&info)->sa_family != AF_INET) {
                        trace_act("ignore %s for AF %d", str,
                                  INFO_DST(&info)->sa_family);
                        continue;
                }

                mask = ((INFO_MASK(&info) != 0)
                        ? ntohl(S_ADDR(INFO_MASK(&info)))
                        : (m.r.rtm.rtm_flags & RTF_HOST)
                        ? HOST_MASK
                        : std_mask(S_ADDR(INFO_DST(&info))));

                strp += sprintf(strp, ": %s",
                                addrname(S_ADDR(INFO_DST(&info)), mask, 0));

                if (IN_MULTICAST(ntohl(S_ADDR(INFO_DST(&info))))) {
                        trace_act("ignore multicast %s", str);
                        continue;
                }

#if defined(RTF_LLINFO) 
                if (m.r.rtm.rtm_flags & RTF_LLINFO) {
                        trace_act("ignore ARP %s", str);
                        continue;
                }
#endif
                
#if defined(RTF_WASCLONED) && defined(__FreeBSD__)
                if (m.r.rtm.rtm_flags & RTF_WASCLONED) {
                        trace_act("ignore cloned %s", str);
                        continue;
                }
#endif

                if (get_info_gate(&INFO_GATE(&info), &gate_sin)) {
                        gate = S_ADDR(INFO_GATE(&info));
                        strp += sprintf(strp, " --> %s", naddr_ntoa(gate));
                } else {
                        gate = 0;
                }

                if (INFO_AUTHOR(&info) != 0)
                        strp += sprintf(strp, " by authority of %s",
                                        saddr_ntoa(INFO_AUTHOR(&info)));

                switch (m.r.rtm.rtm_type) {
                case RTM_ADD:
                case RTM_CHANGE:
                case RTM_REDIRECT:
                        if (m.r.rtm.rtm_errno != 0) {
                                trace_act("ignore %s with \"%s\" error",
                                          str, strerror(m.r.rtm.rtm_errno));
                        } else {
                                trace_act("%s", str);
                                rtm_add(&m.r.rtm,&info,0);
                        }
                        break;

                case RTM_DELETE:
                        if (m.r.rtm.rtm_errno != 0
                            && m.r.rtm.rtm_errno != ESRCH) {
                                trace_act("ignore %s with \"%s\" error",
                                          str, strerror(m.r.rtm.rtm_errno));
                        } else {
                                trace_act("%s", str);
                                del_static(S_ADDR(INFO_DST(&info)), mask,
                                           gate, 1);
                        }
                        break;

                case RTM_LOSING:
                        trace_act("%s", str);
                        rtm_lose(&m.r.rtm,&info);
                        break;

                default:
                        trace_act("ignore %s", str);
                        break;
                }
        }
}


/* after aggregating, note routes that belong in the kernel
 */
static void
kern_out(struct ag_info *ag)
{
        struct khash *k;


        /* Do not install bad routes if they are not already present.
         * This includes routes that had RS_NET_SYN for interfaces that
         * recently died.
         */
        if (ag->ag_metric == HOPCNT_INFINITY) {
                k = kern_find(htonl(ag->ag_dst_h), ag->ag_mask, 0);
                if (k == NULL)
                        return;
        } else {
                k = kern_add(htonl(ag->ag_dst_h), ag->ag_mask);
        }

        if (k->k_state & KS_NEW) {
                /* will need to add new entry to the kernel table */
                k->k_state = KS_ADD;
                if (ag->ag_state & AGS_GATEWAY)
                        k->k_state |= KS_GATEWAY;
                k->k_gate = ag->ag_gate;
                k->k_metric = ag->ag_metric;
                return;
        }

        if (k->k_state & KS_STATIC)
                return;

        /* modify existing kernel entry if necessary */
        if (k->k_gate != ag->ag_gate
            || k->k_metric != ag->ag_metric) {
                /* Must delete bad interface routes etc. to change them. */
                if (k->k_metric == HOPCNT_INFINITY)
                        k->k_state |= KS_DEL_ADD;
                k->k_gate = ag->ag_gate;
                k->k_metric = ag->ag_metric;
                k->k_state |= KS_CHANGE;
        }

        /* If the daemon thinks the route should exist, forget
         * about any redirections.
         * If the daemon thinks the route should exist, eventually
         * override manual intervention by the operator.
         */
        if ((k->k_state & (KS_DYNAMIC | KS_DELETED)) != 0) {
                k->k_state &= ~KS_DYNAMIC;
                k->k_state |= (KS_ADD | KS_DEL_ADD);
        }

        if ((k->k_state & KS_GATEWAY)
            && !(ag->ag_state & AGS_GATEWAY)) {
                k->k_state &= ~KS_GATEWAY;
                k->k_state |= (KS_ADD | KS_DEL_ADD);
        } else if (!(k->k_state & KS_GATEWAY)
                   && (ag->ag_state & AGS_GATEWAY)) {
                k->k_state |= KS_GATEWAY;
                k->k_state |= (KS_ADD | KS_DEL_ADD);
        }

        /* Deleting-and-adding is necessary to change aspects of a route.
         * Just delete instead of deleting and then adding a bad route.
         * Otherwise, we want to keep the route in the kernel.
         */
        if (k->k_metric == HOPCNT_INFINITY
            && (k->k_state & KS_DEL_ADD))
                k->k_state |= KS_DELETE;
        else
                k->k_state &= ~KS_DELETE;
#undef RT
}


/* ARGSUSED */
static int
walk_kern(struct radix_node *rn,
          struct walkarg *argp UNUSED)
{
#define RT ((struct rt_entry *)rn)
        char metric, pref;
        u_int ags = 0;


        /* Do not install synthetic routes */
        if (RT->rt_state & RS_NET_SYN)
                return 0;

        if (!(RT->rt_state & RS_IF)) {
                /* This is an ordinary route, not for an interface.
                 */

                /* aggregate, ordinary good routes without regard to
                 * their metric
                 */
                pref = 1;
                ags |= (AGS_GATEWAY | AGS_SUPPRESS | AGS_AGGREGATE);

                /* Do not install host routes directly to hosts, to avoid
                 * interfering with ARP entries in the kernel table.
                 */
                if (RT_ISHOST(RT)
                    && ntohl(RT->rt_dst) == RT->rt_gate)
                        return 0;

        } else {
                /* This is an interface route.
                 * Do not install routes for "external" remote interfaces.
                 */
                if (RT->rt_ifp != 0 && (RT->rt_ifp->int_state & IS_EXTERNAL))
                        return 0;

                /* Interfaces should override received routes.
                 */
                pref = 0;
                ags |= (AGS_IF | AGS_CORS_GATE);

                /* If it is not an interface, or an alias for an interface,
                 * it must be a "gateway."
                 *
                 * If it is a "remote" interface, it is also a "gateway" to
                 * the kernel if is not an alias.
                 */
                if (RT->rt_ifp == 0
                    || (RT->rt_ifp->int_state & IS_REMOTE))
                        ags |= (AGS_GATEWAY | AGS_SUPPRESS | AGS_AGGREGATE);
        }

        /* If RIP is off and IRDP is on, let the route to the discovered
         * route suppress any RIP routes.  Eventually the RIP routes
         * will time-out and be deleted.  This reaches the steady-state
         * quicker.
         */
        if ((RT->rt_state & RS_RDISC) && rip_sock < 0)
                ags |= AGS_CORS_GATE;

        metric = RT->rt_metric;
        if (metric == HOPCNT_INFINITY) {
                /* if the route is dead, so try hard to aggregate. */
                pref = HOPCNT_INFINITY;
                ags |= (AGS_FINE_GATE | AGS_SUPPRESS);
                ags &= ~(AGS_IF | AGS_CORS_GATE);
        }

        ag_check(RT->rt_dst, RT->rt_mask, RT->rt_gate, 0,
                 metric,pref, 0, 0, ags, kern_out);
        return 0;
#undef RT
}


/* Update the kernel table to match the daemon table.
 */
static void
fix_kern(void)
{
        int i;
        struct khash *k, **pk;


        need_kern = age_timer;

        /* Walk daemon table, updating the copy of the kernel table.
         */
        (void)rn_walktree(rhead, walk_kern, 0);
        ag_flush(0,0,kern_out);

        for (i = 0; i < KHASH_SIZE; i++) {
                for (pk = &khash_bins[i]; (k = *pk) != NULL; ) {
                        /* Do not touch static routes */
                        if (k->k_state & KS_STATIC) {
                                kern_check_static(k,0);
                                pk = &k->k_next;
                                continue;
                        }

                        /* check hold on routes deleted by the operator */
                        if (k->k_keep > now.tv_sec) {
                                /* ensure we check when the hold is over */
                                LIM_SEC(need_kern, k->k_keep);
                                /* mark for the next cycle */
                                k->k_state |= KS_DELETE;
                                pk = &k->k_next;
                                continue;
                        }

                        if ((k->k_state & KS_DELETE)
                            && !(k->k_state & KS_DYNAMIC)) {
                                kern_ioctl(k, RTM_DELETE, 0);
                                *pk = k->k_next;
                                free(k);
                                continue;
                        }

                        if (k->k_state & KS_DEL_ADD)
                                kern_ioctl(k, RTM_DELETE, 0);

                        if (k->k_state & KS_ADD) {
                                kern_ioctl(k, RTM_ADD,
                                           ((0 != (k->k_state & (KS_GATEWAY
                                                        | KS_DYNAMIC)))
                                            ? RTF_GATEWAY : 0));
                        } else if (k->k_state & KS_CHANGE) {
                                kern_ioctl(k,  RTM_CHANGE,
                                           ((0 != (k->k_state & (KS_GATEWAY
                                                        | KS_DYNAMIC)))
                                            ? RTF_GATEWAY : 0));
                        }
                        k->k_state &= ~(KS_ADD|KS_CHANGE|KS_DEL_ADD);

                        /* Mark this route to be deleted in the next cycle.
                         * This deletes routes that disappear from the
                         * daemon table, since the normal aging code
                         * will clear the bit for routes that have not
                         * disappeared from the daemon table.
                         */
                        k->k_state |= KS_DELETE;
                        pk = &k->k_next;
                }
        }
}


/* Delete a static route in the image of the kernel table.
 */
void
del_static(naddr dst,
           naddr mask,
           naddr gate,
           int gone)
{
        struct khash *k;
        struct rt_entry *rt;

        /* Just mark it in the table to be deleted next time the kernel
         * table is updated.
         * If it has already been deleted, mark it as such, and set its
         * keep-timer so that it will not be deleted again for a while.
         * This lets the operator delete a route added by the daemon
         * and add a replacement.
         */
        k = kern_find(dst, mask, 0);
        if (k != NULL && (gate == 0 || k->k_gate == gate)) {
                k->k_state &= ~(KS_STATIC | KS_DYNAMIC | KS_CHECK);
                k->k_state |= KS_DELETE;
                if (gone) {
                        k->k_state |= KS_DELETED;
                        k->k_keep = now.tv_sec + K_KEEP_LIM;
                }
        }

        rt = rtget(dst, mask);
        if (rt != NULL && (rt->rt_state & RS_STATIC))
                rtbad(rt);
}


/* Delete all routes generated from ICMP Redirects that use a given gateway,
 * as well as old redirected routes.
 */
void
del_redirects(naddr bad_gate,
              time_t old)
{
        int i;
        struct khash *k;


        for (i = 0; i < KHASH_SIZE; i++) {
                for (k = khash_bins[i]; k != NULL; k = k->k_next) {
                        if (!(k->k_state & KS_DYNAMIC)
                            || (k->k_state & KS_STATIC))
                                continue;

                        if (k->k_gate != bad_gate
                            && k->k_redirect_time > old
                            && !supplier)
                                continue;

                        k->k_state |= KS_DELETE;
                        k->k_state &= ~KS_DYNAMIC;
                        need_kern.tv_sec = now.tv_sec;
                        trace_act("mark redirected %s --> %s for deletion",
                                  addrname(k->k_dst, k->k_mask, 0),
                                  naddr_ntoa(k->k_gate));
                }
        }
}


/* Start the daemon tables.
 */
extern int max_keylen;

void
rtinit(void)
{
        int i;
        struct ag_info *ag;

        /* Initialize the radix trees */
        max_keylen = sizeof(struct sockaddr_in);
        rn_init();
        rn_inithead(&rhead, 32);

        /* mark all of the slots in the table free */
        ag_avail = ag_slots;
        for (ag = ag_slots, i = 1; i < NUM_AG_SLOTS; i++) {
                ag->ag_fine = ag+1;
                ag++;
        }
}


#ifdef _HAVE_SIN_LEN
static struct sockaddr_in dst_sock = {sizeof(dst_sock), AF_INET, 0, {0}, {0}};
static struct sockaddr_in mask_sock = {sizeof(mask_sock), AF_INET, 0, {0}, {0}};
#else
static struct sockaddr_in_new dst_sock = {_SIN_ADDR_SIZE, AF_INET};
static struct sockaddr_in_new mask_sock = {_SIN_ADDR_SIZE, AF_INET};
#endif


static void
set_need_flash(void)
{
        if (!need_flash) {
                need_flash = 1;
                /* Do not send the flash update immediately.  Wait a little
                 * while to hear from other routers.
                 */
                no_flash.tv_sec = now.tv_sec + MIN_WAITTIME;
        }
}


/* Get a particular routing table entry
 */
struct rt_entry *
rtget(naddr dst, naddr mask)
{
        struct rt_entry *rt;

        dst_sock.sin_addr.s_addr = dst;
        mask_sock.sin_addr.s_addr = htonl(mask);
        masktrim(&mask_sock);
        rt = (struct rt_entry *)rhead->rnh_lookup(&dst_sock,&mask_sock,rhead);
        if (!rt
            || rt->rt_dst != dst
            || rt->rt_mask != mask)
                return 0;

        return rt;
}


/* Find a route to dst as the kernel would.
 */
struct rt_entry *
rtfind(naddr dst)
{
        dst_sock.sin_addr.s_addr = dst;
        return (struct rt_entry *)rhead->rnh_matchaddr(&dst_sock, rhead);
}


/* add a route to the table
 */
void
rtadd(naddr     dst,
      naddr     mask,
      u_int     state,                  /* rt_state for the entry */
      struct    rt_spare *new)
{
        struct rt_entry *rt;
        naddr smask;
        int i;
        struct rt_spare *rts;

        rt = (struct rt_entry *)rtmalloc(sizeof (*rt), "rtadd");
        memset(rt, 0, sizeof(*rt));
        for (rts = rt->rt_spares, i = NUM_SPARES; i != 0; i--, rts++)
                rts->rts_metric = HOPCNT_INFINITY;

        rt->rt_nodes->rn_key = (caddr_t)&rt->rt_dst_sock;
        rt->rt_dst = dst;
        rt->rt_dst_sock.sin_family = AF_INET;
#ifdef _HAVE_SIN_LEN
        rt->rt_dst_sock.sin_len = dst_sock.sin_len;
#endif
        if (mask != HOST_MASK) {
                smask = std_mask(dst);
                if ((smask & ~mask) == 0 && mask > smask)
                        state |= RS_SUBNET;
        }
        mask_sock.sin_addr.s_addr = htonl(mask);
        masktrim(&mask_sock);
        rt->rt_mask = mask;
        rt->rt_state = state;
        rt->rt_spares[0] = *new;
        rt->rt_time = now.tv_sec;
        rt->rt_poison_metric = HOPCNT_INFINITY;
        rt->rt_seqno = update_seqno;

        if (++total_routes == MAX_ROUTES)
                msglog("have maximum (%d) routes", total_routes);
        if (TRACEACTIONS)
                trace_add_del("Add", rt);

        need_kern.tv_sec = now.tv_sec;
        set_need_flash();

        if (0 == rhead->rnh_addaddr(&rt->rt_dst_sock, &mask_sock,
                                    rhead, rt->rt_nodes)) {
                msglog("rnh_addaddr() failed for %s mask=%#lx",
                       naddr_ntoa(dst), (u_long)mask);
                free(rt);
        }
}


/* notice a changed route
 */
void
rtchange(struct rt_entry *rt,
         u_int  state,                  /* new state bits */
         struct rt_spare *new,
         char   *label)
{
        if (rt->rt_metric != new->rts_metric) {
                /* Fix the kernel immediately if it seems the route
                 * has gone bad, since there may be a working route that
                 * aggregates this route.
                 */
                if (new->rts_metric == HOPCNT_INFINITY) {
                        need_kern.tv_sec = now.tv_sec;
                        if (new->rts_time >= now.tv_sec - EXPIRE_TIME)
                                new->rts_time = now.tv_sec - EXPIRE_TIME;
                }
                rt->rt_seqno = update_seqno;
                set_need_flash();
        }

        if (rt->rt_gate != new->rts_gate) {
                need_kern.tv_sec = now.tv_sec;
                rt->rt_seqno = update_seqno;
                set_need_flash();
        }

        state |= (rt->rt_state & RS_SUBNET);

        /* Keep various things from deciding ageless routes are stale.
         */
        if (!AGE_RT(state, new->rts_ifp))
                new->rts_time = now.tv_sec;

        if (TRACEACTIONS)
                trace_change(rt, state, new,
                             label ? label : "Chg   ");

        rt->rt_state = state;
        rt->rt_spares[0] = *new;
}


/* check for a better route among the spares
 */
static struct rt_spare *
rts_better(struct rt_entry *rt)
{
        struct rt_spare *rts, *rts1;
        int i;

        /* find the best alternative among the spares */
        rts = rt->rt_spares+1;
        for (i = NUM_SPARES, rts1 = rts+1; i > 2; i--, rts1++) {
                if (BETTER_LINK(rt,rts1,rts))
                        rts = rts1;
        }

        return rts;
}


/* switch to a backup route
 */
void
rtswitch(struct rt_entry *rt,
         struct rt_spare *rts)
{
        struct rt_spare swap;
        char label[10];


        /* Do not change permanent routes */
        if (0 != (rt->rt_state & (RS_MHOME | RS_STATIC | RS_RDISC
                                  | RS_NET_SYN | RS_IF)))
                return;

        /* find the best alternative among the spares */
        if (rts == NULL)
                rts = rts_better(rt);

        /* Do not bother if it is not worthwhile.
         */
        if (!BETTER_LINK(rt, rts, rt->rt_spares))
                return;

        swap = rt->rt_spares[0];
        (void)sprintf(label, "Use #%d", (int)(rts - rt->rt_spares));
        rtchange(rt, rt->rt_state & ~(RS_NET_SYN | RS_RDISC), rts, label);
        if (swap.rts_metric == HOPCNT_INFINITY) {
                *rts = rts_empty;
        } else {
                *rts = swap;
        }
}


void
rtdelete(struct rt_entry *rt)
{
        struct khash *k;


        if (TRACEACTIONS)
                trace_add_del("Del", rt);

        k = kern_find(rt->rt_dst, rt->rt_mask, 0);
        if (k != NULL) {
                k->k_state |= KS_DELETE;
                need_kern.tv_sec = now.tv_sec;
        }

        dst_sock.sin_addr.s_addr = rt->rt_dst;
        mask_sock.sin_addr.s_addr = htonl(rt->rt_mask);
        masktrim(&mask_sock);
        if (rt != (struct rt_entry *)rhead->rnh_deladdr(&dst_sock, &mask_sock,
                                                        rhead)) {
                msglog("rnh_deladdr() failed");
        } else {
                free(rt);
                total_routes--;
        }
}


void
rts_delete(struct rt_entry *rt,
           struct rt_spare *rts)
{
        trace_upslot(rt, rts, &rts_empty);
        *rts = rts_empty;
}


/* Get rid of a bad route, and try to switch to a replacement.
 */
static void
rtbad(struct rt_entry *rt)
{
        struct rt_spare new;

        /* Poison the route */
        new = rt->rt_spares[0];
        new.rts_metric = HOPCNT_INFINITY;
        rtchange(rt, rt->rt_state & ~(RS_IF | RS_LOCAL | RS_STATIC), &new, 0);
        rtswitch(rt, 0);
}


/* Junk a RS_NET_SYN or RS_LOCAL route,
 *      unless it is needed by another interface.
 */
void
rtbad_sub(struct rt_entry *rt)
{
        struct interface *ifp, *ifp1;
        struct intnet *intnetp;
        u_int state;


        ifp1 = NULL;
        state = 0;

        if (rt->rt_state & RS_LOCAL) {
                /* Is this the route through loopback for the interface?
                 * If so, see if it is used by any other interfaces, such
                 * as a point-to-point interface with the same local address.
                 */
                LIST_FOREACH(ifp, &ifnet, int_list) {
                        /* Retain it if another interface needs it.
                         */
                        if (ifp->int_addr == rt->rt_ifp->int_addr) {
                                state |= RS_LOCAL;
                                ifp1 = ifp;
                                break;
                        }
                }

        }

        if (!(state & RS_LOCAL)) {
                /* Retain RIPv1 logical network route if there is another
                 * interface that justifies it.
                 */
                if (rt->rt_state & RS_NET_SYN) {
                        LIST_FOREACH(ifp, &ifnet, int_list) {
                                if ((ifp->int_state & IS_NEED_NET_SYN)
                                    && rt->rt_mask == ifp->int_std_mask
                                    && rt->rt_dst == ifp->int_std_addr) {
                                        state |= RS_NET_SYN;
                                        ifp1 = ifp;
                                        break;
                                }
                        }
                }

                /* or if there is an authority route that needs it. */
                for (intnetp = intnets;
                     intnetp != NULL;
                     intnetp = intnetp->intnet_next) {
                        if (intnetp->intnet_addr == rt->rt_dst
                            && intnetp->intnet_mask == rt->rt_mask) {
                                state |= (RS_NET_SYN | RS_NET_INT);
                                break;
                        }
                }
        }

        if (ifp1 != NULL || (state & RS_NET_SYN)) {
                struct rt_spare new = rt->rt_spares[0];
                new.rts_ifp = ifp1;
                rtchange(rt, ((rt->rt_state & ~(RS_NET_SYN|RS_LOCAL)) | state),
                         &new, 0);
        } else {
                rtbad(rt);
        }
}


/* Called while walking the table looking for sick interfaces
 * or after a time change.
 */
/* ARGSUSED */
int
walk_bad(struct radix_node *rn,
         struct walkarg *argp UNUSED)
{
#define RT ((struct rt_entry *)rn)
        struct rt_spare *rts;
        int i;


        /* fix any spare routes through the interface
         */
        rts = RT->rt_spares;
        for (i = NUM_SPARES; i != 1; i--) {
                rts++;
                if (rts->rts_metric < HOPCNT_INFINITY
                    && (rts->rts_ifp == NULL
                        || (rts->rts_ifp->int_state & IS_BROKE)))
                        rts_delete(RT, rts);
        }

        /* Deal with the main route
         */
        /* finished if it has been handled before or if its interface is ok
         */
        if (RT->rt_ifp == 0 || !(RT->rt_ifp->int_state & IS_BROKE))
                return 0;

        /* Bad routes for other than interfaces are easy.
         */
        if (0 == (RT->rt_state & (RS_IF | RS_NET_SYN | RS_LOCAL))) {
                rtbad(RT);
                return 0;
        }

        rtbad_sub(RT);
        return 0;
#undef RT
}


/* Check the age of an individual route.
 */
/* ARGSUSED */
static int
walk_age(struct radix_node *rn,
           struct walkarg *argp UNUSED)
{
#define RT ((struct rt_entry *)rn)
        struct interface *ifp;
        struct rt_spare *rts;
        int i;


        /* age all of the spare routes, including the primary route
         * currently in use
         */
        rts = RT->rt_spares;
        for (i = NUM_SPARES; i != 0; i--, rts++) {

                ifp = rts->rts_ifp;
                if (i == NUM_SPARES) {
                        if (!AGE_RT(RT->rt_state, ifp)) {
                                /* Keep various things from deciding ageless
                                 * routes are stale
                                 */
                                rts->rts_time = now.tv_sec;
                                continue;
                        }

                        /* forget RIP routes after RIP has been turned off.
                         */
                        if (rip_sock < 0) {
                                rtdelete(RT);
                                return 0;
                        }
                }

                /* age failing routes
                 */
                if (age_bad_gate == rts->rts_gate
                    && rts->rts_time >= now_stale) {
                        rts->rts_time -= SUPPLY_INTERVAL;
                }

                /* trash the spare routes when they go bad */
                if (rts->rts_metric < HOPCNT_INFINITY
                    && now_garbage > rts->rts_time
                    && i != NUM_SPARES)
                        rts_delete(RT, rts);
        }


        /* finished if the active route is still fresh */
        if (now_stale <= RT->rt_time)
                return 0;

        /* try to switch to an alternative */
        rtswitch(RT, 0);

        /* Delete a dead route after it has been publicly mourned. */
        if (now_garbage > RT->rt_time) {
                rtdelete(RT);
                return 0;
        }

        /* Start poisoning a bad route before deleting it. */
        if (now.tv_sec - RT->rt_time > EXPIRE_TIME) {
                struct rt_spare new = RT->rt_spares[0];
                new.rts_metric = HOPCNT_INFINITY;
                rtchange(RT, RT->rt_state, &new, 0);
        }
        return 0;
}


/* Watch for dead routes and interfaces.
 */
void
age(naddr bad_gate)
{
        struct interface *ifp;
        int need_query = 0;

        /* If not listening to RIP, there is no need to age the routes in
         * the table.
         */
        age_timer.tv_sec = (now.tv_sec
                            + ((rip_sock < 0) ? NEVER : SUPPLY_INTERVAL));

        /* Check for dead IS_REMOTE interfaces by timing their
         * transmissions.
         */
        LIST_FOREACH(ifp, &ifnet, int_list) {
                if (!(ifp->int_state & IS_REMOTE))
                        continue;

                /* ignore unreachable remote interfaces */
                if (!check_remote(ifp))
                        continue;

                /* Restore remote interface that has become reachable
                 */
                if (ifp->int_state & IS_BROKE)
                        if_ok(ifp, "remote ");

                if (ifp->int_act_time != NEVER
                    && now.tv_sec - ifp->int_act_time > EXPIRE_TIME) {
                        msglog("remote interface %s to %s timed out after"
                               " %ld:%ld",
                               ifp->int_name,
                               naddr_ntoa(ifp->int_dstaddr),
                               (long)(now.tv_sec - ifp->int_act_time)/60,
                               (long)(now.tv_sec - ifp->int_act_time)%60);
                        if_sick(ifp);
                }

                /* If we have not heard from the other router
                 * recently, ask it.
                 */
                if (now.tv_sec >= ifp->int_query_time) {
                        ifp->int_query_time = NEVER;
                        need_query = 1;
                }
        }

        /* Age routes. */
        age_bad_gate = bad_gate;
        (void)rn_walktree(rhead, walk_age, 0);

        /* delete old redirected routes to keep the kernel table small
         * and prevent blackholes
         */
        del_redirects(bad_gate, now.tv_sec-STALE_TIME);

        /* Update the kernel routing table. */
        fix_kern();

        /* poke reticent remote gateways */
        if (need_query)
                rip_query();
}