From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lance Richardson Subject: Re: [PATCH net] ipv4: allow local fragmentation in ip_finish_output_gso() Date: Wed, 2 Nov 2016 16:10:16 -0400 (EDT) Message-ID: <1893627626.93159878.1478117416635.JavaMail.zimbra@redhat.com> References: <1478104158-9504-1-git-send-email-lrichard@redhat.com> <20161102172036.GD17689@breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jtluka@redhat.com To: Florian Westphal Return-path: Received: from mx4-phx2.redhat.com ([209.132.183.25]:60268 "EHLO mx4-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756389AbcKBUK0 (ORCPT ); Wed, 2 Nov 2016 16:10:26 -0400 In-Reply-To: <20161102172036.GD17689@breakpoint.cc> Sender: netdev-owner@vger.kernel.org List-ID: ----- Original Message ----- > From: "Florian Westphal" > To: "Lance Richardson" > Cc: netdev@vger.kernel.org, fw@strlen.de, jtluka@redhat.com > Sent: Wednesday, November 2, 2016 1:20:36 PM > Subject: Re: [PATCH net] ipv4: allow local fragmentation in ip_finish_output_gso() > > 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. > Thanks, Florian, I've removed IPSKB_FRAG_SEGS in v2. Lance