fix(network): Respond to getheaders requests with a maximum of 160 block headers

zebra-state/src/constants.rs

@@ -107,20 +107,7 @@ pub const MAX_NON_FINALIZED_CHAIN_FORKS: usize = 10;
 pub const MAX_FIND_BLOCK_HASHES_RESULTS: u32 = 500;
 
 /// The maximum number of block headers allowed in `getheaders` responses in the Zcash network protocol.
-const MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_PROTOCOL: u32 = 160;
-
-/// The maximum number of block headers sent by Zebra in `getheaders` responses.
-///
-/// Older versions of Zcashd will blindly request more block headers as long as it
-/// got 160 block headers in response to a previous query,
-/// _even if those headers are already known_.
-///
-/// To avoid this behavior, return slightly fewer than the maximum,
-/// so `zcashd` thinks it has reached our chain tip.
-///
-/// <https://github.com/bitcoin/bitcoin/pull/4468/files#r17026905>
-pub const MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA: u32 =
-    MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_PROTOCOL - 2;
+pub const MAX_FIND_BLOCK_HEADERS_RESULTS: u32 = 160;
 
 /// These database versions can be recreated from their directly preceding versions.
 pub const RESTORABLE_DB_VERSIONS: [u64; 1] = [26];

zebra-state/src/request.rs

@@ -25,7 +25,7 @@ use zebra_chain::{
 /// will work with inline links.
 #[allow(unused_imports)]
 use crate::{
-    constants::{MAX_FIND_BLOCK_HASHES_RESULTS, MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA},
+    constants::{MAX_FIND_BLOCK_HASHES_RESULTS, MAX_FIND_BLOCK_HEADERS_RESULTS},
     ReadResponse, Response,
 };
 
@@ -721,7 +721,7 @@ pub enum Request {
     /// Stops the list of headers after:
     ///   * adding the best tip,
     ///   * adding the header matching the `stop` hash to the list, if it is in the best chain, or
-    ///   * adding [`MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA`] headers to the list.
+    ///   * adding [`MAX_FIND_BLOCK_HEADERS_RESULTS`] headers to the list.
     ///
     /// Returns an empty list if the state is empty.
     ///
@@ -925,7 +925,7 @@ pub enum ReadRequest {
     /// Stops the list of headers after:
     ///   * adding the best tip,
     ///   * adding the header matching the `stop` hash to the list, if it is in the best chain, or
-    ///   * adding [`MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA`] headers to the list.
+    ///   * adding [`MAX_FIND_BLOCK_HEADERS_RESULTS`] headers to the list.
     ///
     /// Returns an empty list if the state is empty.
     ///

zebra-state/src/service.rs

@@ -44,8 +44,7 @@ use zebra_chain::{block::Height, serialization::ZcashSerialize};
 
 use crate::{
     constants::{
-        MAX_FIND_BLOCK_HASHES_RESULTS, MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA,
-        MAX_LEGACY_CHAIN_BLOCKS,
+        MAX_FIND_BLOCK_HASHES_RESULTS, MAX_FIND_BLOCK_HEADERS_RESULTS, MAX_LEGACY_CHAIN_BLOCKS,
     },
     service::{
         block_iter::any_ancestor_blocks,
@@ -1476,7 +1475,7 @@ impl Service<ReadRequest> for ReadStateService {
                                     &state.db,
                                     known_blocks,
                                     stop,
-                                    MAX_FIND_BLOCK_HEADERS_RESULTS_FOR_ZEBRA,
+                                    MAX_FIND_BLOCK_HEADERS_RESULTS,
                                 )
                             },
                         );