diff options
| author | D.S. Ljungmark <ljungmark@modio.se> | 2015-03-25 09:28:15 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2015-05-09 23:16:36 +0100 |
| commit | f10f7d2a8200fe33c5030c7e32df3a2b3561f3cd (patch) | |
| tree | f9c94c6e0f9101fed914ef541d24744caf9401a7 /net | |
| parent | 3760b67b3e419b9ac42a45417491360a14a35357 (diff) | |
| download | lwn-f10f7d2a8200fe33c5030c7e32df3a2b3561f3cd.tar.gz lwn-f10f7d2a8200fe33c5030c7e32df3a2b3561f3cd.zip | |
ipv6: Don't reduce hop limit for an interface
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 <ljungmark@modio.se>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust ND_PRINTK() usage]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to '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 62096d81f7eb..884d45fdf50f 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1277,7 +1277,14 @@ static void ndisc_router_discovery(struct sk_buff *skb) rt->rt6i_expires = 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_PRINTK2(KERN_WARNING "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); |