grpc: add ability to specify grpc host

This update lets you specify the network interface for gRPC.
For example, using 127.0.0.1 restricts gRPC access to the local machine, enhancing security since gRPC is not publicly exposed.
For backward compatibility, the default remains 0.0.0.0.

Signed-off-by: Vladimir Buyanov <b.vladimir@clickadu.com>

doc/developer/grpc.rst

@@ -7,7 +7,7 @@ Northbound gRPC
 To enable gRPC support one needs to add `--enable-grpc` when running
 `configure`. Additionally, when launching each daemon one needs to request
 the gRPC module be loaded and which port to bind to. This can be done by adding
-`-M grpc:<port>` to the daemon's CLI arguments.
+`-M grpc:<host>:<port>` or `-M grpc:<port>` (default host is `0.0.0.0`)  to the daemon's CLI arguments.
 
 Currently there is no gRPC "routing" so you will need to bind your gRPC
 `channel` to the particular daemon's gRPC port to interact with that daemon's

lib/northbound_grpc.cpp

@@ -1131,18 +1131,15 @@ static grpc::Server *s_server;
 static void *grpc_pthread_start(void *arg)
 {
 	struct frr_pthread *fpt = static_cast<frr_pthread *>(arg);
-	uint port = (uint) reinterpret_cast<intptr_t>(fpt->data);
+	std::string endpoint = *static_cast<std::string *>(fpt->data);
 
 	Candidates candidates;
 	grpc::ServerBuilder builder;
-	std::stringstream server_address;
 	frr::Northbound::AsyncService service;
 
 	frr_pthread_set_name(fpt);
 
-	server_address << "0.0.0.0:" << port;
-	builder.AddListeningPort(server_address.str(),
-				 grpc::InsecureServerCredentials());
+	builder.AddListeningPort(endpoint, grpc::InsecureServerCredentials());
 	builder.RegisterService(&service);
 	builder.AddChannelArgument(
 		GRPC_ARG_HTTP2_MIN_RECV_PING_INTERVAL_WITHOUT_DATA_MS, 5000);
@@ -1172,8 +1169,7 @@ static void *grpc_pthread_start(void *arg)
 	REQUEST_NEWRPC_STREAMING(Get);
 	REQUEST_NEWRPC_STREAMING(ListTransactions);
 
-	zlog_notice("gRPC server listening on %s",
-		    server_address.str().c_str());
+	zlog_notice("gRPC server listening on %s", endpoint.c_str());
 
 	/* Process inbound RPCs */
 	bool ok;
@@ -1225,7 +1221,7 @@ static void *grpc_pthread_start(void *arg)
 }
 
 
-static int frr_grpc_init(uint port)
+static int frr_grpc_init(const std::string &endpoint)
 {
 	struct frr_pthread_attr attr = {
 		.start = grpc_pthread_start,
@@ -1235,12 +1231,14 @@ static int frr_grpc_init(uint port)
 	grpc_debug("%s: entered", __func__);
 
 	fpt = frr_pthread_new(&attr, "frr-grpc", "frr-grpc");
-	fpt->data = reinterpret_cast<void *>((intptr_t)port);
+	std::string *ep = new std::string(endpoint);
+	fpt->data = reinterpret_cast<void *>(ep);
 
 	/* Create a pthread for gRPC since it runs its own event loop. */
 	if (frr_pthread_run(fpt, NULL) < 0) {
 		flog_err(EC_LIB_SYSTEM_CALL, "%s: error creating pthread: %s",
 			 __func__, safe_strerror(errno));
+		delete ep;
 		return -1;
 	}
 
@@ -1288,19 +1286,57 @@ static int frr_grpc_finish(void)
 static void frr_grpc_module_very_late_init(struct event *thread)
 {
 	const char *args = THIS_MODULE->load_args;
-	uint port = GRPC_DEFAULT_PORT;
+	std::string endpoint;
 
 	if (args) {
-		port = std::stoul(args);
-		if (port < 1024 || port > UINT16_MAX) {
-			flog_err(EC_LIB_GRPC_INIT,
-				 "%s: port number must be between 1025 and %d",
-				 __func__, UINT16_MAX);
-			goto error;
+		std::string arg_str(args);
+
+		if (arg_str.find(':') != std::string::npos) {
+			size_t pos = arg_str.rfind(':');
+			std::string port_str = arg_str.substr(pos + 1);
+			uint port = 0;
+			try {
+				port = std::stoul(port_str);
+			} catch (const std::exception &e) {
+				flog_err(EC_LIB_GRPC_INIT,
+					 "%s: invalid port number in host:port format: %s",
+					 __func__, e.what());
+				goto error;
+			}
+
+			if (port < 1024 || port > UINT16_MAX) {
+				flog_err(EC_LIB_GRPC_INIT,
+					 "%s: port number must be between 1025 and %d", __func__,
+					 UINT16_MAX);
+				goto error;
+			}
+			endpoint = arg_str;
+		} else {
+			if (!arg_str.empty() && arg_str[0] == ':')
+				arg_str = arg_str.substr(1);
+
+			uint port = 0;
+			try {
+				port = std::stoul(arg_str);
+			} catch (const std::exception &e) {
+				flog_err(EC_LIB_GRPC_INIT, "%s: invalid port number: %s", __func__,
+					 e.what());
+				goto error;
+			}
+
+			if (port < 1024 || port > UINT16_MAX) {
+				flog_err(EC_LIB_GRPC_INIT,
+					 "%s: port number must be between 1025 and %d", __func__,
+					 UINT16_MAX);
+				goto error;
+			}
+			endpoint = "0.0.0.0:" + arg_str;
 		}
+	} else {
+		endpoint = "0.0.0.0:" + std::to_string(GRPC_DEFAULT_PORT);
 	}
 
-	if (frr_grpc_init(port) < 0)
+	if (frr_grpc_init(endpoint) < 0)
 		goto error;
 
 	return;