text: /*
   * 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.
   * 4. 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"
  
  #ifdef __NetBSD__
  __RCSID("$NetBSD$");
  #elif defined(__FreeBSD__)
  __RCSID("$FreeBSD$");
  #else
  __RCSID("$Revision: 2.27 $");
  #ident "$Revision: 2.27 $"
  #endif
  
  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);
  
  		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();
  }
  