From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: Re: [PATCH net] ipv4: allow local fragmentation in ip_finish_output_gso() Date: Wed, 2 Nov 2016 18:20:36 +0100 Message-ID: <20161102172036.GD17689@breakpoint.cc> References: <1478104158-9504-1-git-send-email-lrichard@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, fw@strlen.de, jtluka@redhat.com To: Lance Richardson Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:53132 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932648AbcKBRWW (ORCPT ); Wed, 2 Nov 2016 13:22:22 -0400 Content-Disposition: inline In-Reply-To: <1478104158-9504-1-git-send-email-lrichard@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Lance Richardson wrote: > Some configurations (e.g. geneve interface with default > MTU of 1500 over an ethernet interface with 1500 MTU) result > in the transmission of packets that exceed the configured MTU. > While this should be considered to be a "bad" configuration, > it is still allowed and should not result in the sending > of packets that exceed the configured MTU. > > Fix by dropping the assumption in ip_finish_output_gso() that > locally originated gso packets will never need fragmentation. > Basic testing using iperf (observing CPU usage and bandwidth) > have shown no measurable performance impact for traffic not > requiring fragmentation. > > Fixes: c7ba65d7b649 ("net: ip: push gso skb forwarding handling down the stack") > Reported-by: Jan Tluka > Signed-off-by: Lance Richardson > --- > net/ipv4/ip_output.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c > index 03e7f73..4971401 100644 > --- a/net/ipv4/ip_output.c > +++ b/net/ipv4/ip_output.c > @@ -239,11 +239,9 @@ static int ip_finish_output_gso(struct net *net, struct sock *sk, > struct sk_buff *segs; > int ret = 0; > > - /* common case: fragmentation of segments is not allowed, > - * or seglen is <= mtu > + /* common case: seglen is <= mtu > */ > - if (((IPCB(skb)->flags & IPSKB_FRAG_SEGS) == 0) || > - skb_gso_validate_mtu(skb, mtu)) > + if (skb_gso_validate_mtu(skb, mtu)) IPSKB_FRAG_SEGS is now useless and should be removed.