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sm-mobile-20261016T185235Z-8e93ecc1b59a Přidáno: · Sestaveno:
icmp_packet.dart Přidáno: Datum není evidováno 5,3 KB · 170 řádků
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1import 'dart:typed_data';
3/// ICMP (RFC 792) and ICMPv6 (RFC 4443) message types used by ping and
4/// traceroute.
5abstract final class IcmpType {
6 static const echoReply4 = 0, unreachable4 = 3, echoRequest4 = 8;
7 static const timeExceeded4 = 11;
8 static const unreachable6 = 1, timeExceeded6 = 3;
9 static const echoRequest6 = 128, echoReply6 = 129;
12/// What a received ICMP message means for an outstanding echo request.
13enum IcmpKind { echoReply, timeExceeded, unreachable, other }
15/// A parsed ICMP message. For error messages, [id] and [seq] come from the
16/// echo request quoted inside the error, so the error can be matched to the
17/// probe that caused it.
18class IcmpMessage {
19 final IcmpKind kind;
20 final int type, code;
21 final int? id, seq;
23 /// For errors about a UDP or TCP packet: the quoted transport protocol
24 /// (17 or 6) and its source and destination ports.
25 final int? protocol, sourcePort, destinationPort;
26 const IcmpMessage(
27 this.kind,
28 this.type,
29 this.code, {
30 this.id,
31 this.seq,
32 this.protocol,
33 this.sourcePort,
34 this.destinationPort,
35 });
37 /// ICMP "port unreachable": the destination itself answered a UDP probe.
38 bool portUnreachable(bool v6) =>
39 kind == IcmpKind.unreachable && code == (v6 ? 4 : 3);
40 @override
41 String toString() =>
42 'IcmpMessage($kind, type $type code $code '
43 'id $id seq $seq)';
46/// Internet checksum (RFC 1071).
47int icmpChecksum(Uint8List data) {
48 var sum = 0;
49 for (var i = 0; i + 1 < data.length; i += 2) {
50 sum += (data[i] << 8) | data[i + 1];
51 }
52 if (data.length.isOdd) sum += data.last << 8;
53 while (sum >> 16 != 0) {
54 sum = (sum & 0xffff) + (sum >> 16);
55 }
56 return ~sum & 0xffff;
59/// An echo request with [size] payload bytes. The IPv4 checksum is filled
60/// in; for ICMPv6 the kernel computes it over the pseudo-header.
61Uint8List buildEchoRequest({
62 required bool v6,
63 required int id,
64 required int seq,
65 int size = 56,
66}) {
67 final packet = Uint8List(8 + size);
68 packet[0] = v6 ? IcmpType.echoRequest6 : IcmpType.echoRequest4;
69 packet[4] = (id >> 8) & 0xff;
70 packet[5] = id & 0xff;
71 packet[6] = (seq >> 8) & 0xff;
72 packet[7] = seq & 0xff;
73 for (var i = 0; i < size; i++) {
74 packet[8 + i] = (0x20 + i) & 0xff;
75 }
76 if (!v6) {
77 final sum = icmpChecksum(packet);
78 packet[2] = sum >> 8;
79 packet[3] = sum & 0xff;
80 }
81 return packet;
84int _u16(Uint8List b, int at) => (b[at] << 8) | b[at + 1];
86/// Parses a received message. Darwin's ICMPv4 datagram sockets deliver the
87/// IPv4 header first ([ipHeader] true); Linux ping sockets and all ICMPv6
88/// sockets deliver the ICMP message alone. Returns null for data too short
89/// or malformed to be an ICMP message.
90IcmpMessage? parseIcmp(
91 Uint8List data, {
92 required bool v6,
93 bool ipHeader = false,
94}) {
95 var at = 0;
96 if (!v6 && ipHeader) {
97 if (data.isEmpty || data[0] >> 4 != 4) return null;
98 at = (data[0] & 0x0f) * 4;
99 if (at < 20) return null;
100 }
101 if (data.length < at + 8) return null;
102 final type = data[at], code = data[at + 1];
103 final reply = v6 ? IcmpType.echoReply6 : IcmpType.echoReply4;
104 if (type == reply) {
105 return IcmpMessage(
106 IcmpKind.echoReply,
107 type,
108 code,
109 id: _u16(data, at + 4),
110 seq: _u16(data, at + 6),
111 );
112 }
113 final exceeded = v6 ? IcmpType.timeExceeded6 : IcmpType.timeExceeded4;
114 final unreachable = v6 ? IcmpType.unreachable6 : IcmpType.unreachable4;
115 final kind = type == exceeded
116 ? IcmpKind.timeExceeded
117 : type == unreachable
118 ? IcmpKind.unreachable
119 : IcmpKind.other;
120 if (kind == IcmpKind.other) return IcmpMessage(kind, type, code);
121 // The error quotes the offending packet: its IP header, then at least the
122 // first 8 bytes of our echo request (type, code, checksum, id, sequence).
123 final quoted = at + 8;
124 int inner, protocol;
125 if (v6) {
126 // Fixed IPv6 header; extension headers are not followed.
127 if (data.length < quoted + 40 + 8) return IcmpMessage(kind, type, code);
128 protocol = data[quoted + 6];
129 inner = quoted + 40;
130 } else {
131 if (data.length < quoted + 20 || data[quoted] >> 4 != 4) {
132 return IcmpMessage(kind, type, code);
133 }
134 final length = (data[quoted] & 0x0f) * 4;
135 if (length < 20 || data.length < quoted + length + 8) {
136 return IcmpMessage(kind, type, code);
137 }
138 protocol = data[quoted + 9];
139 inner = quoted + length;
140 }
141 if (protocol == 17 || protocol == 6) {
142 // UDP and TCP both start with source and destination port.
143 return IcmpMessage(
144 kind,
145 type,
146 code,
147 protocol: protocol,
148 sourcePort: _u16(data, inner),
149 destinationPort: _u16(data, inner + 2),
150 );
151 }
152 if (protocol != (v6 ? 58 : 1)) return IcmpMessage(kind, type, code);
153 final request = v6 ? IcmpType.echoRequest6 : IcmpType.echoRequest4;
154 if (data[inner] != request) return IcmpMessage(kind, type, code);
155 return IcmpMessage(
156 kind,
157 type,
158 code,
159 id: _u16(data, inner + 4),
160 seq: _u16(data, inner + 6),
161 );
164/// The echo id and sequence of a packet this device sent, as returned with
165/// a Linux error-queue notification.
166({int id, int seq})? sentEcho(Uint8List data, {required bool v6}) {
167 final request = v6 ? IcmpType.echoRequest6 : IcmpType.echoRequest4;
168 if (data.length < 8 || data[0] != request) return null;
169 return (id: _u16(data, 4), seq: _u16(data, 6));
SHA-25689a8158d7865e10ebeefcd019b585129573fb247358cffd35e2503c8a2f9c9ca

CH-J Proprietary Software License 1.14 · Zdroje jsou zveřejněny pod CH-J Proprietary Software License 1.14. Jejich dostupnost nemění licenční podmínky ani neposkytuje další oprávnění.

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