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Date: Fri, 25 Mar 2016 15:13:07 +0800
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: dev@dpdk.org
Cc: huawei.xie@intel.com, Thomas Monjalon <thomas.monjalon@6wind.com>,
 Ksiadz MarcinX <marcinx.ksiadz@intel.com>,
 "Xu, Qian Q" <qian.q.xu@intel.com>
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Subject: Re: [dpdk-dev] [PATCH 2/4] vhost: complete TSO settings
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On Fri, Mar 25, 2016 at 02:01:32PM +0800, Yuanhan Liu wrote:
> Commit d0cf91303d73 ("vhost: add Tx offload capabilities") has only
> done partial settings for enabling TSO, and left the following part
> to the application, say vhost-switch example, by commit 9fd72e3cbd29
> ("examples/vhost: add virtio offload").
> 
> - Setting PKT_TX_IP_CKSUM and ipv4_hdr->hdr_checksum = 0 for IPv4.
> 
> - calculate the pseudo header checksum without taking ip_len in
>   account, and set it in the TCP header
> 
> Here we complete the left part in vhost side, so that an user (such
> as OVS) can do minimal (or even no) changes to get TSO enabled.
> 
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
...
> +			ipv4_hdr->hdr_checksum = 0;

Nah.. we can't do that here. This hurts VM2VM case badly.

Thanks Qian for letting me be aware of it.

	--yliu