From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH net] ipv4: fix fnhe usage by non-cached routes Date: Wed, 2 May 2018 16:49:37 -0600 Message-ID: References: <20180502064119.4552-1-ja@ssi.bg> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Martin KaFai Lau , kernel-team@fb.com, Xin Long To: Julian Anastasov , David Miller Return-path: Received: from mail-pf0-f175.google.com ([209.85.192.175]:35514 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751045AbeEBWtk (ORCPT ); Wed, 2 May 2018 18:49:40 -0400 Received: by mail-pf0-f175.google.com with SMTP id j5so13025457pfh.2 for ; Wed, 02 May 2018 15:49:40 -0700 (PDT) In-Reply-To: <20180502064119.4552-1-ja@ssi.bg> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 5/2/18 12:41 AM, Julian Anastasov wrote: > Allow some non-cached routes to use non-expired fnhe: > > 1. ip_del_fnhe: moved above and now called by find_exception. > The 4.5+ commit deed49df7390 expires fnhe only when caching > routes. Change that to: > > 1.1. use fnhe for non-cached local output routes, with the help > from (2) > > 1.2. allow __mkroute_input to detect expired fnhe (outdated > fnhe_gw, for example) when do_cache is false, eg. when itag!=0 > for unicast destinations. > > 2. __mkroute_output: keep fi to allow local routes with orig_oif != 0 > to use fnhe info even when the new route will not be cached into fnhe. > After commit 839da4d98960 ("net: ipv4: set orig_oif based on fib > result for local traffic") it means all local routes will be affected > because they are not cached. This change is used to solve a PMTU > problem with IPVS (and probably Netfilter DNAT) setups that redirect > local clients from target local IP (local route to Virtual IP) > to new remote IP target, eg. IPVS TUN real server. Loopback has > 64K MTU and we need to create fnhe on the local route that will > keep the reduced PMTU for the Virtual IP. Without this change > fnhe_pmtu is updated from ICMP but never exposed to non-cached > local routes. This includes routes with flowi4_oif!=0 for 4.6+ and > with flowi4_oif=any for 4.14+). Can you add a test case to tools/testing/selftests/net/pmtu.sh to cover this situation? > @@ -1310,8 +1340,14 @@ static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr) > > for (fnhe = rcu_dereference(hash[hval].chain); fnhe; > fnhe = rcu_dereference(fnhe->fnhe_next)) { > - if (fnhe->fnhe_daddr == daddr) > + if (fnhe->fnhe_daddr == daddr) { > + if (fnhe->fnhe_expires && > + time_after(jiffies, fnhe->fnhe_expires)) { > + ip_del_fnhe(nh, daddr); I'm surprised this is done in the fast path vs gc time. (the existing code does as well; your change is only moving the call to make the input and output paths the same) The change looks correct to me and all of my functional tests passed. Acked-by: David Ahern