diff options
| author | D.S. Ljungmark <ljungmark@modio.se> | 2015-03-25 09:28:15 +0100 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2015-05-24 10:10:44 +0200 |
| commit | daacd26b5ebfa871be411cf190bd0d42d7712acb (patch) | |
| tree | ad0e665df1fecba1d8e38ef2600e8aaf8ffffb55 /net/ipv6 | |
| parent | 6246ff96da330928a3fef0da741827474f473a11 (diff) | |
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>
(cherry picked from commit f10f7d2a8200fe33c5030c7e32df3a2b3561f3cd)
Signed-off-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'net/ipv6')
| -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 752da217031b..3b77bedca892 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1244,7 +1244,14 @@ 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) rt->u.dst.metrics[RTAX_HOPLIMIT-1] = ra_msg->icmph.icmp6_hop_limit; } |