fix(backend): resolve SQLite deadlock in tunnel entry updates (#334)

- Fix deadlock when updating tunnel entries with offline nodes
- Add test file for tunnel entry SQLite operations
- Update contract tests for entry port conflict and limiter sync
- Add plan documents for SQLite deadlock fix and contract semantics

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

@@ -0,0 +1,104 @@
+package handler
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+
+	"go-backend/internal/store/repo"
+)
+
+func TestValidateTunnelEntryPortConflictsForNewEntriesDoesNotBlockOnSQLiteTx(t *testing.T) {
+	r, err := repo.Open(filepath.Join(t.TempDir(), "panel.db"))
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	t.Cleanup(func() {
+		_ = r.Close()
+	})
+	h := &Handler{repo: r}
+	now := time.Now().UnixMilli()
+
+	if err := r.DB().Exec(`
+		INSERT INTO node(name, secret, server_ip, port, created_time, status, tcp_listen_addr, udp_listen_addr, is_remote)
+		VALUES
+			('entry-old', 'secret-old', '10.0.0.1', '12000-12010', ?, 1, '[::]', '[::]', 0),
+			('entry-new', 'secret-new', '10.0.0.2', '12000-12010', ?, 1, '[::]', '[::]', 0)
+	`, now, now).Error; err != nil {
+		t.Fatalf("insert nodes: %v", err)
+	}
+	var oldEntryID, newEntryID int64
+	if err := r.DB().Raw(`SELECT id FROM node WHERE name = 'entry-old'`).Scan(&oldEntryID).Error; err != nil {
+		t.Fatalf("load old entry id: %v", err)
+	}
+	if err := r.DB().Raw(`SELECT id FROM node WHERE name = 'entry-new'`).Scan(&newEntryID).Error; err != nil {
+		t.Fatalf("load new entry id: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO tunnel(name, traffic_ratio, type, protocol, flow, created_time, updated_time, status, inx, ip_preference)
+		VALUES('sqlite-tunnel', 1, 1, 'tls', 1, ?, ?, 1, 1, '')
+	`, now, now).Error; err != nil {
+		t.Fatalf("insert tunnel: %v", err)
+	}
+	var tunnelID int64
+	if err := r.DB().Raw(`SELECT id FROM tunnel WHERE name = 'sqlite-tunnel'`).Scan(&tunnelID).Error; err != nil {
+		t.Fatalf("load tunnel id: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO chain_tunnel(tunnel_id, chain_type, node_id, inx, protocol)
+		VALUES(?, '1', ?, 1, 'tls')
+	`, tunnelID, oldEntryID).Error; err != nil {
+		t.Fatalf("insert chain_tunnel: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO forward(user_id, user_name, name, tunnel_id, remote_addr, strategy, created_time, updated_time, status, inx)
+		VALUES(1, 'tester', 'forward-a', ?, '127.0.0.1:8080', 'fifo', ?, ?, 1, 1)
+	`, tunnelID, now, now).Error; err != nil {
+		t.Fatalf("insert forward: %v", err)
+	}
+	var forwardID int64
+	if err := r.DB().Raw(`SELECT id FROM forward WHERE name = 'forward-a'`).Scan(&forwardID).Error; err != nil {
+		t.Fatalf("load forward id: %v", err)
+	}
+
+	if err := r.DB().Exec(`
+		INSERT INTO forward_port(forward_id, node_id, port)
+		VALUES(?, ?, 12001)
+	`, forwardID, oldEntryID).Error; err != nil {
+		t.Fatalf("insert forward_port: %v", err)
+	}
+
+	tx := r.BeginTx()
+	if tx == nil {
+		t.Fatal("begin tx: nil transaction")
+	}
+	if tx.Error != nil {
+		t.Fatalf("begin tx: %v", tx.Error)
+	}
+
+	errCh := make(chan error, 1)
+	doneCh := make(chan struct{})
+	go func() {
+		defer close(doneCh)
+		errCh <- h.validateTunnelEntryPortConflictsForNewEntries(tx, tunnelID, []int64{oldEntryID}, []int64{oldEntryID, newEntryID})
+	}()
+
+	select {
+	case err := <-errCh:
+		if err != nil {
+			_ = tx.Rollback().Error
+			t.Fatalf("unexpected validation error: %v", err)
+		}
+	case <-time.After(500 * time.Millisecond):
+		_ = tx.Rollback().Error
+		<-doneCh
+		t.Fatal("validation blocked while transaction was open on sqlite")
+	}
+
+	if err := tx.Rollback().Error; err != nil {
+		t.Fatalf("rollback tx: %v", err)
+	}
+}