[T4] Secondary proof of work difficulty adjustments (#1709)

* First pass at secondary proof of work difficulty adjustments
* Core and chain test fixes
* Next difficulty calc now needs a height. Scaling calculation fixes. Setting scaling on mined block.
* Change factor to u32 instead of u64.
* Cleanup structs used by next_difficulty
* Fix header size calc with u32 scaling

chain/src/error.rs

@@ -45,9 +45,9 @@ pub enum ErrorKind {
 	/// Addition of difficulties on all previous block is wrong
 	#[fail(display = "Addition of difficulties on all previous blocks is wrong")]
 	WrongTotalDifficulty,
-	/// Block header sizeshift is lower than our min
-	#[fail(display = "Cuckoo Size too Low")]
-	LowSizeshift,
+	/// Block header sizeshift is incorrect
+	#[fail(display = "Cuckoo size shift is invalid")]
+	InvalidSizeshift,
 	/// Scaling factor between primary and secondary PoW is invalid
 	#[fail(display = "Wrong scaling factor")]
 	InvalidScaling,

chain/src/pipe.rs

@@ -36,8 +36,6 @@ use txhashset;
 use types::{Options, Tip};
 use util::LOGGER;
 
-use failure::ResultExt;
-
 /// Contextual information required to process a new block and either reject or
 /// accept it.
 pub struct BlockContext<'a> {
@@ -364,16 +362,10 @@ fn validate_header(header: &BlockHeader, ctx: &mut BlockContext) -> Result<(), E
 	}
 
 	if !ctx.opts.contains(Options::SKIP_POW) {
+		if !header.pow.is_primary() && !header.pow.is_secondary() {
+			return Err(ErrorKind::InvalidSizeshift.into());
+		}
 		let shift = header.pow.cuckoo_sizeshift();
-		// size shift can either be larger than the minimum on the primary PoW
-		// or equal to the seconday PoW size shift
-		if shift != consensus::SECOND_POW_SIZESHIFT && global::min_sizeshift() > shift {
-			return Err(ErrorKind::LowSizeshift.into());
-		}
-		// primary PoW must have a scaling factor of 1
-		if shift != consensus::SECOND_POW_SIZESHIFT && header.pow.scaling_difficulty != 1 {
-			return Err(ErrorKind::InvalidScaling.into());
-		}
 		if !(ctx.pow_verifier)(header, shift).is_ok() {
 			error!(
 				LOGGER,
@@ -435,17 +427,20 @@ fn validate_header(header: &BlockHeader, ctx: &mut BlockContext) -> Result<(), E
 		// (during testnet1 we use _block_ difficulty here)
 		let child_batch = ctx.batch.child()?;
 		let diff_iter = store::DifficultyIter::from_batch(header.previous, child_batch);
-		let network_difficulty = consensus::next_difficulty(diff_iter)
-			.context(ErrorKind::Other("network difficulty".to_owned()))?;
-		if target_difficulty != network_difficulty.clone() {
-			error!(
+		let next_header_info = consensus::next_difficulty(header.height, diff_iter);
+		if target_difficulty != next_header_info.difficulty {
+			info!(
 				LOGGER,
 				"validate_header: header target difficulty {} != {}",
 				target_difficulty.to_num(),
-				network_difficulty.to_num()
+				next_header_info.difficulty.to_num()
 			);
 			return Err(ErrorKind::WrongTotalDifficulty.into());
 		}
+		// check the secondary PoW scaling factor if applicable
+		if header.pow.scaling_difficulty != next_header_info.secondary_scaling {
+			return Err(ErrorKind::InvalidScaling.into());
+		}
 	}
 
 	Ok(())
@@ -454,10 +449,8 @@ fn validate_header(header: &BlockHeader, ctx: &mut BlockContext) -> Result<(), E
 fn validate_block(block: &Block, ctx: &mut BlockContext) -> Result<(), Error> {
 	let prev = ctx.batch.get_block_header(&block.header.previous)?;
 	block
-		.validate(
-			&prev.total_kernel_offset,
-			ctx.verifier_cache.clone(),
-		).map_err(|e| ErrorKind::InvalidBlockProof(e))?;
+		.validate(&prev.total_kernel_offset, ctx.verifier_cache.clone())
+		.map_err(|e| ErrorKind::InvalidBlockProof(e))?;
 	Ok(())
 }
 

chain/src/store.rs

@@ -22,7 +22,7 @@ use lru_cache::LruCache;
 
 use util::secp::pedersen::Commitment;
 
-use core::consensus::TargetError;
+use core::consensus::HeaderInfo;
 use core::core::hash::{Hash, Hashed};
 use core::core::{Block, BlockHeader, BlockSums};
 use core::pow::Difficulty;
@@ -613,7 +613,7 @@ impl<'a> DifficultyIter<'a> {
 }
 
 impl<'a> Iterator for DifficultyIter<'a> {
-	type Item = Result<(u64, Difficulty), TargetError>;
+	type Item = HeaderInfo;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		// Get both header and previous_header if this is the initial iteration.
@@ -650,8 +650,14 @@ impl<'a> Iterator for DifficultyIter<'a> {
 				.clone()
 				.map_or(Difficulty::zero(), |x| x.total_difficulty());
 			let difficulty = header.total_difficulty() - prev_difficulty;
+			let scaling = header.pow.scaling_difficulty;
 
-			Some(Ok((header.timestamp.timestamp() as u64, difficulty)))
+			Some(HeaderInfo::new(
+				header.timestamp.timestamp() as u64,
+				difficulty,
+				scaling,
+				header.pow.is_secondary(),
+			))
 		} else {
 			return None;
 		}