Re: [Libguestfs] [PATCH nbdkit 4/4] reflection: Enhance plugin to support client address mode.

On Mon, Sep 16, 2019 at 11:01:49AM -0500, Eric Blake wrote: > On 9/15/19 9:55 AM, Richard W.M. Jones wrote: >> +Another use for the reflection plugin is to send back the client's IP >> +address: >> + >> + $ nbdkit reflection mode=address >> + $ nbdsh -u 'nbd://localhost' -c 'print(h.pread(h.get_size(), 0))' >> + >> +which will print something like: >> + >> + b'[::1]:58912' > > Do we want a mode that attempts to do DNS lookup to convert an address > back to a name, so that this could result in b'localhost:58912'? I suppose this could reveal too much information about the server's (DNS?) configuration?

We do have a few tests which use localhost, but they occasionally fail in Koji especially because our algorithm to pick a free port is racy: https://github.com/libguestfs/nbdkit/blob/03a2cc3d766edb17011dafe939e53d0... As far as I know there's not a good way to fix this except to have nbdkit choose a port, but that way is problematic in other ways. Perhaps there is some way to have an external process hang on to a port and pass it to nbdkit (using -s?)