From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f68.google.com ([74.125.83.68]:37567 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751302AbeCTQVe (ORCPT ); Tue, 20 Mar 2018 12:21:34 -0400 Subject: Re: [PATCH net-next 1/1] net/ipv4: disable SMC TCP option with SYN Cookies To: Ursula Braun , davem@davemloft.net Cc: netdev@vger.kernel.org, linux-s390@vger.kernel.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, raspl@linux.vnet.ibm.com References: <20180320155340.18017-1-ubraun@linux.vnet.ibm.com> <20180320155340.18017-2-ubraun@linux.vnet.ibm.com> From: Eric Dumazet Message-ID: <435f82d0-407e-6675-194a-102d83f418f8@gmail.com> Date: Tue, 20 Mar 2018 09:21:32 -0700 MIME-Version: 1.0 In-Reply-To: <20180320155340.18017-2-ubraun@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org List-ID: On 03/20/2018 08:53 AM, Ursula Braun wrote: > From: Hans Wippel > > Currently, the SMC experimental TCP option in a SYN packet is lost on > the server side when SYN Cookies are active. However, the corresponding > SYNACK sent back to the client contains the SMC option. This causes an > inconsistent view of the SMC capabilities on the client and server. > > This patch disables the SMC option in the SYNACK when SYN Cookies are > active to avoid this issue. > > Signed-off-by: Hans Wippel > Signed-off-by: Ursula Braun > --- > net/ipv4/tcp_output.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 383cac0ff0ec..22894514feae 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -3199,6 +3199,8 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, > /* Under synflood, we do not attach skb to a socket, > * to avoid false sharing. > */ > + if (IS_ENABLED(CONFIG_SMC)) > + ireq->smc_ok = 0; > break; > case TCP_SYNACK_FASTOPEN: > /* sk is a const pointer, because we want to express multiple > I disagree with net-next qualification. This fixes a bug, so please send it for net tree, and including an appropriate Fixes: tag. Thanks !