Zebra sometimes does not connect to FPM

[stepanblyschak]

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Describe the bug

We are switching from using old fpm plugin to new dplane_fpm_nl plugin and observe that sometimes zebra does not connect to fpm server.

The configuration in /etc/frr/zebra.conf is the following:

frr@5beef0983ab7:/$ cat /etc/frr/zebra.conf
log stdout debugging
debug zebra fpm
no fpm use-next-hop-groups
fpm address 127.0.0.1

I start zebra:

/usr/lib/frr/zebra -A 127.0.0.1 --asic-offload=notify_on_offload -M dplane_fpm_nl

I start fpm-stub from https://github.com/donaldsharp/fpm-stub/tree/return_static:

Reflecting some routes with OFFLOAD flag set
Waiting for client connection...

But fpm-stub stucks at waiting for client connection. This issues happens once out of 3 retries.

Important note, if I remove the line no fpm use-next-hop-groups from zebra.conf the issue is not reproducible.

• Did you check if this is a duplicate issue?
• Did you test it on the latest FRRouting/frr master branch?

To Reproduce

Expected behavior

I expect zebra connects to FPM application.

Screenshots

Versions

• OS Version: Ubuntu 20.04.5 LTS

• Kernel: 4.15.0-130-generic

• FRR Version: 8.5-dev (5f37d59 + PR 12075)

Additional context