vrrpd: ignore address deletion if iface is down

See code comment for explanation

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

diff --git a/vrrpd/vrrp.c b/vrrpd/vrrp.c
index 5d97199f4073b42b755c7aa1e794572108058042..d22c245afea9115ad3fee266ae52f58044ef0049 100644 (file)
--- a/vrrpd/vrrp.c
+++ b/vrrpd/vrrp.c
@@ -1961,7 +1961,42 @@ void vrrp_if_address_add(struct interface *ifp)
 
 void vrrp_if_address_del(struct interface *ifp)
 {
-       vrrp_autoconfig_if_address_del(ifp);
+       /*
+        * Zebra is stupid and sends us address deletion notifications
+        * when any of the following condition sets are met:
+        *
+        * - IFF_UP && address deleted
+        * - IFF_UP -> !IFF_UP
+        *
+        * Note that the second one is nonsense, because Zebra behaves as
+        * though an interface going down means all the addresses on that
+        * interface got deleted. Which is a problem for autoconfig because all
+        * the addresses on an interface going away means the VRRP session goes
+        * to Initialize. However interfaces go down whenever we transition to
+        * Backup, so this effectively means that for autoconfigured instances
+        * we actually end up in Initialize whenever we try to go into Backup.
+        *
+        * Also, Zebra does NOT send us notifications when:
+        * - !IFF_UP && address deleted
+        *
+        * Which means if we're in backup and an address is deleted out from
+        * under us, we won't even know.
+        *
+        * The only solution here is to only resynchronize our address list
+        * when:
+        *
+        * - An interfaces comes up
+        * - An interface address is added
+        * - An interface address is deleted AND the interface is up
+        *
+        * Even though this is only a problem with autoconfig at the moment I'm
+        * papering over Zebra's braindead semantics here. Every piece of code
+        * in this function should be protected by a check that the interface
+        * is up.
+        */
+       if (CHECK_FLAG(ifp->flags, IFF_UP)) {
+               vrrp_autoconfig_if_address_del(ifp);
+       }
 }
 
 /* Other ------------------------------------------------------------------- */