Refactor tls and wire up grpc, grpc gateway/api

This commit moves the TLS configuration into a seperate function.

It also wires up the gRPC interface and prepares handing the API
endpoints to the grpc gateway.

app.go

@@ -1,8 +1,11 @@
 package headscale
 
 import (
+	"context"
+	"crypto/tls"
 	"errors"
 	"fmt"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -11,12 +14,16 @@ import (
 	"sync"
 	"time"
 
-	"github.com/rs/zerolog/log"
-
 	"github.com/gin-gonic/gin"
+	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
+	apiV1 "github.com/juanfont/headscale/gen/go/v1"
+	"github.com/rs/zerolog/log"
+	"github.com/soheilhy/cmux"
 	ginprometheus "github.com/zsais/go-gin-prometheus"
 	"golang.org/x/crypto/acme"
 	"golang.org/x/crypto/acme/autocert"
+	"golang.org/x/sync/errgroup"
+	"google.golang.org/grpc"
 	"gorm.io/gorm"
 	"inet.af/netaddr"
 	"tailscale.com/tailcfg"
@@ -24,7 +31,7 @@ import (
 	"tailscale.com/types/wgkey"
 )
 
-// Config contains the initial Headscale configuration
+// Config contains the initial Headscale configuration.
 type Config struct {
 	ServerURL                      string
 	Addr                           string
@@ -64,7 +71,7 @@ type DERPConfig struct {
 	UpdateFrequency time.Duration
 }
 
-// Headscale represents the base app of the service
+// Headscale represents the base app of the service.
 type Headscale struct {
 	cfg        Config
 	db         *gorm.DB
@@ -82,12 +89,13 @@ type Headscale struct {
 	lastStateChange sync.Map
 }
 
-// NewHeadscale returns the Headscale app
+// NewHeadscale returns the Headscale app.
 func NewHeadscale(cfg Config) (*Headscale, error) {
 	content, err := os.ReadFile(cfg.PrivateKeyPath)
 	if err != nil {
 		return nil, err
 	}
+
 	privKey, err := wgkey.ParsePrivate(string(content))
 	if err != nil {
 		return nil, err
@@ -136,14 +144,14 @@ func NewHeadscale(cfg Config) (*Headscale, error) {
 	return &h, nil
 }
 
-// Redirect to our TLS url
+// Redirect to our TLS url.
 func (h *Headscale) redirect(w http.ResponseWriter, req *http.Request) {
 	target := h.cfg.ServerURL + req.URL.RequestURI()
 	http.Redirect(w, req, target, http.StatusFound)
 }
 
 // expireEphemeralNodes deletes ephemeral machine records that have not been
-// seen for longer than h.cfg.EphemeralNodeInactivityTimeout
+// seen for longer than h.cfg.EphemeralNodeInactivityTimeout.
 func (h *Headscale) expireEphemeralNodes(milliSeconds int64) {
 	ticker := time.NewTicker(time.Duration(milliSeconds) * time.Millisecond)
 	for range ticker.C {
@@ -155,18 +163,23 @@ func (h *Headscale) expireEphemeralNodesWorker() {
 	namespaces, err := h.ListNamespaces()
 	if err != nil {
 		log.Error().Err(err).Msg("Error listing namespaces")
+
 		return
 	}
+
 	for _, ns := range *namespaces {
 		machines, err := h.ListMachinesInNamespace(ns.Name)
 		if err != nil {
 			log.Error().Err(err).Str("namespace", ns.Name).Msg("Error listing machines in namespace")
+
 			return
 		}
+
 		for _, m := range *machines {
 			if m.AuthKey != nil && m.LastSeen != nil && m.AuthKey.Ephemeral &&
 				time.Now().After(m.LastSeen.Add(h.cfg.EphemeralNodeInactivityTimeout)) {
 				log.Info().Str("machine", m.Name).Msg("Ephemeral client removed from database")
+
 				err = h.db.Unscoped().Delete(m).Error
 				if err != nil {
 					log.Error().
@@ -176,12 +189,13 @@ func (h *Headscale) expireEphemeralNodesWorker() {
 				}
 			}
 		}
+
 		h.setLastStateChangeToNow(ns.Name)
 	}
 }
 
 // WatchForKVUpdates checks the KV DB table for requests to perform tailnet upgrades
-// This is a way to communitate the CLI with the headscale server
+// This is a way to communitate the CLI with the headscale server.
 func (h *Headscale) watchForKVUpdates(milliSeconds int64) {
 	ticker := time.NewTicker(time.Duration(milliSeconds) * time.Millisecond)
 	for range ticker.C {
@@ -194,24 +208,60 @@ func (h *Headscale) watchForKVUpdatesWorker() {
 	// more functions will come here in the future
 }
 
-// Serve launches a GIN server with the Headscale API
+// Serve launches a GIN server with the Headscale API.
 func (h *Headscale) Serve() error {
+	var err error
+
+	ctx := context.Background()
+	ctx, cancel := context.WithCancel(ctx)
+
+	defer cancel()
+
+	l, err := net.Listen("tcp", h.cfg.Addr)
+	if err != nil {
+		panic(err)
+	}
+
+	// Create the cmux object that will multiplex 2 protocols on the same port.
+	// The two following listeners will be served on the same port below gracefully.
+	m := cmux.New(l)
+	// Match gRPC requests here
+	grpcListener := m.MatchWithWriters(cmux.HTTP2MatchHeaderFieldSendSettings("content-type", "application/grpc"))
+	// Otherwise match regular http requests.
+	httpListener := m.Match(cmux.Any())
+
+	// Now create the grpc server with those options.
+	grpcServer := grpc.NewServer()
+
+	// TODO(kradalby): register the new server when we have authentication ready
+	// apiV1.RegisterHeadscaleServiceServer(grpcServer, newHeadscaleV1APIServer(h))
+
+	grpcGatewayMux := runtime.NewServeMux()
+
+	opts := []grpc.DialOption{grpc.WithInsecure()}
+
+	err = apiV1.RegisterHeadscaleServiceHandlerFromEndpoint(ctx, grpcGatewayMux, h.cfg.Addr, opts)
+	if err != nil {
+		return err
+	}
+
 	r := gin.Default()
 
 	p := ginprometheus.NewPrometheus("gin")
 	p.Use(r)
 
-	r.GET("/health", func(c *gin.Context) { c.JSON(200, gin.H{"healthy": "ok"}) })
+	r.GET("/health", func(c *gin.Context) { c.JSON(http.StatusOK, gin.H{"healthy": "ok"}) })
 	r.GET("/key", h.KeyHandler)
 	r.GET("/register", h.RegisterWebAPI)
 	r.POST("/machine/:id/map", h.PollNetMapHandler)
 	r.POST("/machine/:id", h.RegistrationHandler)
 	r.GET("/apple", h.AppleMobileConfig)
 	r.GET("/apple/:platform", h.ApplePlatformConfig)
-	var err error
 
-	go h.watchForKVUpdates(5000)
-	go h.expireEphemeralNodes(5000)
+	r.Any("/api/v1/*any", gin.WrapF(grpcGatewayMux.ServeHTTP))
+	r.StaticFile("/swagger/swagger.json", "gen/openapiv2/v1/headscale.swagger.json")
+
+	updateMillisecondsWait := int64(5000)
 
 	// Fetch an initial DERP Map before we start serving
 	h.DERPMap = GetDERPMap(h.cfg.DERP)
@@ -222,7 +272,11 @@ func (h *Headscale) Serve() error {
 		go h.scheduledDERPMapUpdateWorker(derpMapCancelChannel)
 	}
 
-	s := &http.Server{
+	// I HATE THIS
+	go h.watchForKVUpdates(updateMillisecondsWait)
+	go h.expireEphemeralNodes(updateMillisecondsWait)
+
+	httpServer := &http.Server{
 		Addr:        h.cfg.Addr,
 		Handler:     r,
 		ReadTimeout: 30 * time.Second,
@@ -233,6 +287,29 @@ func (h *Headscale) Serve() error {
 		WriteTimeout: 0,
 	}
 
+	tlsConfig, err := h.getTLSSettings()
+	if err != nil {
+		log.Error().Err(err).Msg("Failed to set up TLS configuration")
+
+		return err
+	}
+
+	if tlsConfig != nil {
+		httpServer.TLSConfig = tlsConfig
+	}
+
+	g := new(errgroup.Group)
+
+	g.Go(func() error { return grpcServer.Serve(grpcListener) })
+	g.Go(func() error { return httpServer.Serve(httpListener) })
+	g.Go(func() error { return m.Serve() })
+
+	log.Info().Msgf("listening and serving (multiplexed HTTP and gRPC) on: %s", h.cfg.Addr)
+
+	return g.Wait()
+}
+
+func (h *Headscale) getTLSSettings() (*tls.Config, error) {
 	if h.cfg.TLSLetsEncryptHostname != "" {
 		if !strings.HasPrefix(h.cfg.ServerURL, "https://") {
 			log.Warn().Msg("Listening with TLS but ServerURL does not start with https://")
@@ -248,13 +325,11 @@ func (h *Headscale) Serve() error {
 			Email: h.cfg.ACMEEmail,
 		}
 
-		s.TLSConfig = m.TLSConfig()
-
 		if h.cfg.TLSLetsEncryptChallengeType == "TLS-ALPN-01" {
 			// Configuration via autocert with TLS-ALPN-01 (https://tools.ietf.org/html/rfc8737)
 			// The RFC requires that the validation is done on port 443; in other words, headscale
 			// must be reachable on port 443.
-			err = s.ListenAndServeTLS("", "")
+			return m.TLSConfig(), nil
 		} else if h.cfg.TLSLetsEncryptChallengeType == "HTTP-01" {
 			// Configuration via autocert with HTTP-01. This requires listening on
 			// port 80 for the certificate validation in addition to the headscale
@@ -264,22 +339,30 @@ func (h *Headscale) Serve() error {
 					Err(http.ListenAndServe(h.cfg.TLSLetsEncryptListen, m.HTTPHandler(http.HandlerFunc(h.redirect)))).
 					Msg("failed to set up a HTTP server")
 			}()
-			err = s.ListenAndServeTLS("", "")
+
+			return m.TLSConfig(), nil
 		} else {
-			return errors.New("unknown value for TLSLetsEncryptChallengeType")
+			return nil, errors.New("unknown value for TLSLetsEncryptChallengeType")
 		}
 	} else if h.cfg.TLSCertPath == "" {
 		if !strings.HasPrefix(h.cfg.ServerURL, "http://") {
 			log.Warn().Msg("Listening without TLS but ServerURL does not start with http://")
 		}
-		err = s.ListenAndServe()
+
+		return nil, nil
 	} else {
 		if !strings.HasPrefix(h.cfg.ServerURL, "https://") {
 			log.Warn().Msg("Listening with TLS but ServerURL does not start with https://")
 		}
-		err = s.ListenAndServeTLS(h.cfg.TLSCertPath, h.cfg.TLSKeyPath)
+		var err error
+		tlsConfig := &tls.Config{}
+		tlsConfig.ClientAuth = tls.RequireAnyClientCert
+		tlsConfig.NextProtos = []string{"http/1.1"}
+		tlsConfig.Certificates = make([]tls.Certificate, 1)
+		tlsConfig.Certificates[0], err = tls.LoadX509KeyPair(h.cfg.TLSCertPath, h.cfg.TLSKeyPath)
+
+		return tlsConfig, err
 	}
-	return err
 }
 
 func (h *Headscale) setLastStateChangeToNow(namespace string) {