attach-ctn.sh

#!/bin/bash

ctn=${1:-demo}
ip=${2:-2}

ctn_ns_path=$(docker inspect --format="{{ .NetworkSettings.SandboxKey}}" $ctn)
ctn_ns=${ctn_ns_path##*/}

# create veth interfaces
sudo ip link add dev veth1 mtu 1450 type veth peer name veth2 mtu 1450

# attach first peer to the bridge in our overlay namespace
sudo ip link set dev veth1 netns overns
sudo ip netns exec overns ip link set veth1 master br0
sudo ip netns exec overns ip link set veth1 up

# crate symlink to be able to use ip netns commands
sudo ln -sf $ctn_ns_path /var/run/netns/$ctn_ns
sudo ip link set dev veth2 netns $ctn_ns

# move second peer tp container network namespace and configure it
sudo ip netns exec $ctn_ns ip link set dev veth2 name eth0 address 02:42:c0:a8:00:0${ip}
sudo ip netns exec $ctn_ns ip addr add dev eth0 192.168.0.${ip}/24
sudo ip netns exec $ctn_ns ip link set dev eth0 up

# Clean up symlink
sudo rm /var/run/netns/$ctn_ns