DHCP6: Don't spam the log when a RA repeatedly triggers an INFORM

This can occur if the RA reduces the prefix times in accordance
with it's own lifetimes for example.
dhcpcd only checks if the RA contents have changed to trigger a
new INFORM.

As such, only log about new INFORMs.

Fixes #46.

src/dhcp6.c

@@ -1649,7 +1649,7 @@ dhcp6_startinform(void *arg)
 
 	ifp = arg;
 	state = D6_STATE(ifp);
-	if (state->new == NULL && !state->failed)
+	if (state->new_start || (state->new == NULL && !state->failed))
 		llevel = LOG_INFO;
 	else
 		llevel = LOG_DEBUG;
@@ -3046,18 +3046,25 @@ static void
 dhcp6_bind(struct interface *ifp, const char *op, const char *sfrom)
 {
 	struct dhcp6_state *state = D6_STATE(ifp);
-	bool timedout = (op == NULL), has_new = false, confirmed;
+	bool timedout = (op == NULL), confirmed;
 	struct ipv6_addr *ia;
 	int loglevel;
 	struct timespec now;
 
-	TAILQ_FOREACH(ia, &state->addrs, next) {
-		if (ia->flags & IPV6_AF_NEW) {
-			has_new = true;
-			break;
+	if (state->state == DH6S_RENEW && !state->new_start) {
+		loglevel = LOG_DEBUG;
+		TAILQ_FOREACH(ia, &state->addrs, next) {
+			if (ia->flags & IPV6_AF_NEW) {
+				loglevel = LOG_INFO;
+				break;
+			}
 		}
-	}
-	loglevel = has_new || state->state != DH6S_RENEW ? LOG_INFO : LOG_DEBUG;
+	} else if (state->state == DH6S_INFORM)
+		loglevel = state->new_start ? LOG_INFO : LOG_DEBUG;
+	else
+		loglevel = LOG_INFO;
+	state->new_start = false;
+
 	if (!timedout) {
 		logmessage(loglevel, "%s: %s received from %s",
 		    ifp->name, op, sfrom);
@@ -3940,7 +3947,13 @@ dhcp6_start(struct interface *ifp, enum DH6S init_state)
 			    (state->state == DH6S_DISCOVER &&
 			    !(ifp->options->options & DHCPCD_IA_FORCED) &&
 			    !ipv6nd_hasradhcp(ifp, true)))
+			{
+				/* We don't want log spam when the RA
+				 * has just adjusted it's prefix times. */
+				if (state->state != DH6S_INFORMED)
+					state->new_start = true;
 				dhcp6_startinform(ifp);
+			}
 			break;
 		case DH6S_REQUEST:
 			if (ifp->options->options & DHCPCD_DHCP6 &&
@@ -3989,6 +4002,7 @@ dhcp6_start(struct interface *ifp, enum DH6S init_state)
 	TAILQ_INIT(&state->addrs);
 
 gogogo:
+	state->new_start = true;
 	state->state = init_state;
 	state->lerror = 0;
 	state->failed = false;

src/dhcp6.h

@@ -213,6 +213,7 @@ struct dhcp6_state {
 	uint16_t lerror; /* Last error received from DHCPv6 reply. */
 	bool has_no_binding;
 	bool failed; /* Entered the failed state - used to rate limit log. */
+	bool new_start; /* New external start, to determine log type. */
 #ifdef AUTH
 	struct authstate auth;
 #endif