Add simple way of referring to system on the other side of the network

[fhunleth]

Currently, it's not easy to refer to the other side of the network. With nerves_init_gadget, you could use peer.usb0.lan, but that doesn't exist with nerves_pack and vintage_net_direct.

Here's a workaround:

 def peer_address(ifname) do
    VintageNet.get(["interface", ifname, "addresses"])
    |> hd()
    |> Map.get(:address)
    |> add_one()
  end

  defp add_one({a, b, c, d}), do: {a, b, c, d + 1}

Example use:

iex> ifconfig
lo: flags=[:up, :loopback, :running]
    inet 127.0.0.1  netmask 255.0.0.0
    inet ::1  netmask ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
    hwaddr 00:00:00:00:00:00

usb0: flags=[:up, :broadcast, :running, :multicast]
    inet 172.31.6.93  netmask 255.255.255.252  broadcast 172.31.6.93
    inet fe80::38a3:1dff:fe15:ec81  netmask ffff:ffff:ffff:ffff::
    hwaddr 3a:a3:1d:15:ec:81

iex> TestModule.peer_address("usb0")
{172, 31, 6, 94}

It would be useful to add a DNS name like nerves_init_gadget did and to make the address of the other side of the connection visible via a VintageNet property.

[boydm]

Thank you Frank! That is just what I was looking for.