feat: separate golang code by platforms

Author: SCLevi

go.work

@@ -0,0 +1,3 @@
+go 1.21.6
+
+use .

go.work.sum

@@ -0,0 +1,4 @@
+github.com/spf13/cobra v1.7.0/go.mod h1:uLxZILRyS/50WlhOIKD7W6V5bgeIt+4sICxh6uRMrb0=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/tailscale/hujson v0.0.0-20221223112325-20486734a56a/go.mod h1:DFSS3NAGHthKo1gTlmEcSBiZrRJXi28rLNd/1udP1c8=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=

platform/tailscale_unix.go

@@ -0,0 +1,33 @@
+//go:build darwin || linux
+// +build darwin linux
+
+package platform
+
+//#include "errno.h"
+//#include "../socketpair_handler.h"
+import "C"
+
+import (
+	"syscall"
+)
+
+func GetSocketPair() ([2]int, error) {
+	return syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
+}
+
+func CloseSocket(fd interface{}) (err error) {
+	return syscall.Close(fd.(int))
+}
+
+func ReadSocket(fd interface{}, buf *[256]byte) {
+	syscall.Read(fd.(int), (*buf)[:])
+}
+
+func SendMessage(fd interface{}, p []byte, connFd int, to syscall.Sockaddr, flags int) (err error) {
+	rights := syscall.UnixRights(int(connFd))
+	return syscall.Sendmsg(fd.(int), p, rights, to, flags)
+}
+
+func Shutdown(fd interface{}, how int) (err error) {
+	return syscall.Shutdown(fd.(int), how)
+}

platform/tailscale_windows.go

@@ -0,0 +1,43 @@
+// If your file name follows the structure name_{GOOS}_{GOARCH}.go or
+// simply name_{GOOS}.go,
+// then it will be compiled only under the target OS+architecture
+// or OS+any architecture respectively without needing a special comment
+package platform
+
+//#cgo LDFLAGS: -lws2_32
+//#include "errno.h"
+//#include "../socketpair_handler.h"
+import "C"
+
+import (
+	"fmt"
+	"syscall"
+	"unsafe"
+)
+
+func GetSocketPair() ([2]int, error) {
+	var fds [2]int
+	fds_pt := C.get_socket_pair()
+	fds_array := (*[1 << 30]int)(unsafe.Pointer(fds_pt))[:2:2]
+	fds[0] = fds_array[0]
+	fds[1] = fds_array[1]
+	return fds, nil
+}
+
+func CloseSocket(fd interface{}) error {
+	fmt.Println("Closing socket", fd.(syscall.Handle))
+	return syscall.Close(fd.(syscall.Handle))
+}
+
+func ReadSocket(fd interface{}, buf *[256]byte) {
+	syscall.Read(fd.(syscall.Handle), (*buf)[:])
+}
+
+func SendMessage(fd interface{}, p []byte, connFd int, to syscall.Sockaddr, flags int) error {
+	_, err := syscall.Write(fd.(syscall.Handle), p)
+	return err
+}
+
+func Shutdown(fd interface{}, how int) error {
+	return syscall.Shutdown(fd.(syscall.Handle), how)
+}

socketpair.c

@@ -50,7 +50,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <string.h>
 
-#ifdef WIN32
+#ifdef _WIN32
 # include <ws2tcpip.h>  /* socklen_t, et al (MSVC20xx) */
 # include <windows.h>
 # include <io.h>
@@ -60,7 +60,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 # include <errno.h>
 #endif
 
-#ifdef WIN32
+#ifdef _WIN32
 
 /* dumb_socketpair:
  *   If make_overlapped is nonzero, both sockets created will be usable for
@@ -70,7 +70,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *   sockets must be closed with closesocket() regardless.
  */
 
-int dumb_socketpair(SOCKET socks[2], int make_overlapped)
+static int dumb_socketpair(SOCKET socks[2], int make_overlapped)
 {
     union {
        struct sockaddr_in inaddr;
@@ -138,7 +138,7 @@ int dumb_socketpair(SOCKET socks[2], int make_overlapped)
     return SOCKET_ERROR;
 }
 #else
-int dumb_socketpair(int socks[2], int dummy)
+static int dumb_socketpair(int socks[2], int dummy)
 {
     if (socks == 0) {
         errno = EINVAL;

socketpair_handler.c

@@ -4,6 +4,7 @@
 #include <windows.h>
 #include <ws2tcpip.h>
 #include <stdio.h>
+#pragma comment(lib, "ws2_32.lib")
 #endif
 
 int *get_socket_pair() {

tailscale.go

@@ -18,6 +18,8 @@ import (
 	"syscall"
 	"unsafe"
 
+	"github.com/tailscale/libtailscale/platform"
+
 	"tailscale.com/hostinfo"
 	"tailscale.com/tsnet"
 	"tailscale.com/types/logger"
@@ -186,14 +188,8 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 	// epoll on the tailscale_listener to know if it should call
 	// tailscale_accept, which avoids a blocking call on the far side.
 	var fds [2]int
-	if os.Getenv("GOOS") == "windows" {
-		fds_pt := C.get_socket_pair()
-		fds_array := (*[1 << 30]int)(unsafe.Pointer(fds_pt))[:2:2]
-		fds[0] = fds_array[0]
-		fds[1] = fds_array[1]
-	} else {
-		fds, err = syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
-	}
+	fds, err = platform.GetSocketPair()
+
 	if err != nil {
 		return s.recErr(err)
 	}
@@ -214,7 +210,7 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 		listeners.mu.Lock()
 		if tsLn, ok := listeners.m[fdC]; ok && tsLn.ln == ln {
 			delete(listeners.m, fdC)
-			syscall.Close(sp)
+			platform.CloseSocket(sp)
 		}
 		listeners.mu.Unlock()
 
@@ -227,7 +223,7 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 		//
 		// TODO: would using os.NewFile avoid a locked up thread?
 		var buf [256]byte
-		syscall.Read(sp, buf[:])
+		platform.ReadSocket(sp, &buf)
 		cleanup()
 	}()
 	go func() {
@@ -245,12 +241,8 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 				netConn.Close()
 				continue
 			}
-			if os.Getenv("GOOS") == "windows" {
-				_, err = syscall.Write(sp, nil)
-			} else {
-				rights := syscall.UnixRights(int(connFd))
-				err = syscall.Sendmsg(sp, nil, rights, nil, 0)
-			}
+
+			err = platform.SendMessage(sp, nil, int(connFd), nil, 0)
 
 			if err != nil {
 				// We handle sp being closed in the read goroutine above.
@@ -260,7 +252,7 @@ func TsnetListen(sd C.int, network, addr *C.char, listenerOut *C.int) C.int {
 				netConn.Close()
 				// fallthrough to close connFd, then continue Accept()ing
 			}
-			syscall.Close(int(connFd)) // now owned by recvmsg
+			platform.CloseSocket(int(connFd)) // now owned by recvmsg
 		}
 	}()
 
@@ -273,14 +265,7 @@ func newConn(s *server, netConn net.Conn, connOut *C.int) error {
 	// TODO https://github.com/ncm/selectable-socketpair/blob/master/socketpair.c
 	var fds [2]int
 	var err error
-	if os.Getenv("GOOS") == "windows" {
-		fds_pt := C.get_socket_pair()
-		fds_array := (*[1 << 30]int)(unsafe.Pointer(fds_pt))[:2:2]
-		fds[0] = fds_array[0]
-		fds[1] = fds_array[1]
-	} else {
-		fds, err = syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
-	}
+	fds, err = platform.GetSocketPair()
 	if err != nil {
 		return err
 	}
@@ -315,7 +300,7 @@ func newConn(s *server, netConn net.Conn, connOut *C.int) error {
 		defer connCleanup()
 		var b [1 << 16]byte
 		io.CopyBuffer(r, netConn, b[:])
-		syscall.Shutdown(int(r.Fd()), syscall.SHUT_WR)
+		platform.Shutdown(int(r.Fd()), syscall.SHUT_WR)
 		if cr, ok := netConn.(interface{ CloseRead() error }); ok {
 			cr.CloseRead()
 		}
@@ -324,7 +309,7 @@ func newConn(s *server, netConn net.Conn, connOut *C.int) error {
 		defer connCleanup()
 		var b [1 << 16]byte
 		io.CopyBuffer(netConn, r, b[:])
-		syscall.Shutdown(int(r.Fd()), syscall.SHUT_RD)
+		platform.Shutdown(int(r.Fd()), syscall.SHUT_RD)
 		if cw, ok := netConn.(interface{ CloseWrite() error }); ok {
 			cw.CloseWrite()
 		}