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
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
//! Types for encoding/decoding rammux frame headers.
use std::{fmt, ops::Not};
use bitflags::{Flags, bitflags};
use crate::{error::DecodeError, stream_id::StreamId};
/// 8-byte header of a rammux frame, not validated.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct RawHeader {
/// ID of a rammux stream.
///
/// 1. For [`RawFlags::DATA`] and [`RawFlags::WINDOW_UPDATE`] frames,
/// this denotes the stream in which data is transferred.
/// 2. For [`RawFlags::PING`] frames, this is the first part of the payload.
/// 3. For [`RawFlags::TERM`] frames, this is `0`.
pub stream_id: StreamId,
/// Flags set on the frame.
///
/// For [`RawFlags::TERM`] frames, the is [`RawFlags::empty`].
pub flags: RawFlags,
/// Len of the frame.
///
/// 1. For [`RawFlags::DATA`] frames, this denotes the length of the data.
/// 2. For [`RawFlags::WINDOW_UPDATE`] frames, this denotes the number of bytes returned to the receive window.
/// 3. For [`RawFlags::PING`] frames, this is the second part of the payload.
/// 4. For [`RawFlags::TERM`] frames, this is `0`.
pub len: u32,
}
impl RawHeader {
/// Length of the header in bytes.
pub const LEN: usize = 8;
/// Decodes the header from the given wire representation.
///
/// This function does not verify the bytes in any way.
pub const fn decode(raw: [u8; Self::LEN]) -> Self {
let [s1, s2, s3, flags, l1, l2, l3, l4] = raw;
let stream_id = StreamId::from_be_bytes([s1, s2, s3]);
let flags = RawFlags::from_bits_retain(flags);
let len = u32::from_be_bytes([l1, l2, l3, l4]);
Self {
stream_id,
flags,
len,
}
}
/// Encodes the header to the wire representation.
pub const fn encode(self) -> [u8; Self::LEN] {
let [s1, s2, s3] = self.stream_id.to_be_bytes();
let flags = self.flags.bits();
let [l1, l2, l3, l4] = self.len.to_be_bytes();
[s1, s2, s3, flags, l1, l2, l3, l4]
}
/// Validates this raw header, returning a clean enum.
pub fn validate(self) -> Result<Header, DecodeError> {
if self.flags.contains_unknown_bits() {
return Err(DecodeError {
header: self,
message: "unknown flags set",
});
}
let frame_type = self
.flags
.intersection(RawFlags::PING | RawFlags::WINDOW_UPDATE | RawFlags::DATA);
match frame_type {
RawFlags::PING => {
if self
.flags
.intersects(RawFlags::FIN_READ | RawFlags::FIN_WRITE)
{
Err(DecodeError {
header: self,
message: "PING frame with forbidden flags",
})
} else {
Ok(Header::Ping {
payload: PingPayload {
stream_id: self.stream_id,
len: self.len,
},
is_response: self.flags.contains(RawFlags::SYN).not(),
})
}
},
RawFlags::WINDOW_UPDATE => Ok(Header::WindowUpdate {
stream_id: self.stream_id,
flags: self.flags.into(),
len: self.len,
}),
RawFlags::DATA => Ok(Header::Data {
stream_id: self.stream_id,
flags: self.flags.into(),
len: self.len,
}),
RawFlags::TERM => {
if u32::from(self.stream_id) == 0 && self.flags.is_empty() && self.len == 0 {
Ok(Header::Term)
} else {
Err(DecodeError {
header: self,
message: "TERM frame with dirty bits",
})
}
},
_ => Err(DecodeError {
header: self,
message: "invalid frame type",
}),
}
}
}
impl fmt::LowerHex for RawHeader {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let as_u64 = u64::from_be_bytes(self.encode());
fmt::LowerHex::fmt(&as_u64, f)
}
}
bitflags! {
/// Flags of a rammux frame.
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
pub struct RawFlags: u8 {
/// Denotes `PING` type of the frame.
const PING = 0b00000001;
/// Denotes `WINDOW_UPDATE` type of the frame.
const WINDOW_UPDATE = 0b00000010;
/// Denotes `DATA` type of the frame.
const DATA = 0b00000100;
/// Signals that the sender stopped reading from the stream.
const FIN_READ = 0b00001000;
/// Signals that the sender stopped writing to the stream.
const FIN_WRITE = 0b00010000;
/// Set on:
/// 1. `PING` requests
/// 2. `DATA` and `WINDOW_UPDATE` frames that initiate a new stream.
const SYN = 0b00100000;
}
}
impl RawFlags {
/// Flags for a term frame used in rammux connection dowgrade.
///
/// All bits unset.
pub const TERM: Self = Self::empty();
}
/// Clean enum representing a valid rammux frame header.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Header {
Ping {
payload: PingPayload,
is_response: bool,
},
WindowUpdate {
stream_id: StreamId,
flags: ControlFlags,
len: u32,
},
Data {
stream_id: StreamId,
flags: ControlFlags,
len: u32,
},
Term,
}
/// Control flags extracted from [`RawFlags`].
#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
pub struct ControlFlags {
pub fin_read: bool,
pub fin_write: bool,
pub syn: bool,
}
impl From<RawFlags> for ControlFlags {
fn from(value: RawFlags) -> Self {
Self {
fin_read: value.contains(RawFlags::FIN_READ),
fin_write: value.contains(RawFlags::FIN_WRITE),
syn: value.contains(RawFlags::SYN),
}
}
}
impl From<ControlFlags> for RawFlags {
fn from(value: ControlFlags) -> Self {
let mut flags = RawFlags::empty();
if value.fin_read {
flags |= RawFlags::FIN_READ;
}
if value.fin_write {
flags |= RawFlags::FIN_WRITE;
}
if value.syn {
flags |= RawFlags::SYN;
}
flags
}
}
/// Payload of a [`RawFlags::PING`] frame.
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct PingPayload {
/// In ping frames stream ID has no special meaning.
/// It is used as the first 3 bytes of the payload.
pub stream_id: StreamId,
/// In ping frames frame length is used as the last 4 bytes of the payload.
pub len: u32,
}
impl PingPayload {
/// Generates a random payload using the thread-local RNG.
pub fn random() -> Self {
Self {
stream_id: rand::random(),
len: rand::random(),
}
}
}
impl fmt::Display for PingPayload {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let composed = (u64::from(u32::from(self.stream_id)) << 32) | u64::from(self.len);
write!(f, "{composed:#016x}")
}
}
impl fmt::Debug for PingPayload {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(self, f)
}
}
#[cfg(test)]
mod test {
use rstest::rstest;
use crate::{
StreamId,
header::{ControlFlags, Header, PingPayload, RawFlags, RawHeader},
};
#[rstest]
#[case(
RawHeader { stream_id: StreamId::from_be_bytes([1, 2, 3]), flags: RawFlags::PING | RawFlags::SYN, len: 2137 },
Some(Header::Ping {
payload: PingPayload {
stream_id: StreamId::from_be_bytes([1, 2, 3]),
len: 2137,
},
is_response: false,
}),
)]
#[case(
RawHeader { stream_id: StreamId::from_be_bytes([4, 5, 6]), flags: RawFlags::PING, len: 444 },
Some(Header::Ping {
payload: PingPayload {
stream_id: StreamId::from_be_bytes([4, 5, 6]),
len: 444,
},
is_response: true,
}),
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([7, 8, 9]),
flags: RawFlags::WINDOW_UPDATE | RawFlags::FIN_READ | RawFlags::SYN,
len: 99999,
},
Some(Header::WindowUpdate {
stream_id: StreamId::from_be_bytes([7, 8, 9]),
flags: ControlFlags {
fin_read: true,
fin_write: false,
syn: true,
},
len: 99999,
}),
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([7, 8, 9]),
flags: RawFlags::DATA | RawFlags::FIN_WRITE,
len: 88,
},
Some(Header::Data {
stream_id: StreamId::from_be_bytes([7, 8, 9]),
flags: ControlFlags {
fin_read: false,
fin_write: true,
syn: false,
},
len: 88,
}),
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([0, 0, 0]),
flags: RawFlags::TERM,
len: 0,
},
Some(Header::Term),
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([1, 2, 3]),
flags: RawFlags::PING | RawFlags::SYN | RawFlags::FIN_READ,
len: 2137,
},
None,
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([1, 2, 3]),
flags: RawFlags::DATA | RawFlags::WINDOW_UPDATE,
len: 2137,
},
None,
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([1, 0, 0]),
flags: RawFlags::TERM,
len: 0,
},
None,
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([0, 0, 0]),
flags: RawFlags::SYN,
len: 0,
},
None,
)]
#[case(
RawHeader {
stream_id: StreamId::from_be_bytes([0, 0, 0]),
flags: RawFlags::TERM,
len: 1,
},
None,
)]
#[test]
fn decode_validate(#[case] decoded: RawHeader, #[case] validated: Option<Header>) {
let encoded = decoded.encode();
let decoded_again = RawHeader::decode(encoded);
assert_eq!(decoded_again, decoded);
match validated {
Some(expected) => {
let validated = decoded_again.validate().unwrap();
assert_eq!(validated, expected);
},
None => {
decoded_again.validate().unwrap_err();
},
}
}
}