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Message-ID: <20140209025504.GB17395@gondor.apana.org.au> Date: Sun, 9 Feb 2014 10:55:04 +0800 From: Herbert Xu <herbert@...dor.apana.org.au> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Florian Westphal <fw@...len.de>, netdev@...r.kernel.org Subject: Re: [PATCH 2/2] net: ip, ipv6: handle gso skbs in forwarding path On Tue, Jan 28, 2014 at 08:34:43AM -0800, Eric Dumazet wrote: > On Tue, 2014-01-28 at 09:57 +0100, Florian Westphal wrote: > > Eric Dumazet <eric.dumazet@...il.com> wrote: > > > > + do { > > > > + struct sk_buff *nskb = segs->next; > > > > + int err; > > > > + > > > > + segs->next = NULL; > > > > + err = dst_output(segs); > > > > + > > > > + if (err && ret == 0) > > > > + ret = err; > > > > + segs = nskb; > > > > + } while (segs); > > > > + > > > > + return ret; > > > > +} > > > > + > > > > > > Its still unclear if this is the best strategy. > > > > > > TCP stream not using DF flag are very unlikely to care if we adjust > > > their MTU (lowering gso_size) at this point ? > > > > Thanks for this suggestion. It would indeed be nice to avoid sw > > segmentation. I tried: > > > > static void ip_gso_adjust_seglen(struct sk_buff *skb) > > { > > unsigned int mtu; > > > > if (!skb_is_gso(skb)) > > return; > > > > mtu = ip_dst_mtu_maybe_forward(skb_dst(skb), true); > > skb_shinfo(skb)->gso_size = mtu - sizeof(struct iphdr); > > } > > > > But this yields > > > > [ 28.644776] kernel BUG at net/net/core/skbuff.c:2984! > > Yep, lets CC Herbert Xu, as he 'owns' skb_segment() IMHO we should just stop merging ~DF packets altogether, at least for TCP. 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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