Re: [DistroKit] [PATCH 5/5] v7a: run: randomise the SSH forwarding port

[Roland Hieber <rhi@pengutronix.de>]

On Mon, Apr 26, 2021 at 08:33:00AM +0200, Michael Olbrich wrote:
> On Mon, Apr 26, 2021 at 08:05:26AM +0200, Roland Hieber wrote:
> > When multiple ./configs/platform-v7a/run scripts are run at the same
> > time, the first qemu process will open port 4445, and following runs
> > will fail. To prevent that, first look at the environment variable
> > QEMU_SSH_PORT to determine the port to be used (so that users can set
> > this in their shell to keep the port static), or fall back to a random
> > port between 1025 and 65025, which should have a good chance of being
> > unused. Also print the port forwarding before starting qemu, so we don't
> > have to bother with "ps -Af|grep qemu".
> > 
> > Signed-off-by: Roland Hieber <rhi@pengutronix.de>
> > ---
> >  configs/platform-v7a/run | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/configs/platform-v7a/run b/configs/platform-v7a/run
> > index d180ccfa890d..cf529e968fb0 100755
> > --- a/configs/platform-v7a/run
> > +++ b/configs/platform-v7a/run
> > @@ -39,7 +39,7 @@ fi
> >  # the port which an sshd would connect to (in the emulated sysem)
> >  SSH_INTERNAL_PORT=22
> >  # the port which QEMU opens at the host side to give access to the ${SSH_INTERNAL_PORT}
> > -SSH_EXTERNAL_PORT=4445
> > +SSH_EXTERNAL_PORT=${QEMU_SSH_PORT:-${RANDOM%64000+1025}}
> 
> This means I have to change the ssh command-line whenever I restart qemu.
> Not nice. How about '${PPID%64000+1025}'?

QEMU_SSH_PORT was meant to take care of that, but PPID should work too.

 - Roland

> 
> Michael
> 
> >  
> >  # check if vde is available for networking
> >  if [ -z "${VDE_SOCKET}" ]; then
> > @@ -59,6 +59,7 @@ fi
> >  # fall back to user network if necessary
> >  if [ -z "${QEMU_NET}" ]; then
> >  	QEMU_NET=(-netdev user,id=net1,hostfwd=tcp:127.0.0.1:${SSH_EXTERNAL_PORT}-:${SSH_INTERNAL_PORT} )
> > +	echo "Forwarding SSH port 127.0.0.1:${SSH_EXTERNAL_PORT} -> qemu:${SSH_INTERNAL_PORT}"
> >  fi
> >  
> >  BASE_CMDLINE="console=ttyAMA0,115200 loglevel=5 systemd.log_level=warning systemd.show_status=auto"
> > -- 
> > 2.29.2
> > 
> > 
> > _______________________________________________
> > DistroKit mailing list
> > DistroKit@pengutronix.de
> > 
> 
> -- 
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-- 
Roland Hieber, Pengutronix e.K.          | r.hieber@pengutronix.de     |
Steuerwalder Str. 21                     | https://www.pengutronix.de/ |
31137 Hildesheim, Germany                | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686         | Fax:   +49-5121-206917-5555 |

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