networkd: link - ignore missing MAC address

Currently DHCP/IPv4LL only works on ethernet devices, but no reason not to otherwise
manage them.

TODO

@@ -615,13 +615,11 @@ Features:
    - add reduced [Link] support to .network files
    - add Scope= parsing option for [Network]
    - properly handle routerless dhcp leases
-   - set lifetime on the address acquired from dhcp
-   - patch kernel to support module alias for tunnel device (ipip/sit/gre),
-     then remove remove libkmod dependency and CAP_SYS_MODULE
    - add veth netdev support (c.f. http://shorewall.net/bridge-Shorewall-perl.html#veth)
    - add tun/tap netdev support
    - add more attribute support for SIT tunnel
    - make metric of routes configurable
+   - work with non-ethernet devices
 
 * networkd-wait-online:
    - make operstates to wait for configurable?

src/network/networkd-link.c

@@ -78,7 +78,7 @@ static int link_new(Manager *manager, sd_rtnl_message *message, Link **ret) {
 
         r = sd_rtnl_message_read_ether_addr(message, IFLA_ADDRESS, &link->mac);
         if (r < 0)
-                return r;
+                log_debug_link(link, "MAC address not found for new device, continuing without");
 
         r = asprintf(&link->state_file, "/run/systemd/netif/links/%"PRIu64,
                      link->ifindex);

src/network/networkd-manager.c

@@ -292,7 +292,8 @@ static int manager_rtnl_process_link(sd_rtnl *rtnl, sd_rtnl_message *message, vo
                         /* link is new, so add it */
                         r = link_add(m, message, &link);
                         if (r < 0) {
-                                log_debug("could not add new link");
+                                log_debug("could not add new link: %s",
+                                           strerror(-r));
                                 return 0;
                         }
                 }