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>
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@ -1218,7 +1218,14 @@ static void ndisc_router_discovery(struct sk_buff *skb)
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if (rt)
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rt6_set_expires(rt, jiffies + (HZ * lifetime));
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if (ra_msg->icmph.icmp6_hop_limit) {
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in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit;
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/* Only set hop_limit on the interface if it is higher than
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* the current hop_limit.
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*/
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if (in6_dev->cnf.hop_limit < ra_msg->icmph.icmp6_hop_limit) {
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in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit;
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} else {
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ND_PRINTK(2, warn, "RA: Got route advertisement with lower hop_limit than current\n");
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}
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if (rt)
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dst_metric_set(&rt->dst, RTAX_HOPLIMIT,
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ra_msg->icmph.icmp6_hop_limit);
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