More than 65K connections of a proxy on FreeBSD

Salikhov Dinislam nginx-forum at
Wed Apr 11 10:37:32 UTC 2018

> Correct me if I'm wrong but in case of IP_BIND_ADDRESS_NO_PORT doesn't the
unique 4-tuple (sourceip+sourceport+destip+destport) limit still remain?

Yes, it still remains.

> As you only defer/delegate to kernel to assign the ephemeral port in
connect() rather than at the bind() time (when the destination is not yet
known) so in case of a single source ip and single backend/port the ~65k
limit still exists. 

You are right for the case of single source IP and single backend-port
The thing is that in case of single source IP and multiple backend-port
pairs overall amount of connections is still limited by 65K. Linux's
IP_BIND_ADDRESS_NO_PORT increases the limit up to 65K connections per single
backend-port pair (single source IP remains the same for all connections to
all backends) and NGINX supports the feature. So I wonder if there's
something like on FreeBSD.

Posted at Nginx Forum:,279368,279396#msg-279396

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