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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

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
> 
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