fix(backend): respect tunnel IP preference in forward diagnosis (#160)

Forward diagnosis chain-hop probes now inherit the tunnel ipPreference so v6-priority tunnels test IPv6 targets instead of defaulting to IPv4. Add a contract test to lock IPv6 target selection for entry->chain and chain->exit diagnostics.

go-backend/internal/http/handler/control_plane.go

@@ -360,6 +360,8 @@ func (h *Handler) diagnoseForwardRuntime(forward *forwardRecord) (map[string]int
 		return nil, errors.New("隧道配置不完整")
 	}
 
+	ipPreference := h.repo.GetTunnelIPPreference(forward.TunnelID)
+
 	inNodes, chainHops, outNodes := splitChainNodeGroups(chainRows)
 	results := make([]map[string]interface{}, 0, len(chainRows)*2+len(targets))
 	nodeCache := map[int64]*nodeRecord{}
@@ -383,7 +385,7 @@ func (h *Handler) diagnoseForwardRuntime(forward *forwardRecord) (map[string]int
 						"fromChainType": 1,
 						"toChainType":   2,
 						"toInx":         firstNode.Inx,
-					}, "")
+					}, ipPreference)
 				}
 			} else {
 				for _, outNode := range outNodes {
@@ -391,7 +393,7 @@ func (h *Handler) diagnoseForwardRuntime(forward *forwardRecord) (map[string]int
 					h.appendChainHopDiagnosis(&results, nodeCache, inNode.NodeID, outNode, description, map[string]interface{}{
 						"fromChainType": 1,
 						"toChainType":   3,
-					}, "")
+					}, ipPreference)
 				}
 			}
 		}
@@ -406,7 +408,7 @@ func (h *Handler) diagnoseForwardRuntime(forward *forwardRecord) (map[string]int
 							"fromInx":       currentNode.Inx,
 							"toChainType":   2,
 							"toInx":         nextNode.Inx,
-						}, "")
+						}, ipPreference)
 					}
 				} else {
 					for _, outNode := range outNodes {
@@ -415,7 +417,7 @@ func (h *Handler) diagnoseForwardRuntime(forward *forwardRecord) (map[string]int
 							"fromChainType": 2,
 							"fromInx":       currentNode.Inx,
 							"toChainType":   3,
-						}, "")
+						}, ipPreference)
 					}
 				}
 			}

go-backend/tests/contract/diagnosis_contract_test.go

@@ -193,6 +193,126 @@ func TestDiagnosisChainCoverageContracts(t *testing.T) {
 	})
 }
 
+func TestForwardDiagnosisRespectsTunnelIPPreferenceContract(t *testing.T) {
+	secret := "contract-jwt-secret"
+	router, r := setupDiagnosisContractRouter(t, secret)
+	now := time.Now().UnixMilli()
+
+	if err := r.DB().Exec(`
+		INSERT INTO user(id, user, pwd, role_id, exp_time, flow, in_flow, out_flow, flow_reset_time, num, created_time, updated_time, status)
+		VALUES(2, 'normal_user', '3c85cdebade1c51cf64ca9f3c09d182d', 1, 2727251700000, 99999, 0, 0, 1, 99999, ?, ?, 1)
+	`, now, now).Error; err != nil {
+		t.Fatalf("insert user: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO tunnel(name, traffic_ratio, type, protocol, flow, created_time, updated_time, status, in_ip, inx, ip_preference)
+		VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+	`, "diagnose-ip-pref-forward", 1.0, 2, "tls", 99999, now, now, 1, nil, 0, "v6").Error; err != nil {
+		t.Fatalf("insert tunnel: %v", err)
+	}
+	tunnelID := mustLastInsertID(t, r, "diagnose-ip-pref-forward")
+
+	insertNode := func(name, v4, v6 string) int64 {
+		if err := r.DB().Exec(`
+			INSERT INTO node(name, secret, server_ip, server_ip_v4, server_ip_v6, port, interface_name, version, http, tls, socks, created_time, updated_time, status, tcp_listen_addr, udp_listen_addr, inx)
+			VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+		`, name, name+"-secret", v4, v4, v6, "30000-30010", "", "v1", 1, 1, 1, now, now, 1, "[::]", "[::]", 0).Error; err != nil {
+			t.Fatalf("insert node %s: %v", name, err)
+		}
+		return mustLastInsertID(t, r, name)
+	}
+
+	entryNodeID := insertNode("entry-node-v6", "10.10.1.10", "2001:db8:10::10")
+	chainNodeID := insertNode("chain-node-v6", "10.10.1.20", "2001:db8:10::20")
+	exitNodeID := insertNode("exit-node-v6", "10.10.1.30", "2001:db8:10::30")
+
+	if err := r.DB().Exec(`
+		INSERT INTO chain_tunnel(tunnel_id, chain_type, node_id, port, strategy, inx, protocol)
+		VALUES(?, 1, ?, 30001, 'round', 1, 'tls')
+	`, tunnelID, entryNodeID).Error; err != nil {
+		t.Fatalf("insert entry chain: %v", err)
+	}
+	if err := r.DB().Exec(`
+		INSERT INTO chain_tunnel(tunnel_id, chain_type, node_id, port, strategy, inx, protocol)
+		VALUES(?, 2, ?, 30002, 'round', 1, 'tls')
+	`, tunnelID, chainNodeID).Error; err != nil {
+		t.Fatalf("insert middle chain: %v", err)
+	}
+	if err := r.DB().Exec(`
+		INSERT INTO chain_tunnel(tunnel_id, chain_type, node_id, port, strategy, inx, protocol)
+		VALUES(?, 3, ?, 30003, 'round', 1, 'tls')
+	`, tunnelID, exitNodeID).Error; err != nil {
+		t.Fatalf("insert exit chain: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO forward(user_id, user_name, name, tunnel_id, remote_addr, strategy, in_flow, out_flow, created_time, updated_time, status, inx)
+		VALUES(?, ?, ?, ?, ?, ?, 0, 0, ?, ?, 1, ?)
+	`, 2, "normal_user", "ip-pref-forward", tunnelID, "8.8.8.8:53", "fifo", now, now, 0).Error; err != nil {
+		t.Fatalf("insert forward: %v", err)
+	}
+	forwardID := mustLastInsertID(t, r, "ip-pref-forward")
+
+	userToken, err := auth.GenerateToken(2, "normal_user", 1, secret)
+	if err != nil {
+		t.Fatalf("generate user token: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/forward/diagnose", bytes.NewBufferString(`{"forwardId":`+strconv.FormatInt(forwardID, 10)+`}`))
+	req.Header.Set("Authorization", userToken)
+	res := httptest.NewRecorder()
+
+	router.ServeHTTP(res, req)
+
+	var out response.R
+	if err := json.NewDecoder(res.Body).Decode(&out); err != nil {
+		t.Fatalf("decode response: %v", err)
+	}
+	if out.Code != 0 {
+		t.Fatalf("expected code 0, got %d (%s)", out.Code, out.Msg)
+	}
+
+	payload, ok := out.Data.(map[string]interface{})
+	if !ok {
+		t.Fatalf("expected object payload, got %T", out.Data)
+	}
+	results, ok := payload["results"].([]interface{})
+	if !ok || len(results) == 0 {
+		t.Fatalf("expected non-empty results, got %v", payload["results"])
+	}
+
+	hasEntryToChain := false
+	hasChainToExit := false
+	for _, raw := range results {
+		item, ok := raw.(map[string]interface{})
+		if !ok {
+			continue
+		}
+		from := valueAsInt(item["fromChainType"])
+		to := valueAsInt(item["toChainType"])
+		targetIP := strings.TrimSpace(valueAsString(item["targetIp"]))
+
+		if from == 1 && to == 2 {
+			hasEntryToChain = true
+			if targetIP != "2001:db8:10::20" {
+				t.Fatalf("expected entry->chain diagnosis target to use IPv6, got %q", targetIP)
+			}
+		}
+
+		if from == 2 && to == 3 {
+			hasChainToExit = true
+			if targetIP != "2001:db8:10::30" {
+				t.Fatalf("expected chain->exit diagnosis target to use IPv6, got %q", targetIP)
+			}
+		}
+	}
+
+	if !hasEntryToChain || !hasChainToExit {
+		t.Fatalf("expected entry->chain and chain->exit steps, got entry=%v chain=%v", hasEntryToChain, hasChainToExit)
+	}
+}
+
 func TestDiagnosisUsesFederationRuntimeForRemoteNodes(t *testing.T) {
 	secret := "contract-jwt-secret"
 	router, r := setupDiagnosisContractRouter(t, secret)