Error setting up DTLS

Nikos Mavrogiannopoulos nmav at
Fri Sep 26 01:26:52 PDT 2014

On Fri, 2014-09-26 at 10:07 +0200, Niels Peen wrote:
> Hi all,
> What could be the cause of a "Error setting up DTLS” error?
> I’m having a really hard time troubleshooting its cause as it’s very inconsistent. It will happen 10+ times, then suddenly (without making any changes) disappear and not happen for days. 
> It happens only on Windows and only with OpenConnect. When I try OpenConnect on Android or AnyConnect on Windows/Android to the same server there are is no issue.

> 2014-09-26 11:27 Error setting up DTLS

This error is printed when openconnect_setup_dtls() fails. I'd have
expected another log message before that from libopenconnect. The fact
that there was no message is maybe because there are some perrors()
involved, or there is a timeout (more likely) which is printed under
PRG_DEBUG by libopenconnect.

> It’s my impression - but this may just be coincidence - that more
distant/slower servers suffer from the error less often. Could this be a
timing issue of some kind?

The more lost packets from the server the more likely a timeout could
occur. The current value for DTLS is 12 seconds and given that the wait
time doubles per lost packet it would take 4 lost packets for this error
to pop up. I had the impression though that openconnect will retry
connecting using DTLS isn't that the case?


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