#!/bin/sh
# Rouse the host when this machine's network changes.
#
# Installed as a NetworkManager dispatcher script (/etc/NetworkManager/dispatcher.d) and as a
# networkd-dispatcher one. Both hand the interface and the event as arguments; both are ignored
# beyond the event, because *which* interface changed does not matter — what matters is that a
# connection opened over the old route is now pointing at nothing, and that is true whichever
# interface it was.
#
# A machine that moves from wifi to ethernet holds a socket that looks perfectly healthy from
# inside the process: no error, no close, because nothing has tried to send anything. Heartbeats
# find it twenty or thirty seconds later. The machine knew immediately.
set -eu

event="${2:-}"
case "$event" in
  up|dhcp4-change|dhcp6-change|connectivity-change|routes-change)
    # Only events that can change where packets go. `down` is deliberately not one: the link is
    # already gone, reconnecting will fail, and the backoff exists for exactly that.
    systemctl start --no-block nox-mesh-host-roused.service 2>/dev/null || true
    ;;
esac