ipn/localapi: introduce get/set config for serve (#6243)

Updates tailscale/corp#7515

Signed-off-by: Shayne Sweeney <shayne@tailscale.com>

client/tailscale/localclient.go

@@ -859,6 +859,33 @@ type signRequest struct {
 	return nil
 }
 
+// SetServeConfig sets or replaces the serving settings.
+// If config is nil, settings are cleared and serving is disabled.
+func (lc *LocalClient) SetServeConfig(ctx context.Context, config *ipn.ServeConfig) error {
+	b, err := json.Marshal(&config)
+	if err != nil {
+		return fmt.Errorf("encoding config: %w", err)
+	}
+	_, err = lc.send(ctx, "POST", "/localapi/v0/serve-config", 200, bytes.NewReader(b))
+	if err != nil {
+		return fmt.Errorf("sending serve config: %w", err)
+	}
+	return nil
+}
+
+// GetServeConfig return the current serve config.
+func (lc *LocalClient) GetServeConfig(ctx context.Context) (*ipn.ServeConfig, error) {
+	body, err := lc.send(ctx, "GET", "/localapi/v0/serve-config", 200, nil)
+	if err != nil {
+		return nil, fmt.Errorf("getting serve config: %w", err)
+	}
+	sc := new(ipn.ServeConfig)
+	if err := json.Unmarshal(body, sc); err != nil {
+		return nil, err
+	}
+	return sc, nil
+}
+
 // tailscaledConnectHint gives a little thing about why tailscaled (or
 // platform equivalent) is not answering localapi connections.
 //

ipn/ipn_clone.go

@@ -65,7 +65,7 @@ func (src *ServeConfig) Clone() *ServeConfig {
 	dst := new(ServeConfig)
 	*dst = *src
 	if dst.TCP != nil {
-		dst.TCP = map[int]*TCPPortHandler{}
+		dst.TCP = map[uint16]*TCPPortHandler{}
 		for k, v := range src.TCP {
 			dst.TCP[k] = v.Clone()
 		}
@@ -87,7 +87,7 @@ func (src *ServeConfig) Clone() *ServeConfig {
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.
 var _ServeConfigCloneNeedsRegeneration = ServeConfig(struct {
-	TCP          map[int]*TCPPortHandler
+	TCP          map[uint16]*TCPPortHandler
 	Web          map[HostPort]*WebServerConfig
 	AllowIngress map[HostPort]bool
 }{})

ipn/ipn_view.go

@@ -164,7 +164,7 @@ func (v *ServeConfigView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v ServeConfigView) TCP() views.MapFn[int, *TCPPortHandler, TCPPortHandlerView] {
+func (v ServeConfigView) TCP() views.MapFn[uint16, *TCPPortHandler, TCPPortHandlerView] {
 	return views.MapFnOf(v.ж.TCP, func(t *TCPPortHandler) TCPPortHandlerView {
 		return t.View()
 	})
@@ -182,7 +182,7 @@ func (v ServeConfigView) AllowIngress() views.Map[HostPort, bool] {
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.
 var _ServeConfigViewNeedsRegeneration = ServeConfig(struct {
-	TCP          map[int]*TCPPortHandler
+	TCP          map[uint16]*TCPPortHandler
 	Web          map[HostPort]*WebServerConfig
 	AllowIngress map[HostPort]bool
 }{})

ipn/ipnlocal/local.go

@@ -11,7 +11,6 @@
 	"errors"
 	"fmt"
 	"io"
-	"math"
 	"net"
 	"net/http"
 	"net/netip"
@@ -3522,8 +3521,8 @@ func (b *LocalBackend) setTCPPortsInterceptedFromNetmapAndPrefsLocked() {
 				}
 			}
 			if b.serveConfig.Valid() {
-				b.serveConfig.TCP().Range(func(port int, _ ipn.TCPPortHandlerView) bool {
-					if port > 0 && port <= math.MaxUint16 {
+				b.serveConfig.TCP().Range(func(port uint16, _ ipn.TCPPortHandlerView) bool {
+					if port > 0 {
 						handlePorts = append(handlePorts, uint16(port))
 					}
 					return true
@@ -3534,6 +3533,46 @@ func (b *LocalBackend) setTCPPortsInterceptedFromNetmapAndPrefsLocked() {
 	b.setTCPPortsIntercepted(handlePorts)
 }
 
+// SetServeConfig establishes or replaces the current serve config.
+func (b *LocalBackend) SetServeConfig(config *ipn.ServeConfig) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	nm := b.netMap
+	if nm == nil {
+		return errors.New("netMap is nil")
+	}
+	if nm.SelfNode == nil {
+		return errors.New("netMap SelfNode is nil")
+	}
+	profileID := fmt.Sprintf("node-%s", nm.SelfNode.StableID) // TODO(maisem,bradfitz): something else?
+	confKey := ipn.ServeConfigKey(profileID)
+
+	var bs []byte
+	if config != nil {
+		j, err := json.Marshal(config)
+		if err != nil {
+			return fmt.Errorf("encoding serve config: %w", err)
+		}
+		bs = j
+	}
+	if err := b.store.WriteState(confKey, bs); err != nil {
+		return fmt.Errorf("writing ServeConfig to StateStore: %w", err)
+	}
+
+	b.setTCPPortsInterceptedFromNetmapAndPrefsLocked()
+
+	return nil
+}
+
+// ServeConfig provides a view of the current serve mappings.
+// If serving is not configured, the returned view is not Valid.
+func (b *LocalBackend) ServeConfig() ipn.ServeConfigView {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.serveConfig
+}
+
 // operatorUserName returns the current pref's OperatorUser's name, or the
 // empty string if none.
 func (b *LocalBackend) operatorUserName() string {

ipn/ipnlocal/serve.go

@@ -82,7 +82,7 @@ func (b *LocalBackend) HandleInterceptedTCPConn(dport uint16, srcAddr netip.Addr
 		return
 	}
 
-	tcph, ok := sc.TCP().GetOk(int(dport))
+	tcph, ok := sc.TCP().GetOk(dport)
 	if !ok {
 		b.logf("[unexpected] localbackend: got TCP conn without TCP config for port %v; from %v", dport, srcAddr)
 		sendRST()

ipn/localapi/localapi.go

@@ -72,6 +72,7 @@
 	"ping":                    (*Handler).servePing,
 	"prefs":                   (*Handler).servePrefs,
 	"pprof":                   (*Handler).servePprof,
+	"serve-config":            (*Handler).serveServeConfig,
 	"set-dns":                 (*Handler).serveSetDNS,
 	"set-expiry-sooner":       (*Handler).serveSetExpirySooner,
 	"status":                  (*Handler).serveStatus,
@@ -455,6 +456,41 @@ func (h *Handler) servePprof(w http.ResponseWriter, r *http.Request) {
 	servePprofFunc(w, r)
 }
 
+func (h *Handler) serveServeConfig(w http.ResponseWriter, r *http.Request) {
+	if !h.PermitWrite {
+		http.Error(w, "serve config denied", http.StatusForbidden)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+
+	switch r.Method {
+	case "GET":
+		config := h.b.ServeConfig()
+		json.NewEncoder(w).Encode(config)
+	case "POST":
+		configIn := new(ipn.ServeConfig)
+		if err := json.NewDecoder(r.Body).Decode(configIn); err != nil {
+			json.NewEncoder(w).Encode(struct {
+				Error error
+			}{
+				Error: fmt.Errorf("decoding config: %w", err),
+			})
+			return
+		}
+		err := h.b.SetServeConfig(configIn)
+		if err != nil {
+			json.NewEncoder(w).Encode(struct {
+				Error error
+			}{
+				Error: fmt.Errorf("updating config: %w", err),
+			})
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	}
+}
+
 func (h *Handler) serveCheckIPForwarding(w http.ResponseWriter, r *http.Request) {
 	if !h.PermitRead {
 		http.Error(w, "IP forwarding check access denied", http.StatusForbidden)

ipn/store.go

@@ -76,7 +76,7 @@ func ServeConfigKey(profileID string) StateKey {
 type ServeConfig struct {
 	// TCP are the list of TCP port numbers that tailscaled should handle for
 	// the Tailscale IP addresses. (not subnet routers, etc)
-	TCP map[int]*TCPPortHandler `json:",omitempty"`
+	TCP map[uint16]*TCPPortHandler `json:",omitempty"`
 
 	// Web maps from "$SNI_NAME:$PORT" to a set of HTTP handlers
 	// keyed by mount point ("/", "/foo", etc)
@@ -84,7 +84,7 @@ type ServeConfig struct {
 
 	// AllowIngress is the set of SNI:port values for which ingress
 	// traffic is allowed, from trusted ingress peers.
-	AllowIngress map[HostPort]bool
+	AllowIngress map[HostPort]bool `json:",omitempty"`
 }
 
 // HostPort is an SNI name and port number, joined by a colon.