Re: [Xen-devel] Xen checksumming bug with IPsec ESP packets

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 3 Aug 2005, at 17:27, Jonathan M. McCune wrote:

> We fixed this by removing the addition of flag NETIF_F_IP_CSUM in 
> drivers/xen/netfront/netfront.c:create_netdev().  I believe this tells 
> the kernel to just always do the checksum in software.  Thus, the 
> broken optimization for TCP/UDP packets gets bypassed.
>
> Permanent Solution:
>
> ???
>
> That's why I posted this message... :-)
I suspect the ESP code would need to be made aware of the csum_blank 
field, and fill in before forwarding. There are doubtless other paths 
that may need similar tweaks (e.g., NAT IP masquerading is untested I 
think, although there's a fair chance it'll just work).
Apart from the above 'proper fix', simple not-so-hacky solutions 
include:
 * Run 'ethtool -K tx off' in each domU
 * Add an option to netback in domain0 to fill in checksums itself if 
not done by domU.
 * Allow netback to advertise to domUs whether it accepts 
non-checksummed packets, and have an option to set this advertisement 
when you start netback.
 -- Keir


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