add go-tun2socks code

core/tcp_callback_export.go

@@ -0,0 +1,165 @@
+package core
+
+/*
+#cgo CFLAGS: -I./c/include
+#include "lwip/tcp.h"
+*/
+import "C"
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+)
+
+// These exported callback functions must be placed in a seperated file.
+//
+// See also:
+// https://github.com/golang/go/issues/20639
+// https://golang.org/cmd/cgo/#hdr-C_references_to_Go
+
+//export tcpAcceptFn
+func tcpAcceptFn(arg unsafe.Pointer, newpcb *C.struct_tcp_pcb, err C.err_t) C.err_t {
+	if err != C.ERR_OK {
+		return err
+	}
+
+	if tcpConnHandler == nil {
+		panic("must register a TCP connection handler")
+	}
+
+	if _, nerr := newTCPConn(newpcb, tcpConnHandler); nerr != nil {
+		switch nerr.(*lwipError).Code {
+		case LWIP_ERR_ABRT:
+			return C.ERR_ABRT
+		case LWIP_ERR_OK:
+			return C.ERR_OK
+		default:
+			return C.ERR_CONN
+		}
+	}
+
+	return C.ERR_OK
+}
+
+//export tcpRecvFn
+func tcpRecvFn(arg unsafe.Pointer, tpcb *C.struct_tcp_pcb, p *C.struct_pbuf, err C.err_t) C.err_t {
+	if err != C.ERR_OK && err != C.ERR_ABRT {
+		return err
+	}
+
+	// Only free the pbuf when returning ERR_OK or ERR_ABRT,
+	// otherwise must not free the pbuf.
+	shouldFreePbuf := true
+	defer func() {
+		if p != nil && shouldFreePbuf {
+			C.pbuf_free(p)
+		}
+	}()
+
+	conn, ok := tcpConns.Load(getConnKeyVal(arg))
+	if !ok {
+		// The connection does not exists.
+		C.tcp_abort(tpcb)
+		return C.ERR_ABRT
+	}
+
+	if p == nil {
+		// Peer closed, EOF.
+		err := conn.(TCPConn).LocalClosed()
+		switch err.(*lwipError).Code {
+		case LWIP_ERR_ABRT:
+			return C.ERR_ABRT
+		case LWIP_ERR_OK:
+			return C.ERR_OK
+		default:
+			panic("unexpected error")
+		}
+	}
+
+	var buf []byte
+	var totlen = int(p.tot_len)
+	if p.tot_len == p.len {
+		buf = (*[1 << 30]byte)(unsafe.Pointer(p.payload))[:totlen:totlen]
+	} else {
+		buf = NewBytes(totlen)
+		defer FreeBytes(buf)
+		C.pbuf_copy_partial(p, unsafe.Pointer(&buf[0]), p.tot_len, 0)
+	}
+
+	rerr := conn.(TCPConn).Receive(buf[:totlen])
+	if rerr != nil {
+		switch rerr.(*lwipError).Code {
+		case LWIP_ERR_ABRT:
+			return C.ERR_ABRT
+		case LWIP_ERR_OK:
+			return C.ERR_OK
+		case LWIP_ERR_CONN:
+			shouldFreePbuf = false
+			// Tell lwip we can't receive data at the moment,
+			// lwip will store it and try again later.
+			return C.ERR_CONN
+		case LWIP_ERR_CLSD:
+			shouldFreePbuf = false
+			// lwip won't handle ERR_CLSD error for us, manually
+			// shuts down the rx side.
+			C.tcp_shutdown(tpcb, 1, 0)
+			return C.ERR_CLSD
+		default:
+			panic("unexpected error")
+		}
+	}
+
+	return C.ERR_OK
+}
+
+//export tcpSentFn
+func tcpSentFn(arg unsafe.Pointer, tpcb *C.struct_tcp_pcb, len C.u16_t) C.err_t {
+	if conn, ok := tcpConns.Load(getConnKeyVal(arg)); ok {
+		err := conn.(TCPConn).Sent(uint16(len))
+		switch err.(*lwipError).Code {
+		case LWIP_ERR_ABRT:
+			return C.ERR_ABRT
+		case LWIP_ERR_OK:
+			return C.ERR_OK
+		default:
+			panic("unexpected error")
+		}
+	} else {
+		C.tcp_abort(tpcb)
+		return C.ERR_ABRT
+	}
+}
+
+//export tcpErrFn
+func tcpErrFn(arg unsafe.Pointer, err C.err_t) {
+	if conn, ok := tcpConns.Load(getConnKeyVal(arg)); ok {
+		switch err {
+		case C.ERR_ABRT:
+			// Aborted through tcp_abort or by a TCP timer
+			conn.(TCPConn).Err(errors.New("connection aborted"))
+		case C.ERR_RST:
+			// The connection was reset by the remote host
+			conn.(TCPConn).Err(errors.New("connection reseted"))
+		default:
+			conn.(TCPConn).Err(errors.New(fmt.Sprintf("lwip error code %v", int(err))))
+		}
+	}
+}
+
+//export tcpPollFn
+func tcpPollFn(arg unsafe.Pointer, tpcb *C.struct_tcp_pcb) C.err_t {
+	if conn, ok := tcpConns.Load(getConnKeyVal(arg)); ok {
+		err := conn.(TCPConn).Poll()
+		switch err.(*lwipError).Code {
+		case LWIP_ERR_ABRT:
+			return C.ERR_ABRT
+		case LWIP_ERR_OK:
+			return C.ERR_OK
+		default:
+			panic("unexpected error")
+		}
+	} else {
+		C.tcp_abort(tpcb)
+		return C.ERR_ABRT
+	}
+}