Support dscp-based traffic bypass (such as bittorrent)

[mzz2017]

Background

In cross-machine scenarios, pname matching will become ineffective. At this time, it will become difficult to match traffic such as BitTorrent.

We introduce dscp-based routing matching rules to solve this problem.

Image is from https://www.researchgate.net/figure/DSCP-field-in-the-header-of-IPv6-and-IPv4-packets_fig1_272538162.

Usage & Routing Format

routing {
  // decimal
  dscp(4) -> direct
  // hex
  dscp(0x4) -> direct
}

Set dscp for the specific process on Windows

This section assumes you want to set a dscp to qbittorrent.exe.

First, launch the terminal (powershell):

1. Press win+x.
2. Select Terminal (Admin) or PowerShell (Admin).

Second, set up a new QoS policy for qbittorrent.exe:

New-NetQosPolicy -Name "qb" -AppPathNameMatchCondition "qbittorrent.exe" -PolicyStore ActiveStore -DSCPAction 4

In this example, dscp value 4 will be set.

Then, retrive the result to verify the success:

Get-NetQosPolicy -PolicyStore "ActiveStore"

If you want to delete it, use:

Remove-NetQosPolicy -Name "qb" -PolicyStore "ActiveStore"

Set dscp in qBittorrent application

Setting DSCP is supported natively, but it has some issues and will miss some traffic, especially TCP traffic. This is because libtorrent set dscp after the application protocol handshake while proxy software split traffic at the very beginning the TCP handshake. At that moment, dscp is not set by qBittorrent yet.

You can find peer-tos or peer-dscp in the qBittorrent application advanced setting. You may need to pay attention that dscp is the value of tos divided by 4.