From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wtarreau.pck.nerim.net ([62.212.114.60]:36095 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933951AbbEOIPT (ORCPT ); Fri, 15 May 2015 04:15:19 -0400 Message-Id: <20150515080531.311900485@1wt.eu> Date: Fri, 15 May 2015 10:05:54 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "D.S. Ljungmark" , Hannes Frederic Sowa , "David S. Miller" , Ben Hutchings , Willy Tarreau Subject: [ 24/48] ipv6: Dont reduce hop limit for an interface MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: <9c2783dfae10ef2d1e9b08bcc1e562c5@local> Sender: stable-owner@vger.kernel.org List-ID: 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: "D.S. Ljungmark" commit 6fd99094de2b83d1d4c8457f2c83483b2828e75a upstream. A local route may have a lower hop_limit set than global routes do. RFC 3756, Section 4.2.7, "Parameter Spoofing" > 1. The attacker includes a Current Hop Limit of one or another small > number which the attacker knows will cause legitimate packets to > be dropped before they reach their destination. > As an example, one possible approach to mitigate this threat is to > ignore very small hop limits. The nodes could implement a > configurable minimum hop limit, and ignore attempts to set it below > said limit. Signed-off-by: D.S. Ljungmark Acked-by: Hannes Frederic Sowa Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust ND_PRINTK() usage] Signed-off-by: Ben Hutchings (cherry picked from commit f10f7d2a8200fe33c5030c7e32df3a2b3561f3cd) Signed-off-by: Willy Tarreau --- net/ipv6/ndisc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 752da21..3b77bed 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1244,7 +1244,14 @@ static void ndisc_router_discovery(struct sk_buff *skb) rt->rt6i_expires = jiffies + (HZ * lifetime); if (ra_msg->icmph.icmp6_hop_limit) { - in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit; + /* Only set hop_limit on the interface if it is higher than + * the current hop_limit. + */ + if (in6_dev->cnf.hop_limit < ra_msg->icmph.icmp6_hop_limit) { + in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit; + } else { + ND_PRINTK2(KERN_WARNING "RA: Got route advertisement with lower hop_limit than current\n"); + } if (rt) rt->u.dst.metrics[RTAX_HOPLIMIT-1] = ra_msg->icmph.icmp6_hop_limit; } -- 1.7.12.2.21.g234cd45.dirty