network/dhcp4: introduce dhcp4_get_router() helper function

Previously, we use the first router address, and if it is null, we
ignore the address. Now, we use the first non-null address. That is, if
the first router address is null, but the second is not, then we use the
second one.

That should not cause functional change in most cases, except for the case
when a DHCP server provides such spurious reply.

This is mostly for refactoring and preparation for later commits.

diff --git a/src/network/networkd-dhcp4.c b/src/network/networkd-dhcp4.c
index 2f221fc0de4ba26ce2668217621f561288e21355..3880960722a43580616691f7a49831a0e0fa5641 100644 (file)
--- a/src/network/networkd-dhcp4.c
+++ b/src/network/networkd-dhcp4.c
@@ -52,6 +52,31 @@ void network_adjust_dhcp4(Network *network) {
                 network->dhcp_client_identifier = network->dhcp_anonymize ? DHCP_CLIENT_ID_MAC : DHCP_CLIENT_ID_DUID;
 }
 
+static int dhcp4_get_router(Link *link, struct in_addr *ret) {
+        const struct in_addr *routers;
+        int r;
+
+        assert(link);
+        assert(link->dhcp_lease);
+        assert(ret);
+
+        r = sd_dhcp_lease_get_router(link->dhcp_lease, &routers);
+        if (r < 0)
+                return r;
+
+        /* The router option may provide multiple routers, We only use the first non-null address. */
+
+        FOREACH_ARRAY(router, routers, r) {
+                if (in4_addr_is_null(router))
+                        continue;
+
+                *ret = *router;
+                return 0;
+        }
+
+        return -ENODATA;
+}
+
 static int dhcp4_get_classless_static_or_static_routes(Link *link, sd_dhcp_route ***ret_routes, size_t *ret_num) {
         _cleanup_free_ sd_dhcp_route **routes = NULL;
         int r;
@@ -491,8 +516,7 @@ static int dhcp4_request_static_routes(Link *link, struct in_addr *ret_default_g
 
 static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
         _cleanup_(route_freep) Route *route = NULL;
-        const struct in_addr *router;
-        struct in_addr address;
+        struct in_addr address, router;
         int r;
 
         assert(link);
@@ -503,17 +527,13 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
         if (r < 0)
                 return r;
 
-        r = sd_dhcp_lease_get_router(link->dhcp_lease, &router);
-        if (IN_SET(r, 0, -ENODATA)) {
-                log_link_debug(link, "DHCP: No gateway received from DHCP server.");
+        r = dhcp4_get_router(link, &router);
+        if (r == -ENODATA) {
+                log_link_debug(link, "DHCP: No valid router address received from DHCP server.");
                 return 0;
         }
         if (r < 0)
                 return r;
-        if (in4_addr_is_null(&router[0])) {
-                log_link_debug(link, "DHCP: Received gateway address is null.");
-                return 0;
-        }
 
         if (!link->network->dhcp_use_gateway) {
                 /* When no classless static route is provided, even if UseGateway=no, use the gateway
@@ -521,13 +541,13 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
                  * neither UseRoutes= nor UseGateway= is disabled, use the default gateway in classless
                  * static routes if provided (in that case, in4_addr_is_null(gw) below is true). */
                 if (in4_addr_is_null(gw))
-                        *gw = router[0];
+                        *gw = router;
                 return 0;
         }
 
         /* The dhcp netmask may mask out the gateway. First, add an explicit route for the gateway host
          * so that we can route no matter the netmask or existing kernel route tables. */
-        r = dhcp4_request_route_to_gateway(link, &router[0]);
+        r = dhcp4_request_route_to_gateway(link, &router);
         if (r < 0)
                 return r;
 
@@ -537,7 +557,7 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
 
         /* Next, add a default gateway. */
         route->gw_family = AF_INET;
-        route->gw.in = router[0];
+        route->gw.in = router;
         route->prefsrc.in = address;
 
         r = dhcp4_request_route(TAKE_PTR(route), link);
@@ -546,7 +566,7 @@ static int dhcp4_request_gateway(Link *link, struct in_addr *gw) {
 
         /* When no classless static route is provided, or UseRoutes=no, then use the router address to
          * configure semi-static routes and routes to DNS or NTP servers in later steps. */
-        *gw = router[0];
+        *gw = router;
         return 0;
 }