1 files changed, 151 insertions, 0 deletions
diff --git a/pkg/tcpip/link/sharedmem/queue/tx.go b/pkg/tcpip/link/sharedmem/queue/tx.go
new file mode 100755
index 000000000..beffe807b
--- /dev/null
+++ b/pkg/tcpip/link/sharedmem/queue/tx.go
@@ -0,0 +1,151 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package queue
+
+import (
+	"encoding/binary"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/tcpip/link/sharedmem/pipe"
+)
+
+const (
+	// Offsets within a packet header.
+	packetID       = 0
+	packetSize     = 8
+	packetReserved = 12
+
+	sizeOfPacketHeader = 16
+
+	// Offsets with a buffer descriptor
+	bufferOffset = 0
+	bufferSize   = 8
+
+	sizeOfBufferDescriptor = 12
+)
+
+// TxBuffer is the descriptor of a transmit buffer.
+type TxBuffer struct {
+	Next   *TxBuffer
+	Offset uint64
+	Size   uint32
+}
+
+// Tx is a transmit queue. It is implemented with one tx and one rx pipe: the
+// tx pipe is used to request the transmission of packets, while the rx pipe
+// is used to receive which transmissions have completed.
+//
+// This struct is thread-compatible.
+type Tx struct {
+	tx pipe.Tx
+	rx pipe.Rx
+}
+
+// Init initializes the transmit queue with the given pipes.
+func (t *Tx) Init(tx, rx []byte) {
+	t.tx.Init(tx)
+	t.rx.Init(rx)
+}
+
+// Enqueue queues the given linked list of buffers for transmission as one
+// packet. While it is queued, the caller must not modify them.
+func (t *Tx) Enqueue(id uint64, totalDataLen, bufferCount uint32, buffer *TxBuffer) bool {
+	// Reserve room in the tx pipe.
+	totalLen := sizeOfPacketHeader + uint64(bufferCount)*sizeOfBufferDescriptor
+
+	b := t.tx.Push(totalLen)
+	if b == nil {
+		return false
+	}
+
+	// Initialize the packet and buffer descriptors.
+	binary.LittleEndian.PutUint64(b[packetID:], id)
+	binary.LittleEndian.PutUint32(b[packetSize:], totalDataLen)
+	binary.LittleEndian.PutUint32(b[packetReserved:], 0)
+
+	offset := sizeOfPacketHeader
+	for i := bufferCount; i != 0; i-- {
+		binary.LittleEndian.PutUint64(b[offset+bufferOffset:], buffer.Offset)
+		binary.LittleEndian.PutUint32(b[offset+bufferSize:], buffer.Size)
+		offset += sizeOfBufferDescriptor
+		buffer = buffer.Next
+	}
+
+	t.tx.Flush()
+
+	return true
+}
+
+// CompletedPacket returns the id of the last completed transmission. The
+// returned id, if any, refers to a value passed on a previous call to
+// Enqueue().
+func (t *Tx) CompletedPacket() (id uint64, ok bool) {
+	for {
+		b := t.rx.Pull()
+		if b == nil {
+			return 0, false
+		}
+
+		if len(b) != 8 {
+			t.rx.Flush()
+			log.Warningf("Ignoring completed packet: size (%v) is less than expected (%v)", len(b), 8)
+			continue
+		}
+
+		v := binary.LittleEndian.Uint64(b)
+
+		t.rx.Flush()
+
+		return v, true
+	}
+}
+
+// Bytes returns the byte slices on which the queue operates.
+func (t *Tx) Bytes() (tx, rx []byte) {
+	return t.tx.Bytes(), t.rx.Bytes()
+}
+
+// TxPacketInfo holds information about a packet sent on a tx queue.
+type TxPacketInfo struct {
+	ID          uint64
+	Size        uint32
+	Reserved    uint32
+	BufferCount int
+}
+
+// DecodeTxPacketHeader decodes the header of a packet sent over a tx queue.
+func DecodeTxPacketHeader(b []byte) TxPacketInfo {
+	return TxPacketInfo{
+		ID:          binary.LittleEndian.Uint64(b[packetID:]),
+		Size:        binary.LittleEndian.Uint32(b[packetSize:]),
+		Reserved:    binary.LittleEndian.Uint32(b[packetReserved:]),
+		BufferCount: (len(b) - sizeOfPacketHeader) / sizeOfBufferDescriptor,
+	}
+}
+
+// DecodeTxBufferHeader decodes the header of the i-th buffer of a packet sent
+// over a tx queue.
+func DecodeTxBufferHeader(b []byte, i int) TxBuffer {
+	b = b[sizeOfPacketHeader+i*sizeOfBufferDescriptor:]
+	return TxBuffer{
+		Offset: binary.LittleEndian.Uint64(b[bufferOffset:]),
+		Size:   binary.LittleEndian.Uint32(b[bufferSize:]),
+	}
+}
+
+// EncodeTxCompletion encodes a tx completion header.
+func EncodeTxCompletion(b []byte, id uint64) {
+	binary.LittleEndian.PutUint64(b, id)
+}