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Re: [Xen-devel] [PATCH] Network Checksum Removal

On 26 May 2005, at 00:41, Jon Mason wrote:

The bridge device still is the device that the stack sees, and uses its
features to determine what to do during transmission. If you monitor the skb->ip_summed flag going into netif_be_start_xmit(), you will see that it is 0 (meaning that the stack did the checksum in software). Now if you add the following patch to the bridging device, you will notice that ip_summed is now
being used.

For local traffic transmitted via veth0, ip_summed is zero (CHECKSUM_NONE) at netif_be_start_xmit because the bridge forwarding code nobbles the ip_summed field. It does *not* checksum the packet: etherbridge never checksums packets it forwards because that is the destination's job (it's an end-to-end checksum at the protocol level).

If you transmit local traffic directly on the bridge device then yes, you need a patch because it does not advertise NETIF_F_*_CSUM.

 -- Keir

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