Hi all,

I have a strange behaviour on my environment (two servers with Ubuntu + multicast)

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.3 LTS
Release: 14.04
Codename: trusty

ifconfig (node1)
eth4 Link encap:Ethernet HWaddr 00:50:56:a6:28:49
inet addr:10.192.4.161 Bcast:10.192.4.193 Mask:255.255.255.192
inet6 addr: fe80::250:56ff:fea6:2849/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4326 errors:0 dropped:176 overruns:0 frame:0
TX packets:2355 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:410076 (410.0 KB) TX bytes:318159 (318.1 KB)

ifconfig (node2)
eth4 Link encap:Ethernet HWaddr 00:50:56:a6:42:20
inet addr:10.192.4.162 Bcast:10.192.4.193 Mask:255.255.255.192
inet6 addr: fe80::250:56ff:fea6:4220/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5299 errors:0 dropped:203 overruns:0 frame:0
TX packets:2953 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:454333 (454.3 KB) TX bytes:194106 (194.1 KB)

Based on SMCRoute tool, to join multicast group I've set

(node1) - smcroute -j eth4 228.0.0.5
(node2) - smcroute -j eth4 228.0.0.5

(node1) - ipmaddr
[...]
6: eth4
link 01:00:5e:00:00:01
link 33:33:00:00:00:01
link 33:33:ff:a6:28:49
link 33:33:00:00:02:02
link 01:00:5e:00:00:05
inet 228.0.0.5
inet 224.0.0.1
inet6 ff02::202
inet6 ff02::1:ffa6:2849
inet6 ff02::1
inet6 ff01::1

(node2) ipmaddr
[...]
6: eth4
link 01:00:5e:00:00:01
link 33:33:00:00:00:01
link 33:33:ff:a6:42:20
link 33:33:00:00:02:02
link 01:00:5e:00:00:05
inet 228.0.0.5
inet 224.0.0.1
inet6 ff02::202
inet6 ff02::1:ffa6:4220
inet6 ff02::1
inet6 ff01::1

(both nodes)
echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

ping 228.0.0.5
PING 228.0.0.5 (228.0.0.5) 56(84) bytes of data.
64 bytes from 10.192.4.161: icmp_seq=1 ttl=64 time=0.029 ms
64 bytes from 10.192.4.161: icmp_seq=1 ttl=64 time=0.198 ms (DUP!)
64 bytes from 10.192.4.161: icmp_seq=2 ttl=64 time=0.032 ms
64 bytes from 10.192.4.161: icmp_seq=2 ttl=64 time=0.178 ms (DUP!)
64 bytes from 10.192.4.161: icmp_seq=3 ttl=64 time=0.041 ms
64 bytes from 10.192.4.161: icmp_seq=3 ttl=64 time=0.216 ms (DUP!)

Every DUP! packet should came from 10.192.4.162 , not from .161

What's wrong?


PS: TCPDUMP

tcpdump -i eth4 -vvvvnn | grep ICMP
15:26:03.048557 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto ICMP (1), length 84)
10.192.4.161 > 228.0.0.5: ICMP echo request, id 1811, seq 77, length 64
15:26:03.048660 IP (tos 0x0, ttl 64, id 4501, offset 0, flags [none], proto ICMP (1), length 84)
10.192.4.162 > 10.192.4.161: ICMP echo reply, id 1811, seq 77, length 64

cat /proc/net/igmp
Idx Device : Count Querier Group Users Timer Reporter
[...]
6 eth4 : 2 V3
050000E4 1 0:00000000 0
010000E0 1 0:00000000 0