Kernel: sonewconn: Listen queue overflow

[isiroshtan]

Hi all. I'm new here and English not my native language, so sorry for any mistakes both in grammar and in full understanding of logs/problem.

I have pfsense 2.2.1-RELEASE and ovpn servers configured on  it. Yesterday it started to behave strangely. Server randomly drops all connected users, and on immediate  reconnect attempt it gives tls erorr. Server log as follows:

May 14 14:43:46 openvpn[98124]: 85.198.173.63:62078 TLS Error: TLS handshake failed
May 14 14:43:46 openvpn[98124]: 85.198.173.63:62078 TLS Error: TLS key negotiation failed to occur within 60 seconds (check your network connectivity)

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May 14 14:40:03 openvpn[98124]: ynychyporchuk/85.198.173.63:64476 [ynychyporchuk] Inactivity timeout (–ping-restart), restarting

Studying logs spotted in system logs next error:

kernel: sonewconn: pcb 0xfffff80117812870: Listen queue overflow: 2 already in queue awaiting acceptance (1 occurrences)

[2.2.1-RELEASE][**]/home/(13): netstat -An | grep fffff80117812870
fffff80117812870 stream      0      0 fffff800287423b0        0        0        0 /var/etc/openvpn/server5.sock

Server5 is exactly server where all users are dropped from. After some time connections are possible again and all works fine for some time. Today same behavior was spotted on another ovpn server on same machine.

I planing on rebooting machine and see if it fixes anything, as 45 days before it was working flawlessly, but was wondering if anyone can point me on reason of such behavior.