This is a note to let you know that I've just added the patch titled
ipv6: Don't reduce hop limit for an interface
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipv6-don-t-reduce-hop-limit-for-an-interface.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From foo@baz Tue Apr 21 23:05:14 CEST 2015
From: "D.S. Ljungmark" <[email protected]>
Date: Wed, 25 Mar 2015 09:28:15 +0100
Subject: ipv6: Don't reduce hop limit for an interface
From: "D.S. Ljungmark" <[email protected]>
[ 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 <[email protected]>
Acked-by: Hannes Frederic Sowa <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv6/ndisc.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1216,7 +1216,14 @@ 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);
Patches currently in stable-queue which might be from [email protected] are
queue-3.19/ipv6-don-t-reduce-hop-limit-for-an-interface.patch
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