Prevent a panic caused by freeing things in the wrong order, when
unbinding an interface with multicast addresses.  To demonstrate
the panic, try this:
% ip/ipconfig ether /net/ether0 add 2001:db8::1234 /32
% up/ipconfig ether /net/ether0 unbind

Notes:
Tue May 1 19:26:32 BST 2007 miller
    (typo: up/ipconfig -> ip/ipconfig)


Reference: /n/sources/patch/applied/unbind-panic
Date: Tue May  1 20:23:42 CES 2007
Signed-off-by: miller@hamnavoe.com
Reviewed-by: geoff

--- /sys/src/9/ip/ipifc.c	Tue May  1 20:19:11 2007
+++ /sys/src/9/ip/ipifc.c	Tue May  1 20:19:07 2007
@@ -185,6 +185,14 @@
 		ifc->conv->inuse--;
 	ifc->ifcid++;
 
+	/* disassociate logical interfaces */
+	while(ifc->lifc){
+		err = ipifcremlifc(ifc, ifc->lifc);
+		/* note: err nonzero means lifc not found, which can't happen in this case */
+		if(err)
+			error(err);
+	}
+
 	/* disassociate device */
 	if(ifc->m && ifc->m->unbind)
 		(*ifc->m->unbind)(ifc);
@@ -196,13 +204,6 @@
 	qclose(ifc->conv->rq);
 	qclose(ifc->conv->wq);
 	qclose(ifc->conv->sq);
-
-	/* disassociate logical interfaces */
-	while(ifc->lifc){
-		err = ipifcremlifc(ifc, ifc->lifc);
-		if(err)
-			error(err);
-	}
 
 	ifc->m = nil;
 	wunlock(ifc);