[PATCH] ipv4: dont create routes on down devices

[Eric Dumazet <eric.dumazet@gmail.com>]

Le mercredi 22 décembre 2010 à 14:43 +0100, Nicolas Dichtel a écrit :
> Yes, I saw this commit, but I still got the problem:
> 
> shelby:/home/root/src# uname -a
> Linux shelby 2.6.37-rc5+ #10 SMP Wed Dec 22 05:02:53 EST 2010 i686 GNU/Linux
> shelby:/home/root/src# ip tunnel add mode ipip remote 10.16.0.164 local 
> 10.16.0.72 dev eth0
> shelby:/home/root/src# ./a.out tunl1
> shelby:/home/root/src# ip tunnel del tunl1
> 
> Message from syslogd@shelby at Dec 22 10:12:08 ...
>   kernel:[18459.828011] unregister_netdevice: waiting for tunl1 to become free. 
> Usage count = 3
> 

On another machine, and net-next-2.6, I reproduced the problem, so we
need the patch after all, sorry for the delay.

Thanks

[PATCH] ipv4: dont create routes on down devices

In ip_route_output_slow(), instead of allowing a route to be created on
a not UPed device, report -ENETUNREACH immediately.

# ip tunnel add mode ipip remote 10.16.0.164 local 
10.16.0.72 dev eth0
# (Note : tunl1 is down)
# ping -I tunl1 10.1.2.3
PING 10.1.2.3 (10.1.2.3) from 192.168.18.5 tunl1: 56(84) bytes of data.
(nothing)
# ./a.out tunl1
# ip tunnel del tunl1
Message from syslogd@shelby at Dec 22 10:12:08 ...
  kernel: unregister_netdevice: waiting for tunl1 to become free. 
Usage count = 3

After patch:
# ping -I tunl1 10.1.2.3
connect: Network is unreachable


Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/ipv4/route.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d8b4f4d..f1defb7 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2562,9 +2562,10 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 			goto out;
 
 		/* RACE: Check return value of inet_select_addr instead. */
-		if (rcu_dereference(dev_out->ip_ptr) == NULL)
-			goto out;	/* Wrong error code */
-
+		if (!(dev_out->flags & IFF_UP) || !__in_dev_get_rcu(dev_out)) {
+			err = -ENETUNREACH;
+			goto out;
+		}
 		if (ipv4_is_local_multicast(oldflp->fl4_dst) ||
 		    ipv4_is_lbcast(oldflp->fl4_dst)) {
 			if (!fl.fl4_src)