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// 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 sniffer
import (
"encoding"
"encoding/binary"
"time"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
type pcapHeader struct {
// MagicNumber is the file magic number.
MagicNumber uint32
// VersionMajor is the major version number.
VersionMajor uint16
// VersionMinor is the minor version number.
VersionMinor uint16
// Thiszone is the GMT to local correction.
Thiszone int32
// Sigfigs is the accuracy of timestamps.
Sigfigs uint32
// Snaplen is the max length of captured packets, in octets.
Snaplen uint32
// Network is the data link type.
Network uint32
}
var _ encoding.BinaryMarshaler = (*pcapPacket)(nil)
type pcapPacket struct {
timestamp time.Time
packet *stack.PacketBuffer
maxCaptureLen int
}
func (p *pcapPacket) MarshalBinary() ([]byte, error) {
pkt := trimmedClone(p.packet)
defer pkt.DecRef()
packetSize := pkt.Size()
captureLen := p.maxCaptureLen
if packetSize < captureLen {
captureLen = packetSize
}
b := make([]byte, 16+captureLen)
binary.LittleEndian.PutUint32(b[0:4], uint32(p.timestamp.Unix()))
binary.LittleEndian.PutUint32(b[4:8], uint32(p.timestamp.Nanosecond()/1000))
binary.LittleEndian.PutUint32(b[8:12], uint32(captureLen))
binary.LittleEndian.PutUint32(b[12:16], uint32(packetSize))
w := tcpip.SliceWriter(b[16:])
for _, v := range pkt.AsSlices() {
if captureLen == 0 {
break
}
if len(v) > captureLen {
v = v[:captureLen]
}
n, err := w.Write(v)
if err != nil {
panic(err)
}
captureLen -= n
}
return b, nil
}
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