Re: IPsec tunnel forwarding in net-next-2.6 since 452edd59

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

Le mardi 15 mars 2011 à 14:30 -0400, Michael Smith a écrit :
> Hi,
> 
> I'm able to ping across a tunnel to a peer running net-next-2.6, but 
> only to an interface on the peer; trying to ping a host behind the peer 
> fails. The incoming packet shows up in encrypted and decrypted form in 
> tcpdump, but it's not forwarded. None of the XFRM error counters are 
> incremented; the packets just silently fail to be forwarded.
> 
> There are no iptables rules and net.ipv4.ip_forward=1. The same config 
> works on 2.6.38-rc8. git bisect pointed me to commit 452edd59 from March 2:
> 
>      xfrm: Return dst directly from xfrm_lookup()
> 
>      Instead of on the stack.
> 
> 
> ip xfrm policy:
> 
> src 192.168.136.0/24 dst 192.168.137.0/24
>          dir out priority 2344 ptype main
>          tmpl src 1.1.1.136 dst 1.1.1.137
>                  proto esp reqid 16385 mode tunnel
> 
> src 192.168.137.0/24 dst 192.168.136.0/24
>          dir fwd priority 2344 ptype main
>          tmpl src 1.1.1.137 dst 1.1.1.136
>                  proto esp reqid 16385 mode tunnel
> 
> src 192.168.137.0/24 dst 192.168.136.0/24
>          dir in priority 2344 ptype main
>          tmpl src 1.1.1.137 dst 1.1.1.136
>                  proto esp reqid 16385 mode tunnel
> 
> net-next-2.6 host is at 1.1.1.136 and 192.168.136.1. 2.6.35.10 host is 
> at 1.1.1.137 and 192.168.137.1. From that host:
> 
> ping -I 192.168.137.1 192.168.136.1 -> success
> ping -I 192.168.137.1 192.168.136.2 -> silent failure
> 
> Thanks,

Thanks for this excellent bug report !

Could you try following patch ?

[PATCH] xfrm: fix __xfrm_route_forward()

This function should return 0 in case of error, 1 if OK
commit 452edd598f60522 (xfrm: Return dst directly from xfrm_lookup())
got it wrong.

Reported-and-bisected-by: Michael Smith <msmith@cbnco.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 1ba0258..027e3c6 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2175,7 +2175,7 @@ int __xfrm_route_forward(struct sk_buff *skb, unsigned short family)
 	struct net *net = dev_net(skb->dev);
 	struct flowi fl;
 	struct dst_entry *dst;
-	int res = 0;
+	int res = 1;
 
 	if (xfrm_decode_session(skb, &fl, family) < 0) {
 		XFRM_INC_STATS(net, LINUX_MIB_XFRMFWDHDRERROR);
@@ -2186,7 +2186,7 @@ int __xfrm_route_forward(struct sk_buff *skb, unsigned short family)
 
 	dst = xfrm_lookup(net, skb_dst(skb), &fl, NULL, 0);
 	if (IS_ERR(dst)) {
-		res = 1;
+		res = 0;
 		dst = NULL;
 	}
 	skb_dst_set(skb, dst);