fleetctl submit/start for more than 5 units at a time fails

[r0ps3c]

When invoking fleetctl as:

$ fleetctl --tunnel 54.191.250.126 submit 1.service ... 6.service

with more than 5 units, I get
Error creating units: failed creating unit a.service: Put http://domain-sock/fleet/v1/units/6.service?alt=json: ssh: rejected: administratively prohibited (open failed)

This same error occurs whether the operation is submit, start, or load, but destroy with many services appears to work

[kayrus]

relates to #1352

[kayrus]

Have reproduced the issue. It relates to fleetctl fd-forward proxy and somehow to ssh limits. Need more time to investigate.

[kayrus]

Looks like that on any failed request fleetd closes the unix socket. Closed socket terminates fleetctl fd-forward /var/run/fleet.sock, but local fleetctl doesn't know about that and still tries to send data to ssh.

possible solution is fix fleetctl fd-forward to work in forever loop like it is done here. Didn't manage yet how to interrupt goroutine.

[kayrus]

It turned out that it is not a reason. Still investigating.

[kayrus]

The actual reason was multiple "auth-agent-req@openssh.com" requests, which is not supported by SSH daemon. Had to add additional check whether request was sent or not.