Fix usages of readmsg_x

internal/fdbased_darwin/endpoint.go

@@ -74,12 +74,29 @@ const (
 	// dispatch options but the one that is supported by all underlying FD
 	// types.
 	Readv PacketDispatchMode = iota
+	// RecvMMsg enables use of recvmmsg() syscall instead of readv() to
+	// read inbound packets. This reduces # of syscalls needed to process
+	// packets.
+	//
+	// NOTE: recvmmsg() is only supported for sockets, so if the underlying
+	// FD is not a socket then the code will still fall back to the readv()
+	// path.
+	RecvMMsg
+	// PacketMMap enables use of PACKET_RX_RING to receive packets from the
+	// NIC. PacketMMap requires that the underlying FD be an AF_PACKET. The
+	// primary use-case for this is runsc which uses an AF_PACKET FD to
+	// receive packets from the veth device.
+	PacketMMap
 )
 
 func (p PacketDispatchMode) String() string {
 	switch p {
 	case Readv:
 		return "Readv"
+	case RecvMMsg:
+		return "RecvMMsg"
+	case PacketMMap:
+		return "PacketMMap"
 	default:
 		return fmt.Sprintf("unknown packet dispatch mode '%d'", p)
 	}
@@ -283,14 +300,6 @@ func New(opts *Options) (stack.LinkEndpoint, error) {
 	return e, nil
 }
 
-func isSocketFD(fd int) (bool, error) {
-	var stat unix.Stat_t
-	if err := unix.Fstat(fd, &stat); err != nil {
-		return false, fmt.Errorf("unix.Fstat(%v,...) failed: %v", fd, err)
-	}
-	return (stat.Mode & unix.S_IFSOCK) == unix.S_IFSOCK, nil
-}
-
 // Attach launches the goroutine that reads packets from the file descriptor and
 // dispatches them via the provided dispatcher. If one is already attached,
 // then nothing happens.

internal/fdbased_darwin/packet_dispatchers.go

@@ -25,51 +25,31 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// BufConfig defines the shape of the buffer used to read packets from the NIC.
-var BufConfig = []int{4, 128, 256, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768}
-
-// +stateify savable
 type iovecBuffer struct {
-	// buffer is the actual buffer that holds the packet contents. Some contents
+	mtu    int
-	// are reused across calls to pullBuffer if number of requested bytes is
+	views  []*buffer.View
-	// smaller than the number of bytes allocated in the buffer.
-	views []*buffer.View
-
-	// iovecs are initialized with base pointers/len of the corresponding
-	// entries in the views defined above, except when GSO is enabled
-	// (skipsVnetHdr) then the first iovec points to a buffer for the vnet header
-	// which is stripped before the views are passed up the stack for further
-	// processing.
 	iovecs []unix.Iovec `state:"nosave"`
-
-	// sizes is an array of buffer sizes for the underlying views. sizes is
-	// immutable.
-	sizes []int
-
-	// pulledIndex is the index of the last []byte buffer pulled from the
-	// underlying buffer storage during a call to pullBuffers. It is -1
-	// if no buffer is pulled.
-	pulledIndex int
 }
 
-func newIovecBuffer(sizes []int) *iovecBuffer {
+func newIovecBuffer(mtu uint32) *iovecBuffer {
 	b := &iovecBuffer{
-		views:  make([]*buffer.View, len(sizes)),
+		mtu:    int(mtu),
-		iovecs: make([]unix.Iovec, len(sizes)),
+		views:  make([]*buffer.View, 2),
-		sizes:  sizes,
+		iovecs: make([]unix.Iovec, 2),
 	}
 	return b
 }
 
 func (b *iovecBuffer) nextIovecs() []unix.Iovec {
-	for i := range b.views {
+	if b.views[0] == nil {
-		if b.views[i] != nil {
+		b.views[0] = buffer.NewViewSize(4)
-			break
+		b.iovecs[0] = unix.Iovec{Base: b.views[0].BasePtr()}
-		}
+		b.iovecs[0].SetLen(4)
-		v := buffer.NewViewSize(b.sizes[i])
+	}
-		b.views[i] = v
+	if b.views[1] == nil {
-		b.iovecs[i] = unix.Iovec{Base: v.BasePtr()}
+		b.views[1] = buffer.NewViewSize(b.mtu)
-		b.iovecs[i].SetLen(v.Size())
+		b.iovecs[1] = unix.Iovec{Base: b.views[1].BasePtr()}
+		b.iovecs[1].SetLen(b.mtu)
 	}
 	return b.iovecs
 }
@@ -80,25 +60,13 @@ func (b *iovecBuffer) nextIovecs() []unix.Iovec {
 // of b.buffer's storage must be reallocated during the next call to
 // nextIovecs.
 func (b *iovecBuffer) pullBuffer(n int) buffer.Buffer {
-	var views []*buffer.View
-	c := 0
-	// Remove the used views from the buffer.
-	for i, v := range b.views {
-		c += v.Size()
-		if c >= n {
-			b.views[i].CapLength(v.Size() - (c - n))
-			views = append(views, b.views[:i+1]...)
-			break
-		}
-	}
-	for i := range views {
-		b.views[i] = nil
-	}
 	pulled := buffer.Buffer{}
-	for _, v := range views {
+	pulled.Append(b.views[0])
-		pulled.Append(v)
+	pulled.Append(b.views[1])
-	}
 	pulled.Truncate(int64(n))
+	pulled.TrimFront(4)
+	b.views[0] = nil
+	b.views[1] = nil
 	return pulled
 }
 
@@ -147,7 +115,12 @@ func newRecvMMsgDispatcher(fd int, e *endpoint, opts *Options) (linkDispatcher,
 	if err != nil {
 		return nil, err
 	}
-	batchSize := int((512*1024)/(opts.MTU)) + 1
+	var batchSize int
+	if opts.MTU < 49152 {
+		batchSize = int((512*1024)/(opts.MTU)) + 1
+	} else {
+		batchSize = 1
+	}
 	d := &recvMMsgDispatcher{
 		StopFD:  stopFD,
 		fd:      fd,
@@ -155,9 +128,8 @@ func newRecvMMsgDispatcher(fd int, e *endpoint, opts *Options) (linkDispatcher,
 		bufs:    make([]*iovecBuffer, batchSize),
 		msgHdrs: make([]rawfile.MsgHdrX, batchSize),
 	}
-	bufConfig := []int{4, int(opts.MTU)}
 	for i := range d.bufs {
-		d.bufs[i] = newIovecBuffer(bufConfig)
+		d.bufs[i] = newIovecBuffer(opts.MTU)
 	}
 	d.gro.Init(false)
 	d.mgr = newProcessorManager(opts, e)
@@ -178,12 +150,11 @@ func (d *recvMMsgDispatcher) release() {
 func (d *recvMMsgDispatcher) dispatch() (bool, tcpip.Error) {
 	// Fill message headers.
 	for k := range d.msgHdrs {
-		if d.msgHdrs[k].Msg.Iovlen > 0 {
-			break
-		}
 		iovecs := d.bufs[k].nextIovecs()
 		iovLen := len(iovecs)
-		d.msgHdrs[k].DataLen = 0
+		// Cannot clear only the length field. Older versions of the darwin kernel will check whether other data is empty.
+		// https://github.com/Darm64/XNU/blob/xnu-2782.40.9/bsd/kern/uipc_syscalls.c#L2026-L2048
+		d.msgHdrs[k] = rawfile.MsgHdrX{}
 		d.msgHdrs[k].Msg.Iov = &iovecs[0]
 		d.msgHdrs[k].Msg.SetIovlen(iovLen)
 	}
@@ -209,7 +180,6 @@ func (d *recvMMsgDispatcher) dispatch() (bool, tcpip.Error) {
 	for k := 0; k < nMsgs; k++ {
 		n := int(d.msgHdrs[k].DataLen)
 		payload := d.bufs[k].pullBuffer(n)
-		payload.TrimFront(4)
 		pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 			Payload: payload,
 		})

tun_darwin.go

@@ -111,14 +111,14 @@ func New(options Options) (Tun, error) {
 			unix.Close(tunFd)
 			return nil, err
 		}
-		err = configure(tunFd, batchSize)
+		err = configure(tunFd, options.MTU, batchSize)
 		if err != nil {
 			unix.Close(tunFd)
 			return nil, err
 		}
 	} else {
 		tunFd = options.FileDescriptor
-		err := configure(tunFd, batchSize)
+		err := configure(tunFd, options.MTU, batchSize)
 		if err != nil {
 			return nil, err
 		}
@@ -332,15 +332,17 @@ func create(tunFd int, ifIndex int, name string, options Options) error {
 	return nil
 }
 
-func configure(tunFd int, batchSize int) error {
+func configure(tunFd int, tunMTU uint32, batchSize int) error {
 	err := unix.SetNonblock(tunFd, true)
 	if err != nil {
 		return os.NewSyscallError("SetNonblock", err)
 	}
-	const UTUN_OPT_MAX_PENDING_PACKETS = 16
+	if tunMTU < 49152 {
-	err = unix.SetsockoptInt(tunFd, 2, UTUN_OPT_MAX_PENDING_PACKETS, batchSize)
+		const UTUN_OPT_MAX_PENDING_PACKETS = 16
-	if err != nil {
+		err = unix.SetsockoptInt(tunFd, 2, UTUN_OPT_MAX_PENDING_PACKETS, batchSize)
-		return os.NewSyscallError("SetsockoptInt UTUN_OPT_MAX_PENDING_PACKETS", err)
+		if err != nil {
+			return os.NewSyscallError("SetsockoptInt UTUN_OPT_MAX_PENDING_PACKETS", err)
+		}
 	}
 	return nil
 }
@@ -352,12 +354,19 @@ func (t *NativeTun) BatchSize() int {
 func (t *NativeTun) BatchRead() ([]*buf.Buffer, error) {
 	for i := 0; i < t.batchSize; i++ {
 		iovecs := t.iovecs[i].nextIovecs()
-		t.msgHdrs[i].DataLen = 0
+		// Cannot clear only the length field. Older versions of the darwin kernel will check whether other data is empty.
+		// https://github.com/Darm64/XNU/blob/xnu-2782.40.9/bsd/kern/uipc_syscalls.c#L2026-L2048
+		t.msgHdrs[i] = rawfile.MsgHdrX{}
 		t.msgHdrs[i].Msg.Iov = &iovecs[0]
 		t.msgHdrs[i].Msg.Iovlen = 2
 	}
 	n, errno := rawfile.BlockingRecvMMsgUntilStopped(t.stopFd.ReadFD, t.tunFd, t.msgHdrs)
 	if errno != 0 {
+		for k := 0; k < n; k++ {
+			t.iovecs[k].buffer.Release()
+			t.iovecs[k].buffer = nil
+		}
+		t.buffers = t.buffers[:0]
 		return nil, errno
 	}
 	if n < 1 {

tun_darwin_gvisor.go

@@ -12,14 +12,17 @@ var _ GVisorTun = (*NativeTun)(nil)
 
 func (t *NativeTun) NewEndpoint() (stack.LinkEndpoint, stack.NICOptions, error) {
 	ep, err := fdbased.New(&fdbased.Options{
-		FDs:               []int{t.tunFd},
+		FDs:                []int{t.tunFd},
-		MTU:               t.options.MTU,
+		MTU:                t.options.MTU,
-		RXChecksumOffload: true,
+		RXChecksumOffload:  true,
+		PacketDispatchMode: fdbased.RecvMMsg,
 	})
 	if err != nil {
 		return nil, stack.NICOptions{}, err
 	}
-	return ep, stack.NICOptions{
+	var nicOptions stack.NICOptions
-		QDisc: fifo.New(ep, 1, 1000),
+	if t.options.MTU < 49152 {
-	}, nil
+		nicOptions.QDisc = fifo.New(ep, 1, 1000)
+	}
+	return ep, nicOptions, nil
 }