netdev - [PATCH] ipv4: remove all rt cache entries on UNREGISTER event

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Date:	Tue, 28 Sep 2010 17:24:57 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	netdev <netdev@...r.kernel.org>
Subject: [PATCH] ipv4: remove all rt cache entries on UNREGISTER event

Hi,

I face a problem when I try to remove an interface, 
netdev_wait_allrefs() complains about refcount.

Here is a trivial scenario to reproduce the problem:
# ip tunnel add mode ipip remote 10.16.0.164 local 10.16.0.72 dev eth0
# ./a.out tunl1
# ip tunnel del tunl1

Note: a.out binary create an IPv4 raw socket, attach it to tunl1 
(SO_BINDTODEVICE), set it as multicast (IP_MULTICAST_LOOP), set the 
multicast interface to tunl1 (IP_MULTICAST_IF), build the IP header 
(IP_HDRINCL) and then send a single packet (192.168.6.1 -> 224.0.0.18).

Note2: when a.out is executed, tunl1 has no ip address and is down.

Then, I got a serie of "kernel:[1206699.728010] unregister_netdevice: 
waiting for tunl1 to become free. Usage count = 3" and after some time, 
interface is removed.

The problem is that route cache entries are only invalidate on 
UNREGISTER event, and not removed (introduced by commit 
e2ce146848c81af2f6d42e67990191c284bf0c33). We must wait that 
rt_check_expire() remove the remaining route cache entries.

To fix the problem, I propose to remove a part of the previous commit.

Regards,
Nicolas

View attachment "0001-ipv4-remove-all-rt-cache-entries-on-UNREGISTER-even.patch" of type "text/x-diff" (2259 bytes)