[Bug 3243] Introduce multiplex timeout configuration

[bugzilla-daemon at mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=3243

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
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                 CC|                            |djm at mindrot.org

--- Comment #1 from Damien Miller <djm at mindrot.org> ---
There are two possible situations that you're describing here:

1) The main multiplexing session has exited, leaving a stale
ControlPath socket

This happens if the ssh process doesn't get a change to exit
gracefully, e.g. an abnormal exit, sudden reboot, laptop ran out of
power, etc.

In this case, the new ssh connection should notice the stale socket and
reconnect immediately.

2) The main multiplexing session has stuck, leaving a valid but
unresponsive ControlPath

I suspect this is what you're experiencing - the connection might
become stuck because you switched networks, unsuspended a laptop, etc.

In this case, the ssh client will try to interact with the main
multiplexing connection but, because it can no longer communicate with
the peer sshd, nothing good happens.

There already exist settings to detect and fix this:
ServerAliveInterval and ServerAliveCountMax. These control
protocol-level timeouts that will kill the connection if the server is
persistently unresponsive.

Setting them is a balance between responsiveness to stuck connections
and tolerance of transient network problems. I use

ServerAliveInterval 30
ServerAliveCountMax 8

In my ~/.ssh/config to set a 4 minute timeout for unresponsive
connections.

Does this help you?

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