netdev - Issue with ping source address display

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Date:	Tue, 12 Apr 2016 19:52:15 +0200
From:	Daniele Orlandi <daniele@...andi.com>
To:	netdev@...r.kernel.org
Subject: Issue with ping source address display


Hello,

More than one year ago I posted the following message but it hasn't
received a reply, now I've been stung by a similar issue, you may want
to investigate:


I noticed that when ping receives ICMP messages from different sources
the first IP address is always used and displayed:


vihai@...iolab:~$ ping -V
ping utility, iputils-s20121221

This is a (simulated) flapping route:

vihai@...iolab:~$ ping 10.254.10.140
PING 10.254.10.140 (10.254.10.140) 56(84) bytes of data.
From 192.168.1.1 icmp_seq=1 Destination Host Unreachable
From 192.168.1.1 icmp_seq=2 Destination Host Unreachable
From 192.168.1.1 icmp_seq=3 Destination Host Unreachable
64 bytes from 192.168.1.1: icmp_seq=4 ttl=61 time=24.7 ms
64 bytes from 192.168.1.1: icmp_seq=5 ttl=61 time=25.6 ms
64 bytes from 192.168.1.1: icmp_seq=6 ttl=61 time=69.6 ms
From 192.168.1.1 icmp_seq=7 Destination Host Unreachable
From 192.168.1.1 icmp_seq=8 Destination Host Unreachable
From 192.168.1.1 icmp_seq=9 Destination Host Unreachable
^C
--- 10.254.10.140 ping statistics ---
9 packets transmitted, 3 received, +6 errors, 66% packet loss, time 8001ms
rtt min/avg/max/mdev = 24.797/40.061/69.692/20.955 ms


The sources, however are different:

vihai@...iolab:~$ sudo tcpdump -n icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
^[OA^[OA^[OA17:09:55.932981 IP 192.168.1.21 > 10.254.10.140: ICMP echo
request, id 9278, seq 1, length 64
17:09:55.933234 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92
17:09:56.933169 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 2, length 64
17:09:56.933416 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92
17:09:57.933160 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 3, length 64
17:09:57.933404 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92
17:09:58.933163 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 4, length 64
17:09:58.957939 IP 10.254.10.140 > 192.168.1.21: ICMP echo reply, id
9278, seq 4, length 64
17:09:59.935050 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 5, length 64
17:09:59.960724 IP 10.254.10.140 > 192.168.1.21: ICMP echo reply, id
9278, seq 5, length 64
17:10:00.936177 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 6, length 64
17:10:01.005849 IP 10.254.10.140 > 192.168.1.21: ICMP echo reply, id
9278, seq 6, length 64
17:10:01.936313 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 7, length 64
17:10:01.936626 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92
17:10:02.935321 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 8, length 64
17:10:02.935591 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92
17:10:03.934322 IP 192.168.1.21 > 10.254.10.140: ICMP echo request, id
9278, seq 9, length 64
17:10:03.934613 IP 192.168.1.1 > 192.168.1.21: ICMP host 10.254.10.140
unreachable, length 92




Tried with a different ping implementation (RouterOS) and the behaviour
seems correct:

[vihai@...ioLab SW1] > ping 10.254.10.140
HOST                                     SIZE TTL TIME  STATUS
192.168.1.1                             84  64 0ms   host unreachable
192.168.1.1                             84  64 0ms   host unreachable
192.168.1.1                             84  64 0ms   host unreachable
10.254.10.140                           56  61 20ms
10.254.10.140                           56  61 46ms
10.254.10.140                           56  61 37ms
192.168.1.1                             84  64 0ms   host unreachable
192.168.1.1                             84  64 0ms   host unreachable
192.168.1.1                             84  64 0ms   host unreachable
    sent=9 received=3 packet-loss=66% min-rtt=20ms avg-rtt=34ms max-rtt=46ms


Recently I was pinging with IPv6, a router in between filtered the
packet, however the shown source address was not the right one:

root@...itor:~# ping6 -i 0.2 www.google.com
PING www.google.com(mil01s25-in-x04.1e100.net) 56 data bytes
From mil01s25-in-x04.1e100.net icmp_seq=1 Destination unreachable: No route
From mil01s25-in-x04.1e100.net icmp_seq=2 Destination unreachable: No route
From mil01s25-in-x04.1e100.net icmp_seq=3 Destination unreachable: No route

19:33:19.589285 IP6 2a01:2d8:aca0:fce:944e:c8ff:fe4d:96de >
mil01s25-in-x04.1e100.net: ICMP6, echo request, seq 1, length 64
19:33:19.611666 IP6 mix-br2.intercom.it >
2a01:2d8:aca0:fce:944e:c8ff:fe4d:96de: ICMP6, destination unreachable,
unreachable route mil01s25-in-x04.1e100.net, length 112


Bye,


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