Messages in this thread Patch in this message | | | Date | Fri, 15 May 2015 10:05:54 +0200 | From | Willy Tarreau <> | Subject | [ 24/48] ipv6: Dont reduce hop limit for an interface |
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2.6.32-longterm review patch. If anyone has any objections, please let me know.
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From: "D.S. Ljungmark" <ljungmark@modio.se>
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> --- net/ipv6/ndisc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 752da21..3b77bed 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; } -- 1.7.12.2.21.g234cd45.dirty
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