netlink-listen (NS 0) recvmsg overrun: No buffer space available

[f0o]

Frequently (daily) zebra dies sometime in the night with No buffer space available.

I've done some googling and in the ol' Quagga times there is the suggestion to raise net.core.wmem_max and net.core.rmem_max sysctl settings and adjust the --nl-bufsize (-s) parameter in zebra.

Upon checking the default /etc/frr/daemons I saw that -s is specified with 90000000 but the default w/rmem_max is 212992... How is that supposed to work?

In topotest (

frr/tests/topotests/lib/topotest.py

Line 1353 in 7f10381

sysctl_atleast(None, "net.core.wmem_max", 16 * 2**20)

) it is set to 16777216 for example - But even this does not fit the default 90000000 value from the same file (

frr/tests/topotests/lib/topotest.py

Line 2232 in 7f10381

start_daemon("zebra", "-s 90000000")

)

When I read the meaning of --nl-bufsize/-s (https://docs.frrouting.org/en/latest/zebra.html#cmdoption-zebra-s) it seems like the value specified there should align with r/wmem_max - or am I mistaken?

Would this discrepancy explain my frequent No buffer space available errors?

As an experiment I have bumped one of my routers' --nl-bufsize/-s and e/wmem_max to 134217728 - but would still like to know if I'm barking at the right tree here.

Thanks in advance

[f0o]

A day or two have passed and here are some preliminary observations:

Just changing net.core.r/wmem_max without also changing zebra's --nl-bufsize/-s had no effect, zebra still died that night

Luckily I did had /etc/daemons prepped so when it was restarted it picked up the new values for --nl-bufsize/-s.

Having now both sysctl and zebra changed to 134217728 it has survived a night. A bit early to celebrate still but perhaps I am on the right track after all 🤔

[f0o]

So goog news is that Zebra isn't dying anymore.

Odd news is that now ospf6d is throwing similar errors at more or less random intervals:

 ospf6d[1592110]: [QDEV2-4Y01P] sendmsg failed: source: fe80::f857:37ff:fe60:35f3 Dest: ff02::5 ifindex: 38: No buffer space available (105)

Any Clues? Or am I all alone with this issue?...

[f0o]

So 3 days after and zebra did die again...

zebra[1592096]: [ZG5HV-P06V2][EC 4043309091] netlink-listen (NS 0) recvmsg overrun: No buffer space available

This triggered a full restart of all daemons and subsequently some packetloss.

So I guess I try bumping it to 268435456...?