xray-setting: pin api routing rule to index 0 on save (#4124)

when the admin adds a custom outbound (eg vless cascade to a second
server) and a routing rule sending all inbound traffic to it, that
catch-all gets evaluated before the existing api->api rule, so the
panel's internal stats inbound's traffic ends up on the cascade
outbound. the grpc stats query then can't see anything, GetTraffic
returns no inbound/user counters, and every client appears offline
with zero traffic even though the actual proxy path works fine.

before save, find the api rule and move it to the front of
routing.rules. if it's missing entirely, insert a default. other
rules keep their relative order.

closes #4113. probably also fixes the long-standing #2818 where the
documented workaround was "manually move the api rule to the top".

1 files changed, 115 insertions, 0 deletions

diff --git a/web/service/xray_setting_test.go b/web/service/xray_setting_test.go
index 2c165576..22b00ce3 100644
--- a/web/service/xray_setting_test.go
+++ b/web/service/xray_setting_test.go
@@ -88,3 +88,118 @@ func equalJSON(t *testing.T, a, b string) bool {
 	jb, _ := json.Marshal(vb)
 	return string(ja) == string(jb)
 }
+
+// firstRuleOutbound parses the (post-hoisted) config and returns
+// routing.rules[0].outboundTag, or "" if anything is missing.
+func firstRuleOutbound(t *testing.T, raw string) string {
+	t.Helper()
+	var cfg map[string]any
+	if err := json.Unmarshal([]byte(raw), &cfg); err != nil {
+		t.Fatalf("unmarshal cfg: %v", err)
+	}
+	routing, _ := cfg["routing"].(map[string]any)
+	rules, _ := routing["rules"].([]any)
+	if len(rules) == 0 {
+		return ""
+	}
+	first, _ := rules[0].(map[string]any)
+	tag, _ := first["outboundTag"].(string)
+	return tag
+}
+
+func TestEnsureStatsRouting_HoistsApiRuleFromMiddle(t *testing.T) {
+	// #4113 repro shape: admin added a cascade outbound and put a
+	// catch-all routing rule above the api rule. stats query path
+	// gets starved by the catch-all unless we hoist the api rule.
+	in := `{
+		"routing": {
+			"rules": [
+				{"type":"field","inboundTag":["inbound-vless"],"outboundTag":"vless-cascade"},
+				{"type":"field","inboundTag":["api"],"outboundTag":"api"},
+				{"type":"field","outboundTag":"blocked","ip":["geoip:private"]}
+			]
+		}
+	}`
+	out, err := EnsureStatsRouting(in)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if got := firstRuleOutbound(t, out); got != "api" {
+		t.Fatalf("api rule should be at index 0 after hoist, got first outboundTag = %q\nfull: %s", got, out)
+	}
+}
+
+func TestEnsureStatsRouting_NoOpWhenAlreadyFirst(t *testing.T) {
+	// Don't churn the JSON when nothing needs fixing — same string in,
+	// same string out. Lets the diff in the panel UI stay quiet for
+	// well-formed configs.
+	in := `{"routing":{"rules":[{"type":"field","inboundTag":["api"],"outboundTag":"api"},{"type":"field","outboundTag":"blocked","ip":["geoip:private"]}]}}`
+	out, err := EnsureStatsRouting(in)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if out != in {
+		t.Fatalf("expected unchanged input, got: %s", out)
+	}
+}
+
+func TestEnsureStatsRouting_InsertsDefaultWhenMissing(t *testing.T) {
+	// Some admins delete the api rule by accident. Re-add a default
+	// at the front so stats keep working after the next save.
+	in := `{"routing":{"rules":[{"type":"field","outboundTag":"vless-cascade","inboundTag":["inbound-vless"]}]}}`
+	out, err := EnsureStatsRouting(in)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if got := firstRuleOutbound(t, out); got != "api" {
+		t.Fatalf("default api rule should be inserted at index 0, got %q\nfull: %s", got, out)
+	}
+	// The original rule should still be there, just shifted.
+	var cfg map[string]any
+	json.Unmarshal([]byte(out), &cfg)
+	rules := cfg["routing"].(map[string]any)["rules"].([]any)
+	if len(rules) != 2 {
+		t.Fatalf("expected 2 rules after insert, got %d: %v", len(rules), rules)
+	}
+}
+
+func TestEnsureStatsRouting_NoRoutingBlock(t *testing.T) {
+	// Pathological but possible: empty config or one without a routing
+	// section. Don't crash, and create the section with the api rule.
+	in := `{"log":{}}`
+	out, err := EnsureStatsRouting(in)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if got := firstRuleOutbound(t, out); got != "api" {
+		t.Fatalf("api rule should be created when routing was missing, got %q\nfull: %s", got, out)
+	}
+}
+
+func TestEnsureStatsRouting_InvalidJsonReturnsAsIs(t *testing.T) {
+	// SaveXraySetting calls CheckXrayConfig before this helper, so
+	// invalid JSON shouldn't reach us in practice — but be defensive
+	// about garbage in (return same garbage out plus an error) so the
+	// caller can choose to skip the hoist instead of corrupting input.
+	in := "definitely not json"
+	out, err := EnsureStatsRouting(in)
+	if err == nil {
+		t.Fatalf("expected error for invalid json, got none")
+	}
+	if out != in {
+		t.Fatalf("expected raw passthrough on error, got %q", out)
+	}
+}
+
+func TestEnsureStatsRouting_AcceptsInboundTagAsString(t *testing.T) {
+	// Some manually-edited configs use a single string instead of an
+	// array for inboundTag. Make sure we still recognize the api rule.
+	in := `{"routing":{"rules":[{"type":"field","inboundTag":["other"],"outboundTag":"vless-cascade"},{"type":"field","inboundTag":"api","outboundTag":"api"}]}}`
+	out, err := EnsureStatsRouting(in)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if got := firstRuleOutbound(t, out); got != "api" {
+		t.Fatalf("api rule with string-form inboundTag should hoist to front, got %q\nfull: %s", got, out)
+	}
+}