diff options
| author | D.S. Ljungmark | 2015-03-25 09:28:15 +0100 |
|---|---|---|
| committer | David S. Miller | 2015-03-25 11:41:08 -0400 |
| commit | 6fd99094de2b83d1d4c8457f2c83483b2828e75a (patch) | |
| tree | 8cc339316cfde4b3fba16784a44ebff573f44078 | |
| parent | 1452db764c279f8b329f1b3b9469bd01d9e21afd (diff) | |
ipv6: Don't reduce hop limit for an interface
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>
| -rw-r--r-- | net/ipv6/ndisc.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 471ed24aabae..14ecdaf06bf7 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1218,7 +1218,14 @@ 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); |