From 3db765e0f108ad301b9c8063a20a124a4ece71a4 Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Tue, 31 Jan 2023 07:39:26 -0600
Subject: [PATCH 1/3] GH-588 Remove +1 to number of blocks latency calculation.
 With it 0 latency indicates 1 block latency.

---
 plugins/net_plugin/net_plugin.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 5e8909cb91..68a968a4c1 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -1792,8 +1792,8 @@ namespace eosio {
       }
       // number of blocks syncing node is behind from a peer node
       uint32_t nblk_behind_by_net_latency = static_cast<uint32_t>(network_latency_ns / block_interval_ns);
-      // 2x for time it takes for message to reach back to peer node, +1 to compensate for integer division truncation
-      uint32_t nblk_combined_latency = 2 * nblk_behind_by_net_latency + 1;
+      // 2x for time it takes for message to reach back to peer node
+      uint32_t nblk_combined_latency = 2 * nblk_behind_by_net_latency;
       // message in the log below is used in p2p_high_latency_test.py test
       peer_dlog(c, "Network latency is ${lat}ms, ${num} blocks discrepancy by network latency, ${tot_num} blocks discrepancy expected once message received",
                 ("lat", network_latency_ns/1000000)("num", nblk_behind_by_net_latency)("tot_num", nblk_combined_latency));

From f347ab534ebe3e881df5cdd183845404e38990bb Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Wed, 1 Feb 2023 13:42:13 -0600
Subject: [PATCH 2/3] GH-588 Add additional logging that would be helpful for
 debugging

---
 plugins/net_plugin/net_plugin.cpp | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 68a968a4c1..9bbad79e4f 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -1776,7 +1776,6 @@ namespace eosio {
       if( c->is_transactions_only_connection() ) return;
 
       uint32_t lib_num = 0;
-      uint32_t peer_lib = msg.last_irreversible_block_num;
       uint32_t head = 0;
       block_id_type head_id;
       std::tie( lib_num, std::ignore, head,
@@ -1813,8 +1812,8 @@ namespace eosio {
       //-----------------------------
 
       if (head_id == msg.head_id) {
-         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 0",
-                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16)) );
+         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 0, lib ${l}",
+                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16))("l", lib_num) );
          c->syncing = false;
          notice_message note;
          note.known_blocks.mode = none;
@@ -1823,9 +1822,10 @@ namespace eosio {
          c->enqueue( note );
          return;
       }
-      if (head < peer_lib) {
-         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 1",
-                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16)) );
+      if (head < msg.last_irreversible_block_num) {
+         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 1, head ${h}, lib ${l}",
+                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16))
+                    ("h", head)("l", lib_num) );
          c->syncing = false;
          if (c->sent_handshake_count > 0) {
             c->send_handshake();
@@ -1833,8 +1833,9 @@ namespace eosio {
          return;
       }
       if (lib_num > msg.head_num + nblk_combined_latency) {
-         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 2",
-                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16)) );
+         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 2, head ${h}, lib ${l}",
+                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16))
+                    ("h", head)("l", lib_num) );
          if (msg.generation > 1 || c->protocol_version > proto_base) {
             notice_message note;
             note.known_trx.pending = lib_num;
@@ -1848,14 +1849,16 @@ namespace eosio {
       }
 
       if (head + nblk_combined_latency < msg.head_num ) {
-         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 3",
-                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16)) );
+         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 3, head ${h}, lib ${l}",
+                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16))
+                    ("h", head)("l", lib_num) );
          c->syncing = false;
          verify_catchup(c, msg.head_num, msg.head_id);
          return;
       } else if(head >= msg.head_num + nblk_combined_latency) {
-         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 4",
-                  ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16)) );
+         peer_ilog( c, "handshake lib ${lib}, head ${head}, head id ${id}.. sync 4, head ${h}, lib ${l}",
+                    ("lib", msg.last_irreversible_block_num)("head", msg.head_num)("id", msg.head_id.str().substr(8,16))
+                    ("h", head)("l", lib_num) );
          if (msg.generation > 1 ||  c->protocol_version > proto_base) {
             notice_message note;
             note.known_trx.mode = none;

From ec27d3d1f3eb29a5cab6518e24eee1c62adaa0bc Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Wed, 1 Feb 2023 15:10:23 -0600
Subject: [PATCH 3/3] GH-588 Round using lround instead of the original
 hardcoded +1

---
 plugins/net_plugin/net_plugin.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 9bbad79e4f..61b61fdd35 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -26,6 +26,7 @@
 #include <boost/asio/steady_timer.hpp>
 
 #include <atomic>
+#include <cmath>
 #include <shared_mutex>
 
 using namespace eosio::chain::plugin_interface;
@@ -1789,8 +1790,8 @@ namespace eosio {
          peer_wlog(c, "Peer sent a handshake with a timestamp skewed by at least ${t}ms", ("t", network_latency_ns/1000000));
          network_latency_ns = 0;
       }
-      // number of blocks syncing node is behind from a peer node
-      uint32_t nblk_behind_by_net_latency = static_cast<uint32_t>(network_latency_ns / block_interval_ns);
+      // number of blocks syncing node is behind from a peer node, round up
+      uint32_t nblk_behind_by_net_latency = std::lround( static_cast<double>(network_latency_ns) / static_cast<double>(block_interval_ns) );
       // 2x for time it takes for message to reach back to peer node
       uint32_t nblk_combined_latency = 2 * nblk_behind_by_net_latency;
       // message in the log below is used in p2p_high_latency_test.py test