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
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Substrate is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! Bitswap server for Substrate.
//!
//! Allows querying transactions by hash over standard bitswap protocol
//! Only supports bitswap 1.2.0.
//! CID is expected to reference 256-bit Blake2b transaction hash.

use crate::{
	request_responses::{IncomingRequest, OutgoingResponse, ProtocolConfig},
	types::ProtocolName,
	MAX_RESPONSE_SIZE,
};

use cid::{self, Version};
use futures::StreamExt;
use log::{debug, error, trace};
use prost::Message;
use sc_client_api::BlockBackend;
use sc_network_types::PeerId;
use schema::bitswap::{
	message::{wantlist::WantType, Block as MessageBlock, BlockPresence, BlockPresenceType},
	Message as BitswapMessage,
};
use sp_runtime::traits::Block as BlockT;
use std::{io, sync::Arc, time::Duration};
use unsigned_varint::encode as varint_encode;

mod schema;

const LOG_TARGET: &str = "bitswap";

// Undocumented, but according to JS the bitswap messages have a max size of 512*1024 bytes
// https://github.com/ipfs/js-ipfs-bitswap/blob/
// d8f80408aadab94c962f6b88f343eb9f39fa0fcc/src/decision-engine/index.js#L16
// We set it to the same value as max substrate protocol message
const MAX_PACKET_SIZE: u64 = MAX_RESPONSE_SIZE;

/// Max number of queued responses before denying requests.
const MAX_REQUEST_QUEUE: usize = 20;

/// Max number of blocks per wantlist
const MAX_WANTED_BLOCKS: usize = 16;

/// Bitswap protocol name
const PROTOCOL_NAME: &'static str = "/ipfs/bitswap/1.2.0";

/// Prefix represents all metadata of a CID, without the actual content.
#[derive(PartialEq, Eq, Clone, Debug)]
struct Prefix {
	/// The version of CID.
	pub version: Version,
	/// The codec of CID.
	pub codec: u64,
	/// The multihash type of CID.
	pub mh_type: u64,
	/// The multihash length of CID.
	pub mh_len: u8,
}

impl Prefix {
	/// Convert the prefix to encoded bytes.
	pub fn to_bytes(&self) -> Vec<u8> {
		let mut res = Vec::with_capacity(4);
		let mut buf = varint_encode::u64_buffer();
		let version = varint_encode::u64(self.version.into(), &mut buf);
		res.extend_from_slice(version);
		let mut buf = varint_encode::u64_buffer();
		let codec = varint_encode::u64(self.codec, &mut buf);
		res.extend_from_slice(codec);
		let mut buf = varint_encode::u64_buffer();
		let mh_type = varint_encode::u64(self.mh_type, &mut buf);
		res.extend_from_slice(mh_type);
		let mut buf = varint_encode::u64_buffer();
		let mh_len = varint_encode::u64(self.mh_len as u64, &mut buf);
		res.extend_from_slice(mh_len);
		res
	}
}

/// Bitswap request handler
pub struct BitswapRequestHandler<B> {
	client: Arc<dyn BlockBackend<B> + Send + Sync>,
	request_receiver: async_channel::Receiver<IncomingRequest>,
}

impl<B: BlockT> BitswapRequestHandler<B> {
	/// Create a new [`BitswapRequestHandler`].
	pub fn new(client: Arc<dyn BlockBackend<B> + Send + Sync>) -> (Self, ProtocolConfig) {
		let (tx, request_receiver) = async_channel::bounded(MAX_REQUEST_QUEUE);

		let config = ProtocolConfig {
			name: ProtocolName::from(PROTOCOL_NAME),
			fallback_names: vec![],
			max_request_size: MAX_PACKET_SIZE,
			max_response_size: MAX_PACKET_SIZE,
			request_timeout: Duration::from_secs(15),
			inbound_queue: Some(tx),
		};

		(Self { client, request_receiver }, config)
	}

	/// Run [`BitswapRequestHandler`].
	pub async fn run(mut self) {
		while let Some(request) = self.request_receiver.next().await {
			let IncomingRequest { peer, payload, pending_response } = request;

			match self.handle_message(&peer, &payload) {
				Ok(response) => {
					let response = OutgoingResponse {
						result: Ok(response),
						reputation_changes: Vec::new(),
						sent_feedback: None,
					};

					match pending_response.send(response) {
						Ok(()) => {
							trace!(target: LOG_TARGET, "Handled bitswap request from {peer}.",)
						},
						Err(_) => debug!(
							target: LOG_TARGET,
							"Failed to handle light client request from {peer}: {}",
							BitswapError::SendResponse,
						),
					}
				},
				Err(err) => {
					error!(target: LOG_TARGET, "Failed to process request from {peer}: {err}");

					// TODO: adjust reputation?

					let response = OutgoingResponse {
						result: Err(()),
						reputation_changes: vec![],
						sent_feedback: None,
					};

					if pending_response.send(response).is_err() {
						debug!(
							target: LOG_TARGET,
							"Failed to handle bitswap request from {peer}: {}",
							BitswapError::SendResponse,
						);
					}
				},
			}
		}
	}

	/// Handle received Bitswap request
	fn handle_message(
		&mut self,
		peer: &PeerId,
		payload: &Vec<u8>,
	) -> Result<Vec<u8>, BitswapError> {
		let request = schema::bitswap::Message::decode(&payload[..])?;

		trace!(target: LOG_TARGET, "Received request: {:?} from {}", request, peer);

		let mut response = BitswapMessage::default();

		let wantlist = match request.wantlist {
			Some(wantlist) => wantlist,
			None => {
				debug!(target: LOG_TARGET, "Unexpected bitswap message from {}", peer);
				return Err(BitswapError::InvalidWantList)
			},
		};

		if wantlist.entries.len() > MAX_WANTED_BLOCKS {
			trace!(target: LOG_TARGET, "Ignored request: too many entries");
			return Err(BitswapError::TooManyEntries)
		}

		for entry in wantlist.entries {
			let cid = match cid::Cid::read_bytes(entry.block.as_slice()) {
				Ok(cid) => cid,
				Err(e) => {
					trace!(target: LOG_TARGET, "Bad CID {:?}: {:?}", entry.block, e);
					continue
				},
			};

			if cid.version() != cid::Version::V1 ||
				cid.hash().code() != u64::from(cid::multihash::Code::Blake2b256) ||
				cid.hash().size() != 32
			{
				debug!(target: LOG_TARGET, "Ignoring unsupported CID {}: {}", peer, cid);
				continue
			}

			let mut hash = B::Hash::default();
			hash.as_mut().copy_from_slice(&cid.hash().digest()[0..32]);
			let transaction = match self.client.indexed_transaction(hash) {
				Ok(ex) => ex,
				Err(e) => {
					error!(target: LOG_TARGET, "Error retrieving transaction {}: {}", hash, e);
					None
				},
			};

			match transaction {
				Some(transaction) => {
					trace!(target: LOG_TARGET, "Found CID {:?}, hash {:?}", cid, hash);

					if entry.want_type == WantType::Block as i32 {
						let prefix = Prefix {
							version: cid.version(),
							codec: cid.codec(),
							mh_type: cid.hash().code(),
							mh_len: cid.hash().size(),
						};
						response
							.payload
							.push(MessageBlock { prefix: prefix.to_bytes(), data: transaction });
					} else {
						response.block_presences.push(BlockPresence {
							r#type: BlockPresenceType::Have as i32,
							cid: cid.to_bytes(),
						});
					}
				},
				None => {
					trace!(target: LOG_TARGET, "Missing CID {:?}, hash {:?}", cid, hash);

					if entry.send_dont_have {
						response.block_presences.push(BlockPresence {
							r#type: BlockPresenceType::DontHave as i32,
							cid: cid.to_bytes(),
						});
					}
				},
			}
		}

		Ok(response.encode_to_vec())
	}
}

/// Bitswap protocol error.
#[derive(Debug, thiserror::Error)]
pub enum BitswapError {
	/// Protobuf decoding error.
	#[error("Failed to decode request: {0}.")]
	DecodeProto(#[from] prost::DecodeError),

	/// Protobuf encoding error.
	#[error("Failed to encode response: {0}.")]
	EncodeProto(#[from] prost::EncodeError),

	/// Client backend error.
	#[error(transparent)]
	Client(#[from] sp_blockchain::Error),

	/// Error parsing CID
	#[error(transparent)]
	BadCid(#[from] cid::Error),

	/// Packet read error.
	#[error(transparent)]
	Read(#[from] io::Error),

	/// Error sending response.
	#[error("Failed to send response.")]
	SendResponse,

	/// Message doesn't have a WANT list.
	#[error("Invalid WANT list.")]
	InvalidWantList,

	/// Too many blocks requested.
	#[error("Too many block entries in the request.")]
	TooManyEntries,
}

#[cfg(test)]
mod tests {
	use super::*;
	use futures::channel::oneshot;
	use sc_block_builder::BlockBuilderBuilder;
	use schema::bitswap::{
		message::{wantlist::Entry, Wantlist},
		Message as BitswapMessage,
	};
	use sp_consensus::BlockOrigin;
	use sp_runtime::codec::Encode;
	use substrate_test_runtime::ExtrinsicBuilder;
	use substrate_test_runtime_client::{self, prelude::*, TestClientBuilder};

	#[tokio::test]
	async fn undecodable_message() {
		let client = substrate_test_runtime_client::new();
		let (bitswap, config) = BitswapRequestHandler::new(Arc::new(client));

		tokio::spawn(async move { bitswap.run().await });

		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: vec![0x13, 0x37, 0x13, 0x38],
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(result, Err(()));
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());
		} else {
			panic!("invalid event received");
		}
	}

	#[tokio::test]
	async fn empty_want_list() {
		let client = substrate_test_runtime_client::new();
		let (bitswap, mut config) = BitswapRequestHandler::new(Arc::new(client));

		tokio::spawn(async move { bitswap.run().await });

		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.as_mut()
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: BitswapMessage { wantlist: None, ..Default::default() }.encode_to_vec(),
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(result, Err(()));
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());
		} else {
			panic!("invalid event received");
		}

		// Empty WANT list should not cause an error
		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: BitswapMessage {
					wantlist: Some(Default::default()),
					..Default::default()
				}
				.encode_to_vec(),
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(result, Ok(BitswapMessage::default().encode_to_vec()));
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());
		} else {
			panic!("invalid event received");
		}
	}

	#[tokio::test]
	async fn too_long_want_list() {
		let client = substrate_test_runtime_client::new();
		let (bitswap, config) = BitswapRequestHandler::new(Arc::new(client));

		tokio::spawn(async move { bitswap.run().await });

		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: BitswapMessage {
					wantlist: Some(Wantlist {
						entries: (0..MAX_WANTED_BLOCKS + 1)
							.map(|_| Entry::default())
							.collect::<Vec<_>>(),
						full: false,
					}),
					..Default::default()
				}
				.encode_to_vec(),
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(result, Err(()));
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());
		} else {
			panic!("invalid event received");
		}
	}

	#[tokio::test]
	async fn transaction_not_found() {
		let client = TestClientBuilder::with_tx_storage(u32::MAX).build();

		let (bitswap, config) = BitswapRequestHandler::new(Arc::new(client));
		tokio::spawn(async move { bitswap.run().await });

		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: BitswapMessage {
					wantlist: Some(Wantlist {
						entries: vec![Entry {
							block: cid::Cid::new_v1(
								0x70,
								cid::multihash::Multihash::wrap(
									u64::from(cid::multihash::Code::Blake2b256),
									&[0u8; 32],
								)
								.unwrap(),
							)
							.to_bytes(),
							..Default::default()
						}],
						full: false,
					}),
					..Default::default()
				}
				.encode_to_vec(),
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(result, Ok(vec![]));
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());
		} else {
			panic!("invalid event received");
		}
	}

	#[tokio::test]
	async fn transaction_found() {
		let client = TestClientBuilder::with_tx_storage(u32::MAX).build();
		let mut block_builder = BlockBuilderBuilder::new(&client)
			.on_parent_block(client.chain_info().genesis_hash)
			.with_parent_block_number(0)
			.build()
			.unwrap();

		// encoded extrinsic: [161, .. , 2, 6, 16, 19, 55, 19, 56]
		let ext = ExtrinsicBuilder::new_indexed_call(vec![0x13, 0x37, 0x13, 0x38]).build();
		let pattern_index = ext.encoded_size() - 4;

		block_builder.push(ext.clone()).unwrap();
		let block = block_builder.build().unwrap().block;

		client.import(BlockOrigin::File, block).await.unwrap();

		let (bitswap, config) = BitswapRequestHandler::new(Arc::new(client));

		tokio::spawn(async move { bitswap.run().await });

		let (tx, rx) = oneshot::channel();
		config
			.inbound_queue
			.unwrap()
			.send(IncomingRequest {
				peer: PeerId::random(),
				payload: BitswapMessage {
					wantlist: Some(Wantlist {
						entries: vec![Entry {
							block: cid::Cid::new_v1(
								0x70,
								cid::multihash::Multihash::wrap(
									u64::from(cid::multihash::Code::Blake2b256),
									&sp_crypto_hashing::blake2_256(&ext.encode()[pattern_index..]),
								)
								.unwrap(),
							)
							.to_bytes(),
							..Default::default()
						}],
						full: false,
					}),
					..Default::default()
				}
				.encode_to_vec(),
				pending_response: tx,
			})
			.await
			.unwrap();

		if let Ok(OutgoingResponse { result, reputation_changes, sent_feedback }) = rx.await {
			assert_eq!(reputation_changes, Vec::new());
			assert!(sent_feedback.is_none());

			let response =
				schema::bitswap::Message::decode(&result.expect("fetch to succeed")[..]).unwrap();
			assert_eq!(response.payload[0].data, vec![0x13, 0x37, 0x13, 0x38]);
		} else {
			panic!("invalid event received");
		}
	}
}