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ipv6: Don't reduce hop limit for an interface

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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>
This commit is contained in:
D.S. Ljungmark 2015-03-25 09:28:15 +01:00 committed by David S. Miller
parent 1452db764c
commit 6fd99094de
1 changed files with 8 additions and 1 deletions
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7
net/ipv6/ndisc.c
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@ -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) {
/* 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);