netnsmgr.sh

#!/bin/bash
# Network Namespace Manager
# Author: Steven Mirabito (steven@stevenmirabito.com)

# Must run as root to manage namespaces
if [ $EUID != 0 ]; then
    sudo "$0" "$@"
    exit $?
fi

# Helper Functions
function show_help {
    echo "Usage: ./netnsmgr <namespace> <interface> <command>"
}

# Move the arguments into variables
namespace="$1"
interface="$2"
shift
shift
command="$@"

# Make sure required arguments were passed
if [ -z "$namespace" ]; then
    echo "Invalid namespace"
    show_help
    exit 1
fi

if [ -z "$interface" ]; then
    echo "Invalid interface"
    show_help
    exit 1
fi

if [ -z "$command" ]; then
    echo "Invalid command"
    show_help
    exit 1
fi

# Create the namespace if it doesn't exist
/sbin/ip netns list | grep $namespace &> /dev/null
if [ $? -ne 0 ]; then
    # Make sure the interface exists
    /sbin/ip link show | grep $interface &> /dev/null
    if [ $? -ne 0 ]; then
        # Invalid interface
        echo "Invalid interface"
        show_help
        exit 1
    fi

    # Create the configuration folder
    mkdir -p /etc/netns/$namespace

    # Create namespace resolv.conf
    echo "nameserver 8.8.8.8" > /etc/netns/$namespace/resolv.conf
    echo "nameserver 8.8.4.4" >> /etc/netns/$namespace/resolv.conf

    # Create the namespace
    ip netns add $namespace

    # Bring up the loopback device
    ip netns exec $namespace ip link set lo up

    # Add the interface to the namespace
    ip link set $interface netns $namespace

    # Bring up the interface
    ip netns exec $namespace ip link set $interface up

    # Run DHCP on the interface
    ip netns exec $namespace dhclient $interface 2>&1
fi

# Run the command in the namespace
ip netns exec $namespace $command