p2p: Ignore version msgs after initial version msg

Sending a version message after the intial version message is peer
misbehavior. Though, it seems arbitrary and confusing to disconnect only
after exactly 100 version messages. Duplicate version messages affect us
no different than any other unknown message. So remove the Misbehaving
and ignore the redundant msgs.

Author: MarcoFalke

src/net_processing.cpp

@@ -2286,10 +2286,8 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
     if (peer == nullptr) return;
 
     if (msg_type == NetMsgType::VERSION) {
-        // Each connection can only send one version message
-        if (pfrom.nVersion != 0)
-        {
-            Misbehaving(pfrom.GetId(), 1, "redundant version message");
+        if (pfrom.nVersion != 0) {
+            LogPrint(BCLog::NET, "redundant version message from peer=%d\n", pfrom.GetId());
             return;
         }
 

test/functional/p2p_invalid_messages.py

@@ -18,6 +18,7 @@
     msg_inv,
     msg_ping,
     MSG_TX,
+    msg_version,
     ser_string,
 )
 from test_framework.p2p import (
@@ -60,6 +61,7 @@ def set_test_params(self):
 
     def run_test(self):
         self.test_buffer()
+        self.test_duplicate_version_msg()
         self.test_magic_bytes()
         self.test_checksum()
         self.test_size()
@@ -92,6 +94,13 @@ def test_buffer(self):
         conn.sync_with_ping(timeout=1)
         self.nodes[0].disconnect_p2ps()
 
+    def test_duplicate_version_msg(self):
+        self.log.info("Test duplicate version message is ignored")
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['redundant version message from peer']):
+            conn.send_and_ping(msg_version())
+        self.nodes[0].disconnect_p2ps()
+
     def test_magic_bytes(self):
         self.log.info("Test message with invalid magic bytes disconnects peer")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())