net, rpc: Enable AddrFetch connections for functional testing

Co-authored-by: Amiti Uttarwar <amiti@uttarwar.org>

src/net.cpp

@@ -1166,16 +1166,29 @@ void CConnman::CreateNodeFromAcceptedSocket(SOCKET hSocket,
 
 bool CConnman::AddConnection(const std::string& address, ConnectionType conn_type)
 {
-    if (conn_type != ConnectionType::OUTBOUND_FULL_RELAY && conn_type != ConnectionType::BLOCK_RELAY) return false;
+    std::optional<int> max_connections;
-
+    switch (conn_type) {
-    const int max_connections = conn_type == ConnectionType::OUTBOUND_FULL_RELAY ? m_max_outbound_full_relay : m_max_outbound_block_relay;
+    case ConnectionType::INBOUND:
+    case ConnectionType::MANUAL:
+    case ConnectionType::FEELER:
+        return false;
+    case ConnectionType::OUTBOUND_FULL_RELAY:
+        max_connections = m_max_outbound_full_relay;
+        break;
+    case ConnectionType::BLOCK_RELAY:
+        max_connections = m_max_outbound_block_relay;
+        break;
+    // no limit for ADDR_FETCH because -seednode has no limit either
+    case ConnectionType::ADDR_FETCH:
+        break;
+    } // no default case, so the compiler can warn about missing cases
 
     // Count existing connections
     int existing_connections = WITH_LOCK(cs_vNodes,
                                          return std::count_if(vNodes.begin(), vNodes.end(), [conn_type](CNode* node) { return node->m_conn_type == conn_type; }););
 
     // Max connections of specified type already exist
-    if (existing_connections >= max_connections) return false;
+    if (max_connections != std::nullopt && existing_connections >= max_connections) return false;
 
     // Max total outbound connections already exist
     CSemaphoreGrant grant(*semOutbound, true);

src/net.h

@@ -890,6 +890,7 @@ public:
      *
      * @param[in]   address     Address of node to try connecting to
      * @param[in]   conn_type   ConnectionType::OUTBOUND or ConnectionType::BLOCK_RELAY
+     *                          or ConnectionType::ADDR_FETCH
      * @return      bool        Returns false if there are no available
      *                          slots for this connection:
      *                          - conn_type not a supported ConnectionType

src/rpc/net.cpp

@@ -337,7 +337,7 @@ static RPCHelpMan addconnection()
         "\nOpen an outbound connection to a specified node. This RPC is for testing only.\n",
         {
             {"address", RPCArg::Type::STR, RPCArg::Optional::NO, "The IP address and port to attempt connecting to."},
-            {"connection_type", RPCArg::Type::STR, RPCArg::Optional::NO, "Type of connection to open, either \"outbound-full-relay\" or \"block-relay-only\"."},
+            {"connection_type", RPCArg::Type::STR, RPCArg::Optional::NO, "Type of connection to open (\"outbound-full-relay\", \"block-relay-only\" or \"addr-fetch\")."},
         },
         RPCResult{
             RPCResult::Type::OBJ, "", "",
@@ -363,6 +363,8 @@ static RPCHelpMan addconnection()
         conn_type = ConnectionType::OUTBOUND_FULL_RELAY;
     } else if (conn_type_in == "block-relay-only") {
         conn_type = ConnectionType::BLOCK_RELAY;
+    } else if (conn_type_in == "addr-fetch") {
+        conn_type = ConnectionType::ADDR_FETCH;
     } else {
         throw JSONRPCError(RPC_INVALID_PARAMETER, self.ToString());
     }

test/functional/test_framework/test_node.py

@@ -557,9 +557,8 @@ class TestNode():
         return p2p_conn
 
     def add_outbound_p2p_connection(self, p2p_conn, *, p2p_idx, connection_type="outbound-full-relay", **kwargs):
-        """Add an outbound p2p connection from node. Either
+        """Add an outbound p2p connection from node. Must be an
-        full-relay("outbound-full-relay") or
+        "outbound-full-relay", "block-relay-only" or "addr-fetch" connection.
-        block-relay-only("block-relay-only") connection.
 
         This method adds the p2p connection to the self.p2ps list and returns
         the connection to the caller.