From 9999c28a37ede00b33703c75c7dc66be5dd21104 Mon Sep 17 00:00:00 2001
From: Chalith Desaman <desaman.chalith@gmail.com>
Date: Fri, 12 Mar 2021 19:01:58 +0530
Subject: [PATCH] Remove self connection on peer discovery (#269)

* Resetting last shard syncing flags when sync is abandoned. (#268)

* Remove self loopback connection when self is added by peer discovery

* Resolved PR comments

Co-authored-by: Savinda Senevirathne <savindadilsara@gmail.com>
---
 src/p2p/p2p.cpp       | 25 +++++++++++++++++++++++++
 src/p2p/self_node.cpp |  2 ++
 src/p2p/self_node.hpp |  2 ++
 3 files changed, 29 insertions(+)

diff --git a/src/p2p/p2p.cpp b/src/p2p/p2p.cpp
index 54228346..18fa7ff7 100644
--- a/src/p2p/p2p.cpp
+++ b/src/p2p/p2p.cpp
@@ -112,6 +112,24 @@ namespace p2p
         if (res == 0)
         {
             LOG_DEBUG << "Pubkey violation. Rejecting new peer connection [" << session.display_name() << "]";
+            
+            // It's possible, Self node might've been added to the known peers by peer discovery.
+            // If so remove the self from known peers.
+            if (session.known_ipport.has_value())
+            {
+                // We set self ip port values so that we can remove self from the future known peer responses.
+                self::ip_port = conf::peer_ip_port{session.known_ipport->host_address, session.known_ipport->port};
+                {
+                    std::scoped_lock lock(ctx.server->req_known_remotes_mutex);
+                    ctx.server->req_known_remotes.erase(std::remove_if(ctx.server->req_known_remotes.begin(), ctx.server->req_known_remotes.end(),
+                                                                       [&](const p2p::peer_properties &peer) {
+                                                                           return peer.ip_port.port == session.known_ipport->port;
+                                                                       }));
+                    ctx.server->known_remote_count = ctx.server->req_known_remotes.size();
+                }
+                LOG_DEBUG << "Loopback connection detected: Removed self from the peer list.";
+            }
+
             return -1;
         }
 
@@ -413,6 +431,13 @@ namespace p2p
 
         for (const peer_properties &peer : peers)
         {
+            // If the peer is self, we won't add to the known peer list.
+            if (self::ip_port.has_value() && self::ip_port == peer.ip_port)
+            {
+                LOG_DEBUG << "Rejecting " + peer.ip_port.host_address + ":" + std::to_string(peer.ip_port.port) + ". Loopback connection.";
+                continue;
+            }
+
             const auto itr = std::find_if(ctx.server->req_known_remotes.begin(), ctx.server->req_known_remotes.end(), [&](peer_properties &p) { return p.ip_port == peer.ip_port; });
 
             // If the new peer is not in the peer list then add to the req_known_remotes
diff --git a/src/p2p/self_node.cpp b/src/p2p/self_node.cpp
index b62d8688..33cb66e6 100644
--- a/src/p2p/self_node.cpp
+++ b/src/p2p/self_node.cpp
@@ -6,6 +6,8 @@ namespace p2p::self
     // Holds self messages waiting to be processed.
     moodycamel::ConcurrentQueue<std::string> msg_queue;
 
+    std::optional<conf::peer_ip_port> ip_port;
+
     /**
      * Processes the next queued message (if any).
      * @return 0 if no messages in queue. 1 if message was processed successfully. -1 on error.
diff --git a/src/p2p/self_node.hpp b/src/p2p/self_node.hpp
index f26e16b6..8e86a43c 100644
--- a/src/p2p/self_node.hpp
+++ b/src/p2p/self_node.hpp
@@ -5,6 +5,8 @@
 
 namespace p2p::self
 {
+    extern std::optional<conf::peer_ip_port> ip_port;
+
     int process_next_message();
     void send(std::string_view message);