Bug#813471: network access to the loopback device should be allowed

[Osamu Aoki <osamu@debian.org>]

Package: debian-policy
Severity: normal

Bug #770016 "Clarify network access for building packages in main"
was about not downloading files via network.  This created new lines in
4.9 as:

| For packages in the main archive, no required targets may attempt
| network access.

This is too restrictive.

The build target of devscripts has several tests testing http acess to
the http server on the loopback device.

But the above new policy lines may be considered to prohibit this.

I thought the this should be more like:

| For packages in the main archive, no required targets may attempt
| network access except for the access to the loopback device.

I understand downloading from Debian or non-Debian web site is bad for
buildd but network operation to the loopback device (like http access)
should be OK.

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing'), (98, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)