feat: SDWAN data plane + UDP punch port fix + TUN reader

SDWAN:
- protocol: add SDWANConfig/SDWANPeer/SDWANPacket structs, MsgTunnel type
- server: sdwan.go (JSON file store), sdwan_api.go (Get/Set/broadcast/route)
- server: push SDWAN config on login, announce peer online/offline events
- server: RouteSDWANPacket routes TUN packets between nodes via signaling
- client: TUN device setup (optun), tunReadLoop reads IP packets
- client: handle SDWANConfig/SDWANPeer/SDWANDel push messages
- client: apply routes (per-node /32 + broad CIDR fallback)

UDP punch fix:
- nat/detect: capture LocalPort from STUN UDP socket for punch binding
- client: pass publicPort + localPort through login and punch config
- coordinator: include PublicPort in PunchParams for both sides
- protocol: add PublicPort to LoginReq and ReportBasic

Other:
- server: use client-reported PublicIP instead of raw r.RemoteAddr
- server: update PublicIP/Port from ReportBasic if provided
- client: config file loading with zero-value defaults backfill
- .gitignore: exclude run/, *.pid, *.log, sdwan.json
- go.mod: add golang.org/x/sys for TUN ioctl

internal/server/sdwan_api.go

@@ -0,0 +1,147 @@
+package server
+
+import (
+	"net/netip"
+
+	"github.com/openp2p-cn/inp2p/pkg/protocol"
+)
+
+func (s *Server) GetSDWAN() protocol.SDWANConfig {
+	return s.sdwan.get()
+}
+
+func (s *Server) SetSDWAN(cfg protocol.SDWANConfig) error {
+	if err := s.sdwan.save(cfg); err != nil {
+		return err
+	}
+	s.broadcastSDWAN(s.sdwan.get())
+	return nil
+}
+
+func (s *Server) broadcastSDWAN(cfg protocol.SDWANConfig) {
+	if !cfg.Enabled || cfg.GatewayCIDR == "" {
+		return
+	}
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, n := range s.nodes {
+		if !n.IsOnline() {
+			continue
+		}
+		_ = n.Conn.Write(protocol.MsgPush, protocol.SubPushSDWANConfig, cfg)
+	}
+}
+
+func (s *Server) pushSDWANPeer(to *NodeInfo, peer protocol.SDWANPeer) {
+	if to == nil || !to.IsOnline() {
+		return
+	}
+	_ = to.Conn.Write(protocol.MsgPush, protocol.SubPushSDWANPeer, peer)
+}
+
+func (s *Server) pushSDWANDel(to *NodeInfo, peer protocol.SDWANPeer) {
+	if to == nil || !to.IsOnline() {
+		return
+	}
+	_ = to.Conn.Write(protocol.MsgPush, protocol.SubPushSDWANDel, peer)
+}
+
+func (s *Server) announceSDWANNodeOnline(nodeName string) {
+	cfg := s.sdwan.get()
+	if cfg.GatewayCIDR == "" {
+		return
+	}
+	selfIP := ""
+	for _, n := range cfg.Nodes {
+		if n.Node == nodeName {
+			selfIP = n.IP
+			break
+		}
+	}
+	if selfIP == "" {
+		return
+	}
+
+	s.mu.RLock()
+	newNode := s.nodes[nodeName]
+	if newNode == nil || !newNode.IsOnline() {
+		s.mu.RUnlock()
+		return
+	}
+	for _, n := range cfg.Nodes {
+		if n.Node == nodeName {
+			continue
+		}
+		other := s.nodes[n.Node]
+		if other == nil || !other.IsOnline() {
+			continue
+		}
+		// existing -> new
+		s.pushSDWANPeer(newNode, protocol.SDWANPeer{Node: n.Node, IP: n.IP, Online: true})
+		// new -> existing
+		s.pushSDWANPeer(other, protocol.SDWANPeer{Node: nodeName, IP: selfIP, Online: true})
+	}
+	s.mu.RUnlock()
+}
+
+func (s *Server) announceSDWANNodeOffline(nodeName string) {
+	cfg := s.sdwan.get()
+	if cfg.GatewayCIDR == "" {
+		return
+	}
+	selfIP := ""
+	for _, n := range cfg.Nodes {
+		if n.Node == nodeName {
+			selfIP = n.IP
+			break
+		}
+	}
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, n := range s.nodes {
+		if n.Name == nodeName || !n.IsOnline() {
+			continue
+		}
+		s.pushSDWANDel(n, protocol.SDWANPeer{Node: nodeName, IP: selfIP, Online: false})
+	}
+}
+
+func (s *Server) RouteSDWANPacket(from *NodeInfo, pkt protocol.SDWANPacket) {
+	if from == nil {
+		return
+	}
+	cfg := s.sdwan.get()
+	if cfg.GatewayCIDR == "" || pkt.DstIP == "" || len(pkt.Payload) == 0 {
+		return
+	}
+
+	dst, err := netip.ParseAddr(pkt.DstIP)
+	if err != nil {
+		return
+	}
+	toNode := ""
+	for _, n := range cfg.Nodes {
+		if n.IP == pkt.DstIP {
+			toNode = n.Node
+			break
+		}
+		if p, err := netip.ParseAddr(n.IP); err == nil && p == dst {
+			toNode = n.Node
+			break
+		}
+	}
+	if toNode == "" || toNode == from.Name {
+		return
+	}
+
+	s.mu.RLock()
+	to := s.nodes[toNode]
+	s.mu.RUnlock()
+	if to == nil || !to.IsOnline() {
+		return
+	}
+
+	pkt.FromNode = from.Name
+	pkt.ToNode = toNode
+	_ = to.Conn.Write(protocol.MsgTunnel, protocol.SubTunnelSDWANData, pkt)
+}