Interface binding to a tun0 adapter ignored when adapter is not in use

[SnakeSnowflake]

I'm running qBittorrent v3.3.10 on Arch Linux 4.9.8-1, Qt 5.7.1, libtorrent 1.1.1.0

Having network interface bound to tun0 (openvpn) through advanced settings, the client will revert to other network interfaces if the VPN was not connected or connection gets dropped.

As with the Windows machine I run it on, I would expect qBittorrent not to use network interfaces other than the one it is bound to, even when the latter goes inactive.

The behavior I see is similar to what is described within the comments of this thread. Similar, less the differing execution log entries and irregardless of the suspension-resume OP mentions. Hence, the behavior is not an exact match and this new thread.

Repro:

1. Set network interface binding to VPN's adapter tun0, restart.
2. Either start the client with VPN off or disconnect from it when the client is running.
3. Observe torrents downloading irregardless of the binding.

Execution log from starting the client with VPN off and interface bound, binding ignored:

2/13/17 8:31 PM - External IP: xxx.xxx.xxx.xxx
2/13/17 8:31 PM - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: UDP/30229
2/13/17 8:31 PM - UPnP/NAT-PMP: Port mapping successful, message: successfully mapped port using UPnP. external port: TCP/30229
2/13/17 8:31 PM - 'archlinux-2017.02.01-dual.iso' resumed. (fast resume)
2/13/17 8:31 PM - 'checkMyTorrentIp.png' resumed. (fast resume)
2/13/17 8:31 PM - qBittorrent is successfully listening on interface 127.0.0.1 port: UDP/30229
2/13/17 8:31 PM - qBittorrent is successfully listening on interface 127.0.0.1 port: TCP/30229
2/13/17 8:31 PM - Options were saved successfully.
2/13/17 8:31 PM - GeoIP database loaded. Type: GeoLite2-Country. Build time: Wed Feb 8 03:48:37 2017.
2/13/17 8:31 PM - UPnP / NAT-PMP support [ON]
2/13/17 8:31 PM - Embedded Tracker [OFF]
2/13/17 8:31 PM - Encryption support [ON]
2/13/17 8:31 PM - Anonymous mode [OFF]
2/13/17 8:31 PM - PeX support [OFF]
2/13/17 8:31 PM - Local Peer Discovery support [OFF]
2/13/17 8:31 PM - DHT support [OFF]
2/13/17 8:31 PM - HTTP User-Agent is 'qBittorrent v3.3.10'
2/13/17 8:31 PM - Peer ID: -qB33A0-
2/13/17 8:31 PM - qBittorrent is trying to listen on interface 127.0.0.1 port: 30229
2/13/17 8:31 PM - The network interface defined is invalid: tun0
2/13/17 8:31 PM - qBittorrent v3.3.10 started

For what it's worth, Ktorrent behaves in the same way for me.

[zeule]

Closing as duplicate of #5272.