From da0f376befff5cfbe0195606e04df76adbbe8aeb Mon Sep 17 00:00:00 2001
From: SChernykh <sergey.v.chernykh@gmail.com>
Date: Mon, 13 Sep 2021 14:26:52 +0200
Subject: [PATCH] P2PServer: ban peers that don't broadcast blocks

---
 src/p2p_server.cpp | 25 +++++++++++++++++++++++++
 src/p2p_server.h   |  2 ++
 src/side_chain.cpp |  5 +++++
 src/side_chain.h   |  1 +
 4 files changed, 33 insertions(+)

diff --git a/src/p2p_server.cpp b/src/p2p_server.cpp
index f7fbeee..d400d63 100644
--- a/src/p2p_server.cpp
+++ b/src/p2p_server.cpp
@@ -167,6 +167,7 @@ void P2PServer::update_peer_connections()
 	}
 
 	const time_t cur_time = time(nullptr);
+	const time_t last_updated = m_pool->side_chain().last_updated();
 
 	std::vector<raw_ip> connected_clients;
 	{
@@ -181,6 +182,20 @@ void P2PServer::update_peer_connections()
 				LOGWARN(5, "peer " << static_cast<char*>(client->m_addrString) << " has been idle for " << idle_time << " seconds, disconnecting");
 				client->close();
 			}
+
+			if (client->m_handshakeComplete && client->m_lastBroadcastTimestamp) {
+				// - Side chain is at least 5 minutes newer (last_updated >= client->m_lastBroadcastTimestamp + 300)
+				// - It's been at least 10 seconds since side chain updated (cur_time >= last_updated + 10)
+				// - It's been at least 10 seconds since the last block request (peer is not syncing)
+				// - Peer should have sent a broadcast by now
+				if (last_updated && (cur_time >= std::max(last_updated, client->m_lastBlockrequestTimestamp) + 10) && (last_updated >= client->m_lastBroadcastTimestamp + 300)) {
+					const time_t dt = last_updated - client->m_lastBroadcastTimestamp;
+					LOGWARN(5, "peer " << static_cast<char*>(client->m_addrString) << " is not broadcasting blocks (last update " << dt << " seconds ago)");
+					client->ban(DEFAULT_BAN_TIME);
+					remove_peer_from_list(client);
+					client->close();
+				}
+			}
 		}
 	}
 
@@ -754,6 +769,8 @@ P2PServer::P2PClient::P2PClient()
 	, m_listenPort(-1)
 	, m_nextPeerListRequest(0)
 	, m_lastAlive(0)
+	, m_lastBroadcastTimestamp(0)
+	, m_lastBlockrequestTimestamp(0)
 {
 	uv_rwlock_init_checked(&m_broadcastedHashesLock);
 }
@@ -776,6 +793,8 @@ void P2PServer::P2PClient::reset()
 	m_listenPort = -1;
 	m_nextPeerListRequest = 0;
 	m_lastAlive = 0;
+	m_lastBroadcastTimestamp = 0;
+	m_lastBlockrequestTimestamp = 0;
 
 	WriteLock lock(m_broadcastedHashesLock);
 	m_broadcastedHashes.clear();
@@ -1291,6 +1310,8 @@ void P2PServer::P2PClient::on_after_handshake(uint8_t* &p)
 	hash empty;
 	memcpy(p, empty.h, HASH_SIZE);
 	p += HASH_SIZE;
+
+	m_lastBroadcastTimestamp = time(nullptr);
 }
 
 bool P2PServer::P2PClient::on_listen_port(const uint8_t* buf)
@@ -1311,6 +1332,8 @@ bool P2PServer::P2PClient::on_listen_port(const uint8_t* buf)
 
 bool P2PServer::P2PClient::on_block_request(const uint8_t* buf)
 {
+	m_lastBlockrequestTimestamp = time(nullptr);
+
 	hash id;
 	memcpy(id.h, buf, HASH_SIZE);
 
@@ -1418,6 +1441,8 @@ bool P2PServer::P2PClient::on_block_broadcast(const uint8_t* buf, uint32_t size)
 
 	server->m_block->m_wantBroadcast = true;
 
+	m_lastBroadcastTimestamp = time(nullptr);
+
 	return handle_incoming_block_async(server->m_block);
 }
 
diff --git a/src/p2p_server.h b/src/p2p_server.h
index d59ed0a..11d8621 100644
--- a/src/p2p_server.h
+++ b/src/p2p_server.h
@@ -109,6 +109,8 @@ public:
 		int m_listenPort;
 		time_t m_nextPeerListRequest;
 		time_t m_lastAlive;
+		time_t m_lastBroadcastTimestamp;
+		time_t m_lastBlockrequestTimestamp;
 
 		uv_rwlock_t m_broadcastedHashesLock;
 		std::set<hash> m_broadcastedHashes;
diff --git a/src/side_chain.cpp b/src/side_chain.cpp
index 6e8e44a..08b42de 100644
--- a/src/side_chain.cpp
+++ b/src/side_chain.cpp
@@ -737,6 +737,11 @@ uint64_t SideChain::miner_count()
 	return m_seenWallets.size();
 }
 
+time_t SideChain::last_updated() const
+{
+	return m_chainTip ? m_chainTip->m_localTimestamp : 0;
+}
+
 bool SideChain::is_default() const
 {
 	constexpr uint8_t default_consensus_id[HASH_SIZE] = {
diff --git a/src/side_chain.h b/src/side_chain.h
index 6a2d29b..0e33c05 100644
--- a/src/side_chain.h
+++ b/src/side_chain.h
@@ -69,6 +69,7 @@ public:
 	difficulty_type total_hashes() const;
 	uint64_t block_time() const { return m_targetBlockTime; }
 	uint64_t miner_count();
+	time_t last_updated() const;
 	bool is_default() const;
 
 	static bool split_reward(uint64_t reward, const std::vector<MinerShare>& shares, std::vector<uint64_t>& rewards);