Missing blocks in filter_changes RPC (#9947)

* feat + fix: Missing blocks in filter_changes RPC

 * Implement validity check of reported hashes (in case of re-org) and re-set last_block to the last block reported that is still valid.

* Add const to set history size for validity check (32).

* test: in the case of a re-org we get same block number if hash is different

rpc/src/v1/helpers/poll_filter.rs

@@ -17,7 +17,7 @@
 //! Helper type with all filter state data.
 
 use std::{
-	collections::{BTreeSet, HashSet},
+	collections::{BTreeSet, HashSet, VecDeque},
 	sync::Arc,
 };
 use ethereum_types::H256;
@@ -49,7 +49,11 @@ impl SyncPollFilter {
 #[derive(Clone)]
 pub enum PollFilter {
 	/// Number of last block which client was notified about.
-	Block(BlockNumber),
+	Block {
+		last_block_number: BlockNumber,
+		#[doc(hidden)]
+		recent_reported_hashes: VecDeque<(BlockNumber, H256)>,
+	},
 	/// Hashes of all pending transactions the client knows about.
 	PendingTransaction(BTreeSet<H256>),
 	/// Number of From block number, last seen block hash, pending logs and log filter itself.
@@ -62,6 +66,10 @@ pub enum PollFilter {
 	}
 }
 
+impl PollFilter {
+	pub (in v1) const MAX_BLOCK_HISTORY_SIZE: usize = 32;
+}
+
 /// Returns only last `n` logs
 pub fn limit_logs(mut logs: Vec<Log>, limit: Option<usize>) -> Vec<Log> {
 	let len = logs.len();