emissary/internal/agent/controller/mdns/controller.go

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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"
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"github.com/getsentry/sentry-go"
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"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 {
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err = errors.WithStack(err)
logger.Error(ctx, "could not create mdns service", logger.E(err))
sentry.CaptureException(err)
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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 {
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err = errors.WithStack(err)
logger.Error(ctx, "could not add mdns service", logger.E(err))
sentry.CaptureException(err)
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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) {
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err = errors.WithStack(err)
logger.Error(ctx, "could not respond to mdns queries", logger.E(err))
sentry.CaptureException(err)
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}
}()
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{}