DHCPv6 relay: allow configuring DHCPv6 relay servers

src/config.c

@@ -139,6 +139,7 @@ enum {
 	IFACE_ATTR_NTP,
 	IFACE_ATTR_CAPTIVE_PORTAL_URI,
 	IFACE_ATTR_IPV6_ONLY_PREFERRED,
+	IFACE_ATTR_DHCPV6_RELAY_SERVERS,
 	IFACE_ATTR_MAX
 };
 
@@ -193,6 +194,7 @@ static const struct blobmsg_policy iface_attrs[IFACE_ATTR_MAX] = {
 	[IFACE_ATTR_NTP] = { .name = "ntp", .type = BLOBMSG_TYPE_ARRAY },
 	[IFACE_ATTR_CAPTIVE_PORTAL_URI] = { .name = "captive_portal_uri", .type = BLOBMSG_TYPE_STRING },
 	[IFACE_ATTR_IPV6_ONLY_PREFERRED] = { .name = "ipv6_only_preferred", .type = BLOBMSG_TYPE_INT32 },
+	[IFACE_ATTR_DHCPV6_RELAY_SERVERS] = { .name = "dhcpv6_relay_servers", .type = BLOBMSG_TYPE_ARRAY },
 };
 
 const struct uci_blob_param_list interface_attr_list = {
@@ -1710,6 +1712,39 @@ int config_parse_interface(void *data, size_t len, const char *name, bool overwr
 					  &iface->pio_filter_addr,
 					  &iface->pio_filter_length);
 
+	if ((c = tb[IFACE_ATTR_DHCPV6_RELAY_SERVERS])) {
+		struct blob_attr *cur;
+		unsigned rem;
+
+		blobmsg_for_each_attr(cur, c, rem) {
+			struct in6_addr addr6, *tmp6;
+
+			if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING || !blobmsg_check_attr(cur, false))
+				continue;
+
+			if (inet_pton(AF_INET6, blobmsg_get_string(cur), &addr6) == 1) {
+				if (IN6_IS_ADDR_UNSPECIFIED(&addr6)) {
+					error("Invalid %s value configured for interface '%s'",
+					      iface_attrs[IFACE_ATTR_DHCPV6_RELAY_SERVERS].name, iface->name);
+					continue;
+				}
+
+				tmp6 = realloc(iface->dhcpv6_relay_server_addrs6,
+					       (iface->dhcpv6_relay_server_addrs6_cnt + 1) *
+					       sizeof(*iface->dhcpv6_relay_server_addrs6));
+
+				if (!tmp6)
+					goto err;
+
+				iface->dhcpv6_relay_server_addrs6 = tmp6;
+				iface->dhcpv6_relay_server_addrs6[iface->dhcpv6_relay_server_addrs6_cnt++] = addr6;
+			} else {
+				error("Invalid %s value configured for interface '%s'",
+				      iface_attrs[IFACE_ATTR_DHCPV6_RELAY_SERVERS].name, iface->name);
+			}
+		}
+	}
+
 	if (overwrite && (c = tb[IFACE_ATTR_NTP])) {
 		struct blob_attr *cur;
 		unsigned rem;

src/dhcpv6.c

@@ -28,7 +28,8 @@
 #endif
 
 static void relay_client_request(struct sockaddr_in6 *source,
-		const void *data, size_t len, struct interface *iface);
+		const void *data, size_t len, struct interface *iface,
+		struct in6_addr *dest);
 static void relay_server_response(uint8_t *data, size_t len);
 
 static void handle_dhcpv6(void *addr, void *data, size_t len,
@@ -806,10 +807,15 @@ static void handle_dhcpv6(void *addr, void *data, size_t len,
 	if (iface->dhcpv6 == MODE_SERVER) {
 		handle_client_request(addr, data, len, iface, dest_addr);
 	} else if (iface->dhcpv6 == MODE_RELAY) {
-		if (iface->master)
+		if (iface->master) {
 			relay_server_response(data, len);
-		else
-			relay_client_request(addr, data, len, iface);
+		} else if (iface->dhcpv6_relay_server_addrs6_cnt > 0) {
+			for (size_t i = 0; i < iface->dhcpv6_relay_server_addrs6_cnt; i++) {
+				relay_client_request(addr, data, len, iface, &iface->dhcpv6_relay_server_addrs6[i]);
+			}
+		} else {
+			relay_client_request(addr, data, len, iface, NULL);
+		}
 	}
 }
 
@@ -926,7 +932,8 @@ static struct odhcpd_ipaddr *relay_link_address(struct interface *iface)
 
 /* Relay client request (regular DHCPv6-relay) */
 static void relay_client_request(struct sockaddr_in6 *source,
-		const void *data, size_t len, struct interface *iface)
+		const void *data, size_t len, struct interface *iface,
+		struct in6_addr *dest)
 {
 	const struct dhcpv6_relay_header *h = data;
 	/* Construct our forwarding envelope */
@@ -988,7 +995,11 @@ static void relay_client_request(struct sockaddr_in6 *source,
 	memset(&s, 0, sizeof(s));
 	s.sin6_family = AF_INET6;
 	s.sin6_port = htons(DHCPV6_SERVER_PORT);
-	inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &s.sin6_addr);
+
+	if (dest)
+	    s.sin6_addr = *dest;
+	else
+	    inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &s.sin6_addr);
 
 	avl_for_each_element(&interfaces, c, avl) {
 		if (!c->master || c->dhcpv6 != MODE_RELAY)

src/odhcpd.h

@@ -468,6 +468,8 @@ struct interface {
 	bool dhcpv6_na;
 	uint32_t dhcpv6_hostid_len;
 	uint32_t dhcpv6_pd_min_len; // minimum delegated prefix length
+	struct in6_addr *dhcpv6_relay_server_addrs6;
+	size_t dhcpv6_relay_server_addrs6_cnt;
 
 	char *upstream;
 	size_t upstream_len;