From 3eac840084b1d5e54190a0133bc306b8c7e47ae4 Mon Sep 17 00:00:00 2001
From: Dmytro Sydorchenko <dmytro.sydorchenko@block.one>
Date: Mon, 2 Aug 2021 16:29:36 -0400
Subject: [PATCH 1/4] net plugin bugfix for nodes getting out of sync

---
 plugins/net_plugin/net_plugin.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 32464cb8f95..701d5d2cdeb 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -1757,7 +1757,7 @@ namespace eosio {
       if( !is_sync_required( fork_head_block_num ) || target <= lib_num ) {
          fc_dlog( logger, "We are already caught up, my irr = ${b}, head = ${h}, target = ${t}",
                   ("b", lib_num)( "h", fork_head_block_num )( "t", target ) );
-         return;
+         send_handshakes();
       }
 
       if( sync_state == in_sync ) {

From e3d53b46c66037b715fee6d553d7596b5f1c5650 Mon Sep 17 00:00:00 2001
From: Dmytro Sydorchenko <dmytro.sydorchenko@block.one>
Date: Mon, 2 Aug 2021 22:37:30 -0400
Subject: [PATCH 2/4] PR #10590 concerns addressed

---
 plugins/net_plugin/net_plugin.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 701d5d2cdeb..d38d2496b5e 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -1757,7 +1757,7 @@ namespace eosio {
       if( !is_sync_required( fork_head_block_num ) || target <= lib_num ) {
          fc_dlog( logger, "We are already caught up, my irr = ${b}, head = ${h}, target = ${t}",
                   ("b", lib_num)( "h", fork_head_block_num )( "t", target ) );
-         send_handshakes();
+         c->send_handshake();
       }
 
       if( sync_state == in_sync ) {

From fc3ba1a012efb3561702a9bf4387c66bd76f4c6d Mon Sep 17 00:00:00 2001
From: Dmytro Sydorchenko <dmytro.sydorchenko@block.one>
Date: Fri, 13 Aug 2021 22:38:14 -0400
Subject: [PATCH 3/4] back port of net plugin changes from #10390

---
 plugins/net_plugin/net_plugin.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index d38d2496b5e..59feb5d59b7 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -1801,7 +1801,7 @@ namespace eosio {
       // sync need checks; (lib == last irreversible block)
       //
       // 0. my head block id == peer head id means we are all caught up block wise
-      // 1. my head block num < peer lib - start sync locally
+      // 1. my head block num < peer lib - send handshake (if not sent in handle_message) and wait for receipt of notice message to start syncing
       // 2. my lib > peer head num - send an last_irr_catch_up notice if not the first generation
       //
       // 3  my head block num < peer head block num - update sync state and send a catchup request
@@ -1828,6 +1828,9 @@ namespace eosio {
                   ("ep", c->peer_name())("lib", msg.last_irreversible_block_num)("head", msg.head_num)
                   ("id", msg.head_id.str().substr(8,16)) );
          c->syncing = false;
+         if (c->sent_handshake_count > 0) {
+            c->send_handshake(true);
+         }
          return;
       }
       if (lib_num > msg.head_num ) {

From b77e32677ac6409f378989aa459f82d5513b9be0 Mon Sep 17 00:00:00 2001
From: Dmytro Sydorchenko <dmytro.sydorchenko@block.one>
Date: Fri, 13 Aug 2021 22:45:23 -0400
Subject: [PATCH 4/4] net plugin fix for node being stopped syncing

---
 plugins/net_plugin/net_plugin.cpp | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 59feb5d59b7..f3e1eb1b2bd 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -151,7 +151,7 @@ namespace eosio {
 
    public:
       explicit sync_manager( uint32_t span );
-      static void send_handshakes();
+      static void send_handshakes(bool force = false);
       bool syncing_with_peer() const { return sync_state == lib_catchup; }
       void sync_reset_lib_num( const connection_ptr& conn );
       void sync_reassign_fetch( const connection_ptr& c, go_away_reason reason );
@@ -1725,10 +1725,10 @@ namespace eosio {
    }
 
    // static, thread safe
-   void sync_manager::send_handshakes() {
-      for_each_connection( []( auto& ci ) {
+   void sync_manager::send_handshakes(bool force) {
+      for_each_connection( [&]( auto& ci ) {
          if( ci->current() ) {
-            ci->send_handshake();
+            ci->send_handshake(force);
          }
          return true;
       } );
@@ -2033,18 +2033,18 @@ namespace eosio {
 
          if( set_state_to_head_catchup ) {
             if( set_state( head_catchup ) ) {
-                send_handshakes();
+                send_handshakes(true);
             }
          } else {
             set_state( in_sync );
-            send_handshakes();
+            send_handshakes(true);
          }
       } else if( state == lib_catchup ) {
          if( blk_num == sync_known_lib_num ) {
             fc_dlog( logger, "All caught up with last known last irreversible block resending handshake" );
             set_state( in_sync );
             g_sync.unlock();
-            send_handshakes();
+            send_handshakes(true);
          } else if( blk_num == sync_last_requested_num ) {
             request_next_chunk( std::move( g_sync) );
          } else {