add support for NixOS to iputil

[zooko]

Here is a test failure: ​http://allmydata.org/buildbot/builders/Ludo%20NixOS-amd64/builds/0/steps/test/logs/stdio

This is because src/allmydata/util/iputil.py​ tries to invoke /sbin/ifconfig but there isn't a file by that name on NixOS.

Ludo has patches this for the NixOS package of Tahoe-LAFS, like this: ​https://svn.nixos.org/repos/nix/nixpkgs/trunk/pkgs/tools/networking/p2p/tahoe-lafs/default.nix

He says to see the "patchPhase" part of that file.

[zooko]

I don't think ludo is currently planning to work on this ticket, so I'm unassigning it from him. I would personally love to get NixOS which already maintains a package of Tahoe-LAFS (​https://svn.nixos.org/repos/nix/nixpkgs/trunk/pkgs/tools/networking/p2p/tahoe-lafs/ ), to be a Supported system. So I would be grateful if someone would look at this issue.

[davidsarah]

The way we currently determine which command to run in iputil is unnecessarily unportable and high-maintenance. In practice all Unices support one of a small number of command syntaxes to get local IP addresses. We should just try all of them whenever the OS is not Windows.

[zooko]

See #1988

[Daira Hopwood <david-sarah@…>]

In a493ee0bb641175ecf918e28fce4d25df15994b6/trunk:

iputil.py: add tests for recent changes. refs #1381, #1988, #982, #1064, #1536, #1935, #898, #1707, #1918

Signed-off-by: Daira Hopwood <david-sarah@…>

[daira]

iputil on trunk no longer distinguishes between Unix variants, which fixes this bug.