p2p: fix race causing dropped connections during sync

Without this commit:
1) read height from DB
2) add block to chain in separate thread
3) read chain for block id's and request them from peer
4) ERR in handle_response_chain_entry, peer's first block is the
one that was added to the chain, which has block idx=height from
step 1.

This commit reads the chain for height and highest block id's
in one go while holding the m_blockchain_lock to avoid the race.

1 files changed, 4 insertions, 7 deletions

diff --git a/src/cryptonote_protocol/cryptonote_protocol_handler.inl b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
index 1686394c5..fb195b390 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_handler.inl
+++ b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
@@ -274,8 +274,7 @@ namespace cryptonote
     {
       NOTIFY_REQUEST_CHAIN::request r = {};
       context.m_needed_objects.clear();
-      context.m_expect_height = m_core.get_current_blockchain_height();
-      m_core.get_short_chain_history(r.block_ids);
+      m_core.get_short_chain_history(r.block_ids, context.m_expect_height);
       handler_request_blocks_history( r.block_ids ); // change the limit(?), sleep(?)
       r.prune = m_sync_pruned_blocks;
       context.m_last_request_time = boost::posix_time::microsec_clock::universal_time();
@@ -730,8 +729,7 @@ namespace cryptonote
       context.m_needed_objects.clear();
       context.m_state = cryptonote_connection_context::state_synchronizing;
       NOTIFY_REQUEST_CHAIN::request r = {};
-      context.m_expect_height = m_core.get_current_blockchain_height();
-      m_core.get_short_chain_history(r.block_ids);
+      m_core.get_short_chain_history(r.block_ids, context.m_expect_height);
       handler_request_blocks_history( r.block_ids ); // change the limit(?), sleep(?)
       r.prune = m_sync_pruned_blocks;
       context.m_last_request_time = boost::posix_time::microsec_clock::universal_time();
@@ -2340,8 +2338,7 @@ skip:
     {//we have to fetch more objects ids, request blockchain entry
 
       NOTIFY_REQUEST_CHAIN::request r = {};
-      context.m_expect_height = m_core.get_current_blockchain_height();
-      m_core.get_short_chain_history(r.block_ids);
+      m_core.get_short_chain_history(r.block_ids, context.m_expect_height);
       CHECK_AND_ASSERT_MES(!r.block_ids.empty(), false, "Short chain history is empty");
 
       // we'll want to start off from where we are on that peer, which may not be added yet
@@ -2477,7 +2474,7 @@ skip:
   int t_cryptonote_protocol_handler<t_core>::handle_response_chain_entry(int command, NOTIFY_RESPONSE_CHAIN_ENTRY::request& arg, cryptonote_connection_context& context)
   {
     MLOG_P2P_MESSAGE("Received NOTIFY_RESPONSE_CHAIN_ENTRY: m_block_ids.size()=" << arg.m_block_ids.size()
-      << ", m_start_height=" << arg.start_height << ", m_total_height=" << arg.total_height);
+      << ", m_start_height=" << arg.start_height << ", m_total_height=" << arg.total_height << ", expect height=" << context.m_expect_height);
     MLOG_PEER_STATE("received chain");
 
     if (context.m_expect_response != NOTIFY_RESPONSE_CHAIN_ENTRY::ID)