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// Copyright (c) 2017 Cisco and/or its affiliates.
//
// 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 libmemif
import (
"github.com/google/gopacket"
"time"
"sync"
"io"
)
type memoizedPacket struct {
data RawPacketData
ci gopacket.CaptureInfo
}
type MemifPacketHandle struct {
memif *Memif
queueId uint8
rxCount uint16
// Used for caching packets when larger rxburst is called
packetQueue []*memoizedPacket
// Used for synchronization of read/write calls
readMu sync.Mutex
writeMu sync.Mutex
closeMu sync.Mutex
stop bool
}
// Create new GoPacket packet handle from libmemif queue. rxCount determines how many packets will be read
// at once, minimum value is 1
func (memif *Memif) NewPacketHandle(queueId uint8, rxCount uint16) *MemifPacketHandle {
if rxCount == 0 {
rxCount = 1
}
return &MemifPacketHandle{
memif: memif,
queueId: queueId,
rxCount: rxCount,
}
}
// Reads packet data from memif in bursts, based on previously configured rxCount parameterer. Then caches the
// resulting packets and returns them 1 by 1 from this method until queue is empty then tries to call new rx burst
// to read more data. If no data is returned, io.EOF error is thrown and caller should stop reading.
func (handle *MemifPacketHandle) ReadPacketData() (data []byte, ci gopacket.CaptureInfo, err error) {
handle.readMu.Lock()
defer handle.readMu.Unlock()
if handle.stop {
err = io.EOF
return
}
queueLen := len(handle.packetQueue)
if queueLen == 0 {
packets, burstErr := handle.memif.RxBurst(handle.queueId, handle.rxCount)
packetsLen := len(packets)
if burstErr != nil {
err = burstErr
return
}
if packetsLen == 0 {
err = io.EOF
return
}
handle.packetQueue = make([]*memoizedPacket, packetsLen)
for i, packet := range packets {
packetLen := len(packet)
handle.packetQueue[i] = &memoizedPacket{
data: []byte(packet),
ci: gopacket.CaptureInfo{
Timestamp: time.Now(),
CaptureLength: packetLen,
Length: packetLen,
},
}
}
}
packet := handle.packetQueue[0]
handle.packetQueue = handle.packetQueue[1:]
data = packet.data
ci = packet.ci
return
}
// Writes packet data to memif in burst of 1 packet. In case no packet is sent, this method throws io.EOF error and
// called should stop trying to write packets.
func (handle *MemifPacketHandle) WritePacketData(data []byte) (err error) {
handle.writeMu.Lock()
defer handle.writeMu.Unlock()
if handle.stop {
err = io.EOF
return
}
count, err := handle.memif.TxBurst(handle.queueId, []RawPacketData{data})
if err != nil {
return
}
if count == 0 {
err = io.EOF
}
return
}
// Waits for all read and write operations to finish and then prevents more from occurring. Handle can be closed only
// once and then can never be opened again.
func (handle *MemifPacketHandle) Close() {
handle.closeMu.Lock()
defer handle.closeMu.Unlock()
// wait for packet reader to stop
handle.readMu.Lock()
defer handle.readMu.Unlock()
// wait for packet writer to stop
handle.writeMu.Lock()
defer handle.writeMu.Unlock()
// stop reading and writing
handle.stop = true
}
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