netdev - Re: [PATCH net-next 1/3] ipv6: Clear flush

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Message-ID: <1410287886.7106.20.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 09 Sep 2014 11:38:06 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] ipv6: Clear flush_id to make GRO work

On Tue, 2014-09-09 at 11:23 -0700, Tom Herbert wrote:
> In TCP gro we check flush_id which is derived from the IP identifier.
> In IPv4 gro path the flush_id is set with the expectation that every
> matched packet increments IP identifier. In IPv6, the flush_id is
> never set and thus is uinitialized. What's worse is that in IPv6
> over IPv4 encapsulation, the IP identifier is taken from the outer
> header which is currently not incremented on every packet for Linux
> stack, so GRO in this case never matches packets (identifier is
> not increasing).
> 
> This patch clears flush_id for every time for a matched packet in
> IPv6 gro_receive. We need to do this each time to overwrite the
> setting that would be done in IPv4 gro_receive per the outer
> header in IPv6 over Ipv4 encapsulation.
> 
> Signed-off-by: Tom Herbert <therbert@...gle.com>
> ---
>  net/ipv6/ip6_offload.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> index 5bcda33..929bbbcd 100644
> --- a/net/ipv6/ip6_offload.c
> +++ b/net/ipv6/ip6_offload.c
> @@ -261,6 +261,9 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
>  		/* flush if Traffic Class fields are different */
>  		NAPI_GRO_CB(p)->flush |= !!(first_word & htonl(0x0FF00000));
>  		NAPI_GRO_CB(p)->flush |= flush;
> +
> +		/* Clear flush_id, there's really no concept of ID in IPv6. */
> +		NAPI_GRO_CB(p)->flush_id = 0;
>  	}
>  
>  	NAPI_GRO_CB(skb)->flush |= flush;

Yeah, I mentioned this problem months ago and apparently forgot to push
the fix.

http://patchwork.ozlabs.org/patch/311212/

Signed-off-by: Eric Dumazet <edumazet@...gle.com>


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