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Date: Thu, 1 May 2008 12:02:27 +0100 From: Ben Hutchings <bhutchings@...arflare.com> To: Herbert Xu <herbert@...dor.apana.org.au> Cc: davem@...emloft.net, kmansley@...arflare.com, shemminger@...tta.com, netdev@...r.kernel.org Subject: Re: [PATCH 0/2] Disable forwarding of LRO skbs Herbert Xu wrote: > Ben Hutchings <bhutchings@...arflare.com> wrote: > > Large Receive Offload (LRO) destroys packet headers that should be > > preserved when forwarding. Currently it also triggers a BUG() or WARN() > > in skb_gso_segment(). We should disable it wherever forwarding is > > enabled, and discard LRO skbs with a warning if it is turned back on. > > I don't think forwarding GSO packets is bad per se. However, > doing LRO on forwarded traffic is broken because it breaks the > end-to-end connection. So I agree that we should detect this > but preferrably not based on the GSO flag as LRO isn't the only > source of GSO traffic and the rest of them can be forwarded just > fine. My understanding is that at the points I'm adding the check, we're only considering received skbs and gso_size will only be set if LRO was used. I was going to raise the virtualisation issue because Kieran has been in contact with XenSource over this and they believed LRO was not a problem in Xen. So long as the bridges in dom0 each connect a single physical interface to other domains running paravirtualised Linux, this is probably true. But I have no idea how to "whitelist" this sort of case. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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