imgedit.py can't always connect to qemu-nbd

[jpeach]

There are a couple of issues with imgedit.py being able to reliably connect to qemu-nbd.

First, it connects to "localhost". On my Fedora20 VM, "localhost" was configured to resolve to ::1, and emu-nbd seems to only listen on IPv4 addresses. I fixed this by editing imgedit.py to connect to "127.0.0.1".

Second, imgedit.py assumes the port number that qemu-nbd is going to listen to. It should be choosing an explicit port and passing that as the argument to the qemu-nbd --port option and to the nbd_client port= argument.

[wkozaczuk]

We could do something similar to

osv/scripts/upload_manifest.py

Lines 16 to 20 in b3aef65

	def find_free_port():
	with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as s:
	s.bind(('localhost', 0))
	s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
	return s.getsockname()[1]

to fix it.

[nyh]

Two years after this issue was opened, imgedit.py was changed in commit 464f4e0 to open a random port in the same way described here.

The fact we allow qemu-nbd to default to listening to any IPv4 address but then connect to localhost, remains. The real solution is very simple and described in issue #709: imgedit.py should call qemu-nbd with "-b 127.0.0.1" and connect to 127.0.0.1, instead of localhost.
So I'm closing this issue in favor of #709.