netdev - Re: [Xen-devel] xen-netfront sets partial checksum at wrong offset

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Date:	Mon, 11 May 2015 11:08:27 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	ian.campbell@...rix.com
Cc:	netdev@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] xen-netfront sets partial checksum at wrong offset

On Thu, May 07, 2015 at 12:44:24PM -0700, Venkat Venkatsubra wrote:
> Hello All,
> 
> When handle_incoming_queue (xen-netfront.c) calls checksum_setup()
> the transport header didn't seem to be initialized yet.
> skb_checksum_setup_ipv4 ends up initializing the checksum at incorrect offset. 
>         if (recalculate)
>                 *csum = ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
>                                            ip_hdr(skb)->daddr,
>                                            skb->len - off,
>                                            ip_hdr(skb)->protocol, 0);
> 
> where csum is &tcp_hdr(skb)->check.
> 
> This problem got exposed when LRO was ON on the host.
> It hits this case in checksum_setup().
>         /*
>          * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
>          * peers can fail to set NETRXF_csum_blank when sending a GSO
>          * frame. In this case force the SKB to CHECKSUM_PARTIAL and
>          * recalculate the partial checksum.
>          */
> 
> skb->ip_summed was CHECKSUM_UNNECESSARY. 
> The guest was at 3.8.13 kernel.
> 
> I can send a patch if you think the problem exists in current releases too.

Please CC the maintainers of the driver. You can get that from 'scripts/get_maintainer.pl'

I've done that for you.
> 
> Thanks.
> 
> Venkat
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xen.org
> http://lists.xen.org/xen-devel
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