From patchwork Tue Sep 15 03:03:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Ahern X-Patchwork-Id: 260873 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FDA8C43461 for ; Tue, 15 Sep 2020 03:04:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F7CC20897 for ; Tue, 15 Sep 2020 03:04:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600139093; bh=NKc9oqaeexxh3U3k4jEk8eBcR3hQlq1sqpaRc//VbVg=; h=From:To:Cc:Subject:Date:List-ID:From; b=cO7gdOFvv0ww7+50DFqMjHM63EzEKYtt1C1s92B3E8bLVUOHQgRlZ82Zutpz8Ws+T Z3rsZ8RjrnmDFZTWV71PO5u0lhcmfL8ro145hX9r4s5qVXyuwa+bdFqeEutJxvcoCS 5fLWnsDiCldGUTlY3B0Rs8vy01bF/3G9HqNMap9Q= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726143AbgIODEE (ORCPT ); Mon, 14 Sep 2020 23:04:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:51906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726117AbgIODD7 (ORCPT ); Mon, 14 Sep 2020 23:03:59 -0400 Received: from Davids-MacBook-Pro.local.net (c-73-181-34-237.hsd1.co.comcast.net [73.181.34.237]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 49C9720897; Tue, 15 Sep 2020 03:03:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600139038; bh=NKc9oqaeexxh3U3k4jEk8eBcR3hQlq1sqpaRc//VbVg=; h=From:To:Cc:Subject:Date:From; b=TsDbkmdRTV4DBK2ZeAFm4badaqoKI9jtHRHmle9ukT+ZGUQgw7IljGD5k7X9S58Pe Zu+LTIJo7nd7QpqcJux79NNvWX3ovpqOUy2CtH0gLPn6ZFqGo4MJutGGNKezFiPqn+ qfgQvGPxvRwzgO5PihfGOiy2XM/Aqn79aEeobHps= From: David Ahern To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, David Ahern , Kfir Itzhak Subject: [PATCH net] ipv4: Update exception handling for multipath routes via same device Date: Mon, 14 Sep 2020 21:03:54 -0600 Message-Id: <20200915030354.38468-1-dsahern@kernel.org> X-Mailer: git-send-email 2.24.3 (Apple Git-128) MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Kfir reported that pmtu exceptions are not created properly for deployments where multipath routes use the same device. After some digging I see 2 compounding problems: 1. ip_route_output_key_hash_rcu is updating the flowi4_oif *after* the route lookup. This is the second use case where this has been a problem (the first is related to use of vti devices with VRF). I can not find any reason for the oif to be changed after the lookup; the code goes back to the start of git. It does not seem logical so remove it. 2. fib_lookups for exceptions do not call fib_select_path to handle multipath route selection based on the hash. The end result is that the fib_lookup used to add the exception always creates it based using the first leg of the route. An example topology showing the problem: | host1 +------+ | eth0 | .209 +------+ | +------+ switch | br0 | +------+ | +---------+---------+ | host2 | host3 +------+ +------+ | eth0 | .250 | eth0 | 192.168.252.252 +------+ +------+ +-----+ +-----+ | vti | .2 | vti | 192.168.247.3 +-----+ +-----+ \ / ================================= tunnels 192.168.247.1/24 for h in host1 host2 host3; do ip netns add ${h} ip -netns ${h} link set lo up ip netns exec ${h} sysctl -wq net.ipv4.ip_forward=1 done ip netns add switch ip -netns switch li set lo up ip -netns switch link add br0 type bridge stp 0 ip -netns switch link set br0 up for n in 1 2 3; do ip -netns switch link add eth-sw type veth peer name eth-h${n} ip -netns switch li set eth-h${n} master br0 up ip -netns switch li set eth-sw netns host${n} name eth0 done ip -netns host1 addr add 192.168.252.209/24 dev eth0 ip -netns host1 link set dev eth0 up ip -netns host1 route add 192.168.247.0/24 \ nexthop via 192.168.252.250 dev eth0 nexthop via 192.168.252.252 dev eth0 ip -netns host2 addr add 192.168.252.250/24 dev eth0 ip -netns host2 link set dev eth0 up ip -netns host2 addr add 192.168.252.252/24 dev eth0 ip -netns host3 link set dev eth0 up ip netns add tunnel ip -netns tunnel li set lo up ip -netns tunnel li add br0 type bridge ip -netns tunnel li set br0 up for n in $(seq 11 20); do ip -netns tunnel addr add dev br0 192.168.247.${n}/24 done for n in 2 3 do ip -netns tunnel link add vti${n} type veth peer name eth${n} ip -netns tunnel link set eth${n} mtu 1360 master br0 up ip -netns tunnel link set vti${n} netns host${n} mtu 1360 up ip -netns host${n} addr add dev vti${n} 192.168.247.${n}/24 done ip -netns tunnel ro add default nexthop via 192.168.247.2 nexthop via 192.168.247.3 ip netns exec host1 ping -M do -s 1400 -c3 -I 192.168.252.209 192.168.247.11 ip netns exec host1 ping -M do -s 1400 -c3 -I 192.168.252.209 192.168.247.15 ip -netns host1 ro ls cache Before this patch the cache always shows exceptions against the first leg in the multipath route; 192.168.252.250 per this example. Since the hash has an initial random seed, you may need to vary the final octet more than what is listed. In my tests, using addresses between 11 and 19 usually found 1 that used both legs. With this patch, the cache will have exceptions for both legs. Fixes: 4895c771c7f0 ("ipv4: Add FIB nexthop exceptions") Reported-by: Kfir Itzhak Signed-off-by: David Ahern --- net/ipv4/route.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index e5f210d00851..58642b29a499 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -786,8 +786,10 @@ static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flow neigh_event_send(n, NULL); } else { if (fib_lookup(net, fl4, &res, 0) == 0) { - struct fib_nh_common *nhc = FIB_RES_NHC(res); + struct fib_nh_common *nhc; + fib_select_path(net, &res, fl4, skb); + nhc = FIB_RES_NHC(res); update_or_create_fnhe(nhc, fl4->daddr, new_gw, 0, false, jiffies + ip_rt_gc_timeout); @@ -1013,6 +1015,7 @@ out: kfree_skb(skb); static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu) { struct dst_entry *dst = &rt->dst; + struct net *net = dev_net(dst->dev); u32 old_mtu = ipv4_mtu(dst); struct fib_result res; bool lock = false; @@ -1033,9 +1036,11 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu) return; rcu_read_lock(); - if (fib_lookup(dev_net(dst->dev), fl4, &res, 0) == 0) { - struct fib_nh_common *nhc = FIB_RES_NHC(res); + if (fib_lookup(net, fl4, &res, 0) == 0) { + struct fib_nh_common *nhc; + fib_select_path(net, &res, fl4, NULL); + nhc = FIB_RES_NHC(res); update_or_create_fnhe(nhc, fl4->daddr, 0, mtu, lock, jiffies + ip_rt_mtu_expires); } @@ -2668,8 +2673,6 @@ struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *fl4, fib_select_path(net, res, fl4, skb); dev_out = FIB_RES_DEV(*res); - fl4->flowi4_oif = dev_out->ifindex; - make_route: rth = __mkroute_output(res, fl4, orig_oif, dev_out, flags);