[ovs-discuss] ICMP packets getting dropped

[Clément Rault]

Hi,

I am experiencing a weird behaviour when I test my system with ping.

I installed flow/group tables so that an alternative path can be found
in case of a link failure.

In the test I am breaking the link between s2 and s5 (in mininet) and
I am seing a really weird behaviour in s5: some packets disappear
after arriving in this switch...

What I don't understand is that I didn't put any rule to drop the
packets. And actually ovs-appctl doesn't show me that any packets are
dropped (but they are not being forwarded anywhere...):

$ sudo ovs-appctl bridge/dump-flows s5
duration=360s, n_packets=11, n_bytes=1078,
priority=1,ip,nw_dst=11.0.0.1,actions=group:1
duration=360s, n_packets=3, n_bytes=294,
priority=2,ip,nw_dst=11.0.0.2,actions=group:2
duration=360s, n_packets=5, n_bytes=510,
priority=9,ip,in_port=4,dl_vlan=1,nw_dst=11.0.0.1,actions=group:6
duration=360s, n_packets=0, n_bytes=0,
priority=3,ip,in_port=1,dl_vlan=1,nw_dst=11.0.0.1,actions=group:3
duration=360s, n_packets=1, n_bytes=102,
priority=7,ip,in_port=3,dl_vlan=1,nw_dst=11.0.0.1,actions=group:5
duration=360s, n_packets=9, n_bytes=910,
priority=6,ip,in_port=2,dl_vlan=1,nw_dst=11.0.0.2,actions=group:4
duration=360s, n_packets=1, n_bytes=102,
priority=5,ip,in_port=2,dl_vlan=1,nw_dst=11.0.0.1,actions=group:4
duration=360s, n_packets=2, n_bytes=204,
priority=8,ip,in_port=3,dl_vlan=1,nw_dst=11.0.0.2,actions=group:5
duration=360s, n_packets=0, n_bytes=0,
priority=10,ip,in_port=4,dl_vlan=1,nw_dst=11.0.0.2,actions=group:6
duration=360s, n_packets=0, n_bytes=0,
priority=4,ip,in_port=1,dl_vlan=1,nw_dst=11.0.0.2,actions=group:3
table_id=254, duration=527s, n_packets=0, n_bytes=0, priority=1,actions=drop
table_id=254, duration=527s, n_packets=0, n_bytes=0,
priority=0,reg0=0x3,actions=drop
table_id=254, duration=527s, n_packets=0, n_bytes=0,
priority=0,reg0=0x1,actions=controller(reason=no_match)
table_id=254, duration=527s, n_packets=12, n_bytes=900,
priority=0,reg0=0x2,actions=drop
table_id=254, duration=527s, n_packets=0, n_bytes=0,
priority=2,recirc_id=0,actions=resubmit(,0)

Is there a policy for an ovs switch to drop a icmp packet? Because in
Wireshark I am seeing packet 1 then 2 then 3 etc even though sometimes
I am expecting to see both packets traversing the network at the same
time. So I am assuming that maybe the icmp implementation in ovs is
time sensitive?

Or could it come from the fact that there is a port that is changing?
Here is what I see in my controller (ryu):

EVENT ofp_event->dpset EventOFPPortStatus
DPSET: A port was modified.(datapath id = 0000000000000005, port number = 1)
EVENT ofp_event->dpset EventOFPPortStatus
DPSET: A port was modified.(datapath id = 0000000000000002, port number = 4)
EVENT ofp_event->dpset EventOFPPortStatus
DPSET: A port was modified.(datapath id = 0000000000000005, port number = 1)

Thanks in advance for you help!

Best,
Clément