feat: add mdns controller

internal/agent/controller/mdns/controller.go

@@ -0,0 +1,181 @@
+package mdns
+
+import (
+	"context"
+	"net"
+	"sync"
+
+	"forge.cadoles.com/Cadoles/emissary/internal/agent"
+	mdns "forge.cadoles.com/Cadoles/emissary/internal/agent/controller/mdns/spec"
+	"github.com/brutella/dnssd"
+	"github.com/mitchellh/hashstructure/v2"
+	"github.com/pkg/errors"
+	"gitlab.com/wpetit/goweb/logger"
+)
+
+const (
+	DefaultDomain = "local"
+)
+
+type Controller struct {
+	serviceDefHash uint64
+	cancel         context.CancelFunc
+	responder      dnssd.Responder
+	mutex          sync.RWMutex
+}
+
+// Name implements node.Controller.
+func (c *Controller) Name() string {
+	return "mdns-controller"
+}
+
+// Reconcile implements node.Controller.
+func (c *Controller) Reconcile(ctx context.Context, state *agent.State) error {
+	mdnsSpec := mdns.NewSpec()
+
+	if err := state.GetSpec(mdns.Name, mdnsSpec); err != nil {
+		if errors.Is(err, agent.ErrSpecNotFound) {
+			logger.Info(ctx, "could not find mdns spec")
+
+			c.stopResponder(ctx)
+
+			return nil
+		}
+
+		return errors.WithStack(err)
+	}
+
+	logger.Info(ctx, "retrieved spec", logger.F("spec", mdnsSpec.SpecName()), logger.F("revision", mdnsSpec.SpecRevision()))
+
+	if err := c.updateResponder(ctx, mdnsSpec); err != nil {
+		return errors.Wrap(err, "could not update responder")
+	}
+
+	return nil
+}
+
+func (c *Controller) stopResponder(ctx context.Context) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	if c.responder == nil {
+		return
+	}
+
+	c.cancel()
+	c.responder = nil
+	c.cancel = nil
+}
+
+func (c *Controller) updateResponder(ctx context.Context, spec *mdns.Spec) error {
+	serviceDef := struct {
+		Services map[string]mdns.Service
+	}{
+		Services: spec.Services,
+	}
+
+	newServerDefHash, err := hashstructure.Hash(serviceDef, hashstructure.FormatV2, nil)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	c.mutex.RLock()
+	if newServerDefHash == c.serviceDefHash && c.responder != nil {
+		c.mutex.RUnlock()
+		return nil
+	}
+	c.mutex.RUnlock()
+
+	c.stopResponder(ctx)
+
+	defaultIfaces, err := c.getDefaultIfaces()
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	services := make([]dnssd.Service, 0, len(spec.Services))
+
+	for name, service := range spec.Services {
+		domain := service.Domain
+		if domain == "" {
+			domain = DefaultDomain
+		}
+
+		ifaces := service.Ifaces
+		if len(ifaces) == 0 {
+			ifaces = defaultIfaces
+		}
+
+		config := dnssd.Config{
+			Name:   name,
+			Type:   service.Type,
+			Domain: domain,
+			Host:   service.Host,
+			Ifaces: ifaces,
+			Port:   service.Port,
+		}
+
+		service, err := dnssd.NewService(config)
+		if err != nil {
+			logger.Error(ctx, "could not create mdns service", logger.E(errors.WithStack(err)))
+
+			continue
+		}
+
+		services = append(services, service)
+	}
+
+	responder, err := dnssd.NewResponder()
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	for _, service := range services {
+		if _, err := responder.Add(service); err != nil {
+			logger.Error(ctx, "could not add mdns service", logger.E(errors.WithStack(err)))
+
+			continue
+		}
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	c.responder = responder
+	c.cancel = cancel
+	c.serviceDefHash = newServerDefHash
+
+	go func() {
+		defer c.stopResponder(ctx)
+
+		if err := responder.Respond(ctx); err != nil && !errors.Is(err, context.Canceled) {
+			logger.Error(ctx, "could not respond to mdns queries", logger.E(errors.WithStack(err)))
+		}
+	}()
+
+	return nil
+}
+
+func (c *Controller) getDefaultIfaces() ([]string, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	ifaceNames := make([]string, len(ifaces))
+
+	for idx, ifa := range ifaces {
+		ifaceNames[idx] = ifa.Name
+	}
+
+	return ifaceNames, nil
+}
+
+func NewController() *Controller {
+	return &Controller{
+		cancel:         nil,
+		responder:      nil,
+		serviceDefHash: 0,
+	}
+}
+
+var _ agent.Controller = &Controller{}

internal/agent/controller/mdns/spec/init.go

@@ -0,0 +1,17 @@
+package spec
+
+import (
+	_ "embed"
+
+	"forge.cadoles.com/Cadoles/emissary/internal/spec"
+	"github.com/pkg/errors"
+)
+
+//go:embed schema.json
+var schema []byte
+
+func init() {
+	if err := spec.Register(Name, schema); err != nil {
+		panic(errors.WithStack(err))
+	}
+}

internal/agent/controller/mdns/spec/schema.json

@@ -0,0 +1,47 @@
+{
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$id": "https://mdns.edge.emissary.cadoles.com/spec.json",
+    "title": "MDNSSpec",
+    "description": "Emissary 'MDNS' specification",
+    "type": "object",
+    "properties": {
+        "services": {
+            "type": "object",
+            "patternProperties": {
+                ".*": {
+                    "type": "object",
+                    "properties": {
+                        "type": {
+                            "type": "string"
+                        },
+                        "domain": {
+                            "type": "string"
+                        },
+                        "host": {
+                            "type": "string"
+                        },
+                        "ifaces": {
+                            "type": "array",
+                            "items": {
+                                "type": "string"
+                            }
+                        },
+                        "port": {
+                            "type": "number"
+                        }
+                    },
+                    "required": [
+                        "type",
+                        "host",
+                        "port"
+                    ],
+                    "additionalProperties": false
+                }
+            }
+        }
+    },
+    "required": [
+        "services"
+    ],
+    "additionalProperties": false
+}

internal/agent/controller/mdns/spec/spec.go

@@ -0,0 +1,42 @@
+package spec
+
+import (
+	"forge.cadoles.com/Cadoles/emissary/internal/spec"
+)
+
+const Name spec.Name = "mdns.emissary.cadoles.com"
+
+type Spec struct {
+	Revision int                `json:"revision"`
+	Services map[string]Service `json:"services"`
+}
+
+type Service struct {
+	Type   string   `json:"type"`
+	Domain string   `json:"domain"`
+	Host   string   `json:"host"`
+	Ifaces []string `json:"ifaces"`
+	Port   int      `json:"port"`
+}
+
+func (s *Spec) SpecName() spec.Name {
+	return Name
+}
+
+func (s *Spec) SpecRevision() int {
+	return s.Revision
+}
+
+func (s *Spec) SpecData() map[string]any {
+	return map[string]any{
+		"services": s.Services,
+	}
+}
+
+func NewSpec() *Spec {
+	return &Spec{
+		Revision: -1,
+	}
+}
+
+var _ spec.Spec = &Spec{}

internal/agent/controller/mdns/spec/testdata/spec-ok.json

@@ -0,0 +1,15 @@
+{
+  "name": "mdns.emissary.cadoles.com",
+  "data": {
+    "services": {
+      "My Website": {
+        "type": "_http._tcp",
+        "domain": "local",
+        "host": "mywebsite",
+        "ifaces": ["lo", "eth0"],
+        "port": 80
+      }
+    }
+  },
+  "revision": 0
+}

internal/agent/controller/mdns/spec/validator_test.go

@@ -0,0 +1,65 @@
+package spec
+
+import (
+	"context"
+	"encoding/json"
+	"io/ioutil"
+	"testing"
+
+	"forge.cadoles.com/Cadoles/emissary/internal/spec"
+	"github.com/pkg/errors"
+)
+
+type validatorTestCase struct {
+	Name       string
+	Source     string
+	ShouldFail bool
+}
+
+var validatorTestCases = []validatorTestCase{
+	{
+		Name:       "SpecOK",
+		Source:     "testdata/spec-ok.json",
+		ShouldFail: false,
+	},
+}
+
+func TestValidator(t *testing.T) {
+	t.Parallel()
+
+	validator := spec.NewValidator()
+	if err := validator.Register(Name, schema); err != nil {
+		t.Fatalf("+%v", errors.WithStack(err))
+	}
+
+	for _, tc := range validatorTestCases {
+		func(tc validatorTestCase) {
+			t.Run(tc.Name, func(t *testing.T) {
+				t.Parallel()
+
+				rawSpec, err := ioutil.ReadFile(tc.Source)
+				if err != nil {
+					t.Fatalf("+%v", errors.WithStack(err))
+				}
+
+				var spec spec.RawSpec
+
+				if err := json.Unmarshal(rawSpec, &spec); err != nil {
+					t.Fatalf("+%v", errors.WithStack(err))
+				}
+
+				ctx := context.Background()
+
+				err = validator.Validate(ctx, &spec)
+
+				if !tc.ShouldFail && err != nil {
+					t.Errorf("+%v", errors.WithStack(err))
+				}
+
+				if tc.ShouldFail && err == nil {
+					t.Error("validation should have failed")
+				}
+			})
+		}(tc)
+	}
+}