From 02bcb7ecc3fc5afb9bc3502923e615330fa313fa Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Tue, 5 Jan 2010 18:25:41 +0000
Subject: [PATCH] MFC 201196: 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.

---
 sys/net/if.c      | 10 ++++++++++
 sys/net/if.h      |  1 +
 sys/net/if_vlan.c |  7 ++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/sys/net/if.c b/sys/net/if.c
index 55de666a6360..7ffa2687c8ca 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -2161,6 +2161,14 @@ ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t data, struct thread *td)
 			return (EINVAL);
 		if (ifunit(new_name) != NULL)
 			return (EEXIST);
+
+		/*
+		 * XXX: Locking.  Nothing else seems to lock if_flags,
+		 * and there are numerous other races with the
+		 * ifunit() checks not being atomic with namespace
+		 * changes (renames, vmoves, if_attach, etc).
+		 */
+		ifp->if_flags |= IFF_RENAMING;
 		
 		/* Announce the departure of the interface. */
 		rt_ifannouncemsg(ifp, IFAN_DEPARTURE);
@@ -2195,6 +2203,8 @@ ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t data, struct thread *td)
 		EVENTHANDLER_INVOKE(ifnet_arrival_event, ifp);
 		/* Announce the return of the interface. */
 		rt_ifannouncemsg(ifp, IFAN_ARRIVAL);
+
+		ifp->if_flags &= ~IFF_RENAMING;
 		break;
 
 #ifdef VIMAGE
diff --git a/sys/net/if.h b/sys/net/if.h
index 857ab7fb460b..f94b54a1b622 100644
--- a/sys/net/if.h
+++ b/sys/net/if.h
@@ -150,6 +150,7 @@ struct if_data {
 #define	IFF_MONITOR	0x40000		/* (n) user-requested monitor mode */
 #define	IFF_STATICARP	0x80000		/* (n) static ARP */
 #define	IFF_DYING	0x200000	/* (n) interface is winding down */
+#define	IFF_RENAMING	0x400000	/* (n) interface is being renamed */
 
 /*
  * Old names for driver flags so that user space tools can continue to use
diff --git a/sys/net/if_vlan.c b/sys/net/if_vlan.c
index f23541e230d9..f0cd3b31d698 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.