clementnuss

#!/bin/bash
# Auther Clément Nussbaumer <clement@astutus.org>, Aug 2020
#
# CNI interception script: permits to do live debugging of CNI calls.
# Usage: rename the real cni binary file with by prepending the orginal binary name with real_
# E.g. for multus, real_multus. Now put this script in place the binary: 
# Concretely, name it `multus` if you want to intercept multus calls.

cni=$(echo $0 | awk '{split($0,r,"/"); print r[length(r)]}')
echo 'intercepted '$cni' cni with command: ' $CNI_COMMAND ' and caller: ' $(ps -o comm= $PPID) | logger -t cni 

clementnuss

# given $netns the the network namespace id. e.g. netns=46165437

# 1st: we create a virtual interface
ip link add name toto_if type ipip local 10.20.30.46 remote 10.30.30.1

# 2nd, we put this interface in the network namespace of our pod
ip link set dev toto_if netns $netns

# 3rd, we can for example change the ip address or routing parameters:
nsenter -t $netns --network ip addr add 1.2.3.4/30 dev toto_if