Avoid of waiting for Advertise in stateless-only mode

Start with Information-request when configured not to ask
IA_NA/IA_PD. It allows to complete the exchange using only
two messages, instead of four, and fixes infinite Advertise
waiting loop with servers that just ignore Solicit messages.

3 files changed, 23 insertions, 8 deletions

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index bc403b9..425aee1 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -216,10 +216,19 @@ enum {
 	IOV_TOTAL
 };
 
-void dhcpv6_set_ia_mode(enum odhcp6c_ia_mode na, enum odhcp6c_ia_mode pd)
+int dhcpv6_set_ia_mode(enum odhcp6c_ia_mode na, enum odhcp6c_ia_mode pd)
 {
+	int mode = DHCPV6_UNKNOWN;
+
 	na_mode = na;
 	pd_mode = pd;
+
+	if (na_mode == IA_MODE_NONE && pd_mode == IA_MODE_NONE)
+		mode = DHCPV6_STATELESS;
+	else if (na_mode == IA_MODE_FORCE || pd_mode == IA_MODE_FORCE)
+		mode = DHCPV6_STATEFUL;
+
+	return mode;
 }
 
 static void dhcpv6_send(enum dhcpv6_msg type, uint8_t trid[3], uint32_t ecs)
@@ -547,10 +556,15 @@ int dhcpv6_request(enum dhcpv6_msg type)
 			round_end = timeout * 1000 + start;
 
 		// Built and send package
-		if (type != DHCPV6_MSG_UNKNOWN) {
-			if (type != DHCPV6_MSG_SOLICIT)
-				syslog(LOG_NOTICE, "Send %s message (elapsed %llums, rc %d)",
-						retx->name, (unsigned long long)elapsed, rc);
+		switch (type) {
+		case DHCPV6_MSG_UNKNOWN:
+			break;
+		default:
+			syslog(LOG_NOTICE, "Send %s message (elapsed %llums, rc %d)",
+					retx->name, (unsigned long long)elapsed, rc);
+			// Fall through
+		case DHCPV6_MSG_SOLICIT:
+		case DHCPV6_MSG_INFO_REQ:
 			dhcpv6_send(type, trid, elapsed / 10);
 			rc++;
 		}
diff --git a/src/odhcp6c.c b/src/odhcp6c.c
index 4605792..a71218c 100644
--- a/src/odhcp6c.c
+++ b/src/odhcp6c.c
@@ -278,13 +278,14 @@ int main(_unused int argc, char* const argv[])
 		odhcp6c_clear_state(STATE_NTP_FQDN);
 		odhcp6c_clear_state(STATE_SIP_IP);
 		odhcp6c_clear_state(STATE_SIP_FQDN);
-		dhcpv6_set_ia_mode(ia_na_mode, ia_pd_mode);
 		bound = false;
 
 		syslog(LOG_NOTICE, "(re)starting transaction on %s", ifname);
 
 		signal_usr1 = signal_usr2 = false;
-		int mode = dhcpv6_request(DHCPV6_MSG_SOLICIT);
+		int mode = dhcpv6_set_ia_mode(ia_na_mode, ia_pd_mode);
+		if (mode != DHCPV6_STATELESS)
+			mode = dhcpv6_request(DHCPV6_MSG_SOLICIT);
 		odhcp6c_signal_process();
 
 		if (mode < 0)
diff --git a/src/odhcp6c.h b/src/odhcp6c.h
index fb572d0..c9a7398 100644
--- a/src/odhcp6c.h
+++ b/src/odhcp6c.h
@@ -308,7 +308,7 @@ struct odhcp6c_request_prefix {
 };
 
 int init_dhcpv6(const char *ifname, unsigned int client_options, int sol_timeout);
-void dhcpv6_set_ia_mode(enum odhcp6c_ia_mode na, enum odhcp6c_ia_mode pd);
+int dhcpv6_set_ia_mode(enum odhcp6c_ia_mode na, enum odhcp6c_ia_mode pd);
 int dhcpv6_request(enum dhcpv6_msg type);
 int dhcpv6_poll_reconfigure(void);
 int dhcpv6_promote_server_cand(void);