Low WireGuard throughput on 3G/4G networks

Operating system

Android

System version

Android 15

Installation type

sing-box for Android Graphical Client

If you are using a graphical client, please provide the version of the client.

1.12.5

Version

Description

When using outbound WireGuard over a mobile data connection, the speed is limited to about 500 Kbps. With other protocols (e.g., VLESS), the throughput is normal and can reach up to 50 Mbps.

If I use the same phone as a Wi-Fi hotspot (so the internet channel is still 3G/4G), and run sing-box with the same configuration on another device connected via Wi-Fi, WireGuard works at normal speed.

This issue only occurs when sing-box sends its traffic directly over the mobile data connection.

The problem has been observed on versions 1.11.15 and 1.12.5.

Reproduction

...
  "endpoints": [
    {
      "type": "wireguard",
      "tag": "wg",
      "address": "10.0.3.33/24",
      "private_key": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=",
      "peers": [
        {
          "address": "xxx.xxx.xxx.xxx",
          "port": 51820,
          "public_key": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=",
          "allowed_ips": "0.0.0.0/0"
        }
      ]
    }
  ],
...

Logs

Supporter

• I am a sponsor

Integrity requirements

• I confirm that I have read the documentation, understand the meaning of all the configuration items I wrote, and did not pile up seemingly useful options or default values.
• I confirm that I have provided the server and client configuration files and process that can be reproduced locally, instead of a complicated client configuration file that has been stripped of sensitive data.
• I confirm that I have provided the simplest configuration that can be used to reproduce the error I reported, instead of depending on remote servers, TUN, graphical interface clients, or other closed-source software.
• I confirm that I have provided the complete configuration files and logs, rather than just providing parts I think are useful out of confidence in my own intelligence.

Start with the sing-box Android client version 1.12.5 and the minimal WireGuard endpoint configuration in this report. Reproduce on Android 15 using direct 3G/4G, then compare it with the same configuration through a Wi-Fi hotspot and with VLESS; collect the missing logs and identify what causes the throughput difference. Done means the cause is confirmed and WireGuard throughput is restored or the limitation is documented.