netdev - Re: [PATCH net-2.6] net: bug fix for vlan + gro issue

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Message-ID: <20100217062541.GA10350@serverengines.com>
Date:	Wed, 17 Feb 2010 11:55:43 +0530
From:	Ajit Khaparde <ajitkhaparde@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	davem@...emloft.net, kaber@...sh.net,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-2.6] net: bug fix for vlan + gro issue

On 16/02/10 19:40 +0800, Herbert Xu wrote:
> On Fri, Feb 12, 2010 at 11:04:53AM +0530, Ajit Khaparde wrote:
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index be9924f..16aac06 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -2761,7 +2761,10 @@ gro_result_t napi_frags_finish(struct napi_struct *napi, struct sk_buff *skb,
> >  	switch (ret) {
> >  	case GRO_NORMAL:
> >  	case GRO_HELD:
> > -		skb->protocol = eth_type_trans(skb, napi->dev);
> > +		if (skb->vlan_tci)
> > +			skb->protocol = eth_type_trans(skb, skb->dev);
> > +		else
> > +			skb->protocol = eth_type_trans(skb, napi->dev);
> 
> We should be able to just use skb->dev here.

Thanks Herbert. I think you meant something like this:
+		skb->protocol = eth_type_trans(skb, skb->dev);

Here is the patch:-

Traffic (tcp) doesnot start on a vlan interface when gro is enabled.
Even the tcp handshake was not taking place.
This is because, the eth_type_trans call before the netif_receive_skb
in napi_gro_finish() resets the skb->dev to napi->dev from the previously
set vlan netdev interface. This causes the ip_route_input to drop the
incoming packet considering it as a packet coming from a martian source.

I could repro this on 2.6.32.7 (stable) and 2.6.33-rc7.
With this fix, the traffic starts and the test runs fine on both vlan
and non-vlan interfaces.

CC: Herbert Xu <herbert@...dor.apana.org.au>
CC: Patrick McHardy <kaber@...sh.net>
Signed-off-by: Ajit Khaparde <ajitk@...verengines.com>
---
 net/core/dev.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index be9924f..ec87421 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2761,7 +2761,7 @@ gro_result_t napi_frags_finish(struct napi_struct *napi, struct sk_buff *skb,
 	switch (ret) {
 	case GRO_NORMAL:
 	case GRO_HELD:
-		skb->protocol = eth_type_trans(skb, napi->dev);
+		skb->protocol = eth_type_trans(skb, skb->dev);
 
 		if (ret == GRO_HELD)
 			skb_gro_pull(skb, -ETH_HLEN);
-- 
1.6.3.3

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