Re: Problem reports for version control systems

[Anders Magnusson <ragge%tethuvudet.se@localhost>]

Den 2021-05-02 kl. 13:44, skrev Johnny Billquist:
> I suspect what is commonly the problem here is related to the fact 
> that cvs has such a phase at the beginning where it is scanning 
> through the file system, which can take quite a while. Some NAT 
> devices along the path sometimes have timeouts on existing connections 
> that if no traffic is happening for a while, they are dropped, even 
> though there hasn't been any FINs on the connection.
> So a connection that just don't have any traffic for a while are hit 
> by this, which is exactly the pattern you have with cvs.
>
> I've seen the same effect on a simple telnet session, where ssh 
> survives fine. And there it's just that when the connection is idle, 
> telnet is not creating any traffic at all, while ssh do generate a bit 
> of traffic even if there is no activity.
>
> So one obvious solution is to use something like ssh as a carries for 
> the cvs traffic, if possible, or else see if some kind of keepalives 
> can be enabled on a connection, to defeat NAT and similar devices 
> which aggressively drop connections on which there is no traffic for a 
> while.
> (Or, of course, if there is a NAT you have control over, you might be 
> able to change how it behaves...)
This is quite common, yes.
I ususlly add ssh keepalive to ssh_config for all hosts to avoid this 
problem (which may occur, as written, when doing cvs update).

-- R