1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
// 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 header
import (
"encoding/binary"
"math"
"gvisor.dev/gvisor/pkg/tcpip"
)
const (
udpSrcPort = 0
udpDstPort = 2
udpLength = 4
udpChecksum = 6
)
const (
// UDPMaximumPacketSize is the largest possible UDP packet.
UDPMaximumPacketSize = 0xffff
)
// UDPFields contains the fields of a UDP packet. It is used to describe the
// fields of a packet that needs to be encoded.
type UDPFields struct {
// SrcPort is the "Source Port" field of a UDP packet.
SrcPort uint16
// DstPort is the "Destination Port" field of a UDP packet.
DstPort uint16
// Length is the "length" field of a UDP packet.
Length uint16
// Checksum is the "checksum" field of a UDP packet.
Checksum uint16
}
// UDP represents a UDP header stored in a byte array.
type UDP []byte
const (
// UDPMinimumSize is the minimum size of a valid UDP packet.
UDPMinimumSize = 8
// UDPMaximumSize is the maximum size of a valid UDP packet. The length field
// in the UDP header is 16 bits as per RFC 768.
UDPMaximumSize = math.MaxUint16
// UDPProtocolNumber is UDP's transport protocol number.
UDPProtocolNumber tcpip.TransportProtocolNumber = 17
)
// SourcePort returns the "Source Port" field of the UDP header.
func (b UDP) SourcePort() uint16 {
return binary.BigEndian.Uint16(b[udpSrcPort:])
}
// DestinationPort returns the "Destination Port" field of the UDP header.
func (b UDP) DestinationPort() uint16 {
return binary.BigEndian.Uint16(b[udpDstPort:])
}
// Length returns the "Length" field of the UDP header.
func (b UDP) Length() uint16 {
return binary.BigEndian.Uint16(b[udpLength:])
}
// Payload returns the data contained in the UDP datagram.
func (b UDP) Payload() []byte {
return b[:b.Length()][UDPMinimumSize:]
}
// Checksum returns the "checksum" field of the UDP header.
func (b UDP) Checksum() uint16 {
return binary.BigEndian.Uint16(b[udpChecksum:])
}
// SetSourcePort sets the "source port" field of the UDP header.
func (b UDP) SetSourcePort(port uint16) {
binary.BigEndian.PutUint16(b[udpSrcPort:], port)
}
// SetDestinationPort sets the "destination port" field of the UDP header.
func (b UDP) SetDestinationPort(port uint16) {
binary.BigEndian.PutUint16(b[udpDstPort:], port)
}
// SetChecksum sets the "checksum" field of the UDP header.
func (b UDP) SetChecksum(checksum uint16) {
binary.BigEndian.PutUint16(b[udpChecksum:], checksum)
}
// SetLength sets the "length" field of the UDP header.
func (b UDP) SetLength(length uint16) {
binary.BigEndian.PutUint16(b[udpLength:], length)
}
// PayloadLength returns the length of the payload following the UDP header.
func (b UDP) PayloadLength() uint16 {
return b.Length() - UDPMinimumSize
}
// CalculateChecksum calculates the checksum of the UDP packet, given the
// checksum of the network-layer pseudo-header and the checksum of the payload.
func (b UDP) CalculateChecksum(partialChecksum uint16) uint16 {
// Calculate the rest of the checksum.
return Checksum(b[:UDPMinimumSize], partialChecksum)
}
// Encode encodes all the fields of the udp header.
func (b UDP) Encode(u *UDPFields) {
binary.BigEndian.PutUint16(b[udpSrcPort:], u.SrcPort)
binary.BigEndian.PutUint16(b[udpDstPort:], u.DstPort)
binary.BigEndian.PutUint16(b[udpLength:], u.Length)
binary.BigEndian.PutUint16(b[udpChecksum:], u.Checksum)
}
|
