3 Testing MPTCP Subflows Using mptcpize

The mptcpize utility can be used to confirm that MPTCP is working and using different subflows between hosts. The mptcpize utility lets existing network-aware programs use MPTCP by loading a special library before executing the program.

Installing mptcpize

On Oracle Linux release 10, mptcpize is provided by the mptcpd package. To install mptcpd, run the following command: 

sudo dnf install mptcpd

Verify installation by running the following command and reviewing the help:

mptcpize --help

Using mptcpize to Test MPTCP

This example shows how to test an HTTP connection between two systems (System A and System B).

On System B, start an HTTP server. Use any available server, for example, using Python:

python3 -m http.server 80

The output is similar to the following:

Serving HTTP on 0.0.0.0 port 80

On System A, use curl to connect to System B using mptcpize. For example: 

mptcpize run curl http://192.0.2.20/

The response is an HTML page containing a directory listing:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Directory listing for /</title>
</head>
<body>
<h2>Directory listing for /</h2>
<hr>
...

Note:

You can use mptcpize with many other network tools, such as wget and iperf3.

Checking Subflow Usage

After running the test connection, you can verify that different subflows are active by running the following command on either host and receiving results similar to those shown:

ss --mptcp

In the following command output, the field mptcp_subflows:2 indicates that two subflows are established: 

State      Recv-Q Send-Q        Local Address:Port       Peer Address:Port
ESTAB      0      0             192.0.2.10:50412         192.0.2.20:80      users:(("curl",pid=20748,fd=3)) mptcp_subflows:2