feat: Support dynamic port allocation for SSH forwarding

internal/port/port.go

@@ -0,0 +1,75 @@
+package port
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+	"tunnel_pls/utils"
+)
+
+type PortManager struct {
+	ports       map[uint16]bool
+	sortedPorts []uint16
+}
+
+var Manager = PortManager{
+	ports:       make(map[uint16]bool),
+	sortedPorts: []uint16{},
+}
+
+func init() {
+	rawRange := utils.Getenv("ALLOWED_PORTS")
+	splitRange := strings.Split(rawRange, "-")
+	if len(splitRange) != 2 {
+		Manager.AddPortRange(30000, 31000)
+	} else {
+		start, err := strconv.ParseUint(splitRange[0], 10, 16)
+		if err != nil {
+			start = 30000
+		}
+		end, err := strconv.ParseUint(splitRange[1], 10, 16)
+		if err != nil {
+			end = 31000
+		}
+		Manager.AddPortRange(uint16(start), uint16(end))
+	}
+}
+
+func (pm *PortManager) AddPortRange(startPort, endPort uint16) error {
+	if startPort > endPort {
+		return fmt.Errorf("start port cannot be greater than end port")
+	}
+	for port := startPort; port <= endPort; port++ {
+		if _, exists := pm.ports[port]; !exists {
+			pm.ports[port] = false
+			pm.sortedPorts = append(pm.sortedPorts, port)
+		}
+	}
+	sort.Slice(pm.sortedPorts, func(i, j int) bool {
+		return pm.sortedPorts[i] < pm.sortedPorts[j]
+	})
+	return nil
+}
+
+func (pm *PortManager) GetUnassignedPort() (uint16, bool) {
+	for _, port := range pm.sortedPorts {
+		if !pm.ports[port] {
+			return port, true
+		}
+	}
+	return 0, false
+}
+
+func (pm *PortManager) SetPortStatus(port uint16, assigned bool) error {
+	if _, exists := pm.ports[port]; !exists {
+		return fmt.Errorf("port %d is not in the allowed range", port)
+	}
+	pm.ports[port] = assigned
+	return nil
+}
+
+func (pm *PortManager) GetPortStatus(port uint16) (bool, bool) {
+	status, exists := pm.ports[port]
+	return status, exists
+}