Re: [gentoo-portage-dev] [PATCH v2] process: Unshare UTS namespace, and set hostname to 'localhost'

[Michał Górny]

On Sat, 2020-03-28 at 11:16 -0700, Zac Medico wrote:
> On 3/28/20 12:13 AM, Michał Górny wrote:
> > Use UTS namespace to override hostname when network-sandbox is enabled.
> > Set it to 'localhost' as that has a better chance of being present
> > in /etc/hosts.  This fixes tests in some packages that try to connect
> > to localhost via hostname obtained using gethostname(), e.g. docker-py,
> > and suffer resolution problems due to the system hostname not being
> > defined in /etc/hosts.
> > ---
> >  lib/portage/process.py | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/portage/process.py b/lib/portage/process.py
> > index c1fc4bcf6..c48503208 100644
> > --- a/lib/portage/process.py
> > +++ b/lib/portage/process.py
> > @@ -348,12 +348,14 @@ def spawn(mycommand, env=None, opt_name=None, fd_pipes=None, returnpid=False,
> >  	if unshare_net or unshare_ipc or unshare_mount or unshare_pid:
> >  		# from /usr/include/bits/sched.h
> >  		CLONE_NEWNS = 0x00020000
> > +		CLONE_NEWUTS = 0x04000000
> >  		CLONE_NEWIPC = 0x08000000
> >  		CLONE_NEWPID = 0x20000000
> >  		CLONE_NEWNET = 0x40000000
> >
> >  		if unshare_net:
> > -			unshare_flags |= CLONE_NEWNET
> > +			# UTS namespace to override hostname
> > +			unshare_flags |= CLONE_NEWNET | CLONE_NEWUTS
> >  		if unshare_ipc:
> >  			unshare_flags |= CLONE_NEWIPC
> >  		if unshare_mount:
> > @@ -704,6 +706,13 @@ def _exec(binary, mycommand, opt_name, fd_pipes,
> >  									noiselevel=-1)
> >  								os._exit(1)
> >  						if unshare_net:
> > +							# use 'localhost' to avoid hostname resolution problems
> > +							try:
> > +								socket.sethostname('localhost')
> > +							except Exception as e:
> > +								writemsg("Unable to set hostname: %s (for FEATURES=\"network-sandbox\")\n" % (
> > +									e),
>
> Existing code uses (e,) in cases like this, in order to wrap the
> exception in a tuple, preventing ambiguity in python2 where exceptions
> may behave like tuples. If you don't include the comma, then the
> parenthesis do nothing here, but these days the string formatting
> appears to work correctly with python2.7 either way.

Oops, I meant to leave it there.  I'll fix and push.

>
> > +									noiselevel=-1)
> >  							_configure_loopback_interface()
> >  				except AttributeError:
> >  					# unshare() not supported by libc
> >
>
> Looks good. Please merge.

-- 
Best regards,
Michał Górny