Docker Networking With Plugin

Docker handles almost all the stuff. When it is about setting networking, docker works great. It creates a bridge when docker is set up. You can see it with ifconfig, it’s called Docker0 bridge.

Docker provides you network plugins to make your own configurations. Docker has an interface, you can edit this interface to make your own network plugin.

I’ve prepare a simple example to show usage of this interface. This plugin becomes very useful when you need to manage your networking with containers. You can get the example here.
I’ve first implemented all the functions and create my own Driver as MyDriver.
You can make any changes with your implementation.

I do not use docker’s bridge and create my own bridge to make configuration.

Firstly, we check docker existing networks

$ docker network ls
NETWORKID       NAME      DRIVER     SCOPE
670db5asd122    bridge    bridge     local
670db5derfs2    host      host       local
670db5fqwer1    none      null       local

Those are the default networks of Docker. We will create a new network driver and plugin to create new networks.
We create a json file and put it to the /etc/docker/plugins/. This file name is your network driver’s name.
I’ll call it mynetwork.json
file is like this:

{
“Name”: “mynetwork”,
“Addr”: “tcp://127.0.0.1:8010”
}

This driver tells that, it will forward the docker requests to the localhost 8010 port. Now, we need to create a plugin to listen this this port.
You can get the project with

go get https://github.com/tugbadartici/docker-network-plugin

You need a plugin to listen this port.
Create a go file, you can find example here.
File should be like this

You need to run this file, so it will listen all the requests on 8010 port.

It’s time to test it!
Since this plugin uses system bridge, you need to create one.

$addbr br1
# set an ip to this bridge
$ifconfig br1 10.0.1.1
$ifconfig br1 up

Create new network, set subnet as 10.0.1.1. In this way, this containers cannot reach any other device outside of this subnet.

$docker network create -d mynetwork mynet -o bridge=br1 — ip-range=10.0.1.1/24 — subnet=10.0.1.1/24
asdfwert14asd8325c358a8035b6c12345663504c0710addce51be2998ddbf2asdd1

This command will tell your plugin to create a new network.

The plugin checks as if br1 is actually exists, then it creates network.
You can check new network “mynet”

$docker network ls
NETWORKID        NAME      DRIVER     SCOPE
670db5asd122     bridge    bridge     local
670db5derfs2     host      host       local
670db5df123z     mynet     mynetwork  local
670db5fqwer1     none      null       local

In this example I return error, if bridge does not exist. If you do not return error, Docker will create network anyway.

Now, run a simple container and set the new network. Open shell of this container and type ifconfig to check networking.

$ docker run -ti -network=mynet ubuntu:14.04 bash
 # root@63299e8c6c3f# ifconfig
   eth0 Link encap:Ethernet HWaddr 71:22:x2:3z:5d:9c
   inet addr:10.0.1.2

The container takes an IP from our network plugin’s IP range.
If you check bridge interface you’ll see that veth pair is attached to the bridge.

$brctl show
bridge name         bridge id        STP enabled    interfaces
br1                 8000.dec30884df57 no            veth-zXFvHb
docker0             8000.02422b5e9ca3 no

In this stage, mydriver plugin creates a veth pair and sets one of them to the host’s bridge, and other one to the container.
So, we are all set up to communicate with our container!

Test connection from host to container

$ ping 10.0.1.2
PING 10.0.1.2 (10.0.1.2) 56(84) bytes of data.
64 bytes from 10.0.1.2: icmp_seq=1 ttl=64 time=0.068 ms
64 bytes from 10.0.1.2: icmp_seq=2 ttl=64 time=0.056 ms

You can reach to the container from host but another container that created with Docker default networking, cannot reach this container.

This driver plugin creates isolated networks. You might want to create isolated containers.
You can edit my example, or create your own driver from scratch.
Happy Dockering!