116 lines
3.3 KiB
Go
116 lines
3.3 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package header
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import (
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"encoding/binary"
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"gvisor.dev/gvisor/pkg/tcpip"
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)
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const (
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udpSrcPort = 0
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udpDstPort = 2
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udpLength = 4
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udpChecksum = 6
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)
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const (
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// UDPMaximumPacketSize is the largest possible UDP packet.
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UDPMaximumPacketSize = 0xffff
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)
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// UDPFields contains the fields of a UDP packet. It is used to describe the
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// fields of a packet that needs to be encoded.
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type UDPFields struct {
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// SrcPort is the "source port" field of a UDP packet.
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SrcPort uint16
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// DstPort is the "destination port" field of a UDP packet.
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DstPort uint16
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// Length is the "length" field of a UDP packet.
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Length uint16
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// Checksum is the "checksum" field of a UDP packet.
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Checksum uint16
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}
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// UDP represents a UDP header stored in a byte array.
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type UDP []byte
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const (
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// UDPMinimumSize is the minimum size of a valid UDP packet.
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UDPMinimumSize = 8
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// UDPProtocolNumber is UDP's transport protocol number.
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UDPProtocolNumber tcpip.TransportProtocolNumber = 17
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)
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// SourcePort returns the "source port" field of the udp header.
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func (b UDP) SourcePort() uint16 {
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return binary.BigEndian.Uint16(b[udpSrcPort:])
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}
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// DestinationPort returns the "destination port" field of the udp header.
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func (b UDP) DestinationPort() uint16 {
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return binary.BigEndian.Uint16(b[udpDstPort:])
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}
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// Length returns the "length" field of the udp header.
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func (b UDP) Length() uint16 {
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return binary.BigEndian.Uint16(b[udpLength:])
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}
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// Payload returns the data contained in the UDP datagram.
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func (b UDP) Payload() []byte {
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return b[UDPMinimumSize:]
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}
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// Checksum returns the "checksum" field of the udp header.
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func (b UDP) Checksum() uint16 {
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return binary.BigEndian.Uint16(b[udpChecksum:])
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}
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// SetSourcePort sets the "source port" field of the udp header.
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func (b UDP) SetSourcePort(port uint16) {
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binary.BigEndian.PutUint16(b[udpSrcPort:], port)
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}
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// SetDestinationPort sets the "destination port" field of the udp header.
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func (b UDP) SetDestinationPort(port uint16) {
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binary.BigEndian.PutUint16(b[udpDstPort:], port)
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}
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// SetChecksum sets the "checksum" field of the udp header.
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func (b UDP) SetChecksum(checksum uint16) {
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binary.BigEndian.PutUint16(b[udpChecksum:], checksum)
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}
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// CalculateChecksum calculates the checksum of the udp packet, given the
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// checksum of the network-layer pseudo-header and the checksum of the payload.
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func (b UDP) CalculateChecksum(partialChecksum uint16) uint16 {
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// Calculate the rest of the checksum.
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return Checksum(b[:UDPMinimumSize], partialChecksum)
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}
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// Encode encodes all the fields of the udp header.
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func (b UDP) Encode(u *UDPFields) {
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binary.BigEndian.PutUint16(b[udpSrcPort:], u.SrcPort)
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binary.BigEndian.PutUint16(b[udpDstPort:], u.DstPort)
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binary.BigEndian.PutUint16(b[udpLength:], u.Length)
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binary.BigEndian.PutUint16(b[udpChecksum:], u.Checksum)
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}
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