no connectivity to some hosts behind tinc for the first few seconds

Tomasz Chmielewski mangoo at
Tue Feb 21 08:39:19 CET 2017

On 2017-02-21 12:38, Tomasz Chmielewski wrote:
> I have the following tinc setup:
> client -- tinc DC1 -- tinc DC2 -- subnet
> It generally works well, however, there is one issue I'm not able to
> solve: *sometimes*, connectivity to *some* destinations does not work
> for the first few seconds.

I was able to reproduce it reliably in the following simplified 

    tinc DC1 -- tinc DC2 -- MASQUERADE -- (webserver)

Script to reproduce (it tries to fetch the URL for 5 seconds, exits if 
it fails):


set -e
while true ; do
     echo "Run number $i"
     curl -s -m 5 >/dev/null
     echo $?

Usually, it will break after about 30 iterations.

"time curl -s -m 5" takes around 0.2-0.3 secs to 
execute - so 5 seconds should be enough time.

tshark shows "TCP Spurious Retransmission" for cases where curl is not 
able to fetch any data.

Both tinc servers are running Ubuntu 16.04 (64 bit) with tinc 1.0.26.

DC1 is Europe (Hetzner); DC2 is in USA (Amazon AWS).

What's interesting, I don't have these timeouts when I replace tinc with 

Any help appreciated!

Tomasz Chmielewski

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