add go-tun2socks code

core/lwip.go

@@ -0,0 +1,121 @@
+package core
+
+/*
+#cgo CFLAGS: -I./c/include
+#include "lwip/tcp.h"
+#include "lwip/udp.h"
+#include "lwip/timeouts.h"
+*/
+import "C"
+import (
+	"sync"
+	"time"
+	"unsafe"
+)
+
+const CHECK_TIMEOUTS_INTERVAL = 250 // in millisecond
+const TCP_POLL_INTERVAL = 8         // poll every 4 seconds
+
+type LWIPStack interface {
+	Write([]byte) (int, error)
+	Close() error
+	RestartTimeouts()
+}
+
+// lwIP runs in a single thread, locking is needed in Go runtime.
+var lwipMutex = &sync.Mutex{}
+
+type lwipStack struct {
+	tpcb *C.struct_tcp_pcb
+	upcb *C.struct_udp_pcb
+}
+
+// NewLWIPStack listens for any incoming connections/packets and registers
+// corresponding accept/recv callback functions.
+func NewLWIPStack() LWIPStack {
+	tcpPCB := C.tcp_new()
+	if tcpPCB == nil {
+		panic("tcp_new return nil")
+	}
+
+	err := C.tcp_bind(tcpPCB, C.IP_ADDR_ANY, 0)
+	switch err {
+	case C.ERR_OK:
+		break
+	case C.ERR_VAL:
+		panic("invalid PCB state")
+	case C.ERR_USE:
+		panic("port in use")
+	default:
+		C.memp_free(C.MEMP_TCP_PCB, unsafe.Pointer(tcpPCB))
+		panic("unknown tcp_bind return value")
+	}
+
+	tcpPCB = C.tcp_listen_with_backlog(tcpPCB, C.TCP_DEFAULT_LISTEN_BACKLOG)
+	if tcpPCB == nil {
+		panic("can not allocate tcp pcb")
+	}
+
+	setTCPAcceptCallback(tcpPCB)
+
+	udpPCB := C.udp_new()
+	if udpPCB == nil {
+		panic("could not allocate udp pcb")
+	}
+
+	err = C.udp_bind(udpPCB, C.IP_ADDR_ANY, 0)
+	if err != C.ERR_OK {
+		panic("address already in use")
+	}
+
+	setUDPRecvCallback(udpPCB, nil)
+
+	go func() {
+		for {
+			select {
+			case <-time.After(CHECK_TIMEOUTS_INTERVAL * time.Millisecond):
+				lwipMutex.Lock()
+				C.sys_check_timeouts()
+				lwipMutex.Unlock()
+			}
+		}
+	}()
+
+	return &lwipStack{
+		tpcb: tcpPCB,
+		upcb: udpPCB,
+	}
+}
+
+func (s *lwipStack) Write(data []byte) (int, error) {
+	return Input(data)
+}
+
+func (s *lwipStack) RestartTimeouts() {
+	C.sys_restart_timeouts()
+}
+
+func (s *lwipStack) Close() error {
+	tcpConns.Range(func(_, c interface{}) bool {
+		c.(*tcpConn).Abort()
+		return true
+	})
+	udpConns.Range(func(_, c interface{}) bool {
+		c.(*udpConn).Close()
+		return true
+	})
+	return nil
+}
+
+func init() {
+	// Initialize lwIP.
+	//
+	// There is a little trick here, a loop interface (127.0.0.1)
+	// is created in the initialization stage due to the option
+	// `#define LWIP_HAVE_LOOPIF 1` in `lwipopts.h`, so we need
+	// not create our own interface.
+	//
+	// Now the loop interface is just the first element in
+	// `C.netif_list`, i.e. `*C.netif_list`.
+	lwipInit()
+}