From 29097d3dae02dd8c69382e2ecec2a60c2050e722 Mon Sep 17 00:00:00 2001
From: ethDreamer <37123614+ethDreamer@users.noreply.github.com>
Date: Tue, 28 Sep 2021 18:09:08 -0500
Subject: [PATCH] Fork boundary fix (#2646)

* Fixed Gossip Topics on Fork Boundary
---
 beacon_node/network/src/service.rs | 54 ++++++++++++++++--------------
 1 file changed, 28 insertions(+), 26 deletions(-)

diff --git a/beacon_node/network/src/service.rs b/beacon_node/network/src/service.rs
index 05fccbba41..937fe2b5de 100644
--- a/beacon_node/network/src/service.rs
+++ b/beacon_node/network/src/service.rs
@@ -25,8 +25,8 @@ use task_executor::ShutdownReason;
 use tokio::sync::mpsc;
 use tokio::time::Sleep;
 use types::{
-    ChainSpec, EthSpec, ForkContext, ForkName, RelativeEpoch, Slot, SubnetId,
-    SyncCommitteeSubscription, SyncSubnetId, Unsigned, ValidatorSubscription,
+    ChainSpec, EthSpec, ForkContext, RelativeEpoch, Slot, SubnetId, SyncCommitteeSubscription,
+    SyncSubnetId, Unsigned, ValidatorSubscription,
 };
 
 mod tests;
@@ -281,32 +281,34 @@ impl<T: BeaconChainTypes> NetworkService<T> {
     pub fn required_gossip_fork_digests(&self) -> Vec<[u8; 4]> {
         let fork_context = &self.fork_context;
         let spec = &self.beacon_chain.spec;
-        match fork_context.current_fork() {
-            ForkName::Base => {
-                // If we are SUBSCRIBE_DELAY_SLOTS before the fork slot, subscribe only to Base,
-                // else subscribe to Base and Altair.
-                let current_slot = self.beacon_chain.slot().unwrap_or(spec.genesis_slot);
-                match spec.next_fork_epoch::<T::EthSpec>(current_slot) {
-                    Some((_, fork_epoch)) => {
-                        if current_slot.saturating_add(Slot::new(SUBSCRIBE_DELAY_SLOTS))
-                            >= fork_epoch.start_slot(T::EthSpec::slots_per_epoch())
-                        {
-                            fork_context.all_fork_digests()
-                        } else {
-                            vec![fork_context.genesis_context_bytes()]
-                        }
-                    }
-                    None => vec![fork_context.genesis_context_bytes()],
-                }
+        let current_slot = self.beacon_chain.slot().unwrap_or(spec.genesis_slot);
+        let current_fork = fork_context.current_fork();
+
+        let mut result = vec![fork_context
+            .to_context_bytes(current_fork)
+            .unwrap_or_else(|| {
+                panic!(
+                    "{} fork bytes should exist as it's initialized in ForkContext",
+                    current_fork
+                )
+            })];
+
+        if let Some((next_fork, fork_epoch)) = spec.next_fork_epoch::<T::EthSpec>(current_slot) {
+            if current_slot.saturating_add(Slot::new(SUBSCRIBE_DELAY_SLOTS))
+                >= fork_epoch.start_slot(T::EthSpec::slots_per_epoch())
+            {
+                let next_fork_context_bytes =
+                    fork_context.to_context_bytes(next_fork).unwrap_or_else(|| {
+                        panic!(
+                            "context bytes should exist as spec.next_fork_epoch({}) returned Some({})",
+                            current_slot, next_fork
+                        )
+                    });
+                result.push(next_fork_context_bytes);
             }
-            ForkName::Altair => vec![fork_context
-                .to_context_bytes(ForkName::Altair)
-                .expect("Altair fork bytes should exist as it's initialized in ForkContext")],
-            // TODO: check this.. what even is this?
-            ForkName::Merge => vec![fork_context
-                .to_context_bytes(ForkName::Merge)
-                .expect("Merge fork bytes should exist as it's initialized in ForkContext")],
         }
+
+        result
     }
 }