openssh unix dev - Apr 2015 - KEEPALIVE timeout? default taken from server, or other? length settable?

I see options for turning keepalive on or off, in both
the server and client config files.

Does one or the other take precendence?

If it is "on", does it use the OS's default values?
Or, if not, are the values settable?

I am running a win-client to OpenSuse/linux server that
has a default TCP_KEEPALIVE set to the linux default of 2 hours.

I don't know if the Win client has its own KEEPALIVE value
(or where I'd set it).

Either way, is there a way to change the default value?

Right now, from the docs (6.2p2-3.1.2.x86_64), it looks
like if I turn off keepalive on Clnt+Serv, then the default on
the server would be used (2 hours?) -- or would some default
on Windows kill it sooner?

(which is why I want to find out if there are KeepAlive vals
on both ends -- and if so, how to change them globally and/or
per openssh-config).

Thanks!

On Fri, Apr 24, 2015 at 7:40 AM, L. A. Walsh <openssh at tlinx.org> wrote:
>
> I see options for turning keepalive on or off, in both
> the server and client config files.
>
There are 2 types of keepalives: the TCP level one (TCPKeepAlive) and
application level keepalives (ServerAliveInterval+ServerAliveCountMax in
the client, ClientAliveInterval+ClientAliveCountMax).

Does one or the other take precendence?
>
The're independent.  If they're enabled on a particular end then
it'll send
the keepalive and act on the presence (or not) of the response from the
other end.

> If it is "on", does it use the OS's default values?
>
TCPKeepAlive: yes.  The others: no.

Or, if not, are the values settable?
>
TCPKeepAlive: it's a system-wide setting.  The others: yes.

> I am running a win-client to OpenSuse/linux server that
> has a default TCP_KEEPALIVE set to the linux default of 2 hours.
>
On Linux that's usually the net.ipv4.tcp_keepalive_time sysctl or maybe the
equivalent under /proc or /sys.

> I don't know if the Win client has its own KEEPALIVE value
> (or where I'd set it).
Either way, is there a way to change the default value?
>
> Right now, from the docs (6.2p2-3.1.2.x86_64), it looks
> like if I turn off keepalive on Clnt+Serv, then the default on
> the server would be used (2 hours?) -- or would some default
> on Windows kill it sooner?
>
That's a question for the author of the client software.

> (which is why I want to find out if there are KeepAlive vals
> on both ends -- and if so, how to change them globally and/or
> per openssh-config).
>
-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.