On Fri, 6 Jul 2007, Per Öberg wrote:
> Hi all
>
> > after you've made the changes. Don't be logged in over the network when
> > you do this :-)
> >
> > Jim
>
> Generally I agree with Jim, this is a very good way to screw yourself if
> you have untested changes. :-)
>
> However, I have noticed that it often works to restart the network
> without ssh complaining.
You must have kept the same IP address then, otherwise the ssh client
packets would have problems getting to you[1]. I suspect the Kernel socket
info stays there for the old connection. You can check this by do the
experiment and using netstat to show the kernel socket info before and
after.
> This leads to another question:
> - Does anyone know exactly when the linux TCP-stack drops the
> connection? Obviously not when the interface is brought down and right
> back up again.
As I said, I think the socket connection details remain[2], and
eventually tcp or application timeout's will start to kick in.
cheers
Jim
[1] if the address is in the same subnet, then ARP cache persistance
may mean some packets will get thru', what the kernel would do with
such network packets is an intriguing question.
[2] Indeed they do I've just done on my desktop (2.4.18 kernel so pretty
close)...
# netstat -an | grep 10.80
tcp 0 0 192.168.10.77:1022 192.168.10.80:1023 ESTABLISHED
tcp 0 0 192.168.10.77:1023 192.168.10.80:514 ESTABLISHED
# ifdown eth0
# netstat -an | grep 10.80
tcp 0 0 192.168.10.77:1022 192.168.10.80:1023 ESTABLISHED
tcp 0 0 192.168.10.77:1023 192.168.10.80:514 ESTABLISHED
# ifup eth0
# netstat -an | grep 10.80
tcp 0 0 192.168.10.77:1022 192.168.10.80:1023 ESTABLISHED
tcp 0 0 192.168.10.77:1023 192.168.10.80:514 ESTABLISHED
and indeed these connections were uninterrupted by the interface being
taken down for a short period.
All of course a bit OT, I crave everyone's indulgance.
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