[ovs-discuss] watch_group liveness check for OVS groups

Alexander Constantinescu aconstan at redhat.com
Thu Jan 21 19:20:16 UTC 2021


Hi,

TL;DR: I am wondering if there's any specific action/convention that needs
to be defined for groups which are referenced by a watch_group, as to have
the liveness check correctly working? FYI: I can't use a liveness check on
a dedicated OVS port in this case.

I have not been able to find much documentation surrounding watch_group,
the only doc I've been basing myself on is:
http://www.openvswitch.org/support/dist-docs/ovs-ofctl.8.html

I am working on a POC where the goal of my work is to load balance packets
between two nexthops for packets matching a given flow. Essentially, I have
this flow which gets hit:

 cookie=0x0, duration=12657.001s, table=100, n_packets=1423,
n_bytes=113190, priority=100,ip,reg0=0x5d41f9 actions=group:2

for which I have the following groups defined:

 group_id=3,type=select,bucket=weight:100,actions=ct(commit),move:NXM_NX_REG0[]->NXM_NX_TUN_ID[0..31],set_field:172.19.0.2->tun_dst,output:vxlan0

group_id=2,type=select,bucket=weight:100,watch_group:3,actions=group:3,bucket=weight:100,watch_group:4,actions=group:4
 group_id=4,type=select,bucket=weight:100,actions=ct(commit),move:NXM_NX_REG0[]->NXM_NX_TUN_ID[0..31],set_field:172.19.0.4->tun_dst,output:vxlan0

Group 2 thus load balances between group 3 (which forwards packets to
nexthop 172.19.0.2) and 4 (corresponding to nexthop 172.19.0.4) in an equal
way.

The load balancing works, however the watch_group does not seem to have any
impact, and what I mean by that is: if I shutdown the nodes corresponding
to either of my nexthops, group 2 will still try to send packets to the
nexthop (node) which I've just shut down.

Honestly, I don't expect OVS to be able to determine the liveness of my
group based off of what I've written....but I don't have any better idea of
what to do. I am unable to tell if there's a specific action / convention
that needs to be defined for groups which are referenced by a watch_group.

Thanks in advance for any help!
-- 

Best regards,


Alexander Constantinescu

Software Engineer, Openshift SDN

Red Hat <https://www.redhat.com/>

aconstan at redhat.com
<https://www.redhat.com/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openvswitch.org/pipermail/ovs-discuss/attachments/20210121/36bcef3e/attachment.html>


More information about the discuss mailing list