From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Cavallari Subject: [RFC] ipv4: Do not cache routing failures due to disabled forwarding. Date: Fri, 12 Sep 2014 16:14:20 +0200 Message-ID: <1410531260-13794-2-git-send-email-nicolas.cavallari@green-communications.fr> References: <1410531260-13794-1-git-send-email-nicolas.cavallari@green-communications.fr> Cc: "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy To: netdev@vger.kernel.org Return-path: Received: from mout.kundenserver.de ([212.227.17.13]:63715 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753637AbaILOPl (ORCPT ); Fri, 12 Sep 2014 10:15:41 -0400 In-Reply-To: <1410531260-13794-1-git-send-email-nicolas.cavallari@green-communications.fr> Sender: netdev-owner@vger.kernel.org List-ID: If we cache them, the kernel will reuse them, independently of whether forwarding is enabled or not. Which means that if forwarding is disabled on the input interface where the first routing request comes from, then that unreachable result will be cached and reused for other interfaces, even if forwarding is enabled on them. This can be verified with two interfaces A and B and an output interface C, where B has forwarding enabled, but not A and trying ip route get $dst iif A from $src && ip route get $dst iif B from $src Signed-off-by: Nicolas Cavallari --- based on net-next, but not really tested on top of it. net/ipv4/route.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 234a43e..b537997 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1655,7 +1655,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr, struct rtable *rth; int err = -EINVAL; struct net *net = dev_net(dev); - bool do_cache; + bool do_cache = true; /* IP on this device is disabled. */ @@ -1723,6 +1723,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr, if (!IN_DEV_FORWARD(in_dev)) { err = -EHOSTUNREACH; + do_cache = false; goto no_route; } if (res.type != RTN_UNICAST) @@ -1746,16 +1747,14 @@ brd_input: RT_CACHE_STAT_INC(in_brd); local_input: - do_cache = false; - if (res.fi) { - if (!itag) { - rth = rcu_dereference(FIB_RES_NH(res).nh_rth_input); - if (rt_cache_valid(rth)) { - skb_dst_set_noref(skb, &rth->dst); - err = 0; - goto out; - } - do_cache = true; + if (!res.fi || itag) { + do_cache = false; + } else if (do_cache) { + rth = rcu_dereference(FIB_RES_NH(res).nh_rth_input); + if (rt_cache_valid(rth)) { + skb_dst_set_noref(skb, &rth->dst); + err = 0; + goto out; } } -- 2.1.0