From 7a0cf3fea50ffe425cf2066a09b3d6e9eb8f2300 Mon Sep 17 00:00:00 2001
From: Jacek Sieka <jacek@status.im>
Date: Thu, 8 Sep 2022 09:13:25 +0200
Subject: [PATCH] Don't consider stubbed terminal block hash terminal (fixes
 #4094)

---
 beacon_chain/eth1/eth1_monitor.nim | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/beacon_chain/eth1/eth1_monitor.nim b/beacon_chain/eth1/eth1_monitor.nim
index 68f305d4d4..4cdeaa7e0c 100644
--- a/beacon_chain/eth1/eth1_monitor.nim
+++ b/beacon_chain/eth1/eth1_monitor.nim
@@ -134,6 +134,7 @@ type
     depositsChain: Eth1Chain
     eth1Progress: AsyncEvent
 
+    exchangedConfiguration*: bool
     terminalBlockHash*: Option[BlockHash]
     terminalBlockNumber*: Option[Quantity]
 
@@ -586,8 +587,17 @@ proc exchangeTransitionConfiguration*(p: Eth1Monitor): Future[EtcStatus] {.async
          localValue = consensusCfg.terminalTotalDifficulty
     return EtcStatus.mismatch
 
+  if not p.exchangedConfiguration:
+    # Log successful engine configuration exchange once at startup
+    p.exchangedConfiguration = true
+    info "Exchanged engine configuration",
+      ttd = executionCfg.terminalTotalDifficulty,
+      terminalBlockHash = executionCfg.terminalBlockHash,
+      terminalBlockNumber = executionCfg.terminalBlockNumber.uint64
+
   if p.terminalBlockNumber.isSome and p.terminalBlockHash.isSome:
     var res = EtcStatus.match
+
     if consensusCfg.terminalBlockNumber != executionCfg.terminalBlockNumber:
       warn "Engine API reporting different terminal block number",
             engineAPI_value = executionCfg.terminalBlockNumber.uint64,
@@ -600,6 +610,13 @@ proc exchangeTransitionConfiguration*(p: Eth1Monitor): Future[EtcStatus] {.async
       res = EtcStatus.mismatch
     return res
   else:
+    if executionCfg.terminalBlockHash == default BlockHash:
+      # If TERMINAL_BLOCK_HASH is stubbed with
+      # 0x0000000000000000000000000000000000000000000000000000000000000000 then
+      # TERMINAL_BLOCK_HASH and TERMINAL_BLOCK_NUMBER parameters MUST NOT take
+      # an effect.
+      return EtcStatus.match
+
     p.terminalBlockNumber = some executionCfg.terminalBlockNumber
     p.terminalBlockHash = some executionCfg.terminalBlockHash
     return EtcStatus.localConfigurationUpdated