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Date: Fri, 11 Feb 2011 17:37:53 +1100 From: Herbert Xu <herbert@...dor.apana.org.au> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, netfilter-devel@...r.kernel.org Subject: Re: GRO/GSO hiding PMTU? On Thu, Feb 10, 2011 at 10:22:16PM -0800, David Miller wrote: > > I gave it a shot but it isn't easy. We can figure out the length of > the IP headers just fine, but the rest of the value we need to add > to the MSS (the TCP header length) is transport specific which kind > of implies a transport dependent gso proto op of some sort. That's pretty much where I gave up :) > Or we just hack it, admit that only TCP creates GSO packets, and > directly check for TCP protcol and then inspect the TCP header > length :-) Sure we can do that for now. What I wanted to do if I ever get enough time to work on this is to record the transport header length in a gso_hlen field so we can fix this properly. We currently have a useless gso_segs field that only has one or two users that don't even need it. We could easily get rid of it and use that space for gso_hlen instead. The gso_hlen field only needs to be filled in at the few spots that generate GSO packets, i.e., 1) TCP 2) Virt backends like tun.c 3) GRO Cheers, -- Email: Herbert Xu <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- 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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