IPv6: Only advertise addresses when needed

Remember when we have advertised an address.
If we want to advertise it again, check this first.
If we still want to advertise it, clear this flag for all other
matching addresses.
Clear advertised flags from all addresses on carrier up.

This reduces needless NA spam from dhcpcd when the IPv6 Router
is needlessly chatty with RA.

src/ipv6.c

@@ -1832,16 +1832,19 @@ ipv6_startstatic(struct interface *ifp)
 int
 ipv6_start(struct interface *ifp)
 {
-#ifdef IPV6_POLLADDRFLAG
+#if defined(ND6_ADVERTISE) || defined(IPV6_POLLADDRFLAG)
 	struct ipv6_state *state;
 
 	/* We need to update the address flags. */
 	if ((state = IPV6_STATE(ifp)) != NULL) {
 		struct ipv6_addr *ia;
+#ifdef IPV6_POLLADDRFLAG
 		const char *alias;
 		int flags;
+#endif
 
 		TAILQ_FOREACH(ia, &state->addrs, next) {
+#ifdef IPV6_POLLADDRFLAG
 #ifdef ALIAS_ADDR
 			alias = ia->alias;
 #else
@@ -1850,6 +1853,9 @@ ipv6_start(struct interface *ifp)
 			flags = if_addrflags6(ia->iface, &ia->addr, alias);
 			if (flags != -1)
 				ia->addr_flags = flags;
+#endif
+			/* hwaddr could have changed */
+			ia->flags &= ~IPV6_AF_ADVERTISED;
 		}
 	}
 #endif

src/ipv6.h

@@ -160,7 +160,8 @@
 
 /*
  * ND6 Advertising is only used for IP address sharing to prefer
- * the address on a specific interface.
+ * the address on a specific interface or when the hardware address
+ * of the interface changes.
  * This just fails to work on OpenBSD and causes erroneous duplicate
  * address messages on BSD's other then DragonFly and NetBSD.
  */
@@ -227,8 +228,9 @@ struct ipv6_addr {
 #define	IPV6_AF_EXTENDED	(1U << 13)
 #define	IPV6_AF_REGEN		(1U << 14)
 #define	IPV6_AF_ROUTER		(1U << 15)
+#define	IPV6_AF_ADVERTISED	(1U << 16)
 #ifdef IPV6_MANAGETEMPADDR
-#define	IPV6_AF_TEMPORARY	(1U << 16)
+#define	IPV6_AF_TEMPORARY	(1U << 17)
 #endif
 
 struct ll_callback {

src/ipv6nd.c

@@ -514,6 +514,7 @@ ipv6nd_advertise(struct ipv6_addr *ia)
 	struct interface *ifp;
 	struct ipv6_state *state;
 	struct ipv6_addr *iap, *iaf;
+	bool found_another = false;
 	struct nd_neighbor_advert *na;
 
 	if (IN6_IS_ADDR_MULTICAST(&ia->addr))
@@ -529,30 +530,53 @@ ipv6nd_advertise(struct ipv6_addr *ia)
 	iaf = NULL;
 	TAILQ_FOREACH(ifp, ctx->ifaces, next) {
 		state = IPV6_STATE(ifp);
-		if (state == NULL || !if_is_link_up(ifp))
+		if (state == NULL)
 			continue;
 
 		TAILQ_FOREACH(iap, &state->addrs, next) {
 			if (!IN6_ARE_ADDR_EQUAL(&iap->addr, &ia->addr))
 				continue;
 
-			/* Cancel any current advertisement. */
-			eloop_timeout_delete(ctx->eloop,
-			    ipv6nd_sendadvertisement, iap);
+			if (iaf != NULL)
+				found_another = true;
 
 			/* Don't advertise what we can't use. */
 			if (iap->prefix_vltime == 0 ||
-			    iap->addr_flags & IN6_IFF_NOTUSEABLE)
+			    iap->addr_flags & IN6_IFF_NOTUSEABLE ||
+			    !if_is_link_up(ifp))
 				continue;
 
 			if (iaf == NULL ||
 			    iaf->iface->metric > iap->iface->metric)
 				iaf = iap;
 		}
 	}
-	if (iaf == NULL)
+
+	/* If we have already advertised the address, return. */
+	if (iaf == NULL || iaf->flags & IPV6_AF_ADVERTISED)
 		return;
 
+	/* Now cancel any other advertisements for the same address. */
+	if (found_another) {
+		TAILQ_FOREACH(ifp, ctx->ifaces, next) {
+			state = IPV6_STATE(ifp);
+			if (state == NULL)
+				continue;
+
+			TAILQ_FOREACH(iap, &state->addrs, next) {
+				if (!IN6_ARE_ADDR_EQUAL(&iap->addr, &ia->addr))
+					continue;
+
+				iap->flags &= ~IPV6_AF_ADVERTISED;
+				eloop_timeout_delete(ctx->eloop,
+				    ipv6nd_sendadvertisement, iap);
+			}
+		}
+	} else {
+		eloop_timeout_delete(ctx->eloop,
+		    ipv6nd_sendadvertisement, iaf);
+	}
+
 	/* Make the packet. */
 	ifp = iaf->iface;
 	iaf->na_len = sizeof(*na);
@@ -588,7 +612,7 @@ ipv6nd_advertise(struct ipv6_addr *ia)
 	iaf->na_count = 0;
 	free(iaf->na);
 	iaf->na = na;
-	eloop_timeout_delete(ctx->eloop, ipv6nd_sendadvertisement, iaf);
+	iaf->flags |= IPV6_AF_ADVERTISED;
 	ipv6nd_sendadvertisement(iaf);
 }
 #elif !defined(SMALL)