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46 lines
1.8 KiB
Diff
46 lines
1.8 KiB
Diff
From 6fd99094de2b83d1d4c8457f2c83483b2828e75a Mon Sep 17 00:00:00 2001
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From: "D.S. Ljungmark" <ljungmark@modio.se>
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Date: Wed, 25 Mar 2015 09:28:15 +0100
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Subject: [PATCH] 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.
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RFC 3756, Section 4.2.7, "Parameter Spoofing"
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> 1. The attacker includes a Current Hop Limit of one or another small
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> number which the attacker knows will cause legitimate packets to
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> be dropped before they reach their destination.
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> As an example, one possible approach to mitigate this threat is to
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> ignore very small hop limits. The nodes could implement a
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> configurable minimum hop limit, and ignore attempts to set it below
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> said limit.
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Signed-off-by: D.S. Ljungmark <ljungmark@modio.se>
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Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/ipv6/ndisc.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
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index 471ed24aabaec..14ecdaf06bf74 100644
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--- a/net/ipv6/ndisc.c
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+++ b/net/ipv6/ndisc.c
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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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