Changed the behavior when an interface-direct prefix being advertised

was removed from the kernel;
Advertise the prefix with zero lifetimes rather than to remove the prefix
from the prefix list to be advertised.
This will help renumber a receiving host by deprecating the address
derived from the old prefix.

Obtained from:	KAME
MFC after:	2 weeks

usr.sbin/rtadvd/config.c

@@ -71,12 +71,15 @@
 #include "if.h"
 #include "config.h"
 
+static time_t prefix_timo = (60 * 120);	/* 2 hours.
+					 * XXX: should be configurable. */
+extern struct rainfo *ralist;
+
+static struct rtadvd_timer *prefix_timeout __P((void *));
 static void makeentry __P((char *, size_t, int, char *, int));
 static void get_prefix __P((struct rainfo *));
 static int getinet6sysctl __P((int));
 
-extern struct rainfo *ralist;
-
 void
 getconfig(intface)
 	char *intface;
@@ -309,6 +312,7 @@ getconfig(intface)
 
 			/* link into chain */
 			insque(pfx, &tmp->prefix);
+			pfx->rainfo = tmp;
 
 			pfx->origin = PREFIX_FROM_CONFIG;
 
@@ -681,6 +685,7 @@ add_prefix(struct rainfo *rai, struct in6_prefixreq *ipr)
 	prefix->origin = PREFIX_FROM_DYNAMIC;
 
 	insque(prefix, &rai->prefix);
+	prefix->rainfo = rai;
 
 	syslog(LOG_DEBUG, "<%s> new prefix %s/%d was added on %s",
 	       __FUNCTION__, inet_ntop(AF_INET6, &ipr->ipr_prefix.sin6_addr,
@@ -709,18 +714,82 @@ add_prefix(struct rainfo *rai, struct in6_prefixreq *ipr)
  * The prefix must be in the list.
  */
 void
-delete_prefix(struct rainfo *rai, struct prefix *prefix)
+delete_prefix(struct prefix *prefix)
 {
 	u_char ntopbuf[INET6_ADDRSTRLEN];
+	struct rainfo *rai = prefix->rainfo;
 
 	remque(prefix);
 	syslog(LOG_DEBUG, "<%s> prefix %s/%d was deleted on %s",
 	       __FUNCTION__, inet_ntop(AF_INET6, &prefix->prefix,
 				       ntopbuf, INET6_ADDRSTRLEN),
 	       prefix->prefixlen, rai->ifname);
+	if (prefix->timer)
+		rtadvd_remove_timer(&prefix->timer);
 	free(prefix);
 	rai->pfxs--;
-	make_packet(rai);
+}
+
+void
+invalidate_prefix(struct prefix *prefix)
+{
+	u_char ntopbuf[INET6_ADDRSTRLEN];
+	struct timeval timo;
+	struct rainfo *rai = prefix->rainfo;
+
+	if (prefix->timer) {	/* sanity check */
+		syslog(LOG_ERR,
+		    "<%s> assumption failure: timer already exists",
+		    __FUNCTION__);
+		exit(1);
+	}
+
+	syslog(LOG_DEBUG, "<%s> prefix %s/%d was invalidated on %s, "
+	    "will expire in %ld seconds", __FUNCTION__,
+	    inet_ntop(AF_INET6, &prefix->prefix, ntopbuf, INET6_ADDRSTRLEN),
+	    prefix->prefixlen, rai->ifname, (long)prefix_timo);
+
+	/* set the expiration timer */
+	prefix->timer = rtadvd_add_timer(prefix_timeout, NULL, prefix, NULL);
+	if (prefix->timer == NULL) {
+		syslog(LOG_ERR, "<%s> failed to add a timer for a prefix. "
+		    "remove the prefix", __FUNCTION__);
+		delete_prefix(prefix);
+	}
+	timo.tv_sec = prefix_timo;
+	timo.tv_usec = 0;
+	rtadvd_set_timer(&timo, prefix->timer);
+}
+
+static struct rtadvd_timer *
+prefix_timeout(void *arg)
+{
+	struct prefix *prefix = (struct prefix *)arg;
+	
+	delete_prefix(prefix);
+
+	return(NULL);
+}
+
+void
+update_prefix(struct prefix * prefix)
+{
+	u_char ntopbuf[INET6_ADDRSTRLEN];
+	struct rainfo *rai = prefix->rainfo;
+
+	if (prefix->timer == NULL) { /* sanity check */
+		syslog(LOG_ERR,
+		    "<%s> assumption failure: timer does not exist",
+		    __FUNCTION__);
+		exit(1);
+	}
+
+	syslog(LOG_DEBUG, "<%s> prefix %s/%d was re-enabled on %s",
+	    __FUNCTION__, inet_ntop(AF_INET6, &prefix->prefix, ntopbuf,
+	    INET6_ADDRSTRLEN), prefix->prefixlen, rai->ifname);
+
+	/* stop the expiration timer */
+	rtadvd_remove_timer(&prefix->timer);
 }
 
 /*
@@ -934,18 +1003,26 @@ make_packet(struct rainfo *rainfo)
 			ndopt_pi->nd_opt_pi_flags_reserved |=
 				ND_OPT_PI_FLAG_ROUTER;
 #endif
-		if (pfx->vltimeexpire || pfx->pltimeexpire)
-			gettimeofday(&now, NULL);
-		if (pfx->vltimeexpire == 0)
-			vltime = pfx->validlifetime;
-		else
-			vltime = (pfx->vltimeexpire > now.tv_sec) ?
-				pfx->vltimeexpire - now.tv_sec : 0;
-		if (pfx->pltimeexpire == 0)
-			pltime = pfx->preflifetime;
-		else
-			pltime = (pfx->pltimeexpire > now.tv_sec) ? 
-				pfx->pltimeexpire - now.tv_sec : 0;
+		if (pfx->timer)
+			vltime = 0;
+		else {
+			if (pfx->vltimeexpire || pfx->pltimeexpire)
+				gettimeofday(&now, NULL);
+			if (pfx->vltimeexpire == 0)
+				vltime = pfx->validlifetime;
+			else
+				vltime = (pfx->vltimeexpire > now.tv_sec) ?
+				    pfx->vltimeexpire - now.tv_sec : 0;
+		}
+		if (pfx->timer)
+			pltime = 0;
+		else {
+			if (pfx->pltimeexpire == 0)
+				pltime = pfx->preflifetime;
+			else
+				pltime = (pfx->pltimeexpire > now.tv_sec) ? 
+				    pfx->pltimeexpire - now.tv_sec : 0;
+		}
 		if (vltime < pltime) {
 			/*
 			 * this can happen if vltime is decrement but pltime

usr.sbin/rtadvd/config.h

@@ -31,6 +31,8 @@
  */
 
 extern void getconfig __P((char *));
-extern void delete_prefix __P((struct rainfo *, struct prefix *));
+extern void delete_prefix __P((struct prefix *));
+extern void invalidate_prefix __P((struct prefix *));
+extern void update_prefix __P((struct prefix *));
 extern void make_prefix __P((struct rainfo *, int, struct in6_addr *, int));
 extern void make_packet __P((struct rainfo *));

usr.sbin/rtadvd/dump.c

@@ -221,6 +221,15 @@ if_dump()
 				pfx->routeraddr ? "R" :
 #endif
 				"");
+			if (pfx->timer) {
+				struct timeval *rest;
+
+				rest = rtadvd_timer_rest(pfx->timer);
+				if (rest) { /* XXX: what if not? */
+					fprintf(fp, ", expire in: %ld",
+					    (long)rest->tv_sec);
+				}
+			}
 			fprintf(fp, ")\n");
 		}
 	}

usr.sbin/rtadvd/rtadvd.8

@@ -63,20 +63,42 @@ them as on-link prefixes.
 .Pp
 .Nm
 also watches the routing table.
-By default, if an interface direct route is
-added/deleted on an advertising interface and no static prefixes are
+If an interface direct route is
+added on an advertising interface and no static prefixes are
 specified by the configuration file,
 .Nm
-adds/deletes the corresponding prefix to/from its advertising list,
-respectively.
-The
-.Fl s
-option may be used to disable this behavior.
+adds the corresponding prefix to its advertising list.
+.Pp
+Similarly, when an interface direct route is deleted,
+.Nm
+will start advertising the prefixes with zero valid and preferred
+lifetimes to help the receiving hosts switch to a new prefix when
+renumbering.
+Note, however, that the zero valid lifetime cannot invalidate the
+autoconfigured addresses at a receiving host immediately.
+According to the specification, the host will retain the address
+for a certain period, which will typically be two hours.
+The zero lifetimes rather intend to make the address deprecated,
+indicating that a new non-deprecated address should be used as the
+source address of a new connection.
+This behavior will last for two hours.
+Then
+.Nm
+will completely remove the prefix from the advertising list,
+and succeeding advertisements will not contain the prefix information.
+.Pp
 Moreover, if the status of an advertising interface changes,
 .Nm
 will start or stop sending router advertisements according
 to the latest status.
 .Pp
+The
+.Fl s
+option may be used to disable this behavior;
+.Nm
+will not watch the routing table and the whole functionality described
+above will be suppressed.
+.Pp
 Basically, hosts MUST NOT send Router Advertisement messages at any
 time (RFC 2461, Section 6.2.3).
 However, it would sometimes be useful to allow hosts to advertise some

usr.sbin/rtadvd/rtadvd.c

@@ -450,7 +450,13 @@ rtmsg_input()
 			}
 			prefix = find_prefix(rai, addr, plen);
 			if (prefix) {
-				if (dflag > 1) {
+				if (prefix->timer) {
+					/*
+					 * If the prefix has been invalidated,
+					 * make it available again.
+					 */
+					update_prefix(prefix);
+				} else if (dflag > 1) {
 					syslog(LOG_DEBUG,
 					    "<%s> new prefix(%s/%d) "
 					    "added on %s, "
@@ -497,7 +503,7 @@ rtmsg_input()
 				}
 				break;
 			}
-			delete_prefix(rai, prefix);
+			invalidate_prefix(prefix);
 			break;
 		case RTM_NEWADDR:
 		case RTM_DELADDR:
@@ -1550,7 +1556,7 @@ struct rainfo *rainfo;
 }
 
 /* process RA timer */
-void
+struct rtadvd_timer *
 ra_timeout(void *data)
 {
 	struct rainfo *rai = (struct rainfo *)data;
@@ -1564,6 +1570,8 @@ ra_timeout(void *data)
 	       __FUNCTION__, rai->ifname);
 
 	ra_output(rai);
+
+	return(rai->timer);
 }
 
 /* update RA timer */

usr.sbin/rtadvd/rtadvd.h

@@ -74,6 +74,12 @@ struct prefix {
 	struct prefix *next;	/* forward link */
 	struct prefix *prev;	/* previous link */
 
+	struct rainfo *rainfo;	/* back pointer to the interface */
+
+	struct rtadvd_timer *timer; /* expiration timer.  used when a prefix
+				     * derived from the kernel is deleted.
+				     */
+
 	u_int32_t validlifetime; /* AdvValidLifetime */
 	long	vltimeexpire;	/* expiration of vltime; decrement case only */
 	u_int32_t preflifetime;	/* AdvPreferredLifetime */
@@ -159,7 +165,7 @@ struct	rainfo {
 	struct soliciter *soliciter;	/* recent solication source */
 };
 
-void ra_timeout __P((void *));
+struct rtadvd_timer *ra_timeout __P((void *));
 void ra_timer_update __P((void *, struct timeval *));
 
 int prefix_match __P((struct in6_addr *, int, struct in6_addr *, int));

usr.sbin/rtadvd/timer.c

@@ -59,9 +59,9 @@ rtadvd_timer_init()
 }
 
 struct rtadvd_timer *
-rtadvd_add_timer(void (*timeout) __P((void *)),
-		void (*update) __P((void *, struct timeval *)),
-		 void *timeodata, void *updatedata)
+rtadvd_add_timer(struct rtadvd_timer *(*timeout) __P((void *)),
+    void (*update) __P((void *, struct timeval *)),
+    void *timeodata, void *updatedata)
 {
 	struct rtadvd_timer *newtimer;
 
@@ -78,11 +78,6 @@ rtadvd_add_timer(void (*timeout) __P((void *)),
 		       "<%s> timeout function unspecfied", __FUNCTION__);
 		exit(1);
 	}
-	if (update == NULL) {
-		syslog(LOG_ERR,
-		       "<%s> update function unspecfied", __FUNCTION__);
-		exit(1);
-	}
 	newtimer->expire = timeout;
 	newtimer->update = update;
 	newtimer->expire_data = timeodata;
@@ -121,7 +116,7 @@ rtadvd_set_timer(struct timeval *tm, struct rtadvd_timer *timer)
 }
 
 /*
- * Check expiration for each timer. If a timer is expired,
+ * Check expiration for each timer. If a timer expires,
  * call the expire function for the timer and update the timer.
  * Return the next interval for select() call.
  */
@@ -130,23 +125,25 @@ rtadvd_check_timer()
 {
 	static struct timeval returnval;
 	struct timeval now;
-	struct rtadvd_timer *tm = timer_head.next;
+	struct rtadvd_timer *tm = timer_head.next, *tm_next;
 
 	gettimeofday(&now, NULL);
 
 	timer_head.tm = tm_max;
 
-	while(tm != &timer_head) {
+	for (tm = timer_head.next; tm != &timer_head; tm = tm_next) {
+		tm_next = tm->next;
+
 		if (TIMEVAL_LEQ(tm->tm, now)) {
-			(*tm->expire)(tm->expire_data);
-			(*tm->update)(tm->update_data, &tm->tm);
+			if (((*tm->expire)(tm->expire_data) == NULL))
+				continue; /* the timer was removed */
+			if (tm->update)
+				(*tm->update)(tm->update_data, &tm->tm);
 			TIMEVAL_ADD(&tm->tm, &now, &tm->tm);
 		}
 
 		if (TIMEVAL_LT(tm->tm, timer_head.tm))
 			timer_head.tm = tm->tm;
-
-		tm = tm->next;
 	}
 
 	if (TIMEVAL_EQUAL(&tm_max, &timer_head.tm)) {

usr.sbin/rtadvd/timer.h

@@ -46,14 +46,14 @@ struct rtadvd_timer {
 	struct rainfo *rai;
 	struct timeval tm;
 
-	void (*expire) __P((void *));	/* expiration function */
+	struct rtadvd_timer *(*expire) __P((void *)); /* expiration function */
 	void *expire_data;
 	void (*update) __P((void *, struct timeval *));	/* update function */
 	void *update_data;
 };
 
 void rtadvd_timer_init __P((void));
-struct rtadvd_timer *rtadvd_add_timer __P((void (*) __P((void *)),
+struct rtadvd_timer *rtadvd_add_timer __P((struct rtadvd_timer *(*) __P((void *)),
 		void (*) __P((void *, struct timeval *)), void *, void *));
 void rtadvd_set_timer __P((struct timeval *, struct rtadvd_timer *));
 void rtadvd_remove_timer __P((struct rtadvd_timer **));