[lldp] Increase lldp netlink buffer limits to fix neighbors missing on swss restart #24752
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Fixes "No buffer space available" issue in lldp during swss restart that casues neighbors to disappear in lldp. Signed-off-by: Connor Roos <[email protected]>
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vivekrnv
approved these changes
Dec 5, 2025
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Fixes "No buffer space available" issue in lldp during swss restart that casues neighbors to disappear in lldp.
Why I did it
When enough neighbors exit for a switch (>211), LLDP will stop reporting the last few neighbors after swss restarts. This happens even though the tcp packets from those neighbors are still arriving over the ports. This is because the netlink buffer is filled up when the restart occurs and the netlink delete messages are not received by lldp, this leads to the service not including the new neighbors over those ports, which will persist until lldp is restarted:
root@sonic:/home/admin# docker exec -it lldp lldpcli show interfaces | grep -A 5 Ethernet520
Interface: Ethernet520
Administrative status: RX and TX
Chassis:
ChassisID: mac
SysName: sonic
SysDescr: SONiC Software Version: SONiC.202412_RC
Interface: Ethernet520
Administrative status: RX and TX
Chassis:
ChassisID: mac
SysName: sonic
SysDescr: SONiC Software Version: SONiC.202412_RC
root@sonic:/home/admin# show lldp table | grep "Ethernet520"
root@sonic:/home/admin#
LLDP buffer errors:
syslog.1:2025 Dec 4 14:39:20.084820 sonic WARNING lldp#lldpd[30]: unable to receive netlink answer: No buffer space available
syslog.1:2025 Dec 4 14:39:20.0850sonic INFO lldp#supervisord: lldpd 2025-12-04T14:39:20 [WARN/netlink] unable to receive netlink answer: No buffer space available
How I did it
By increasing both the minimum and maximum netlink receive buffer in LLDP I was able to fix this issue
How to verify it
Run:
show lldp table
systemctl restart swss
Check without the change to see if the lldp buffer cannot handle all of the neighbors, then install a version of Sonic with the change to check that the larger buffer fixes this issue.
Which release branch to backport (provide reason below if selected)
Description for the changelog
Increase lldp netlink buffer limits to fix neighbors missing on swss restart
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