net: use V2Transport when NODE_P2P_V2 service flag is present

Co-authored-by: Dhruv Mehta <856960+dhruv@users.noreply.github.com>

5 files changed, 63 insertions, 13 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 72aef92e62..844a615873 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -439,7 +439,7 @@ static CAddress GetBindAddress(const Sock& sock)
     return addr_bind;
 }
 
-CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type)
+CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type, bool use_v2transport)
 {
     AssertLockNotHeld(m_unused_i2p_sessions_mutex);
     assert(conn_type != ConnectionType::INBOUND);
@@ -457,7 +457,8 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
         }
     }
 
-    LogPrintLevel(BCLog::NET, BCLog::Level::Debug, "trying connection %s lastseen=%.1fhrs\n",
+    LogPrintLevel(BCLog::NET, BCLog::Level::Debug, "trying %s connection %s lastseen=%.1fhrs\n",
+        use_v2transport ? "v2" : "v1",
         pszDest ? pszDest : addrConnect.ToStringAddrPort(),
         Ticks<HoursDouble>(pszDest ? 0h : Now<NodeSeconds>() - addrConnect.nTime));
 
@@ -580,6 +581,7 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
                              CNodeOptions{
                                  .i2p_sam_session = std::move(i2p_transient_session),
                                  .recv_flood_size = nReceiveFloodSize,
+                                 .use_v2transport = use_v2transport,
                              });
     pnode->AddRef();
 
@@ -1794,6 +1796,10 @@ void CConnman::CreateNodeFromAcceptedSocket(std::unique_ptr<Sock>&& sock,
     }
 
     const bool inbound_onion = std::find(m_onion_binds.begin(), m_onion_binds.end(), addr_bind) != m_onion_binds.end();
+    // The V2Transport transparently falls back to V1 behavior when an incoming V1 connection is
+    // detected, so use it whenever we signal NODE_P2P_V2.
+    const bool use_v2transport(nodeServices & NODE_P2P_V2);
+
     CNode* pnode = new CNode(id,
                              std::move(sock),
                              addr,
@@ -1807,6 +1813,7 @@ void CConnman::CreateNodeFromAcceptedSocket(std::unique_ptr<Sock>&& sock,
                                  .permission_flags = permission_flags,
                                  .prefer_evict = discouraged,
                                  .recv_flood_size = nReceiveFloodSize,
+                                 .use_v2transport = use_v2transport,
                              });
     pnode->AddRef();
     m_msgproc->InitializeNode(*pnode, nodeServices);
@@ -1855,7 +1862,7 @@ bool CConnman::AddConnection(const std::string& address, ConnectionType conn_typ
     CSemaphoreGrant grant(*semOutbound, true);
     if (!grant) return false;
 
-    OpenNetworkConnection(CAddress(), false, &grant, address.c_str(), conn_type);
+    OpenNetworkConnection(CAddress(), false, &grant, address.c_str(), conn_type, /*use_v2transport=*/false);
     return true;
 }
 
@@ -2289,7 +2296,7 @@ void CConnman::ProcessAddrFetch()
     CAddress addr;
     CSemaphoreGrant grant(*semOutbound, true);
     if (grant) {
-        OpenNetworkConnection(addr, false, &grant, strDest.c_str(), ConnectionType::ADDR_FETCH);
+        OpenNetworkConnection(addr, false, &grant, strDest.c_str(), ConnectionType::ADDR_FETCH, /*use_v2transport=*/false);
     }
 }
 
@@ -2391,7 +2398,7 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
             for (const std::string& strAddr : connect)
             {
                 CAddress addr(CService(), NODE_NONE);
-                OpenNetworkConnection(addr, false, nullptr, strAddr.c_str(), ConnectionType::MANUAL);
+                OpenNetworkConnection(addr, false, nullptr, strAddr.c_str(), ConnectionType::MANUAL, /*use_v2transport=*/false);
                 for (int i = 0; i < 10 && i < nLoop; i++)
                 {
                     if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
@@ -2694,7 +2701,9 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
             // Don't record addrman failure attempts when node is offline. This can be identified since all local
             // network connections (if any) belong in the same netgroup, and the size of `outbound_ipv46_peer_netgroups` would only be 1.
             const bool count_failures{((int)outbound_ipv46_peer_netgroups.size() + outbound_privacy_network_peers) >= std::min(nMaxConnections - 1, 2)};
-            OpenNetworkConnection(addrConnect, count_failures, &grant, /*strDest=*/nullptr, conn_type);
+            // Use BIP324 transport when both us and them have NODE_V2_P2P set.
+            const bool use_v2transport(addrConnect.nServices & GetLocalServices() & NODE_P2P_V2);
+            OpenNetworkConnection(addrConnect, count_failures, &grant, /*strDest=*/nullptr, conn_type, use_v2transport);
         }
     }
 }
@@ -2783,7 +2792,7 @@ void CConnman::ThreadOpenAddedConnections()
                 }
                 tried = true;
                 CAddress addr(CService(), NODE_NONE);
-                OpenNetworkConnection(addr, false, &grant, info.strAddedNode.c_str(), ConnectionType::MANUAL);
+                OpenNetworkConnection(addr, false, &grant, info.strAddedNode.c_str(), ConnectionType::MANUAL, /*use_v2transport=*/false);
                 if (!interruptNet.sleep_for(std::chrono::milliseconds(500)))
                     return;
             }
@@ -2795,7 +2804,7 @@ void CConnman::ThreadOpenAddedConnections()
 }
 
 // if successful, this moves the passed grant to the constructed node
-void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound, const char *pszDest, ConnectionType conn_type)
+void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound, const char *pszDest, ConnectionType conn_type, bool use_v2transport)
 {
     AssertLockNotHeld(m_unused_i2p_sessions_mutex);
     assert(conn_type != ConnectionType::INBOUND);
@@ -2817,7 +2826,7 @@ void CConnman::OpenNetworkConnection(const CAddress& addrConnect, bool fCountFai
     } else if (FindNode(std::string(pszDest)))
         return;
 
-    CNode* pnode = ConnectNode(addrConnect, pszDest, fCountFailure, conn_type);
+    CNode* pnode = ConnectNode(addrConnect, pszDest, fCountFailure, conn_type, use_v2transport);
 
     if (!pnode)
         return;
@@ -3579,6 +3588,15 @@ ServiceFlags CConnman::GetLocalServices() const
     return nLocalServices;
 }
 
+static std::unique_ptr<Transport> MakeTransport(NodeId id, bool use_v2transport, bool inbound) noexcept
+{
+    if (use_v2transport) {
+        return std::make_unique<V2Transport>(id, /*initiating=*/!inbound, SER_NETWORK, INIT_PROTO_VERSION);
+    } else {
+        return std::make_unique<V1Transport>(id, SER_NETWORK, INIT_PROTO_VERSION);
+    }
+}
+
 CNode::CNode(NodeId idIn,
              std::shared_ptr<Sock> sock,
              const CAddress& addrIn,
@@ -3589,7 +3607,7 @@ CNode::CNode(NodeId idIn,
              ConnectionType conn_type_in,
              bool inbound_onion,
              CNodeOptions&& node_opts)
-    : m_transport{std::make_unique<V1Transport>(idIn, SER_NETWORK, INIT_PROTO_VERSION)},
+    : m_transport{MakeTransport(idIn, node_opts.use_v2transport, conn_type_in == ConnectionType::INBOUND)},
       m_permission_flags{node_opts.permission_flags},
       m_sock{sock},
       m_connected{GetTime<std::chrono::seconds>()},
diff --git a/src/net.h b/src/net.h
index c4bd89099a..8862efa76a 100644
--- a/src/net.h
+++ b/src/net.h
@@ -657,6 +657,7 @@ struct CNodeOptions
     std::unique_ptr<i2p::sam::Session> i2p_sam_session = nullptr;
     bool prefer_evict = false;
     size_t recv_flood_size{DEFAULT_MAXRECEIVEBUFFER * 1000};
+    bool use_v2transport = false;
 };
 
 /** Information about a peer */
@@ -1098,7 +1099,7 @@ public:
     bool GetNetworkActive() const { return fNetworkActive; };
     bool GetUseAddrmanOutgoing() const { return m_use_addrman_outgoing; };
     void SetNetworkActive(bool active);
-    void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant* grantOutbound, const char* strDest, ConnectionType conn_type) EXCLUSIVE_LOCKS_REQUIRED(!m_unused_i2p_sessions_mutex);
+    void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant* grantOutbound, const char* strDest, ConnectionType conn_type, bool use_v2transport) EXCLUSIVE_LOCKS_REQUIRED(!m_unused_i2p_sessions_mutex);
     bool CheckIncomingNonce(uint64_t nonce);
 
     // alias for thread safety annotations only, not defined
@@ -1314,7 +1315,7 @@ private:
     bool AlreadyConnectedToAddress(const CAddress& addr);
 
     bool AttemptToEvictConnection();
-    CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type) EXCLUSIVE_LOCKS_REQUIRED(!m_unused_i2p_sessions_mutex);
+    CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type, bool use_v2transport) EXCLUSIVE_LOCKS_REQUIRED(!m_unused_i2p_sessions_mutex);
     void AddWhitelistPermissionFlags(NetPermissionFlags& flags, const CNetAddr &addr) const;
 
     void DeleteNode(CNode* pnode);
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index 6af62641bd..86d3eef436 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -311,7 +311,7 @@ static RPCHelpMan addnode()
     if (command == "onetry")
     {
         CAddress addr;
-        connman.OpenNetworkConnection(addr, /*fCountFailure=*/false, /*grantOutbound=*/nullptr, node_arg.c_str(), ConnectionType::MANUAL);
+        connman.OpenNetworkConnection(addr, /*fCountFailure=*/false, /*grantOutbound=*/nullptr, node_arg.c_str(), ConnectionType::MANUAL, /*use_v2transport=*/false);
         return UniValue::VNULL;
     }
 
diff --git a/test/functional/p2p_v2_transport.py b/test/functional/p2p_v2_transport.py
new file mode 100755
index 0000000000..9df4c297e4
--- /dev/null
+++ b/test/functional/p2p_v2_transport.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+# Copyright (c) 2021-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""
+Test v2 transport
+"""
+
+from test_framework.messages import NODE_P2P_V2
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+class V2TransportTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain=True
+        self.num_nodes = 1
+        self.extra_args = [["-v2transport=0"]]
+
+    def run_test(self):
+        network_info = self.nodes[0].getnetworkinfo()
+        assert_equal(int(network_info["localservices"], 16) & NODE_P2P_V2, 0)
+        assert "P2P_V2" not in network_info["localservicesnames"]
+
+        self.restart_node(0, ["-v2transport=1"])
+        network_info = self.nodes[0].getnetworkinfo()
+        assert_equal(int(network_info["localservices"], 16) & NODE_P2P_V2, NODE_P2P_V2)
+        assert "P2P_V2" in network_info["localservicesnames"]
+
+if __name__ == '__main__':
+    V2TransportTest().main()
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 9a0b5c6f0a..4645557655 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -246,6 +246,7 @@ BASE_SCRIPTS = [
     'p2p_invalid_locator.py',
     'p2p_invalid_block.py',
     'p2p_invalid_tx.py',
+    'p2p_v2_transport.py',
     'example_test.py',
     'wallet_txn_doublespend.py --legacy-wallet',
     'wallet_multisig_descriptor_psbt.py --descriptors',