Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752582AbbDZNr7 (ORCPT ); Sun, 26 Apr 2015 09:47:59 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:40571 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752490AbbDZNrz (ORCPT ); Sun, 26 Apr 2015 09:47:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "D.S. Ljungmark" , Hannes Frederic Sowa , "David S. Miller" Subject: [PATCH 3.10 04/31] ipv6: Dont reduce hop limit for an interface Date: Sun, 26 Apr 2015 15:46:24 +0200 Message-Id: <20150426134209.439784058@linuxfoundation.org> X-Mailer: git-send-email 2.3.6 In-Reply-To: <20150426134209.255099785@linuxfoundation.org> References: <20150426134209.255099785@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2010 Lines: 54 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: "D.S. Ljungmark" [ Upstream commit 6fd99094de2b83d1d4c8457f2c83483b2828e75a ] 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: Greg Kroah-Hartman --- net/ipv6/ndisc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1193,7 +1193,14 @@ static void ndisc_router_discovery(struc 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/