Fix broken DNS on macOS's primary interface. 60% of the time, it works every time.

fix-dns.sh

#!/bin/bash

# Start trace.
set -x

# Get active primary interface.
IFACE=$(route -n get 0.0.0.0 2>/dev/null | awk '/interface: / {print $2}')

# Get networkservice name for interface.
NETSVC=$(networksetup -listnetworkserviceorder | grep "$IFACE" | cut -d ' ' -f3- | sed 's/,.*$//')

# Erase any DNS server entries, restoring entries provided by DHCP.
networksetup -setdnsservers "$NETSVC" empty
networksetup -setsearchdomains "$NETSVC" empty

# Bounce interface.
sleep 1
networksetup -setnetworkserviceenabled "$NETSVC" off
sleep 2
networksetup -setnetworkserviceenabled "$NETSVC" on

# End trace.
set +x