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// Copyright 2018 Google Inc.
//
// 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 header
import (
"encoding/binary"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
)
const (
dstMAC = 0
srcMAC = 6
ethType = 12
)
// EthernetFields contains the fields of an ethernet frame header. It is used to
// describe the fields of a frame that needs to be encoded.
type EthernetFields struct {
// SrcAddr is the "MAC source" field of an ethernet frame header.
SrcAddr tcpip.LinkAddress
// DstAddr is the "MAC destination" field of an ethernet frame header.
DstAddr tcpip.LinkAddress
// Type is the "ethertype" field of an ethernet frame header.
Type tcpip.NetworkProtocolNumber
}
// Ethernet represents an ethernet frame header stored in a byte array.
type Ethernet []byte
const (
// EthernetMinimumSize is the minimum size of a valid ethernet frame.
EthernetMinimumSize = 14
// EthernetAddressSize is the size, in bytes, of an ethernet address.
EthernetAddressSize = 6
)
// SourceAddress returns the "MAC source" field of the ethernet frame header.
func (b Ethernet) SourceAddress() tcpip.LinkAddress {
return tcpip.LinkAddress(b[srcMAC:][:EthernetAddressSize])
}
// DestinationAddress returns the "MAC destination" field of the ethernet frame
// header.
func (b Ethernet) DestinationAddress() tcpip.LinkAddress {
return tcpip.LinkAddress(b[dstMAC:][:EthernetAddressSize])
}
// Type returns the "ethertype" field of the ethernet frame header.
func (b Ethernet) Type() tcpip.NetworkProtocolNumber {
return tcpip.NetworkProtocolNumber(binary.BigEndian.Uint16(b[ethType:]))
}
// Encode encodes all the fields of the ethernet frame header.
func (b Ethernet) Encode(e *EthernetFields) {
binary.BigEndian.PutUint16(b[ethType:], uint16(e.Type))
copy(b[srcMAC:][:EthernetAddressSize], e.SrcAddr)
copy(b[dstMAC:][:EthernetAddressSize], e.DstAddr)
}
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