To understand the Linux network namespaces a bit better, we'll try to spin up an HTTP server using python in one namespace and connect with it using another namespace.
We'll start by creating two namespaces and connecting them using a virtual ethernet (veth). The previous tutorial covers this in a step-by-step process. This tutorial is a part of personal project where we can find a docker-compose file that spins up the environment with a single command docker compose up -d. This will start a docker container named network-companion. We can enter into the container using docker exec -it network-companion bash from the terminal (let's call it terminal 1). There we'll find prepare_env.sh script inside the libs/connect_to_python_server/ directory. The script can be used to generate and connect the namespaces quickly. This essentially automates the process entailed here. Once we run the script, we'll have two namespaces with the following specifications -
| Namespace | veth Interface | Gateway IP |
|---|---|---|
| ns1 | n1e | 10.10.1.1 |
| ns2 | n2e | 10.10.2.1 |
Table 1 - Specifications of Created Network Namespaces
Now, we'll spin up the python server on ns1 namespace and bind the gateway IP with the server using 👉 python -m http.server <PORT> --bind <GATEWAY_IP> in the current terminal (let's call it terminal 1). As the gateway IP for n1e is 10.10.1.1 we'll use the command 👇 to spin up the server
ip netns exec "ns1" python3 -m http.server 9000 --bind 10.10.1.1
Fig.1 - Starting the python server
Now, let's open up another terminal and access the docker env docker run exec -it network-companion bash. Now, connect to the python server using telnet as follows
ip netns exec "ns2" telnet 10.10.1.1 9000
Fig.2 - Making request using telnet
If we can see similar to Fig.2 in our terminal then we're connected to the server.
Now, let's make an HTTP request to the python server by typing the following to the cli -
GET / HTTP/1.0
Host: 10.10.1.1
Fig.3 - Requesting using HTTP protocol
Once we request by pressing the enter key, we can see that the server responds with HTML which essentially lists out the contents in the directory -
Fig.4 - Response on HTTP request
We can also see the logs of the python server on terminal 1 -
Fig.5 - Logs of Python Server (1)
Let's create the telnet connection again and make a request to the python server that does not comply with the HTTP protocol. This will result in an error response with HTML as follows -
Fig.6 - Error response on improper request
We can again check the logs in terminal 1 -
Fig.7 - Logs of Python Server (2)
This marks the end of our experiment! Keep exploring the network namespaces and thanks for reading.
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