Don't sync with peer unless we already received Status message from it

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Added: [#5537](https://github.com/ethereum/aleth/pull/5537) Creating Ethereum Node Record (ENR) at program start.
 - Added: [#5557](https://github.com/ethereum/aleth/pull/5557) Improved debug logging of full sync.
 - Changed: [#5559](https://github.com/ethereum/aleth/pull/5559) Update peer validation error messages.
+- Fixed: [#5562](https://github.com/ethereum/aleth/pull/5562) Don't send header request messages to peers that haven't sent us Status yet.
 
 ## [1.6.0] - Unreleased
 

libethereum/BlockChainSync.cpp

@@ -223,9 +223,16 @@ bool BlockChainSync::requestDaoForkBlockHeader(NodeID const& _peerID)
 
 void BlockChainSync::syncPeer(NodeID const& _peerID, bool _force)
 {
-    if (m_host.peer(_peerID).isConversing())
+    auto& peer = m_host.peer(_peerID);
+    if (!peer.statusReceived())
     {
-        LOG(m_loggerDetail) << "Can't sync with this peer - outstanding asks.";
+        LOG(m_loggerDetail) << "Can't sync with peer " << _peerID << " - Status not received yet.";
+        return;
+    }
+
+    if (peer.isConversing())
+    {
+        LOG(m_loggerDetail) << "Can't sync with peer " << _peerID << " - outstanding asks.";
         return;
     }
 
@@ -238,7 +245,6 @@ void BlockChainSync::syncPeer(NodeID const& _peerID, bool _force)
 
     u256 syncingDifficulty = std::max(m_syncingTotalDifficulty, td);
 
-    auto& peer = m_host.peer(_peerID);
     u256 peerTotalDifficulty = peer.totalDifficulty();
 
     if (_force || peerTotalDifficulty > syncingDifficulty)

libethereum/EthereumPeer.h

@@ -37,6 +37,8 @@ class EthereumPeer
       : m_host(std::move(_host)), m_id(_peerID)
     {}
 
+    bool statusReceived() const { return m_protocolVersion != 0; }
+
     void setStatus(unsigned _protocolVersion, u256 const& _networkId, u256 const& _totalDifficulty,
         h256 const& _latestHash, h256 const& _genesisHash);