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// Copyright 2020 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 tun
import (
"encoding/binary"
"gvisor.dev/gvisor/pkg/tcpip"
)
const (
// PacketInfoHeaderSize is the size of the packet information header.
PacketInfoHeaderSize = 4
offsetFlags = 0
offsetProtocol = 2
)
// PacketInfoFields contains fields sent through the wire if IFF_NO_PI flag is
// not set.
type PacketInfoFields struct {
Flags uint16
Protocol tcpip.NetworkProtocolNumber
}
// PacketInfoHeader is the wire representation of the packet information sent if
// IFF_NO_PI flag is not set.
type PacketInfoHeader []byte
// Encode encodes f into h.
func (h PacketInfoHeader) Encode(f *PacketInfoFields) {
binary.BigEndian.PutUint16(h[offsetFlags:][:2], f.Flags)
binary.BigEndian.PutUint16(h[offsetProtocol:][:2], uint16(f.Protocol))
}
// Flags returns the flag field in h.
func (h PacketInfoHeader) Flags() uint16 {
return binary.BigEndian.Uint16(h[offsetFlags:])
}
// Protocol returns the protocol field in h.
func (h PacketInfoHeader) Protocol() tcpip.NetworkProtocolNumber {
return tcpip.NetworkProtocolNumber(binary.BigEndian.Uint16(h[offsetProtocol:]))
}
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