NRD rules and "recent" kernel pos index (#3302)

* variants for output_pos linked list entries (head/tail/middle/unique)
next and prev and Vec<u8> lmdb keys

* get_pos on enum

* break list and list entries out into separate enums

* track output features in the new output_pos index, so we can determine coinbase maturity

* push entry impl for none and unique

* some test coverage for output_pos_list

* commit

* wip - FooListEntry

* use instance of the index

* linked list of output_pos and commit_pos both now supported

* linked_list

* cleanup and rename

* rename

* peek_pos

* push some, peek some, pop some

* cleanup

* commit pos
cleanup

* split list and entry out into separate db prefixes

* cleanup and add placeholder for pop_back

* pop_pos_back (for popping off the back of the linked list)
test coverage for pop_pos_back

* wip

* placeholder for prune via a trait
pos must always increase in the index

* rewind kernel_pos_idx when calling rewind_single_block

* RewindableListIndex with rewind support.

* test coverage for rewindable list index

* test coverage for rewind back to 0

* rewind past end of list

* add tests for kernel_pos_idx with multiple commits

* commit

* cleanup

* hook NRD relative lock height validation into block processing and tx validation

* cleanup

* set local chain type for kernel_idx tests

* add test coverage for NRD rules in block processing

* NRD test coverage and cleanup

* NRD relative height 1 test

* test coverage for NRD kernels in block processing

* cleanup

* start of test coverage for txpool NRD kernel rules

* wip

* rework pool tests to use real chain (was mock chain) to better reflect reality (tx/block validation rules etc.)

* cleanup

* cleanup pruneable trait for kernel pos index

* add clear() to kernel_pos idx and test coverage

* hook kernel_pos rebuild into node startup, compaction and fast sync

* verify full NRD history on fast sync

* return early if nrd disabled

* fix header sync issue

core/src/core/transaction.rs

@@ -909,6 +909,36 @@ impl TransactionBody {
 		Ok(())
 	}
 
+	// It is never valid to have multiple duplicate NRD kernels (by public excess)
+	// in the same transaction or block. We check this here.
+	// We skip this check if NRD feature is not enabled.
+	fn verify_no_nrd_duplicates(&self) -> Result<(), Error> {
+		if !global::is_nrd_enabled() {
+			return Ok(());
+		}
+
+		let mut nrd_excess: Vec<Commitment> = self
+			.kernels
+			.iter()
+			.filter(|x| match x.features {
+				KernelFeatures::NoRecentDuplicate { .. } => true,
+				_ => false,
+			})
+			.map(|x| x.excess())
+			.collect();
+
+		// Sort and dedup and compare length to look for duplicates.
+		nrd_excess.sort();
+		let original_count = nrd_excess.len();
+		nrd_excess.dedup();
+		let dedup_count = nrd_excess.len();
+		if original_count == dedup_count {
+			Ok(())
+		} else {
+			Err(Error::InvalidNRDRelativeHeight)
+		}
+	}
+
 	// Verify that inputs|outputs|kernels are sorted in lexicographical order
 	// and that there are no duplicates (they are all unique within this transaction).
 	fn verify_sorted(&self) -> Result<(), Error> {
@@ -970,6 +1000,7 @@ impl TransactionBody {
 	/// * kernel signature verification
 	pub fn validate_read(&self, weighting: Weighting) -> Result<(), Error> {
 		self.verify_weight(weighting)?;
+		self.verify_no_nrd_duplicates()?;
 		self.verify_sorted()?;
 		self.verify_cut_through()?;
 		Ok(())
@@ -1227,8 +1258,8 @@ impl Transaction {
 		weighting: Weighting,
 		verifier: Arc<RwLock<dyn VerifierCache>>,
 	) -> Result<(), Error> {
-		self.body.validate(weighting, verifier)?;
 		self.body.verify_features()?;
+		self.body.validate(weighting, verifier)?;
 		self.verify_kernel_sums(self.overage(), self.offset.clone())?;
 		Ok(())
 	}