It's related to /proc/sys/net/ipv4/tcp_max_orphans

"Maximal number of TCP sockets not attached to any user file handle, held by system. If this number is exceeded orphaned connections are reset immediately and warning is printed."

So, I'd start by checking the value of tcp_max_orphans (with "cat /proc/sys/net/ipv4/tcp_max_orphans"). The widely distributed sysctl.conf tweaks for Linux relays suggests a value of 262144. I think the default in many distros may be 4096, perhaps too low for an Exit. 

Some references:

https://serverfault.com/questions/624911/what-does-tcp-too-many-orphaned-sockets-mean

https://raw.githubusercontent.com/torservers/server-config-templates/master/sysctl.conf

If you need help making the sysctl tweaks let me know.

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