[stunnel-users] problem with buffering data on stunnel

Fri Jul 10 20:17:24 CEST 2015

	Hi Mike,

	

	Thank you for your answer.

	I've made many tests using those parameters you've suggested. It is very 
good solution for decreasing buffer in Stunnel, but in my case it is not 
enough. Encrypted session on path beetwen slow client in GPRS network and 
Stunnel server is using TCPWindowSize on the level 5KB or less. But 
unencrypted session on path between Stunnel server and hi-speed end server 
(both in LAN) is using TcpWindowSize on level 64KB - 131KB (in Windows 2008 
or newer it is calculated automatically). So I steel have at least 64KB 
buffer in stunnel.

	

	Is there any possibility to force stunnel to use on faster part of 
connection (LAN side) the value of TcpWindowSize similar to calculated on 
slower part (on WAN side)?

	

	Best regards,

	

	Adalbert

	

	

	

	Dnia 2015-07-09 12:18 Michal Trojnara napisał(a):

	

	

	

	

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	Hi Adalbert,

	

	My guess would be:

	socket = l:SO_RCVBUF=2048

	socket = r:SO_SNDBUF=2048

	

	Mike

	

	On 09.07.2015 11:53, wujot wrote:

	

	I have a problem with transmission from LAN server, which use

	another server on LAN with running stunnel, to pass encrypted data

	to remote SSL clients if they are on very slow GPRS network. If

	server in LAN starts to transfer big amount of data to such slow

	remote client, stunnel is buffering data and slowly transmits them

	to the GPRS client. TCP Window on connection from LAN server to

	stunnel is big (64 - 131kB), and TCP Window on connection from

	stunnel to slow client is small (about 5kB). And additionally

	stunnel is buffering data. So, server is finishing transmission in

	seconds, but in fact most of data are still in buffers of stunnel.

	And it makes a timeout problem (server is waiting for the

	confirmation from client if it received all data, but time between

	last byte sent from server and confirmation from client could be

	even several minutes).

	

	So, stunnel is working in "store and forward" model. Is it possible

	to switch it to something like "cut through"? Or how to force

	stunnel to more synchronized transmission between client and

	server?

	

	Regards,

	

	Adalbert

	

	

	

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