[PIBD_IMPL] BitmapAccumulator Serialization Fix (#3705)

* fix for writing / calculating incorrect length for negative indices

* update capabilities with new version of PIBD hist

* remove incorrect comment

* fix capabilities flag, trace output

* test fix

chain/src/txhashset/bitmap_accumulator.rs

@@ -418,7 +418,11 @@ impl Writeable for BitmapBlock {
 		writer.write_u8((length / BitmapChunk::LEN_BITS) as u8)?;
 
 		let count_pos = self.inner.iter().filter(|&v| v).count() as u32;
-		let count_neg = Self::NBITS - count_pos;
+
+		// Negative count needs to be adjusted if the block is not full,
+		// which affects the choice of serialization mode and size written
+		let count_neg = length as u32 - count_pos;
+
 		let threshold = Self::NBITS / 16;
 		if count_pos < threshold {
 			// Write positive indices
@@ -518,17 +522,19 @@ mod tests {
 	use rand::thread_rng;
 	use std::io::Cursor;
 
-	fn test_roundtrip(entries: usize, inverse: bool, encoding: u8, length: usize) {
+	fn test_roundtrip(entries: usize, inverse: bool, encoding: u8, length: usize, n_blocks: usize) {
 		let mut rng = thread_rng();
-		let mut block = BitmapBlock::new(64);
+		let mut block = BitmapBlock::new(n_blocks);
 		if inverse {
 			block.inner.negate();
 		}
 
+		let range_size = n_blocks * BitmapChunk::LEN_BITS as usize;
+
 		// Flip `entries` bits in random spots
 		let mut count = 0;
 		while count < entries {
-			let idx = rng.gen_range(0, BitmapBlock::NBITS as usize);
+			let idx = rng.gen_range(0, range_size);
 			if block.inner.get(idx).unwrap() == inverse {
 				count += 1;
 				block.inner.set(idx, !inverse);
@@ -562,21 +568,35 @@ mod tests {
 	fn block_ser_roundtrip() {
 		let threshold = BitmapBlock::NBITS as usize / 16;
 		let entries = thread_rng().gen_range(threshold, 4 * threshold);
-		test_roundtrip(entries, false, 0, 2 + BitmapBlock::NBITS as usize / 8);
-		test_roundtrip(entries, true, 0, 2 + BitmapBlock::NBITS as usize / 8);
+		test_roundtrip(entries, false, 0, 2 + BitmapBlock::NBITS as usize / 8, 64);
+		test_roundtrip(entries, true, 0, 2 + BitmapBlock::NBITS as usize / 8, 64);
 	}
 
 	#[test]
 	fn sparse_block_ser_roundtrip() {
 		let entries =
 			thread_rng().gen_range(BitmapChunk::LEN_BITS, BitmapBlock::NBITS as usize / 16);
-		test_roundtrip(entries, false, 1, 4 + 2 * entries);
+		test_roundtrip(entries, false, 1, 4 + 2 * entries, 64);
+	}
+
+	#[test]
+	fn sparse_unfull_block_ser_roundtrip() {
+		let entries =
+			thread_rng().gen_range(BitmapChunk::LEN_BITS, BitmapBlock::NBITS as usize / 16);
+		test_roundtrip(entries, false, 1, 4 + 2 * entries, 61);
 	}
 
 	#[test]
 	fn abdundant_block_ser_roundtrip() {
 		let entries =
 			thread_rng().gen_range(BitmapChunk::LEN_BITS, BitmapBlock::NBITS as usize / 16);
-		test_roundtrip(entries, true, 2, 4 + 2 * entries);
+		test_roundtrip(entries, true, 2, 4 + 2 * entries, 64);
+	}
+
+	#[test]
+	fn abdundant_unfull_block_ser_roundtrip() {
+		let entries =
+			thread_rng().gen_range(BitmapChunk::LEN_BITS, BitmapBlock::NBITS as usize / 16);
+		test_roundtrip(entries, true, 2, 4 + 2 * entries, 61);
 	}
 }

p2p/src/types.rs

@@ -391,6 +391,8 @@ bitflags! {
 		const PIBD_HIST = 0b0001_0000;
 		/// Can provide historical blocks for archival sync.
 		const BLOCK_HIST = 0b0010_0000;
+		/// As above, with crucial serialization fix #3705 applied
+		const PIBD_HIST_1 = 0b0100_0000;
 	}
 }
 
@@ -402,6 +404,7 @@ impl Default for Capabilities {
 			| Capabilities::PEER_LIST
 			| Capabilities::TX_KERNEL_HASH
 			| Capabilities::PIBD_HIST
+			| Capabilities::PIBD_HIST_1
 	}
 }
 

p2p/tests/capabilities.rs

@@ -42,6 +42,7 @@ fn default_capabilities() {
 	assert!(x.contains(Capabilities::PEER_LIST));
 	assert!(x.contains(Capabilities::TX_KERNEL_HASH));
 	assert!(x.contains(Capabilities::PIBD_HIST));
+	assert!(x.contains(Capabilities::PIBD_HIST_1));
 
 	assert_eq!(
 		x,
@@ -50,5 +51,6 @@ fn default_capabilities() {
 			| Capabilities::PEER_LIST
 			| Capabilities::TX_KERNEL_HASH
 			| Capabilities::PIBD_HIST
+			| Capabilities::PIBD_HIST_1
 	);
 }

p2p/tests/ser_deser.rs

@@ -55,11 +55,7 @@ fn test_capabilities() {
 
 	assert_eq!(
 		expected,
-		p2p::types::Capabilities::from_bits_truncate(0b11111 as u32),
-	);
-	assert_eq!(
-		expected,
-		p2p::types::Capabilities::from_bits_truncate(0b00011111 as u32),
+		p2p::types::Capabilities::from_bits_truncate(0b1011111 as u32),
 	);
 
 	assert_eq!(

servers/src/grin/sync/state_sync.rs

@@ -305,10 +305,10 @@ impl StateSync {
 			let max_diff = peers_iter().max_difficulty().unwrap_or(Difficulty::zero());
 			let peers_iter_max = || peers_iter().with_difficulty(|x| x >= max_diff);
 
-			// Then, further filter by PIBD capabilities
+			// Then, further filter by PIBD capabilities v1
 			let peers_iter_pibd = || {
 				peers_iter_max()
-					.with_capabilities(Capabilities::PIBD_HIST)
+					.with_capabilities(Capabilities::PIBD_HIST_1)
 					.connected()
 			};
 
@@ -335,10 +335,10 @@ impl StateSync {
 			}
 
 			// Choose a random "most work" peer, preferring outbound if at all possible.
-			let peer = peers_iter_pibd().outbound().choose_random().or_else(|| {
-				warn!("no suitable outbound peer for pibd message, considering inbound");
-				peers_iter_pibd().inbound().choose_random()
-			});
+			let peer = peers_iter_pibd()
+				.outbound()
+				.choose_random()
+				.or_else(|| peers_iter_pibd().inbound().choose_random());
 			trace!("Chosen peer is {:?}", peer);
 
 			if let Some(p) = peer {