libsystemd-network: sd-ipv4ll: acquire new address after claimed address conflict

If a conflict occurs on a claimed ipv4ll address, the device releases
the address and then does not attempt to acquire a new ipv4ll
address. According to RFC3927, releasing the address in this
situation is correct. However, this should be followed by an attempt
to configure a new ipv4ll address.

This commit restarts the ipv4ll address acquisition state machine
after releasing the conflicting address.

From RFC3927 Section 2.5 conflict defense method (b):
...
However, if this is not the first conflicting ARP packet the host has
seen, and the time recorded for the previous conflicting ARP packet is
recent, within DEFEND_INTERVAL seconds, then the host MUST immediately
cease using this address and configure a new IPv4 Link-Local address
as described above.
...

Signed-off-by: Jason Reeder <jasonreeder@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/network/networkd-ipv4ll.c b/src/network/networkd-ipv4ll.c
index 7ba05dbec3..e2578a298b 100644
--- a/src/network/networkd-ipv4ll.c
+++ b/src/network/networkd-ipv4ll.c
@@ -179,12 +179,22 @@ static void ipv4ll_handler(sd_ipv4ll *ll, int event, void *userdata) {
 
         switch(event) {
                 case SD_IPV4LL_EVENT_STOP:
+                        r = ipv4ll_address_lost(link);
+                        if (r < 0) {
+                                link_enter_failed(link);
+                                return;
+                        }
+                        break;
                 case SD_IPV4LL_EVENT_CONFLICT:
                         r = ipv4ll_address_lost(link);
                         if (r < 0) {
                                 link_enter_failed(link);
                                 return;
                         }
+
+                        r = sd_ipv4ll_restart(ll);
+                        if (r < 0)
+                                log_link_warning(link, "Could not acquire IPv4 link-local address");
                         break;
                 case SD_IPV4LL_EVENT_BIND:
                         r = ipv4ll_address_claimed(ll, link);