constellation/nix/container/vpn/sidecar.sh
2024-07-10 10:55:48 +02:00

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#!/bin/sh
set -u
if [ "$$" -eq "1" ]; then
echo 'This script must run in the root PID namespace, but $$ == 1!' >&2
exit 1
fi
myip() {
ip -j addr show eth0 | jq -r '.[0].addr_info[] | select(.family == "inet") | .local'
}
# Disable source IP verification on our network interface. Otherwise, VPN
# packets will be dropped by Cilium.
reconcile_sip_verification() {
# We want all of the cilium calls in this function to target the same
# process, so that we fail if the agent restarts in between. Thus, we only
# query the pid once per reconciliation.
cilium_agent=$(pidof cilium-agent) || return 0
cilium() {
nsenter -t "${cilium_agent}" -a -r -w cilium "$@"
}
myendpoint=$(cilium endpoint get "ipv4:$(myip)" | jq '.[0].id') || return 0
if [ "$(cilium endpoint config "${myendpoint}" -o json | jq -r .realized.options.SourceIPVerification)" = "Enabled" ]; then
cilium endpoint config "${myendpoint}" SourceIPVerification=Disabled
fi
}
optional_mtu() {
if [ -n "${VPN_MTU}" ]; then
printf "mtu %s" "${VPN_MTU}"
fi
}
# Set up the route from the node network namespace to the VPN pod.
reconcile_route() {
for cidr in ${VPN_PEER_CIDRS}; do
# shellcheck disable=SC2046 # Word splitting is intentional here.
nsenter -t 1 -n ip route replace "${cidr}" via "$(myip)" $(optional_mtu)
done
}
while true; do
reconcile_route
reconcile_sip_verification
sleep 10
done