dhcpv4: iface->dhcpv4_router -> iface->dhcpv4_routers

This makes it clearer that the variable stores multiple addresses, also
fix a potential realloc memleak.

Signed-off-by: David Härdeman <david@hardeman.nu>
Link: https://github.com/openwrt/odhcpd/pull/320
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

4 files changed, 15 insertions, 13 deletions

diff --git a/README.md b/README.md
index 2d8c3f2..663986a 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,7 @@ and may also receive information from ubus
 | dhcpv6_pd		|bool	| 1	| DHCPv6 stateful addressing hands out IA_PD - Internet Address - Prefix Delegation (PD) |
 | dhcpv6_pd_preferred   |bool | 0 | Set the DHCPv6-PD Preferred (P) flag in outgoing ICMPv6 RA message PIOs (RFC9762); requires `dhcpv6` and `dhcpv6_pd`. |
 | dhcpv6_pd_min_len	|integer| -	| Minimum prefix length to delegate with IA_PD (value is adjusted if needed to be greater than the interface prefix length).  Range [1,62] |
-| router		|list	|`<local address>`| Routers to announce, accepts IPv4 only |
+| router		|list	|`<local address>`| IPv4 addresses of routers on a given subnet (provided via DHCPv4, should be in order of preference) |
 | dns			|list	|`<local address>`| DNS servers to announce, accepts IPv4 and IPv6 |
 | dnr			|list	|disabled| Encrypted DNS servers to announce, `<priority> <domain name> [<comma separated IP addresses> <SvcParams (key=value)>...]` |
 | dns_service		|bool	| 1	| Announce the address of interface as DNS service if the list of dns is empty |
diff --git a/src/config.c b/src/config.c
index 30609a6..68ef3ab 100644
--- a/src/config.c
+++ b/src/config.c
@@ -346,7 +346,7 @@ static void clean_interface(struct interface *iface)
 	free(iface->dns_addrs6);
 	free(iface->dns_search);
 	free(iface->upstream);
-	free(iface->dhcpv4_router);
+	free(iface->dhcpv4_routers);
 	free(iface->dhcpv6_raw);
 	free(iface->dhcpv4_ntp);
 	free(iface->dhcpv6_ntp);
@@ -1291,21 +1291,23 @@ int config_parse_interface(void *data, size_t len, const char *name, bool overwr
 		unsigned rem;
 
 		blobmsg_for_each_attr(cur, c, rem) {
-			struct in_addr addr4;
+			struct in_addr addr4, *tmp;
 
 			if (blobmsg_type(cur) != BLOBMSG_TYPE_STRING || !blobmsg_check_attr(cur, false))
 				continue;
 
 			if (inet_pton(AF_INET, blobmsg_get_string(cur), &addr4) == 1) {
-				iface->dhcpv4_router = realloc(iface->dhcpv4_router,
-						(++iface->dhcpv4_router_cnt) * sizeof(*iface->dhcpv4_router));
-				if (!iface->dhcpv4_router)
+				tmp = realloc(iface->dhcpv4_routers,
+					      (iface->dhcpv4_routers_cnt + 1) * sizeof(*iface->dhcpv4_routers));
+				if (!tmp)
 					goto err;
 
-				iface->dhcpv4_router[iface->dhcpv4_router_cnt - 1] = addr4;
-			} else
+				iface->dhcpv4_routers = tmp;
+				iface->dhcpv4_routers[iface->dhcpv4_routers_cnt++] = addr4;
+			} else {
 				error("Invalid %s value configured for interface '%s'",
 				      iface_attrs[IFACE_ATTR_ROUTER].name, iface->name);
+			}
 		}
 	}
 
diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 545c814..97c1ec2 100644
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -1094,9 +1094,9 @@ void dhcpv4_handle_msg(void *src_addr, void *data, size_t len,
 
 		case DHCPV4_OPT_ROUTER:
 			iov[IOV_ROUTER].iov_len = sizeof(reply_router);
-			if (iface->dhcpv4_router_cnt) {
-				reply_router.len = iface->dhcpv4_router_cnt * sizeof(*iface->dhcpv4_router);
-				iov[IOV_ROUTER_ADDR].iov_base = iface->dhcpv4_router;
+			if (iface->dhcpv4_routers_cnt) {
+				reply_router.len = iface->dhcpv4_routers_cnt * sizeof(*iface->dhcpv4_routers);
+				iov[IOV_ROUTER_ADDR].iov_base = iface->dhcpv4_routers;
 			} else {
 				reply_router.len = sizeof(iface->dhcpv4_own_ip.addr.in);
 				iov[IOV_ROUTER_ADDR].iov_base = &iface->dhcpv4_own_ip.addr.in;
diff --git a/src/odhcpd.h b/src/odhcpd.h
index a74c295..a5ba496 100644
--- a/src/odhcpd.h
+++ b/src/odhcpd.h
@@ -447,8 +447,8 @@ struct interface {
 	struct in_addr dhcpv4_start_ip;
 	struct in_addr dhcpv4_end_ip;
 	struct odhcpd_ipaddr dhcpv4_own_ip;
-	struct in_addr *dhcpv4_router;
-	size_t dhcpv4_router_cnt;
+	struct in_addr *dhcpv4_routers;	// IPv4 addresses for routers on this subnet
+	size_t dhcpv4_routers_cnt;	// Count of router addresses
 	bool dhcpv4_forcereconf;
 
 	// DNS