feat(outbounds): support custom subscription user agents (#6398)

Some subscription providers require a client-specific User-Agent before returning outbound links. Persist an optional value per subscription and use it for refreshes and previews while preserving the existing default for blank values.

internal/web/service/outbound_subscription.go

@@ -58,6 +58,8 @@ func filterOutboundsRejectedByCore(label string, outbounds []any) ([]any, []stri
 // subscription may aggregate many upstream outbounds into one document.
 const maxOutboundSubscriptionBytes int64 = 8 << 20
 
+const defaultOutboundSubscriptionUserAgent = "3x-ui-outbound-sub/1.0"
+
 var errOutboundSubscriptionBodyTooLarge = errors.New("outbound subscription response body exceeds size limit")
 
 func readBoundedOutboundSubscriptionBody(r io.Reader) ([]byte, error) {
@@ -164,7 +166,7 @@ func (s *OutboundSubscriptionService) nextDefaultSubPrefix(excludeId int) (strin
 	return fmt.Sprintf("sub%d-", defaultPrefixNumber(subs, excludeId)), nil
 }
 
-func (s *OutboundSubscriptionService) Create(remark, rawURL, tagPrefix string, enabled bool, updateInterval int, allowPrivate, prepend, allowInsecure bool) (*model.OutboundSubscription, error) {
+func (s *OutboundSubscriptionService) Create(remark, rawURL, tagPrefix, userAgent string, enabled bool, updateInterval int, allowPrivate, prepend, allowInsecure bool) (*model.OutboundSubscription, error) {
 	cleanURL, err := SanitizePublicHTTPURL(rawURL, allowPrivate)
 	if err != nil {
 		return nil, common.NewError("invalid subscription URL:", err)
@@ -193,6 +195,7 @@ func (s *OutboundSubscriptionService) Create(remark, rawURL, tagPrefix string, e
 		Enabled:        enabled,
 		AllowPrivate:   allowPrivate,
 		AllowInsecure:  allowInsecure,
+		UserAgent:      strings.TrimSpace(userAgent),
 		Prepend:        prepend,
 		Priority:       int(count),
 		TagPrefix:      prefix,
@@ -205,7 +208,7 @@ func (s *OutboundSubscriptionService) Create(remark, rawURL, tagPrefix string, e
 }
 
 // Update updates editable fields.
-func (s *OutboundSubscriptionService) Update(id int, remark, rawURL, tagPrefix string, enabled bool, updateInterval int, allowPrivate, prepend, allowInsecure bool) error {
+func (s *OutboundSubscriptionService) Update(id int, remark, rawURL, tagPrefix, userAgent string, enabled bool, updateInterval int, allowPrivate, prepend, allowInsecure bool) error {
 	sub, err := s.Get(id)
 	if err != nil {
 		return err
@@ -232,6 +235,7 @@ func (s *OutboundSubscriptionService) Update(id int, remark, rawURL, tagPrefix s
 	sub.Enabled = enabled
 	sub.AllowPrivate = allowPrivate
 	sub.AllowInsecure = allowInsecure
+	sub.UserAgent = strings.TrimSpace(userAgent)
 	sub.Prepend = prepend
 	sub.TagPrefix = prefix
 	sub.UpdateInterval = updateInterval
@@ -363,7 +367,11 @@ func (s *OutboundSubscriptionService) fetchAndStore(sub *model.OutboundSubscript
 		s.recordError(sub, err)
 		return nil, err
 	}
-	req.Header.Set("User-Agent", "3x-ui-outbound-sub/1.0")
+	userAgent := strings.TrimSpace(sub.UserAgent)
+	if userAgent == "" {
+		userAgent = defaultOutboundSubscriptionUserAgent
+	}
+	req.Header.Set("User-Agent", userAgent)
 
 	resp, err := client.Do(req)
 	if err != nil {

internal/web/service/outbound_subscription_test.go

@@ -3,6 +3,8 @@ package service
 import (
 	"bytes"
 	"errors"
+	"net/http"
+	"net/http/httptest"
 	"slices"
 	"testing"
 
@@ -40,7 +42,7 @@ func TestOutboundSubscriptionCreatePropagatesAllocationDatabaseFailures(t *testi
 		{name: "priority count query", tagPrefix: "custom-", operation: "priority allocation"},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			created, err := (&OutboundSubscriptionService{}).Create("test", "https://1.1.1.1/sub", tc.tagPrefix, true, 600, false, false, false)
+			created, err := (&OutboundSubscriptionService{}).Create("test", "https://1.1.1.1/sub", tc.tagPrefix, "", true, 600, false, false, false)
 			if !errors.Is(err, errInjected) {
 				t.Fatalf("Create error = %v, want injected %s query failure", err, tc.operation)
 			}
@@ -83,7 +85,7 @@ func TestOutboundSubscriptionUpdatePropagatesPrefixQueryFailureWithoutMutation(t
 	})
 
 	err := (&OutboundSubscriptionService{}).Update(
-		original.Id, "after", "https://1.1.1.1/changed", "", false, 1200, false, false, false,
+		original.Id, "after", "https://1.1.1.1/changed", "", "", false, 1200, false, false, false,
 	)
 	if !errors.Is(err, errInjected) {
 		t.Fatalf("Update error = %v, want injected prefix query failure", err)
@@ -102,6 +104,30 @@ func TestOutboundSubscriptionUpdatePropagatesPrefixQueryFailureWithoutMutation(t
 	}
 }
 
+func TestOutboundSubscriptionRefreshUsesCustomUserAgent(t *testing.T) {
+	setupSettingTestDB(t)
+	const wantUserAgent = "ClashMetaForAndroid/2.11.13"
+	var gotUserAgent string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotUserAgent = r.UserAgent()
+		_, _ = w.Write([]byte("vless://00000000-0000-4000-8000-000000000000@1.1.1.1:443?security=tls&type=tcp#node"))
+	}))
+	t.Cleanup(server.Close)
+
+	sub := &model.OutboundSubscription{
+		Url: server.URL, AllowPrivate: true, UserAgent: wantUserAgent, TagPrefix: "test-",
+	}
+	if err := database.GetDB().Create(sub).Error; err != nil {
+		t.Fatalf("seed subscription: %v", err)
+	}
+	if _, err := (&OutboundSubscriptionService{}).Refresh(sub.Id); err != nil {
+		t.Fatalf("Refresh: %v", err)
+	}
+	if gotUserAgent != wantUserAgent {
+		t.Fatalf("User-Agent = %q, want %q", gotUserAgent, wantUserAgent)
+	}
+}
+
 func TestReadBoundedOutboundSubscriptionBody(t *testing.T) {
 	t.Run("accepts body at the limit", func(t *testing.T) {
 		want := bytes.Repeat([]byte("a"), int(maxOutboundSubscriptionBytes))