wg-quick: darwin: restore DNS on down

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/wg-quick/darwin.bash b/src/wg-quick/darwin.bash
index 5c25961ccde1b341e8e2ae556a4ccc69e29a133b..ba1e49ba5330375ff187386dc1b7fc1b842d818c 100755 (executable)
--- a/src/wg-quick/darwin.bash
+++ b/src/wg-quick/darwin.bash
@@ -233,30 +233,42 @@ set_endpoint_direct_route() {
        ENDPOINTS=( "${added[@]}" )
 }
 
-set_dns() {
-       # TODO: this should use scutil and be slightly more clever. But for now
-       # we simply overwrite any _manually set_ DNS servers for all network
-       # services. This means we get into trouble if the user doesn't actually
-       # want DNS via DHCP when setting this back to "empty". Because macOS is
-       # so horrible to deal with here, we'll simply wait for irate users to
-       # provide a patch themselves.
-       local service response
+declare -A SERVICE_DNS
+collect_new_service_dns() {
+       # TODO: switch to scutil for all DNS modification
+       local service get_response
+       local -A found_services
        { read -r _; while read -r service; do
                [[ $service == "*"* ]] && service="${service:1}"
+               found_services["$service"]=1
+               [[ -n ${SERVICE_DNS["$service"]} ]] && continue
+               get_response="$(cmd networksetup -getdnsservers "$service")"
+               [[ $get_response == *" "* ]] && get_response="Empty"
+               [[ -n $get_response ]] && SERVICE_DNS["$service"]="$get_response"
+       done; } < <(networksetup -listallnetworkservices)
+
+       for service in "${!SERVICE_DNS[@]}"; do
+               [[ ${found_services["$service"]} == 1 ]] || unset SERVICE_DNS["$service"]
+       done
+}
+
+set_dns() {
+       collect_new_service_dns
+       local service response
+       for service in "${!SERVICE_DNS[@]}"; do
                while read -r response; do
                        [[ $response == *Error* ]] && echo "$response" >&2
                done < <(cmd networksetup -setdnsservers "$service" "${DNS[@]}")
-       done; } < <(networksetup -listallnetworkservices)
+       done
 }
 
 del_dns() {
        local service response
-       { read -r _; while read -r service; do
-               [[ $service == "*"* ]] && service="${service:1}"
+       for service in "${!SERVICE_DNS[@]}"; do
                while read -r response; do
                        [[ $response == *Error* ]] && echo "$response" >&2
-               done < <(cmd networksetup -setdnsservers "$service" Empty)
-       done; } < <(networksetup -listallnetworkservices)
+               done < <(cmd networksetup -setdnsservers "$service" ${SERVICE_DNS["$service"]} || true)
+       done
 }
 
 monitor_daemon() {