From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754812AbdBET24 (ORCPT + 2 others); Sun, 5 Feb 2017 14:28:56 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:28534 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753608AbdBET2t (ORCPT ); Sun, 5 Feb 2017 14:28:49 -0500 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Stephen Suryaputra Lin , Stephen Suryaputra Lin , "David S . Miller" , Willy Tarreau Subject: [PATCH 3.10 265/319] ipv4: use new_gw for redirect neigh lookup Date: Sun, 5 Feb 2017 20:21:27 +0100 Message-Id: <1486322541-8206-166-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1486322541-8206-1-git-send-email-w@1wt.eu> References: <1486322541-8206-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Stephen Suryaputra Lin commit 969447f226b451c453ddc83cac6144eaeac6f2e3 upstream. In v2.6, ip_rt_redirect() calls arp_bind_neighbour() which returns 0 and then the state of the neigh for the new_gw is checked. If the state isn't valid then the redirected route is deleted. This behavior is maintained up to v3.5.7 by check_peer_redirect() because rt->rt_gateway is assigned to peer->redirect_learned.a4 before calling ipv4_neigh_lookup(). After commit 5943634fc559 ("ipv4: Maintain redirect and PMTU info in struct rtable again."), ipv4_neigh_lookup() is performed without the rt_gateway assigned to the new_gw. In the case when rt_gateway (old_gw) isn't zero, the function uses it as the key. The neigh is most likely valid since the old_gw is the one that sends the ICMP redirect message. Then the new_gw is assigned to fib_nh_exception. The problem is: the new_gw ARP may never gets resolved and the traffic is blackholed. So, use the new_gw for neigh lookup. Changes from v1: - use __ipv4_neigh_lookup instead (per Eric Dumazet). Fixes: 5943634fc559 ("ipv4: Maintain redirect and PMTU info in struct rtable again.") Signed-off-by: Stephen Suryaputra Lin Signed-off-by: David S. Miller Signed-off-by: Willy Tarreau --- net/ipv4/route.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index cbad9b8..e59d633 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -713,7 +713,9 @@ static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flow goto reject_redirect; } - n = ipv4_neigh_lookup(&rt->dst, NULL, &new_gw); + n = __ipv4_neigh_lookup(rt->dst.dev, new_gw); + if (!n) + n = neigh_create(&arp_tbl, &new_gw, rt->dst.dev); if (!IS_ERR(n)) { if (!(n->nud_state & NUD_VALID)) { neigh_event_send(n, NULL); -- 2.8.0.rc2.1.gbe9624a