builtin/settingtypes.txt

@@ -810,6 +810,14 @@ bind_address (Bind address) string
 #    to new servers, but they may not support all new features that you are expecting.
 strict_protocol_version_checking (Strict protocol checking) bool false
 
+#    Define the oldest clients allowed to connect.
+#    Older clients are compatible in the sense that they will not crash when connecting
+#    to new servers, but they may not support all new features that you are expecting.
+#    This allows for more fine-grained control than strict_protocol_version_checking.
+#    Minetest still enforces its own internal minimum, and enabling
+#    strict_protocol_version_checking will effectively override this.
+protocol_version_min (Protocol version minimum) int 1 1 65535
+
 #    Specifies URL from which client fetches media instead of using UDP.
 #    $filename should be accessible from $remote_media$filename via cURL
 #    (obviously, remote_media should end with a slash).

minetest.conf.example

@@ -760,6 +760,15 @@
 #    type: bool
 # strict_protocol_version_checking = false
 
+#    Define the oldest clients allowed to connect.
+#    Older clients are compatible in the sense that they will not crash when connecting
+#    to new servers, but they may not support all new features that you are expecting.
+#    This allows more fine-grained control than strict_protocol_version_checking.
+#    Minetest may still enforce its own internal minimum, and enabling
+#    strict_protocol_version_checking will effectively override this.
+#    type: int min: 1 max: 65535
+# protocol_version_min = 1
+
 #    Specifies URL from which client fetches media instead of using UDP.
 #    $filename should be accessible from $remote_media$filename via cURL
 #    (obviously, remote_media should end with a slash).

src/defaultsettings.cpp

@@ -365,6 +365,7 @@ void set_default_settings()
 	settings->setDefault("max_packets_per_iteration", "1024");
 	settings->setDefault("port", "30000");
 	settings->setDefault("strict_protocol_version_checking", "false");
+	settings->setDefault("protocol_version_min", "1");
 	settings->setDefault("player_transfer_distance", "0");
 	settings->setDefault("max_simultaneous_block_sends_per_client", "40");
 	settings->setDefault("time_send_interval", "5");

src/network/serverpackethandler.cpp

@@ -147,10 +147,8 @@ void Server::handleCommand_Init(NetworkPacket* pkt)
 
 	client->net_proto_version = net_proto_version;
 
-	if ((g_settings->getBool("strict_protocol_version_checking") &&
+	if (net_proto_version < Server::getProtocolVersionMin() ||
-			net_proto_version != LATEST_PROTOCOL_VERSION) ||
+			net_proto_version > Server::getProtocolVersionMax()) {
-			net_proto_version < SERVER_PROTOCOL_VERSION_MIN ||
-			net_proto_version > SERVER_PROTOCOL_VERSION_MAX) {
 		actionstream << "Server: A mismatched client tried to connect from " <<
 			addr_s << " proto_max=" << (int)max_net_proto_version << std::endl;
 		DenyAccess(peer_id, SERVER_ACCESSDENIED_WRONG_VERSION);

src/server.cpp

@@ -4191,3 +4191,20 @@ bool Server::migrateModStorageDatabase(const GameParams &game_params, const Sett
 
 	return succeeded;
 }
+
+u16 Server::getProtocolVersionMin()
+{
+	u16 min_proto = g_settings->getU16("protocol_version_min");
+	if (g_settings->getBool("strict_protocol_version_checking"))
+		min_proto = LATEST_PROTOCOL_VERSION;
+	return rangelim(min_proto,
+		SERVER_PROTOCOL_VERSION_MIN,
+		SERVER_PROTOCOL_VERSION_MAX);
+}
+
+u16 Server::getProtocolVersionMax()
+{
+	return g_settings->getBool("strict_protocol_version_checking")
+		? LATEST_PROTOCOL_VERSION
+		: SERVER_PROTOCOL_VERSION_MAX;
+}

src/server.h

@@ -383,6 +383,9 @@ public:
 	static bool migrateModStorageDatabase(const GameParams &game_params,
 			const Settings &cmd_args);
 
+	static u16 getProtocolVersionMin();
+	static u16 getProtocolVersionMax();
+
 	// Lua files registered for init of async env, pair of modname + path
 	std::vector<std::pair<std::string, std::string>> m_async_init_files;
 

src/serverlist.cpp

@@ -27,6 +27,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <json/json.h>
 #include "convert_json.h"
 #include "httpfetch.h"
+#include "server.h"
 
 namespace ServerList
 {
@@ -50,12 +51,11 @@ void sendAnnounce(AnnounceAction action,
 		server["address"] = g_settings->get("server_address");
 	}
 	if (action != AA_DELETE) {
-		bool strict_checking = g_settings->getBool("strict_protocol_version_checking");
 		server["name"]         = g_settings->get("server_name");
 		server["description"]  = g_settings->get("server_description");
 		server["version"]      = g_version_string;
-		server["proto_min"]    = strict_checking ? LATEST_PROTOCOL_VERSION : SERVER_PROTOCOL_VERSION_MIN;
+		server["proto_min"]    = Server::getProtocolVersionMin();
-		server["proto_max"]    = strict_checking ? LATEST_PROTOCOL_VERSION : SERVER_PROTOCOL_VERSION_MAX;
+		server["proto_max"]    = Server::getProtocolVersionMax();
 		server["url"]          = g_settings->get("server_url");
 		server["creative"]     = g_settings->getBool("creative_mode");
 		server["damage"]       = g_settings->getBool("enable_damage");