From c46a4a17183f4d9e6294bbfa927c59a6ecdc91a6 Mon Sep 17 00:00:00 2001
From: Sergey Kroshnin <sergiysw@gmail.com>
Date: Thu, 10 Jan 2019 19:56:41 +0300
Subject: [PATCH] Limit recursive confirm_back () (#1570)

---
 nano/node/node.cpp | 15 +++++++++------
 nano/node/node.hpp |  4 ++--
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/nano/node/node.cpp b/nano/node/node.cpp
index 759577e29..e3bb30d1f 100644
--- a/nano/node/node.cpp
+++ b/nano/node/node.cpp
@@ -2980,8 +2980,9 @@ void nano::election::compute_rep_votes (nano::transaction const & transaction_a)
 	}
 }
 
-void nano::election::confirm_once (nano::transaction const & transaction_a)
+void nano::election::confirm_once (nano::transaction const & transaction_a, uint8_t & depth_a)
 {
+	depth_a++;
 	if (!confirmed.exchange (true))
 	{
 		status.election_end = std::chrono::duration_cast<std::chrono::milliseconds> (std::chrono::system_clock::now ().time_since_epoch ());
@@ -2993,21 +2994,22 @@ void nano::election::confirm_once (nano::transaction const & transaction_a)
 			node_l->process_confirmed (winner_l);
 			confirmation_action_l (winner_l);
 		});
-		confirm_back (transaction_a);
+		confirm_back (transaction_a, depth_a);
 	}
 }
 
-void nano::election::confirm_back (nano::transaction const & transaction_a)
+void nano::election::confirm_back (nano::transaction const & transaction_a, uint8_t & depth_a)
 {
 	std::vector<nano::block_hash> hashes = { status.winner->previous (), status.winner->source (), status.winner->link () };
 	for (auto & hash : hashes)
 	{
-		if (!hash.is_zero () && !node.ledger.is_epoch_link (hash))
+		// Depth is limited to 200
+		if (!hash.is_zero () && !node.ledger.is_epoch_link (hash) && depth_a < 200)
 		{
 			auto existing (node.active.blocks.find (hash));
 			if (existing != node.active.blocks.end () && !existing->second->confirmed && !existing->second->stopped && existing->second->blocks.size () == 1)
 			{
-				existing->second->confirm_once (transaction_a);
+				existing->second->confirm_once (transaction_a, depth_a);
 			}
 		}
 	}
@@ -3077,7 +3079,8 @@ void nano::election::confirm_if_quorum (nano::transaction const & transaction_a)
 		{
 			log_votes (tally_l);
 		}
-		confirm_once (transaction_a);
+		uint8_t depth (0);
+		confirm_once (transaction_a, depth);
 	}
 }
 
diff --git a/nano/node/node.hpp b/nano/node/node.hpp
index 13bf27b5d..2a161a7b9 100644
--- a/nano/node/node.hpp
+++ b/nano/node/node.hpp
@@ -50,8 +50,8 @@ public:
 class election : public std::enable_shared_from_this<nano::election>
 {
 	std::function<void(std::shared_ptr<nano::block>)> confirmation_action;
-	void confirm_once (nano::transaction const &);
-	void confirm_back (nano::transaction const &);
+	void confirm_once (nano::transaction const &, uint8_t &);
+	void confirm_back (nano::transaction const &, uint8_t &);
 
 public:
 	election (nano::node &, std::shared_ptr<nano::block>, std::function<void(std::shared_ptr<nano::block>)> const &);