nbd-client: Exit with error code other than EXIT_FAILURE

When nbd-client tries to connect to nbd device, it talks to kernel
via netlink. If the nbd device is taken and locked by other process
like systemd-udevd, kernel will return EBUSY to nbd client. However,
nbd client just hide this error code with error message to check
dmesg logs.

Checking the dmesg logs is error-prone and not friendly for other
caller program. Instead, nbd-client should return the error code
to the caller to handle it properly.

Signed-off-by: Lin Liu <[email protected]>

cliserv.c

@@ -78,6 +78,12 @@ void nbd_err(const char *s) {
 	exit(EXIT_FAILURE);
 }
 
+void nbd_err_code(const char *s, int code) {
+	err_nonfatal(s);
+	fprintf(stderr, "Exiting.\n");
+	exit(abs(code));
+}
+
 void logging(const char* name) {
 #ifdef ISSERVER
 	openlog(name, LOG_PID, LOG_DAEMON);

cliserv.h

@@ -77,7 +77,9 @@ void setmysockopt(int sock);
 void err_nonfatal(const char *s);
 
 void nbd_err(const char *s) G_GNUC_NORETURN;
+void nbd_err_code(const char *s, int code) G_GNUC_NORETURN;
 #define err(S) nbd_err(S)
+#define err_code(S, C) nbd_err_code(S, C)
 
 void logging(const char* name);
 

nbd-client.c

@@ -169,6 +169,7 @@ static void netlink_configure(int index, int *sockfds, int num_connects,
 	struct nlattr *sock_attr;
 	struct nl_msg *msg;
 	int driver_id, i;
+	int ret;
 
 	socket = get_nbd_socket(&driver_id);
 	nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, callback, NULL);
@@ -199,11 +200,12 @@ static void netlink_configure(int index, int *sockfds, int num_connects,
 	}
 	nla_nest_end(msg, sock_attr);
 
-	if (nl_send_sync(socket, msg) < 0) {
+	ret = nl_send_sync(socket, msg);
+	if (ret < 0) {
                 if(geteuid() != 0) {
-                        err("Failed to setup device. Are you root?\n");
+                        err_code("Failed to setup device. Are you root?\n", ret);
                 } else {
-		        err("Failed to setup device, check dmesg\n");
+		        err_code("Failed to setup device, check dmesg\n", ret);
                 }
         }
 	return;
@@ -215,6 +217,7 @@ static void netlink_disconnect(char *nbddev) {
 	struct nl_sock *socket;
 	struct nl_msg *msg;
 	int driver_id;
+	int ret;
 
 	int index = -1;
 	if (nbddev) {
@@ -232,8 +235,9 @@ static void netlink_disconnect(char *nbddev) {
 	genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, driver_id, 0, 0,
 		    NBD_CMD_DISCONNECT, 0);
 	NLA_PUT_U32(msg, NBD_ATTR_INDEX, index);
-	if (nl_send_sync(socket, msg) < 0)
-		err("Failed to disconnect device, check dmsg\n");
+	ret = nl_send_sync(socket, msg);
+	if (ret < 0)
+		err_code("Failed to disconnect device, check dmsg\n", ret);
 	nl_socket_free(socket);
 	return;
 nla_put_failure: