autossh quits because ssh (dropbear) can't resolve host - ssh

Question

I run autossh on a system which might have internet connectivity or might not. I don't really know when it has a connection but if so I want autossh to establish a ssh tunnel by:
autossh -M 2000 -i /etc/dropbear/id_rsa -R 5022:localhost:22 -R user#host.name -p 6022 -N
After several seconds it throws:
/usr/bin/ssh: Exited: Error resolving 'host.name' port '6022'. Name or service not known
And thats it. Isn't autossh meant to keep the ssh process running no matter what? Do I really have to check for a connection by ping or so?

Answer 1

You need to set the AUTOSSH_GATETIME environment variable to 0. From autossh(1):
Startup behaviour
If the ssh session fails with an exit status of 1 on the very first try, autossh
1. will assume that there is some problem with syntax or the connection setup,
and will exit rather than retrying;
2. There is a "starting gate" time. If the first ssh process fails within the
first few seconds of being started, autossh assumes that it never made it
"out of the starting gate", and exits. This is to handle initial failed
authentication, connection, etc. This time is 30 seconds by default, and can
be adjusted (see the AUTOSSH_GATETIME environment variable below). If
AUTOSSH_GATETIME is set to 0, then both behaviours are disabled: there is no
"starting gate", and autossh will restart even if ssh fails on the first run
with an exit status of 1. The "starting gate" time is also set to 0 when the
-f flag to autossh is used.
AUTOSSH_GATETIME
Specifies how long ssh must be up before we consider it a successful connec‐
tion. The default is 30 seconds. Note that if AUTOSSH_GATETIME is set to 0,
then not only is the gatetime behaviour turned off, but autossh also ignores
the first run failure of ssh. This may be useful when running autossh at
boot.
Usage:
AUTOSSH_GATETIME=0 autossh -M 2000 -i /etc/dropbear/id_rsa -R 5022:localhost:22 -R user#host.name -p 6022 -N