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authorD.S. Ljungmark <ljungmark@modio.se>2015-03-25 09:28:15 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-04-29 10:31:46 +0200
commit01f69adac109867f892f12057660d891b34182f6 (patch)
tree10844ce3acf290394522ab27577ac6df0ba59c90 /net
parent8aa9de4c9b7c43c7861fd398ae141d7979f4896c (diff)
downloadlinux-linaro-stable-01f69adac109867f892f12057660d891b34182f6.tar.gz
ipv6: Don't reduce hop limit for an interface
[ 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 <ljungmark@modio.se> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/ndisc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 09a22f4f36c9..bcd65186b497 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1193,7 +1193,14 @@ 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);