nbd-get-status.c

   1 #include "config.h"
   2 #include "lfs.h"
   3
   4 #include <stdio.h>
   5 #include <netlink/netlink.h>
   6 #include <netlink/genl/genl.h>
   7 #include <netlink/genl/ctrl.h>
   8 #include "cliserv.h"
   9 #include "nbd-netlink.h"
  10
  11 static struct nla_policy nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
  12         [NBD_DEVICE_INDEX]              =       { .type = NLA_U32 },
  13         [NBD_DEVICE_CONNECTED]          =       { .type = NLA_U8 },
  14 };
  15
  16 static struct nl_sock *get_nbd_socket(int *driver_id)
  17 {
  18         struct nl_sock *socket;
  19         int id;
  20
  21         socket = nl_socket_alloc();
  22         if (!socket)
  23                 err("Couldn't allocate netlink socket\n");
  24
  25         if (genl_connect(socket))
  26                 err("Couldn't connect to the generic netlink socket\n");
  27         id = genl_ctrl_resolve(socket, "nbd");
  28         if (id < 0)
  29                 err("Couldn't resolve the nbd netlink family, make sure the nbd module is loaded and your nbd driver supports the netlink interface.\n");
  30         if (driver_id)
  31                 *driver_id = id;
  32         return socket;
  33 }
  34
  35 static int callback(struct nl_msg *msg, void *arg)
  36 {
  37         struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
  38         struct nlattr *msg_attr[NBD_ATTR_MAX + 1];
  39         struct nlattr *attr;
  40         int ret, rem;
  41
  42         ret = nla_parse(msg_attr, NBD_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
  43                         genlmsg_attrlen(gnlh, 0), NULL);
  44         if (ret)
  45                 err("Invalid response from get status?\n");
  46
  47         nla_for_each_nested(attr, msg_attr[NBD_ATTR_DEVICE_LIST], rem) {
  48                 struct nlattr *device[NBD_DEVICE_ATTR_MAX + 1];
  49                 u32 index;
  50                 uint8_t connected;
  51
  52                 if (nla_type(attr) != NBD_DEVICE_ITEM)
  53                         err("Invalid attr type in the device list\n");
  54                 ret = nla_parse_nested(device, NBD_DEVICE_ATTR_MAX, attr,
  55                                        nbd_device_policy);
  56                 if (ret)
  57                         err("Invalid attr device attr\n");
  58                 index = nla_get_u32(device[NBD_DEVICE_INDEX]);
  59                 connected = nla_get_u8(device[NBD_DEVICE_CONNECTED]);
  60                 printf("/dev/nbd%d: %s\n", (int)index,
  61                        connected ? "connected" : "disconnected");
  62         }
  63         return NL_OK;
  64 }
  65
  66 int main(int argc, char **argv)
  67 {
  68         struct nl_sock *socket;
  69         struct nlattr *sock_attr;
  70         struct nl_msg *msg;
  71         int driver_id;
  72         int index = -1;
  73
  74         if (argc > 1) {
  75                 if (sscanf(argv[1], "/dev/nbd%d", &index) != 1)
  76                         err("Invalid nbd device target\n");
  77         }
  78
  79         socket = get_nbd_socket(&driver_id);
  80         nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, callback, NULL);
  81
  82         msg = nlmsg_alloc();
  83         if (!msg)
  84                 err("Couldn't allocate netlink message\n");
  85         genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, driver_id, 0, 0,
  86                     NBD_CMD_STATUS, 0);
  87         if (index >= 0)
  88                 NLA_PUT_U32(msg, NBD_ATTR_INDEX, index);
  89         if (nl_send_sync(socket, msg) < 0)
  90                 err("Failed to get status\n");
  91         return 0;
  92 nla_put_failure:
  93         err("Failed to create netlink message\n");
  94 }