Don't use qemu's "-redir" option in run.py

[nyh]

QEMU's "-redir" option has been deprecated for at least 5 years now, but silently supported. Since QEMU 2.6, it started to be annoyingly loud about it:

$ scripts/run.py -e tests/tst-rename.so 
qemu-system-x86_64: -redir tcp:2222::22: The -redir option is deprecated. Please use '-netdev user,hostfwd=...' instead.
OSv v0.24-157-gab34727

We can probably fix it exactly as the message suggests.

[geraldo-netto]

Dear @nyh ,

I have played for a while with it today and it turns out,
we require a little more than a simple string replacement...

According to the documentation [1], we should set something like this:

-netdev user,id=<iface name>,hostfwd=tcp:<ip in>:<port in>-<ip out>:<port out>

So, I tried this:

...
if options.api:
  args += ["-netdev", "user,id=hn%d,hostfwd=tcp::8000-:8000" % idx]

for rule in options.forward:
  args += ["-netdev", "user,id=hn{},hostfwd={}".format(idx, rule)]
...

But because we set netdev before handling "--api" or "--forward", qemu fails with the following message:

netto@besta01 ~/osv-3 $ sudo scripts/run.py -nV --api
qemu-system-x86_64: -netdev user,id=hn0,hostfwd=tcp::8000-:8000: Duplicate ID 'hn0' for netdev
qemu failed.

It's strange that it fails because the same documentation says it can handle multiple -netdev entries...
The solution seems to be concatenate the forwards when the first -netdev is defined

[1] https://wiki.qemu.org/Documentation/Networking

Kind Regards,
Geraldo Netto

[nyh]

@geraldo-netto I think the redirection options ("api" and "forward") are only relevant to the emulated network (qemu's "user" network), not to bridging mode, so I think the solution is to do something like your above code, but only in the one specific case (an "else:" section of if options.networking) where the "user" netdev is being set up by run.py.

So it's more or less what you suggested, just that you need to do it only for the user netdev, not the bridge ones. Looks pretty straightforward.