[PATCH] Net: Don't send ICMP_FRAG_NEEDED for GSO packets

[PATCH] Net: Don't send ICMP_FRAG_NEEDED for GSO packets

[Rusty Russell]

Commit 9af3912ec9e30509b76cb376abb65a4d8af27df3 added a new check to
send ICMP fragmentation needed for large packets.

Unlike the check in ip_finish_output(), it doesn't check for GSO.  I
triggered this with the GSO TUN patches, so not sure if it needs to be
in 2.6.25 or not (do we otherwise forward GSO packets?).

Cc: John Heffner <jheffner@psc.edu>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff -r 69b8317ff51c net/ipv4/ip_forward.c
--- a/net/ipv4/ip_forward.c	Fri Mar 28 14:04:48 2008 +1100
+++ b/net/ipv4/ip_forward.c	Fri Mar 28 19:18:15 2008 +1100
@@ -85,7 +85,7 @@ int ip_forward(struct sk_buff *skb)
 	if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 		goto sr_failed;
 
-	if (unlikely(skb->len > dst_mtu(&rt->u.dst) &&
+	if (unlikely(skb->len > dst_mtu(&rt->u.dst) && !skb_is_gso(skb) &&
 		     (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
 		IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,

Re: [PATCH] Net: Don't send ICMP_FRAG_NEEDED for GSO packets

[Herbert Xu]

On Fri, Mar 28, 2008 at 07:34:08PM +1100, Rusty Russell wrote:
> Commit 9af3912ec9e30509b76cb376abb65a4d8af27df3 added a new check to
> send ICMP fragmentation needed for large packets.
> 
> Unlike the check in ip_finish_output(), it doesn't check for GSO.  I
> triggered this with the GSO TUN patches, so not sure if it needs to be
> in 2.6.25 or not (do we otherwise forward GSO packets?).
> 
> Cc: John Heffner <jheffner@psc.edu>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Since this is a regression for Xen, I would say yes.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] Net: Don't send ICMP_FRAG_NEEDED for GSO packets

[David Miller]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 28 Mar 2008 16:40:43 +0800

> On Fri, Mar 28, 2008 at 07:34:08PM +1100, Rusty Russell wrote:
> > Commit 9af3912ec9e30509b76cb376abb65a4d8af27df3 added a new check to
> > send ICMP fragmentation needed for large packets.
> > 
> > Unlike the check in ip_finish_output(), it doesn't check for GSO.  I
> > triggered this with the GSO TUN patches, so not sure if it needs to be
> > in 2.6.25 or not (do we otherwise forward GSO packets?).
> > 
> > Cc: John Heffner <jheffner@psc.edu>
> > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> 
> Since this is a regression for Xen, I would say yes.

Applied.

But Rusty, when referencing commits, always provide a
text string of the commit's header line because in
different trees and backports the commit ID may
change.

I fixed it up this time...

Thanks.