nbd: add nbd-get-status

Add support for the netlink get status command to get the connection
status of one or all of the nbd devices in a system.

Signed-off-by: Josef Bacik <[email protected]>
[Forward-ported after seven (!) years by Wouter Verhelst]
Signed-off-by: Wouter Verhelst <[email protected]>

Makefile.am

@@ -51,3 +51,9 @@ nbdtab_parser.tab.h: $(srcdir)/nbdtab_parser.y
 	bison -d $^ > $@
 
 AM_DISTCHECK_CONFIGURE_FLAGS=--enable-syslog
+
+if NETLINK
+bin_PROGRAMS += nbd-get-status
+nbd_get_status_SOURCES = nbd-get-status.c cliserv.c
+nbd_get_status_CFLAGS = @CFLAGS@
+endif

configure.ac

@@ -311,6 +311,8 @@ else
 	AC_DEFINE(HAVE_NETLINK, 0, [Define to 1 if we have netlink support])
 fi
 
+AM_CONDITIONAL(NETLINK, [test "$HAVE_NETLINK" = "1"])
+
 AC_MSG_CHECKING([whether man pages are requested])
 AC_ARG_ENABLE([manpages],
 	AS_HELP_STRING([--disable-manpages], [Do not install man pages]),

nbd-get-status.c

@@ -0,0 +1,94 @@
+#include "config.h"
+#include "lfs.h"
+
+#include <stdio.h>
+#include <netlink/netlink.h>
+#include <netlink/genl/genl.h>
+#include <netlink/genl/ctrl.h>
+#include "cliserv.h"
+#include "nbd-netlink.h"
+
+static struct nla_policy nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
+	[NBD_DEVICE_INDEX]		=	{ .type = NLA_U32 },
+	[NBD_DEVICE_CONNECTED]		=	{ .type = NLA_U8 },
+};
+
+static struct nl_sock *get_nbd_socket(int *driver_id)
+{
+	struct nl_sock *socket;
+	int id;
+
+	socket = nl_socket_alloc();
+	if (!socket)
+		err("Couldn't allocate netlink socket\n");
+
+	if (genl_connect(socket))
+		err("Couldn't connect to the generic netlink socket\n");
+	id = genl_ctrl_resolve(socket, "nbd");
+	if (id < 0)
+		err("Couldn't resolve the nbd netlink family, make sure the nbd module is loaded and your nbd driver supports the netlink interface.\n");
+	if (driver_id)
+		*driver_id = id;
+	return socket;
+}
+
+static int callback(struct nl_msg *msg, void *arg)
+{
+	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
+	struct nlattr *msg_attr[NBD_ATTR_MAX + 1];
+	struct nlattr *attr;
+	int ret, rem;
+
+	ret = nla_parse(msg_attr, NBD_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
+			genlmsg_attrlen(gnlh, 0), NULL);
+	if (ret)
+		err("Invalid response from get status?\n");
+
+	nla_for_each_nested(attr, msg_attr[NBD_ATTR_DEVICE_LIST], rem) {
+		struct nlattr *device[NBD_DEVICE_ATTR_MAX + 1];
+		u32 index;
+		uint8_t connected;
+
+		if (nla_type(attr) != NBD_DEVICE_ITEM)
+			err("Invalid attr type in the device list\n");
+		ret = nla_parse_nested(device, NBD_DEVICE_ATTR_MAX, attr,
+				       nbd_device_policy);
+		if (ret)
+			err("Invalid attr device attr\n");
+		index = nla_get_u32(device[NBD_DEVICE_INDEX]);
+		connected = nla_get_u8(device[NBD_DEVICE_CONNECTED]);
+		printf("/dev/nbd%d: %s\n", (int)index,
+		       connected ? "connected" : "disconnected");
+	}
+	return NL_OK;
+}
+
+int main(int argc, char **argv)
+{
+	struct nl_sock *socket;
+	struct nlattr *sock_attr;
+	struct nl_msg *msg;
+	int driver_id;
+	int index = -1;
+
+	if (argc > 1) {
+		if (sscanf(argv[1], "/dev/nbd%d", &index) != 1)
+			err("Invalid nbd device target\n");
+	}
+
+	socket = get_nbd_socket(&driver_id);
+	nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, callback, NULL);
+
+	msg = nlmsg_alloc();
+	if (!msg)
+		err("Couldn't allocate netlink message\n");
+	genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, driver_id, 0, 0,
+		    NBD_CMD_STATUS, 0);
+	if (index >= 0)
+		NLA_PUT_U32(msg, NBD_ATTR_INDEX, index);
+	if (nl_send_sync(socket, msg) < 0)
+		err("Failed to get status\n");
+	return 0;
+nla_put_failure:
+	err("Failed to create netlink message\n");
+}

nbd-netlink.h

@@ -31,10 +31,35 @@ enum {
 	NBD_ATTR_SERVER_FLAGS,
 	NBD_ATTR_CLIENT_FLAGS,
 	NBD_ATTR_SOCKETS,
+	NBD_ATTR_DEAD_CONN_TIMEOUT,
+	NBD_ATTR_DEVICE_LIST,
 	__NBD_ATTR_MAX,
 };
 #define NBD_ATTR_MAX (__NBD_ATTR_MAX - 1)
 
+/*
+ * This is the format for multiple devices with NBD_ATTR_DEVICE_LIST
+ *
+ * [NBD_ATTR_DEVICE_LIST]
+ *   [NBD_DEVICE_ITEM]
+ *     [NBD_DEVICE_INDEX]
+ *     [NBD_DEVICE_CONNECTED]
+ */
+enum {
+	NBD_DEVICE_ITEM_UNSPEC,
+	NBD_DEVICE_ITEM,
+	__NBD_DEVICE_ITEM_MAX,
+};
+#define NBD_DEVICE_ITEM_MAX (__NBD_DEVICE_ITEM_MAX - 1)
+
+enum {
+	NBD_DEVICE_UNSPEC,
+	NBD_DEVICE_INDEX,
+	NBD_DEVICE_CONNECTED,
+	__NBD_DEVICE_MAX,
+};
+#define NBD_DEVICE_ATTR_MAX (__NBD_DEVICE_MAX - 1)
+
 /*
  * This is the format for multiple sockets with NBD_ATTR_SOCKETS
  *
@@ -62,6 +87,9 @@ enum {
 	NBD_CMD_UNSPEC,
 	NBD_CMD_CONNECT,
 	NBD_CMD_DISCONNECT,
+	NBD_CMD_RECONFIGURE,
+	NBD_CMD_LINK_DEAD,
+	NBD_CMD_STATUS,
 	__NBD_CMD_MAX,
 };
 #define NBD_CMD_MAX	(__NBD_CMD_MAX - 1)