[OpenSIPS-Users] tls blocking question

Bogdan-Andrei Iancu bogdan at opensips.org
Thu Mar 7 04:33:39 EST 2019

Hi Ryan,

Indeed, thetcp_no_new_conn_bflag will prevent opensips to open new TCP 
connections when sending out a request. The key questions is: the 
blocking was during a connect (trying to open a new conn) or during a 
write (over an existing conn). If the second case (which is likely based 
on the logs you posted), you should take a closer look at the write 
timeout settings:


Bogdan-Andrei Iancu

OpenSIPS Founder and Developer
OpenSIPS Summit 2019

On 02/19/2019 08:50 PM, Ryan Delgrosso wrote:
> So I have a situation where 100% of my endpoints are TLS behind NAT 
> bridging to UDP in core.
> I have tcp_async enabled and have set tcp_no_new_conn_bflag on packets 
> coming from UDP side to TLS side, as well as setting it on the 
> registered AOR's in mid-registrar.
> Setting up test scenarios I always seem to hit a wall where opensips 
> stops passing packets where it seems to be waiting for some kind of 
> timeout.
> I am also seeing these messages:
> Feb 19 18:46:16 sbc2 /opt/ringrx_edge_proxy/sbin/opensips[20755]: 
> ERROR:proto_tls:tls_write: TLS write error:
> Feb 19 18:46:16 sbc2 /opt/ringrx_edge_proxy/sbin/opensips[20755]: 
> ERROR:proto_tls:tls_blocking_write: TLS failed to send data
> Feb 19 18:46:16 sbc2 /opt/ringrx_edge_proxy/sbin/opensips[20755]: 
> ERROR:proto_tls:proto_tls_send: failed to send
> Feb 19 18:46:16 sbc2 /opt/ringrx_edge_proxy/sbin/opensips[20755]: 
> ERROR:sl:msg_send: send() to for proto tls/3 failed
> The IP is outside so its from a UDP to TCP flow. Is there another flag 
> I need to set to prevent packets from originating new TLS sessions 
> when none exist?
> Once it gets into this state it takes 30s or so before it starts 
> passing packets again, but it does so from a buffer it seems since i 
> can stop my tls generator, wait 30s and the core side sipp instance 
> will again begin receiving packets.
> How can I prevent opensips from blocking like this on TLS sessions?
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