From 2adf81c0f7b04f9f10e55f5634b1eb7e0a783276 Mon Sep 17 00:00:00 2001 From: Francesco Ruggeri Date: Thu, 31 Oct 2019 17:44:13 -0700 Subject: [PATCH] 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 Signed-off-by: Francesco Ruggeri Reviewed-by: David Ahern Signed-off-by: David S. Miller --- net/ipv4/icmp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 4298aae74e0e..a72fbdf1fb85 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -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(); -- 2.20.1