Re: [gentoo-portage-dev] [PATCH] Configure a dummy network interface for network-sandbox

[Zac Medico]

On 7/31/19 9:06 AM, Mike Gilbert wrote:
> This works around some strange behavior in glibc's getaddrinfo()
> implementation when the AI_ADDRCONFIG flag is set.
>
> For example:
>
>   struct addrinfo *res, hints = { .ai_family = AF_INET, .ai_flags = AI_ADDRCONFIG };
>   getaddrinfo("localhost", NULL, &hints, &res);
>
> This returns no results if there is no non-loopback interface configured with an
> IPv4 address.
>
> Bug: https://bugs.gentoo.org/690758
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=12377#c13
> Signed-off-by: Mike Gilbert <floppym@g.o>
> ---
>  lib/portage/process.py | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/lib/portage/process.py b/lib/portage/process.py
> index dfbda75de..c284c04f3 100644
> --- a/lib/portage/process.py
> +++ b/lib/portage/process.py
> @@ -446,6 +446,29 @@ def spawn(mycommand, env=None, opt_name=None, fd_pipes=None, returnpid=False,
>  	# Everything succeeded
>  	return 0
>
> +def _configure_dummy_interface():
> +	"""
> +	Configure a dummy interface to work around odd behavior in glibc's
> +	getaddrinfo() implementation when the AI_ADDRCONFIG flag is set.
> +
> +	For example:
> +
> +	  struct addrinfo *res, hints = { .ai_family = AF_INET, .ai_flags = AI_ADDRCONFIG };
> +	  getaddrinfo("localhost", NULL, &hints, &res);
> +
> +	This returns no results if there is no non-loopback interface configured with an
> +	IPv4 address.
> +
> +	Bug: https://bugs.gentoo.org/690758
> +	Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=12377#c13
> +	"""
> +	try:
> +		subprocess.check_call(['ip','link','add','dummy','type','dummy'])
> +		subprocess.check_call(['ip','link','set','dummy','up'])
> +		subprocess.check_call(['ip','address','add','10.0.0.1/8','dev','dummy'])
> +	except subprocess.CalledProcessError:
> +		writemsg("Unable to configure dummy network interface\n")
> +
>  def _exec(binary, mycommand, opt_name, fd_pipes,
>  	env, gid, groups, uid, umask, cwd,
>  	pre_exec, close_fds, unshare_net, unshare_ipc, unshare_mount, unshare_pid,
> @@ -637,6 +660,7 @@ def _exec(binary, mycommand, opt_name, fd_pipes,
>  									errno.errorcode.get(e.errno, '?')),
>  									noiselevel=-1)
>  							sock.close()
> +							_configure_dummy_interface()
>  				except AttributeError:
>  					# unshare() not supported by libc
>  					pass
>

Maybe it will suffice to add the address to the loopback interface?
-- 
Thanks,
Zac