ipn,tailcfg: add VIPService struct and c2n to fetch them from client (#14046)

* ipn,tailcfg: add VIPService struct and c2n to fetch them from client

Updates tailscale/corp#22743, tailscale/corp#22955

Signed-off-by: Naman Sood <mail@nsood.in>

* more review fixes

Signed-off-by: Naman Sood <mail@nsood.in>

* don't mention PeerCapabilityServicesDestination since it's currently unused

Signed-off-by: Naman Sood <mail@nsood.in>

---------

Signed-off-by: Naman Sood <mail@nsood.in>

ipn/ipnlocal/c2n.go

@@ -77,6 +77,9 @@ var c2nHandlers = map[methodAndPath]c2nHandler{
 
 	// Linux netfilter.
 	req("POST /netfilter-kind"): handleC2NSetNetfilterKind,
+
+	// VIP services.
+	req("GET /vip-services"): handleC2NVIPServicesGet,
 }
 
 type c2nHandler func(*LocalBackend, http.ResponseWriter, *http.Request)
@@ -269,6 +272,12 @@ func handleC2NSetNetfilterKind(b *LocalBackend, w http.ResponseWriter, r *http.R
 	w.WriteHeader(http.StatusNoContent)
 }
 
+func handleC2NVIPServicesGet(b *LocalBackend, w http.ResponseWriter, r *http.Request) {
+	b.logf("c2n: GET /vip-services received")
+
+	json.NewEncoder(w).Encode(b.VIPServices())
+}
+
 func handleC2NUpdateGet(b *LocalBackend, w http.ResponseWriter, r *http.Request) {
 	b.logf("c2n: GET /update received")
 

ipn/ipnlocal/local.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"cmp"
 	"context"
+	"crypto/sha256"
 	"encoding/base64"
 	"encoding/json"
 	"errors"
@@ -4888,6 +4889,14 @@ func (b *LocalBackend) applyPrefsToHostinfoLocked(hi *tailcfg.Hostinfo, prefs ip
 	}
 	hi.SSH_HostKeys = sshHostKeys
 
+	services := vipServicesFromPrefs(prefs)
+	if len(services) > 0 {
+		buf, _ := json.Marshal(services)
+		hi.ServicesHash = fmt.Sprintf("%02x", sha256.Sum256(buf))
+	} else {
+		hi.ServicesHash = ""
+	}
+
 	// The Hostinfo.WantIngress field tells control whether this node wants to
 	// be wired up for ingress connections. If harmless if it's accidentally
 	// true; the actual policy is controlled in tailscaled by ServeConfig. But
@@ -7485,3 +7494,42 @@ func maybeUsernameOf(actor ipnauth.Actor) string {
 	}
 	return username
 }
+
+// VIPServices returns the list of tailnet services that this node
+// is serving as a destination for.
+// The returned memory is owned by the caller.
+func (b *LocalBackend) VIPServices() []*tailcfg.VIPService {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return vipServicesFromPrefs(b.pm.CurrentPrefs())
+}
+
+func vipServicesFromPrefs(prefs ipn.PrefsView) []*tailcfg.VIPService {
+	// keyed by service name
+	var services map[string]*tailcfg.VIPService
+
+	// TODO(naman): this envknob will be replaced with service-specific port
+	// information once we start storing that.
+	var allPortsServices []string
+	if env := envknob.String("TS_DEBUG_ALLPORTS_SERVICES"); env != "" {
+		allPortsServices = strings.Split(env, ",")
+	}
+
+	for _, s := range allPortsServices {
+		mak.Set(&services, s, &tailcfg.VIPService{
+			Name:  s,
+			Ports: []tailcfg.ProtoPortRange{{Ports: tailcfg.PortRangeAny}},
+		})
+	}
+
+	for _, s := range prefs.AdvertiseServices().AsSlice() {
+		if services == nil || services[s] == nil {
+			mak.Set(&services, s, &tailcfg.VIPService{
+				Name: s,
+			})
+		}
+		services[s].Active = true
+	}
+
+	return slices.Collect(maps.Values(services))
+}

ipn/ipnlocal/local_test.go

@@ -30,6 +30,7 @@ import (
 	"tailscale.com/control/controlclient"
 	"tailscale.com/drive"
 	"tailscale.com/drive/driveimpl"
+	"tailscale.com/envknob"
 	"tailscale.com/health"
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
@@ -4464,3 +4465,90 @@ func TestConfigFileReload(t *testing.T) {
 		t.Fatalf("got %q; want %q", hn, "bar")
 	}
 }
+
+func TestGetVIPServices(t *testing.T) {
+	tests := []struct {
+		name       string
+		advertised []string
+		mapped     []string
+		want       []*tailcfg.VIPService
+	}{
+		{
+			"advertised-only",
+			[]string{"svc:abc", "svc:def"},
+			[]string{},
+			[]*tailcfg.VIPService{
+				{
+					Name:   "svc:abc",
+					Active: true,
+				},
+				{
+					Name:   "svc:def",
+					Active: true,
+				},
+			},
+		},
+		{
+			"mapped-only",
+			[]string{},
+			[]string{"svc:abc"},
+			[]*tailcfg.VIPService{
+				{
+					Name:  "svc:abc",
+					Ports: []tailcfg.ProtoPortRange{{Ports: tailcfg.PortRangeAny}},
+				},
+			},
+		},
+		{
+			"mapped-and-advertised",
+			[]string{"svc:abc"},
+			[]string{"svc:abc"},
+			[]*tailcfg.VIPService{
+				{
+					Name:   "svc:abc",
+					Active: true,
+					Ports:  []tailcfg.ProtoPortRange{{Ports: tailcfg.PortRangeAny}},
+				},
+			},
+		},
+		{
+			"mapped-and-advertised-separately",
+			[]string{"svc:def"},
+			[]string{"svc:abc"},
+			[]*tailcfg.VIPService{
+				{
+					Name:  "svc:abc",
+					Ports: []tailcfg.ProtoPortRange{{Ports: tailcfg.PortRangeAny}},
+				},
+				{
+					Name:   "svc:def",
+					Active: true,
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			envknob.Setenv("TS_DEBUG_ALLPORTS_SERVICES", strings.Join(tt.mapped, ","))
+			prefs := &ipn.Prefs{
+				AdvertiseServices: tt.advertised,
+			}
+			got := vipServicesFromPrefs(prefs.View())
+			slices.SortFunc(got, func(a, b *tailcfg.VIPService) int {
+				return strings.Compare(a.Name, b.Name)
+			})
+			if !reflect.DeepEqual(tt.want, got) {
+				t.Logf("want:")
+				for _, s := range tt.want {
+					t.Logf("%+v", s)
+				}
+				t.Logf("got:")
+				for _, s := range got {
+					t.Logf("%+v", s)
+				}
+				t.Fail()
+				return
+			}
+		})
+	}
+}