Upgrade nameserver to take over the DNS port when in use by another process

nameserver/takeover.go

@@ -0,0 +1,59 @@
+package nameserver
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"time"
+
+	"github.com/Safing/portbase/log"
+	"github.com/Safing/portbase/notifications"
+	"github.com/Safing/portmaster/network/packet"
+	"github.com/Safing/portmaster/process"
+)
+
+func checkForConflictingService(err error) {
+	pid, err := takeover()
+	if err != nil || pid == 0 {
+		log.Info("nameserver: restarting server in 10 seconds")
+		time.Sleep(10 * time.Second)
+		return
+	}
+
+	log.Infof("nameserver: stopped conflicting name service with pid %d", pid)
+
+	// notify user
+	(&notifications.Notification{
+		ID:      "nameserver-stopped-conflicting-service",
+		Message: fmt.Sprintf("Portmaster stopped a conflicting name service (pid %d) to gain required system integration.", pid),
+	}).Init().Save()
+
+	// wait for a short duration for the other service to shut down
+	time.Sleep(100 * time.Millisecond)
+}
+
+func takeover() (int, error) {
+	pid, _, err := process.GetPidByEndpoints(net.IPv4(127, 0, 0, 1), 53, net.IPv4(127, 0, 0, 1), 65535, packet.UDP)
+	if err != nil {
+		// there may be nothing listening on :53
+		log.Tracef("nameserver: expected conflicting name service, but could not find anything listenting on :53")
+		return 0, nil
+	}
+
+	proc, err := os.FindProcess(pid)
+	if err != nil {
+		// huh. gone already? I guess we'll wait then...
+		return 0, err
+	}
+
+	err = proc.Signal(os.Interrupt)
+	if err != nil {
+		err = proc.Kill()
+		if err != nil {
+			log.Errorf("nameserver: failed to stop conflicting service (pid %d): %s", pid, err)
+			return 0, err
+		}
+	}
+
+	return pid, nil
+}