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

[Michael Olbrich <m.olbrich@pengutronix.de>]

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}'?

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
> 
> 
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> 

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