nylon/polyamide/device/traffic_manip.go at main · encodeous/nylon · GitHub

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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
package device

import (
	"encoding/binary"
	"golang.org/x/net/ipv4"
	"golang.org/x/net/ipv6"
	"net"
	"net/netip"
)

// poly packets use other "IP Versions"
const (
	PolyHeaderSize          = 3
	PolyOffsetPayloadLength = 1
)

func (elem *TCElement) InitPacket(ver int, len uint16) {
	elem.Packet = elem.Buffer[MessageTransportHeaderSize : MessageTransportHeaderSize+len]
	elem.SetIPVersion(ver)
	elem.SetLength(len)
}

func (elem *TCElement) ParsePacket() {
	elem.Packet = elem.Buffer[MessageTransportHeaderSize:]
	l := elem.GetLength()
	elem.Packet = elem.Buffer[MessageTransportHeaderSize : MessageTransportHeaderSize+l]
}

func (elem *TCElement) Incoming() bool {
	return elem.FromPeer != nil
}

func (elem *TCElement) GetIPVersion() int {
	return int(elem.Packet[0] >> 4)
}

func (elem *TCElement) GetSrcBytes() []byte {
	ver := elem.GetIPVersion()
	if ver == 4 {
		return elem.Packet[IPv4offsetSrc : IPv4offsetSrc+net.IPv4len]
	} else if ver == 6 {
		return elem.Packet[IPv6offsetSrc : IPv6offsetSrc+net.IPv6len]
	}
	return nil
}

func (elem *TCElement) GetDstBytes() []byte {
	ver := elem.GetIPVersion()
	if ver == 4 {
		return elem.Packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len]
	} else if ver == 6 {
		return elem.Packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len]
	}
	return nil
}

func (elem *TCElement) GetSrc() netip.Addr {
	ver := elem.GetIPVersion()
	b := elem.GetSrcBytes()
	if ver == 4 {
		return netip.AddrFrom4([4]byte(b))
	} else if ver == 6 {
		return netip.AddrFrom16([16]byte(b))
	}
	return netip.IPv4Unspecified()
}

func (elem *TCElement) SetSrc(addr netip.Addr) {
	bin, err := addr.MarshalBinary()
	if err != nil {
		panic(err)
	}
	copy(elem.GetSrcBytes(), bin)
}

func (elem *TCElement) GetDst() netip.Addr {
	ver := elem.GetIPVersion()
	b := elem.GetDstBytes()
	if ver == 4 {
		return netip.AddrFrom4([4]byte(b))
	} else if ver == 6 {
		return netip.AddrFrom16([16]byte(b))
	}
	return netip.IPv4Unspecified()
}

func (elem *TCElement) SetDst(addr netip.Addr) {
	bin, err := addr.MarshalBinary()
	if err != nil {
		panic(err)
	}
	copy(elem.GetDstBytes(), bin)
}

func (elem *TCElement) SetIPVersion(ver int) {
	elem.Packet[0] = byte(ver << 4)
}

// GetLength returns the length of the packet, including the header
func (elem *TCElement) GetLength() uint16 {
	ver := elem.GetIPVersion()
	if ver == 4 {
		field := elem.Packet[IPv4offsetTotalLength : IPv4offsetTotalLength+2]
		return binary.BigEndian.Uint16(field)
	} else if ver == 6 {
		field := elem.Packet[IPv6offsetPayloadLength : IPv6offsetPayloadLength+2]
		return binary.BigEndian.Uint16(field) + ipv6.HeaderLen
	} else {
		field := elem.Packet[PolyOffsetPayloadLength : PolyOffsetPayloadLength+2]
		return binary.BigEndian.Uint16(field) + PolyHeaderSize
	}
}

func (elem *TCElement) SetLength(len uint16) {
	ver := elem.GetIPVersion()
	if ver == 4 {
		binary.BigEndian.PutUint16(elem.Packet[IPv4offsetTotalLength:IPv4offsetTotalLength+2], len)
	} else if ver == 6 {
		binary.BigEndian.PutUint16(elem.Packet[IPv6offsetPayloadLength:IPv6offsetPayloadLength+2], len-ipv6.HeaderLen)
	} else {
		binary.BigEndian.PutUint16(elem.Packet[PolyOffsetPayloadLength:PolyOffsetPayloadLength+2], len-PolyHeaderSize)
	}
}

func (elem *TCElement) Payload() []byte {
	ver := elem.GetIPVersion()
	if ver == 4 {
		return elem.Packet[ipv4.HeaderLen:]
	} else if ver == 6 {
		return elem.Packet[ipv6.HeaderLen:]
	} else {
		return elem.Packet[PolyHeaderSize:]
	}
}

func (elem *TCElement) Validate() bool {
	if elem == nil || len(elem.Packet) == 0 {
		return false
	}
	ver := elem.GetIPVersion()
	if ver == 4 {
		if elem.GetLength() < ipv4.HeaderLen {
			return false
		}
	} else if ver == 6 {
		if elem.GetLength() < ipv6.HeaderLen {
			return false
		}
	} else {
		if elem.GetLength() < PolyHeaderSize {
			return false
		}
	}
	return true
}

func (elem *TCElement) TTLBytes() []byte {
	if elem.GetIPVersion() == 4 {
		return elem.Packet[8:9]
	} else if elem.GetIPVersion() == 6 {
		return elem.Packet[7:8]
	} else {
		panic("invalid IP version")
	}
}

func (elem *TCElement) GetTTL() byte {
	return elem.TTLBytes()[0]
}

func (elem *TCElement) DecrementTTL() {
	const (
		checksumOffset = 10
	)
	elem.TTLBytes()[0]--
	// using algorithm described in https://datatracker.ietf.org/doc/html/rfc1141
	if elem.GetIPVersion() == 4 {
		// fast incremental checksum calculation
		csum := uint32(binary.BigEndian.Uint16(elem.Packet[checksumOffset:checksumOffset+2])) + 0x100
		csum = csum + (csum >> 16)
		binary.BigEndian.PutUint16(elem.Packet[checksumOffset:checksumOffset+2], uint16(csum))
	}
}