Add netlink address add/del

Straight forward addition/removal of IPv4 and IPv6 addresses on
interfaces. One thing I noticed, which isn't a concern but an
unfortunate issue, looking at the following sequence:

ip addr add 10.0.1.1/30 dev e0
debug      linux-cp/nl    addr_add: netlink route/addr: add idx 1488 family inet local 10.0.1.1/30 flags 0x0080 (permanent)
warn       linux-cp/nl    dispatch: ignored route/route: add family inet type 2 proto 2 table 255 dst 10.0.1.1 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: add family inet type 1 proto 2 table 254 dst 10.0.1.0/30 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: add family inet type 3 proto 2 table 255 dst 10.0.1.0 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: add family inet type 3 proto 2 table 255 dst 10.0.1.3 nexthops { idx 1488 }

ping 10.0.1.2
debug      linux-cp/nl    neigh_add: netlink route/neigh: add idx 1488 family inet lladdr 68:05:ca:32:45:94 dst 10.0.1.2 state 0x0002 (reachable) flags 0x0000
notice     linux-cp/nl    neigh_add: Added 10.0.1.2 lladdr 68:05:ca:32:45:94 iface TenGigabitEthernet3/0/0

ip addr del 10.0.1.1/30 dev e0
debug      linux-cp/nl    addr_del: netlink route/addr: del idx 1488 family inet local 10.0.1.1/30 flags 0x0080 (permanent)
notice     linux-cp/nl    addr_del: Deleted 10.0.1.1/30 iface TenGigabitEthernet3/0/0
warn       linux-cp/nl    dispatch: ignored route/route: del family inet type 1 proto 2 table 254 dst 10.0.1.0/30 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: del family inet type 3 proto 2 table 255 dst 10.0.1.3 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: del family inet type 3 proto 2 table 255 dst 10.0.1.0 nexthops { idx 1488 }
warn       linux-cp/nl    dispatch: ignored route/route: del family inet type 2 proto 2 table 255 dst 10.0.1.1 nexthops { idx 1488 }
debug      linux-cp/nl    neigh_del: netlink route/neigh: del idx 1488 family inet lladdr 68:05:ca:32:45:94 dst 10.0.1.2 state 0x0002 (reachable) flags 0x0000
error      linux-cp/nl    neigh_del: Failed 10.0.1.2 iface TenGigabitEthernet3/0/0

It is this very last message that's a bit of a concern -- the ping
brought the lladdr into the neighbor cache; and the subsequent address
deletion first removed the address, then all the typical local routes
(the connected, the broadcast, the network, and the self/local); but
then as well explicitly deleted the neighbor, which is correct behavior
for Linux, except that VPP already invalidates the neighbor cache and
adds/removes the connected routes for example in ip/ip4_forward.c L826-L830
and L583.

I predict more of these false positive 'errors' like the one on neigh_del()
beacuse interface/route addition/deletion is slightly different in VPP than
in Linux. I may have to reclassify the errors as warnings otherwise.

lcpng_netlink.c

@@ -207,6 +207,10 @@ lcp_nl_dispatch (struct nl_object *obj, void *arg)
       return lcp_nl_neigh_add ((struct rtnl_neigh *) obj);
     case RTM_DELNEIGH:
       return lcp_nl_neigh_del ((struct rtnl_neigh *) obj);
+    case RTM_NEWADDR:
+      return lcp_nl_addr_add ((struct rtnl_addr *) obj);
+    case RTM_DELADDR:
+      return lcp_nl_addr_del ((struct rtnl_addr *) obj);
     default:
       NL_WARN ("dispatch: ignored %U", format_nl_object, obj);
       break;