fix(web): install the share-link provider before the panel serves (#6914)

The panel started answering requests before the share-link generator was
registered, so an "all links", client sub-links or Telegram link request that
arrived during start-up got "sub link provider not registered". NewServer now
takes the provider and installs it before anything listens, and the provider
registry is guarded by a lock, since start-up writes it while requests read it.

internal/web/service/inbound_sublink.go

@@ -1,6 +1,8 @@
 package service
 
 import (
+	"sync"
+
 	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
 	"github.com/mhsanaei/3x-ui/v3/internal/util/common"
 )
@@ -11,35 +13,50 @@ type SubLinkProvider interface {
 	LinksForInbounds(host string, inbounds []*model.Inbound) []string
 }
 
-var registeredSubLinkProvider SubLinkProvider
+var (
+	subLinkProviderMu         sync.RWMutex
+	registeredSubLinkProvider SubLinkProvider
+)
 
 func RegisterSubLinkProvider(p SubLinkProvider) {
+	subLinkProviderMu.Lock()
+	defer subLinkProviderMu.Unlock()
 	registeredSubLinkProvider = p
 }
 
+// subLinkProvider guards the registry: startup writes it while link requests read it.
+func subLinkProvider() SubLinkProvider {
+	subLinkProviderMu.RLock()
+	defer subLinkProviderMu.RUnlock()
+	return registeredSubLinkProvider
+}
+
 func (s *InboundService) GetSubLinks(host, subId string) ([]string, error) {
-	if registeredSubLinkProvider == nil {
+	provider := subLinkProvider()
+	if provider == nil {
 		return nil, common.NewError("sub link provider not registered")
 	}
-	return registeredSubLinkProvider.SubLinksForSubId(host, subId)
+	return provider.SubLinksForSubId(host, subId)
 }
 
 func (s *InboundService) GetAllInboundLinks(host string, userId int) ([]string, error) {
-	if registeredSubLinkProvider == nil {
+	provider := subLinkProvider()
+	if provider == nil {
 		return nil, common.NewError("sub link provider not registered")
 	}
 	inbounds, err := s.GetInbounds(userId)
 	if err != nil {
 		return nil, err
 	}
-	return registeredSubLinkProvider.LinksForInbounds(host, inbounds), nil
+	return provider.LinksForInbounds(host, inbounds), nil
 }
 
 func (s *InboundService) GetAllClientLinks(host string, email string) ([]string, error) {
 	if email == "" {
 		return nil, common.NewError("client email is required")
 	}
-	if registeredSubLinkProvider == nil {
+	provider := subLinkProvider()
+	if provider == nil {
 		return nil, common.NewError("sub link provider not registered")
 	}
 	rec, err := s.clientService.GetRecordByEmail(nil, email)
@@ -56,7 +73,7 @@ func (s *InboundService) GetAllClientLinks(host string, email string) ([]string,
 		if getErr != nil {
 			return nil, getErr
 		}
-		links = append(links, registeredSubLinkProvider.LinksForClient(host, inbound, email)...)
+		links = append(links, provider.LinksForClient(host, inbound, email)...)
 	}
 	return links, nil
 }

internal/web/service/sublink_registry_test.go

@@ -0,0 +1,44 @@
+package service
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
+)
+
+type fakeSubLinkProvider struct {
+	links []string
+}
+
+func (f fakeSubLinkProvider) SubLinksForSubId(host, subId string) ([]string, error) {
+	return f.links, nil
+}
+
+func (f fakeSubLinkProvider) LinksForClient(host string, inbound *model.Inbound, email string) []string {
+	return f.links
+}
+
+func (f fakeSubLinkProvider) LinksForInbounds(host string, inbounds []*model.Inbound) []string {
+	return f.links
+}
+
+// Startup writes the provider registry while link requests read it; under -race an
+// unguarded registry fails here.
+func TestSubLinkProviderRegistrationIsRaceFree(t *testing.T) {
+	t.Cleanup(func() { RegisterSubLinkProvider(nil) })
+
+	var wg sync.WaitGroup
+	for range 8 {
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			RegisterSubLinkProvider(fakeSubLinkProvider{links: []string{"vless://example"}})
+		}()
+		go func() {
+			defer wg.Done()
+			_, _ = (&InboundService{}).GetSubLinks("panel.example", "subid")
+		}()
+	}
+	wg.Wait()
+}