Improve darwin tun performance

tun_linux_gvisor.go

@@ -3,8 +3,11 @@
 package tun
 
 import (
+	"github.com/sagernet/gvisor/pkg/rawfile"
 	"github.com/sagernet/gvisor/pkg/tcpip/link/fdbased"
 	"github.com/sagernet/gvisor/pkg/tcpip/stack"
+
+	"golang.org/x/sys/unix"
 )
 
 func init() {
@@ -13,6 +16,28 @@ func init() {
 
 var _ GVisorTun = (*NativeTun)(nil)
 
+func (t *NativeTun) WritePacket(pkt *stack.PacketBuffer) (int, error) {
+	iovecs := t.iovecsOutputDefault
+	var dataLen int
+	for _, packetSlice := range pkt.AsSlices() {
+		dataLen += len(packetSlice)
+		iovec := unix.Iovec{
+			Base: &packetSlice[0],
+		}
+		iovec.SetLen(len(packetSlice))
+		iovecs = append(iovecs, iovec)
+	}
+	if cap(iovecs) > cap(t.iovecsOutputDefault) {
+		t.iovecsOutputDefault = iovecs[:0]
+	}
+	errno := rawfile.NonBlockingWriteIovec(t.tunFd, iovecs)
+	if errno == 0 {
+		return dataLen, nil
+	} else {
+		return 0, errno
+	}
+}
+
 func (t *NativeTun) NewEndpoint() (stack.LinkEndpoint, stack.NICOptions, error) {
 	if t.vnetHdr {
 		ep, err := fdbased.New(&fdbased.Options{