Mesh Topology Demo on Linux in Namespaces

mesh-topology-example.sh

#!/bin/bash
#   Mesh Topology with Namespace
#   Graph
NAMESPACE_COUNT=3

###
# ! I recommend to run this script in temporary container.
# docker run -it --rm --privileged ahmetozer/cna
# in container curl https://gist.githubusercontent.com/ahmetozer/d01538327a98ed70cf04e48e89fe8c31/raw/mesh-topology-example.sh -o mesh-topology-example.sh ; chmod +x mesh-topology-example.sh
###

# IANA TEST NET 3  - 203.0.113.0/24 - https://tools.ietf.org/html/rfc5737
IP_BLOCK="203.0.113" 

if [ "$1" == "print" ]; then
    RUN_COMMAND='echo'
else
    RUN_COMMAND='command'
fi

# Create namespaces
echo -e "\n\tCreateting namespaces"
for ((i = 1; i <= $NAMESPACE_COUNT; i++)); do
    $RUN_COMMAND ip netns add node-$i
    $RUN_COMMAND ip netns add node-$i-end
    $RUN_COMMAND ip netns exec node-$i ifconfig lo up
done

set -e
for ((i = 1; i <= $NAMESPACE_COUNT; i++)); do

    echo -e "\n\tFor node-$i"
    $RUN_COMMAND ip netns exec node-$i brctl addbr br0
    $RUN_COMMAND ip netns exec node-$i brctl stp br0 on

    # !  IPv6 Disabled due to endless ndp packet loop on nodes
    $RUN_COMMAND ip netns exec node-$i sysctl -w net.ipv6.icmp.echo_ignore_all=1
    $RUN_COMMAND ip netns exec node-$i sysctl -w net.ipv6.icmp.echo_ignore_all=1
    $RUN_COMMAND ip netns exec node-$i sysctl -w net.ipv6.conf.all.disable_ipv6=1
    $RUN_COMMAND ip netns exec node-$i sysctl -w net.ipv6.conf.default.disable_ipv6=1

    for ((n = (($i + 1)); n <= $NAMESPACE_COUNT; n++)); do
        $RUN_COMMAND ip link add vertex$i-$n netns node-$i type veth peer name vertex$n-$i netns node-$n
        $RUN_COMMAND ip netns exec node-$i ifconfig vertex$i-$n up
        $RUN_COMMAND ip netns exec node-$n ifconfig vertex$n-$i up
    done

    for ((n = 1; n < $i; n++)); do
        $RUN_COMMAND ip netns exec node-$i brctl addif br0 vertex$i-$n
    done

    for ((n = (($i + 1)); n <= $NAMESPACE_COUNT; n++)); do
        $RUN_COMMAND ip netns exec node-$i brctl addif br0 vertex$i-$n
    done

    $RUN_COMMAND ip netns exec node-$i ifconfig br0 $IP_BLOCK.$i up

done