connecting to non-responding hosts: 1 hr timeout (fwd)

[Dave Dykstra]

On Tue, May 01, 2001 at 03:03:54PM +0300, Pekka Savola wrote:
> Hello all,
> 
> If you try to make a TCP connection to a host, and the host is down,
> timeouts can be as long as an hour.  This is not specific to ssh, or OS.

It is specific to the O.S.   Linux has a longer default timeout than
Solaris, which is about 2 minutes.  2 minutes is much too long too though.

> Is this a scenario worth working around, e.g. with a timer when
> connecting or the like?

I just brought up the same issue on the GnuPG mailing list yesterday.  Last
week I wrote some code to get around the long timeout in ssh but I
implemented it as an external program that ssh calls via -oProxyCommand.
There's no reason why it can't be done inside ssh itself though, and I
think it should and perhaps even have a config option to adjust the length
of the timer.

Here's what I wrote to gnupg-devel at gnupg.org:

On Mon, Apr 30, 2001 at 01:30:02PM -0500, Dave Dykstra wrote:
...
> you just need to do fcntl(fd, F_SETFL, O_NONBLOCK) on the socket before the
> connect(), check for EINPROGRESS from the connect(), and then do a select()
> for writability on the fd with a timeout of however long you want.  Note
> that if the connection is then refused it will come as an error message
> from the next read() or write().  Some older systems may not have
> O_NONBLOCK or EINPROGRESS defines so I'd #ifdef out the code if they're
> missing.

A reply said where you can get some code to do it portably:

On Wed, May 02, 2001 at 06:33:28AM +1200, Peter Gutmann wrote:
...
> I wrote my own wrappers for this which work under
> every Unix I've been able to get my hands on as well as Win32, if whoever's
> working on this for GPG wants the code they can grab it from the latest
> cryptlib version, ftp://ftp.franken.de/pub/crypt/cryptlib/beta/cl30beta05.zip,
> as misc/net_tcp.c.

- Dave Dykstra