init: add -v2onlyclearnet config option

if this option is set by the user, v1 connections on unencrypted
networks like IPV4/IPV6 will be disallowed. Only users with real
need are recommended to turn this on because it could risk network
partitioning in the unlikely scenario that everyone turns it on.

Author: stratospher

src/init.cpp

@@ -550,6 +550,7 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     argsman.AddArg("-i2pacceptincoming", strprintf("Whether to accept inbound I2P connections (default: %i). Ignored if -i2psam is not set. Listening for inbound I2P connections is done through the SAM proxy, not by binding to a local address and port.", DEFAULT_I2P_ACCEPT_INCOMING), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-onlynet=<net>", "Make automatic outbound connections only to network <net> (" + Join(GetNetworkNames(), ", ") + "). Inbound and manual connections are not affected by this option. It can be specified multiple times to allow multiple networks.", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-v2transport", strprintf("Support v2 transport (default: %u)", DEFAULT_V2_TRANSPORT), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
+    argsman.AddArg("-v2onlyclearnet", strprintf("Disallow v1 connections on IPV4/IPV6 (default: %u). Enabling this is not recommended unless absolutely necessary, as it may risk network partitions if all users enable it.", false), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-peerbloomfilters", strprintf("Support filtering of blocks and transaction with bloom filters (default: %u)", DEFAULT_PEERBLOOMFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-peerblockfilters", strprintf("Serve compact block filters to peers per BIP 157 (default: %u)", DEFAULT_PEERBLOCKFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-txreconciliation", strprintf("Enable transaction reconciliations per BIP 330 (default: %d)", DEFAULT_TXRECONCILIATION_ENABLE), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CONNECTION);
@@ -843,6 +844,7 @@ int available_fds;
 ServiceFlags nLocalServices = ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS);
 int64_t peer_connect_timeout;
 std::set<BlockFilterType> g_enabled_filter_types;
+bool disable_v1conn_clearnet = false;
 
 } // namespace
 
@@ -956,6 +958,11 @@ bool AppInitParameterInteraction(const ArgsManager& args)
     // Signal NODE_P2P_V2 if BIP324 v2 transport is enabled.
     if (args.GetBoolArg("-v2transport", DEFAULT_V2_TRANSPORT)) {
         nLocalServices = ServiceFlags(nLocalServices | NODE_P2P_V2);
+        if (args.GetBoolArg("-v2onlyclearnet", false)) {
+            disable_v1conn_clearnet = true;
+        }
+    } else if (args.GetBoolArg("-v2onlyclearnet", false)) {
+            return InitError(_("Cannot set -v2onlyclearnet to true when v2transport is disabled."));
     }
 
     // Signal NODE_COMPACT_FILTERS if peerblockfilters and basic filters index are both enabled.
@@ -1874,6 +1881,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     connOptions.m_peer_connect_timeout = peer_connect_timeout;
     connOptions.whitelist_forcerelay = args.GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY);
     connOptions.whitelist_relay = args.GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY);
+    connOptions.disable_v1conn_clearnet = disable_v1conn_clearnet;
 
     // Port to bind to if `-bind=addr` is provided without a `:port` suffix.
     const uint16_t default_bind_port =