From 9fc9c65c8ae853233337bdd3e483269187c82ef1 Mon Sep 17 00:00:00 2001
From: Pierre Krieger <pierre.krieger1708@gmail.com>
Date: Thu, 10 Aug 2023 15:40:46 +0000
Subject: [PATCH] Properly report the best parablock in block announces
 handshakes (#1012)

* Properly report the best parablock in block announces handshakes

* PR link
---
 light-base/src/sync_service.rs           |  1 +
 light-base/src/sync_service/parachain.rs | 33 ++++++++++++++++++++++++
 wasm-node/CHANGELOG.md                   |  1 +
 3 files changed, 35 insertions(+)

diff --git a/light-base/src/sync_service.rs b/light-base/src/sync_service.rs
index b379b2980d..17b7ffbb3e 100644
--- a/light-base/src/sync_service.rs
+++ b/light-base/src/sync_service.rs
@@ -165,6 +165,7 @@ impl<TPlat: PlatformRef> SyncService<TPlat> {
                         config_parachain.relay_chain_block_number_bytes,
                         config_parachain.parachain_id,
                         from_foreground,
+                        config.network_service.0.clone(),
                         config.network_service.1,
                         config.network_events_receiver,
                     )),
diff --git a/light-base/src/sync_service/parachain.rs b/light-base/src/sync_service/parachain.rs
index 68a6773003..792ad9d15b 100644
--- a/light-base/src/sync_service/parachain.rs
+++ b/light-base/src/sync_service/parachain.rs
@@ -49,6 +49,7 @@ pub(super) async fn start_parachain<TPlat: PlatformRef>(
     relay_chain_block_number_bytes: usize,
     parachain_id: u32,
     from_foreground: async_channel::Receiver<ToBackground>,
+    network_service: Arc<network_service::NetworkService<TPlat>>,
     network_chain_index: usize,
     from_network_service: stream::BoxStream<'static, network_service::Event>,
 ) {
@@ -58,6 +59,7 @@ pub(super) async fn start_parachain<TPlat: PlatformRef>(
         block_number_bytes,
         relay_chain_block_number_bytes,
         parachain_id,
+        network_service,
         network_chain_index,
         from_network_service: from_network_service.fuse(),
         sync_sources: sources::AllForksSources::new(
@@ -117,6 +119,9 @@ struct ParachainBackgroundTask<TPlat: PlatformRef> {
     /// Id of the parachain registered within the relay chain. Chosen by the user.
     parachain_id: u32,
 
+    /// Networking service connected to the peer-to-peer network of the parachain.
+    network_service: Arc<network_service::NetworkService<TPlat>>,
+
     /// Index of the chain within the associated network service.
     ///
     /// Used to filter events from [`ParachainBackgroundTask::from_network_service`].
@@ -924,6 +929,20 @@ impl<TPlat: PlatformRef> ParachainBackgroundTask<TPlat> {
                     {
                         runtime_subscription.reported_best_parahead_hash = Some(parahash);
 
+                        // The networking service needs to be kept up to date with what the local
+                        // node considers as the best block.
+                        if let Ok(header) =
+                            header::decode(finalized_parahead, self.block_number_bytes)
+                        {
+                            self.network_service
+                                .set_local_best_block(
+                                    self.network_chain_index,
+                                    parahash,
+                                    header.number,
+                                )
+                                .await;
+                        }
+
                         log::debug!(
                             target: &self.log_target,
                             "Subscriptions <= BestBlockChanged(hash={})",
@@ -980,6 +999,20 @@ impl<TPlat: PlatformRef> ParachainBackgroundTask<TPlat> {
                         {
                             runtime_subscription.reported_best_parahead_hash = Some(parahash);
 
+                            // The networking service needs to be kept up to date with what the
+                            // local node considers as the best block.
+                            if let Ok(header) =
+                                header::decode(finalized_parahead, self.block_number_bytes)
+                            {
+                                self.network_service
+                                    .set_local_best_block(
+                                        self.network_chain_index,
+                                        parahash,
+                                        header.number,
+                                    )
+                                    .await;
+                            }
+
                             log::debug!(
                                 target: &self.log_target,
                                 "Subscriptions <= BestBlockChanged(hash={})",
diff --git a/wasm-node/CHANGELOG.md b/wasm-node/CHANGELOG.md
index dbbb1b5003..47ffaaef07 100644
--- a/wasm-node/CHANGELOG.md
+++ b/wasm-node/CHANGELOG.md
@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- The block announces substream handshake of a parachain peer-to-peer network now properly contains the block that smoldot thinks is the best. The genesis block was previously always reported. ([#1012](https://github.com/smol-dot/smoldot/pull/1012))
 - Fix panic when removing a chain while a networking connection is being opened. ([#1011](https://github.com/smol-dot/smoldot/pull/1011))
 - Fix epoch start slot calculation when epochs have been skipped. ([#1015](https://github.com/smol-dot/smoldot/pull/1015))