NetworkManager Dispatcher: Configure systemd-resolved DNS server with custom port on connection up event

nm-create-resolved-custom-port-dns-dispatcher.sh

# NetworkManager connection config does not like custom ports for DNS servers
# we work around this by using a dispatcher to configure this on up events

# change these to your desired configs
CONNECTION_ID=wg0
DNS_TARGET=10.10.0.1:5300
DNS_SEARCH_DOMAIN=~testing

cat > /etc/NetworkManager/dispatcher.d/99-${CONNECTION_ID}.sh <<EOF
#!/usr/bin/env bash

[[ \${CONNECTION_ID} != "${CONNECTION_ID}" ]] || return 0


if [[ ${NM_DISPATCHER_ACTION} == "up" ]]
then
  systemd-resolve --interface "${CONNECTION_ID}' --set-dns $DNS_TARGET --set-domain "$DNS_SEARCH_DOMAIN"
fi
EOF