AUTH-2588 add DoH to service mode

cmd/cloudflared/app_resolver_service.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"github.com/cloudflare/cloudflared/cmd/cloudflared/config"
+	"github.com/cloudflare/cloudflared/tunneldns"
+	"github.com/sirupsen/logrus"
+)
+
+// ResolverServiceType is used to identify what kind of overwatch service this is
+const ResolverServiceType = "resolver"
+
+// ResolverService is used to wrap the tunneldns package's DNS over HTTP
+// into a service model for the overwatch package.
+// it also holds a reference to the config object that represents its state
+type ResolverService struct {
+	resolver config.DNSResolver
+	shutdown chan struct{}
+	logger   *logrus.Logger
+}
+
+// NewResolverService creates a new resolver service
+func NewResolverService(r config.DNSResolver, logger *logrus.Logger) *ResolverService {
+	return &ResolverService{resolver: r,
+		shutdown: make(chan struct{}),
+		logger:   logger,
+	}
+}
+
+// Name is used to figure out this service is related to the others (normally the addr it binds to)
+// this is just "resolver" since there can only be one DNS resolver running
+func (s *ResolverService) Name() string {
+	return ResolverServiceType
+}
+
+// Type is used to identify what kind of overwatch service this is
+func (s *ResolverService) Type() string {
+	return ResolverServiceType
+}
+
+// Hash is used to figure out if this forwarder is the unchanged or not from the config file updates
+func (s *ResolverService) Hash() string {
+	return s.resolver.Hash()
+}
+
+// Shutdown stops the tunneldns listener
+func (s *ResolverService) Shutdown() {
+	s.shutdown <- struct{}{}
+}
+
+// Run is the run loop that is started by the overwatch service
+func (s *ResolverService) Run() error {
+	// create a listener
+	l, err := tunneldns.CreateListener(s.resolver.AddressOrDefault(), s.resolver.PortOrDefault(),
+		s.resolver.UpstreamsOrDefault(), s.resolver.BootstrapsOrDefault())
+	if err != nil {
+		return err
+	}
+
+	// start the listener.
+	readySignal := make(chan struct{})
+	err = l.Start(readySignal)
+	if err != nil {
+		l.Stop()
+		return err
+	}
+	<-readySignal
+	s.logger.Infof("start resolver on: %s:%d", s.resolver.AddressOrDefault(), s.resolver.PortOrDefault())
+
+	// wait for shutdown signal
+	<-s.shutdown
+	s.logger.Infof("shutdown on: %s:%d", s.resolver.AddressOrDefault(), s.resolver.PortOrDefault())
+	return l.Stop()
+}