odhcp6c: add option to ignore Server Unicast option

Add option -U to ignore Server Unicast option and force odhcp6c to use
the multicast address. This allows a workaround for broken setups.

Signed-off-by: Adrian Friedli <adi@koalatux.ch>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

3 files changed, 21 insertions, 5 deletions

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index d70d533..01dd497 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -183,7 +183,6 @@ int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout)
 			htons(DHCPV6_OPT_SIP_SERVER_A),
 			htons(DHCPV6_OPT_DNS_SERVERS),
 			htons(DHCPV6_OPT_DNS_DOMAIN),
-			htons(DHCPV6_OPT_UNICAST),
 			htons(DHCPV6_OPT_SNTP_SERVERS),
 			htons(DHCPV6_OPT_NTP_SERVER),
 			htons(DHCPV6_OPT_AFTR_NAME),
@@ -198,6 +197,12 @@ int init_dhcpv6(const char *ifname, unsigned int options, int sol_timeout)
 			htons(DHCPV6_OPT_S46_CONT_LW),
 		};
 		odhcp6c_add_state(STATE_ORO, oro, sizeof(oro));
+
+		if (!(client_options & DHCPV6_IGNORE_OPT_UNICAST)) {
+			uint16_t otype = htons(DHCPV6_OPT_UNICAST);
+
+			odhcp6c_add_state(STATE_ORO, &otype, sizeof(otype));
+		}
 	}
 
 	// Configure IPv6-options
@@ -856,7 +861,9 @@ static int dhcpv6_handle_advert(enum dhcpv6_msg orig, const int rc,
 				cand.preference >= 0) {
 			cand.preference = pref = odata[0];
 		} else if (otype == DHCPV6_OPT_UNICAST && olen == sizeof(cand.server_addr)) {
-			cand.server_addr = *(struct in6_addr *)odata;
+			if (!(client_options & DHCPV6_IGNORE_OPT_UNICAST))
+				cand.server_addr = *(struct in6_addr *)odata;
+
 		} else if (otype == DHCPV6_OPT_RECONF_ACCEPT) {
 			cand.wants_reconfigure = true;
 		} else if (otype == DHCPV6_OPT_SOL_MAX_RT && olen == 4) {
@@ -1048,8 +1055,11 @@ static int dhcpv6_handle_reply(enum dhcpv6_msg orig, _unused const int rc,
 					continue;
 
 				updated_IAs += dhcpv6_parse_ia(ia_hdr, odata + olen);
-			} else if (otype == DHCPV6_OPT_UNICAST && olen == sizeof(server_addr))
-				server_addr = *(struct in6_addr *)odata;
+			} else if (otype == DHCPV6_OPT_UNICAST && olen == sizeof(server_addr)) {
+				if (!(client_options & DHCPV6_IGNORE_OPT_UNICAST))
+					server_addr = *(struct in6_addr *)odata;
+
+			}
 			else if (otype == DHCPV6_OPT_STATUS && olen >= 2) {
 				uint8_t *mdata = (olen > 2) ? &odata[2] : NULL;
 				uint16_t mlen = (olen > 2) ? olen - 2 : 0;
diff --git a/src/odhcp6c.c b/src/odhcp6c.c
index 261513d..e0c9b76 100644
--- a/src/odhcp6c.c
+++ b/src/odhcp6c.c
@@ -138,7 +138,7 @@ int main(_unused int argc, char* const argv[])
 	unsigned int ra_options = RA_RDNSS_DEFAULT_LIFETIME;
 	unsigned int ra_holdoff_interval = RA_MIN_ADV_INTERVAL;
 
-	while ((c = getopt(argc, argv, "S::N:V:P:FB:c:i:r:Ru:x:s:kt:m:Lhedp:fav")) != -1) {
+	while ((c = getopt(argc, argv, "S::N:V:P:FB:c:i:r:Ru:Ux:s:kt:m:Lhedp:fav")) != -1) {
 		switch (c) {
 		case 'S':
 			allow_slaac_only = (optarg) ? atoi(optarg) : -1;
@@ -280,6 +280,10 @@ int main(_unused int argc, char* const argv[])
 			free(o_data);
 			break;
 
+		case 'U':
+			client_options |= DHCPV6_IGNORE_OPT_UNICAST;
+			break;
+
 		case 's':
 			script = optarg;
 			break;
@@ -572,6 +576,7 @@ static int usage(void)
 	"	-t <seconds>	Maximum timeout for DHCPv6-SOLICIT (120)\n"
 	"	-m <seconds>	Minimum time between accepting RA updates (3)\n"
 	"	-L		Ignore default lifetime for RDNSS records\n"
+	"	-U		Ignore Server Unicast option\n"
 	"\nInvocation options:\n"
 	"	-p <pidfile>	Set pidfile (/var/run/odhcp6c.pid)\n"
 	"	-d		Daemonize\n"
diff --git a/src/odhcp6c.h b/src/odhcp6c.h
index 97809f1..ad4f793 100644
--- a/src/odhcp6c.h
+++ b/src/odhcp6c.h
@@ -119,6 +119,7 @@ enum dhcpv6_config {
 	DHCPV6_STRICT_OPTIONS = 1,
 	DHCPV6_CLIENT_FQDN = 2,
 	DHCPV6_ACCEPT_RECONFIGURE = 4,
+	DHCPV6_IGNORE_OPT_UNICAST = 8,
 };
 
 typedef int(reply_handler)(enum dhcpv6_msg orig, const int rc,