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[Xen-devel] Re: [1/4] [NET] back: Fix maximum fragment check

On 1 Jul 2006, at 10:59, Herbert Xu wrote:

netback to advertise support for the ECN flag? I'm not sure exactly
what it will mean, and whether it can just be ignored by netbacks that
don't support it?

If netback does not advertise the flag then netfront will perform
segmentation before passing TCP packets with CWR set through.

Ah, okay, can that not be handled properly by some TSO-supporting NICs then? You need to do something smarter than simply duplicate the ECN bits in every segment header? What would happen if netfront sent through a packet with ECE/CWR and didn't set the GSO_ECN flag -- is it safe but stupid, will it break something, should dodgy packets have the GSO_ECN flag recomputed?


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