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net: icmp: use input address in traceroute 

Even with icmp_errors_use_inbound_ifaddr set, traceroute returns the
primary address of the interface the packet was received on, even if
the path goes through a secondary address. In the example:

                    1.0.3.1/24
 ---- 1.0.1.3/24    1.0.1.1/24 ---- 1.0.2.1/24    1.0.2.4/24 ----
 |H1|--------------------------|R1|--------------------------|H2|
 ----            N1            ----            N2            ----

where 1.0.3.1/24 is R1's primary address on N1, traceroute from
H1 to H2 returns:

traceroute to 1.0.2.4 (1.0.2.4), 30 hops max, 60 byte packets
 1  1.0.3.1 (1.0.3.1)  0.018 ms  0.006 ms  0.006 ms
 2  1.0.2.4 (1.0.2.4)  0.021 ms  0.007 ms  0.007 ms

After applying this patch, it returns:

traceroute to 1.0.2.4 (1.0.2.4), 30 hops max, 60 byte packets
 1  1.0.1.1 (1.0.1.1)  0.033 ms  0.007 ms  0.006 ms
 2  1.0.2.4 (1.0.2.4)  0.011 ms  0.007 ms  0.007 ms

Original-patch-by: Bill Fenner <fenner@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Francesco Ruggeri 2019-10-31 17:44:13 -07:00 committed by David S. Miller
parent c219a16622
commit 2adf81c0f7
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/icmp.c
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@ -682,7 +682,8 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
if (dev)
saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
saddr = inet_select_addr(dev, iph->saddr,
RT_SCOPE_LINK);
else
saddr = 0;
rcu_read_unlock();