Better size limits. (#3572)

* Better size limits.

* Remove reference to private repo.

* Update node/network/protocol/src/request_response/mod.rs

Fix statement response size.

Co-authored-by: Andronik Ordian <write@reusable.software>

Co-authored-by: Andronik Ordian <write@reusable.software>

polkadot/node/network/protocol/src/request_response/mod.rs

@@ -102,6 +102,19 @@ const STATEMENTS_TIMEOUT: Duration = Duration::from_secs(1);
 /// to have 3 slow nodes connected, to delay transfer for others by `STATEMENTS_TIMEOUT`.
 pub const MAX_PARALLEL_STATEMENT_REQUESTS: u32 = 3;
 
+/// Response size limit for responses of POV like data.
+///
+/// This is larger than `MAX_POV_SIZE` to account for protocol overhead and for additional data in
+/// `CollationFetching` or `AvailableDataFetching` for example. We try to err on larger limits here
+/// as a too large limit only allows an attacker to waste our bandwidth some more, a too low limit
+/// might have more severe effects.
+const POV_RESPONSE_SIZE: u64 = MAX_POV_SIZE as u64 + 10_000;
+
+/// Maximum response sizes for `StatementFetching`.
+///
+/// This is `MAX_CODE_SIZE` plus some additional space for protocol overhead.
+const STATEMENT_RESPONSE_SIZE: u64 = MAX_CODE_SIZE as u64 + 10_000;
+
 impl Protocol {
 	/// Get a configuration for a given Request response protocol.
 	///
@@ -114,7 +127,7 @@ impl Protocol {
 			Protocol::ChunkFetching => RequestResponseConfig {
 				name: p_name,
 				max_request_size: 1_000,
-				max_response_size: MAX_POV_SIZE as u64 / 10,
+				max_response_size: POV_RESPONSE_SIZE as u64 / 10,
 				// We are connected to all validators:
 				request_timeout: DEFAULT_REQUEST_TIMEOUT_CONNECTED,
 				inbound_queue: Some(tx),
@@ -122,7 +135,7 @@ impl Protocol {
 			Protocol::CollationFetching => RequestResponseConfig {
 				name: p_name,
 				max_request_size: 1_000,
-				max_response_size: MAX_POV_SIZE as u64 + 1000,
+				max_response_size: POV_RESPONSE_SIZE,
 				// Taken from initial implementation in collator protocol:
 				request_timeout: POV_REQUEST_TIMEOUT_CONNECTED,
 				inbound_queue: Some(tx),
@@ -130,7 +143,7 @@ impl Protocol {
 			Protocol::PoVFetching => RequestResponseConfig {
 				name: p_name,
 				max_request_size: 1_000,
-				max_response_size: MAX_POV_SIZE as u64,
+				max_response_size: POV_RESPONSE_SIZE,
 				request_timeout: POV_REQUEST_TIMEOUT_CONNECTED,
 				inbound_queue: Some(tx),
 			},
@@ -138,7 +151,7 @@ impl Protocol {
 				name: p_name,
 				max_request_size: 1_000,
 				// Available data size is dominated by the PoV size.
-				max_response_size: MAX_POV_SIZE as u64 + 1000,
+				max_response_size: POV_RESPONSE_SIZE,
 				request_timeout: POV_REQUEST_TIMEOUT_CONNECTED,
 				inbound_queue: Some(tx),
 			},
@@ -146,8 +159,7 @@ impl Protocol {
 				name: p_name,
 				max_request_size: 1_000,
 				// Available data size is dominated code size.
-				// + 1000 to account for protocol overhead (should be way less).
-				max_response_size: MAX_CODE_SIZE as u64 + 1000,
+				max_response_size: STATEMENT_RESPONSE_SIZE,
 				// We need statement fetching to be fast and will try our best at the responding
 				// side to answer requests within that timeout, assuming a bandwidth of 500Mbit/s
 				// - which is the recommended minimum bandwidth for nodes on Kusama as of April