network: when Gateway=_dhcp4, set several properties based on lease if they are not explicitly specified

Before this commit, event when Gateway=_dhcp4 or _ra is set, the
route was configured with 'protocol static', and other properties
specified by RouteTable=, RouteMTU=, or etc, were ignored.

This commit makes set the route protocol based on the protocol the
gateway address is obtained, and apply other settings if it is not
explicitly specified in the [Route] section.

src/network/networkd-dhcp4.c

@@ -395,6 +395,14 @@ static int link_set_dhcp_routes(Link *link) {
                                         continue;
 
                                 rt->gw.in = router[0];
+                                if (!rt->protocol_set)
+                                        rt->protocol = RTPROT_DHCP;
+                                if (!rt->priority_set)
+                                        rt->priority = link->network->dhcp_route_metric;
+                                if (!rt->table_set)
+                                        rt->table = table;
+                                if (rt->mtu == 0)
+                                        rt->mtu = link->network->dhcp_route_mtu;
 
                                 r = dhcp_route_configure(rt, link);
                                 if (r < 0)

src/network/networkd-ndisc.c

@@ -461,7 +461,7 @@ static int ndisc_router_process_default(Link *link, sd_ndisc_router *rt) {
         union in_addr_union gateway;
         uint16_t lifetime;
         unsigned preference;
-        uint32_t mtu;
+        uint32_t table, mtu;
         usec_t time_now;
         int r;
 
@@ -504,12 +504,14 @@ static int ndisc_router_process_default(Link *link, sd_ndisc_router *rt) {
         else if (r < 0)
                 return log_link_error_errno(link, r, "Failed to get default router MTU from RA: %m");
 
+        table = link_get_ipv6_accept_ra_route_table(link);
+
         r = route_new(&route);
         if (r < 0)
                 return log_oom();
 
         route->family = AF_INET6;
-        route->table = link_get_ipv6_accept_ra_route_table(link);
+        route->table = table;
         route->priority = link->network->dhcp6_route_metric;
         route->protocol = RTPROT_RA;
         route->pref = preference;
@@ -531,6 +533,17 @@ static int ndisc_router_process_default(Link *link, sd_ndisc_router *rt) {
                         continue;
 
                 route_gw->gw = gateway;
+                if (!route_gw->table_set)
+                        route_gw->table = table;
+                if (!route_gw->priority_set)
+                        route_gw->priority = link->network->dhcp6_route_metric;
+                if (!route_gw->protocol_set)
+                        route_gw->protocol = RTPROT_RA;
+                if (!route_gw->pref_set)
+                        route->pref = preference;
+                route_gw->lifetime = time_now + lifetime * USEC_PER_SEC;
+                if (route_gw->mtu == 0)
+                        route_gw->mtu = mtu;
 
                 r = ndisc_route_configure(route_gw, link, rt);
                 if (r < 0)

src/network/networkd-route.c

@@ -1902,6 +1902,7 @@ int config_parse_route_priority(
                 return 0;
         }
 
+        n->priority_set = true;
         TAKE_PTR(n);
         return 0;
 }
@@ -2086,6 +2087,7 @@ int config_parse_ipv6_route_preference(
                 return 0;
         }
 
+        n->pref_set = true;
         TAKE_PTR(n);
         return 0;
 }

src/network/networkd-route.h

@@ -32,20 +32,24 @@ typedef struct Route {
         unsigned char dst_prefixlen;
         unsigned char src_prefixlen;
         unsigned char scope;
-        bool scope_set;
         unsigned char protocol;  /* RTPROT_* */
         unsigned char type; /* RTN_* */
         unsigned char tos;
         uint32_t priority; /* note that ip(8) calls this 'metric' */
         uint32_t table;
-        bool table_set;
         uint32_t mtu;
         uint32_t initcwnd;
         uint32_t initrwnd;
         unsigned char pref;
         unsigned flags;
         int gateway_onlink;
-        bool gateway_from_dhcp_or_ra;
+
+        bool scope_set:1;
+        bool table_set:1;
+        bool priority_set:1;
+        bool protocol_set:1;
+        bool pref_set:1;
+        bool gateway_from_dhcp_or_ra:1;
 
         union in_addr_union gw;
         union in_addr_union dst;

test/test-network/systemd-networkd-tests.py

@@ -3899,7 +3899,7 @@ class NetworkdDHCPClientTests(unittest.TestCase, Utilities):
 
         output = check_output('ip route list dev veth99 10.0.0.0/8')
         print(output)
-        self.assertRegex(output, '10.0.0.0/8 via 192.168.5.1 proto static')
+        self.assertRegex(output, '10.0.0.0/8 via 192.168.5.1 proto dhcp')
 
     def test_dhcp_client_gateway_ipv6(self):
         copy_unit_to_networkd_unit_path('25-veth.netdev', 'dhcp-server-veth-peer.network',