Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933692AbbDUQAI (ORCPT ); Tue, 21 Apr 2015 12:00:08 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:57662 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932516AbbDUPet (ORCPT ); Tue, 21 Apr 2015 11:34:49 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "D.S. Ljungmark" , "David S. Miller" , Luis Henriques Subject: [PATCH 3.16.y-ckt 105/144] ipv6: Don't reduce hop limit for an interface Date: Tue, 21 Apr 2015 16:31:30 +0100 Message-Id: <1429630329-21748-106-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1429630329-21748-1-git-send-email-luis.henriques@canonical.com> References: <1429630329-21748-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2113 Lines: 54 3.16.7-ckt10 -stable 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 Signed-off-by: Luis Henriques --- 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 ca8d4ea48a5d..e2eb53c719dc 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1190,7 +1190,14 @@ static void ndisc_router_discovery(struct sk_buff *skb) if (rt) rt6_set_expires(rt, 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_PRINTK(2, warn, "RA: Got route advertisement with lower hop_limit than current\n"); + } if (rt) dst_metric_set(&rt->dst, RTAX_HOPLIMIT, ra_msg->icmph.icmp6_hop_limit); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/