Change vlan interfaces to cope more usefully with the parent interface being

renamed.  Previously the vlan interfaces would lose their configuration as if
the parent interface had been physically removed.  Now vlan interfaces ignore
rename events.
- Add a new ifnet flag (IFF_RENAMING) that is set while an ifnet is being
  renamed.  This flag can be checked in ifnet departure/arrival event
  handlers to treat rename events differently.
- Change the ifnet departure event handler in the if_vlan(4) driver to
  ignore departure events due to a trunk interface being renamed.

Reviewed by:	brooks, rwatson
MFC after:	1 week

1 files changed, 6 insertions, 1 deletions

diff --git a/sys/net/if_vlan.c b/sys/net/if_vlan.c
index bb906828..99f714e 100644
--- a/sys/net/if_vlan.c
+++ b/sys/net/if_vlan.c
@@ -466,7 +466,8 @@ vlan_setmulti(struct ifnet *ifp)
  * A handler for network interface departure events.
  * Track departure of trunks here so that we don't access invalid
  * pointers or whatever if a trunk is ripped from under us, e.g.,
- * by ejecting its hot-plug card.
+ * by ejecting its hot-plug card.  However, if an ifnet is simply
+ * being renamed, then there's no need to tear down the state.
  */
 static void
 vlan_ifdetach(void *arg __unused, struct ifnet *ifp)
@@ -481,6 +482,10 @@ vlan_ifdetach(void *arg __unused, struct ifnet *ifp)
 	if (ifp->if_vlantrunk == NULL)
 		return;
 
+	/* If the ifnet is just being renamed, don't do anything. */
+	if (ifp->if_flags & IFF_RENAMING)
+		return;
+
 	VLAN_LOCK();
 	/*
 	 * OK, it's a trunk.  Loop over and detach all vlan's on it.