/**
* Receive a set of messages from a netlink socket.
* @arg sk Netlink socket.
* @arg cb set of callbacks to control behaviour.
*
* Repeatedly calls nl_recv() or the respective replacement if provided
* by the application (see nl_cb_overwrite_recv()) and parses the
* received data as netlink messages. Stops reading if one of the
* callbacks returns NL_STOP or nl_recv returns either 0 or a negative error code.
*
* A non-blocking sockets causes the function to return immediately if
* no data is available.
*
* @see nl_recvmsgs_report()
*
* @return 0 on success or a negative error code from nl_recv().
*/
int nl_recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
{
int err;
if ((err = nl_recvmsgs_report(sk, cb)) > 0)
err = 0;
return err;
}
int main()
{
struct nl_sock * sk;
int cbarg;
// nl_debug = 4;
// setup netlink socket
sk = nl_socket_alloc();
nl_socket_disable_seq_check(sk); // disable sequence number check
genl_connect(sk);
int id = genl_ctrl_resolve(sk, DEMO_FAMILY_NAME);
struct nl_msg * msg;
// create a messgae
msg = nlmsg_alloc();
genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, id, 0, // hdrlen
0, // flags
DEMO_CMD, // numeric command identifier
DEMO_VERSION // interface version
);
nla_put_string(msg, DEMO_ATTR1_STRING, "hola");
nla_put_u16(msg, DEMO_ATTR2_UINT16, 0xf1);
// send it
nl_send_auto(sk, msg);
// handle reply
struct nl_cb * cb = NULL;
cb = nl_cb_alloc(NL_CB_CUSTOM);
//nl_cb_set_all(cb, NL_CB_DEBUG, NULL, NULL);
nl_cb_set_all(cb, NL_CB_CUSTOM, cb_handler, &cbarg);
nl_cb_err(cb, NL_CB_DEBUG, NULL, NULL);
int nrecv = nl_recvmsgs_report(sk, cb);
printf("cbarg %d nrecv %d\n", cbarg, nrecv);
// cleanup
nlmsg_free(msg);
nl_close(sk);
nl_socket_free(sk);
return 0;
}
/**
* Check for event notifications
* @arg mngr Cache Manager
* @arg timeout Upper limit poll() will block, in milliseconds.
*
* Causes poll() to be called to check for new event notifications
* being available. Calls nl_cache_mngr_data_ready() to process
* available data.
*
* This functionally is ideally called regularly during an idle
* period.
*
* A timeout can be specified in milliseconds to limit the time the
* function will wait for updates.
*
* @see nl_cache_mngr_data_ready()
*
* @return The number of messages processed or a negative error code.
*/
int nl_cache_mngr_poll(struct nl_cache_mngr *mngr, int timeout)
{
int ret;
struct pollfd fds = {
.fd = nl_socket_get_fd(mngr->cm_sock),
.events = POLLIN,
};
NL_DBG(3, "Cache manager %p, poll() fd %d\n", mngr, fds.fd);
ret = poll(&fds, 1, timeout);
NL_DBG(3, "Cache manager %p, poll() returned %d\n", mngr, ret);
if (ret < 0)
return -nl_syserr2nlerr(errno);
/* No events, return */
if (ret == 0)
return 0;
return nl_cache_mngr_data_ready(mngr);
}
/**
* Receive available event notifications
* @arg mngr Cache manager
*
* This function can be called if the socket associated to the manager
* contains updates to be received. This function should only be used
* if nl_cache_mngr_poll() is not used.
*
* The function will process messages until there is no more data to
* be read from the socket.
*
* @see nl_cache_mngr_poll()
*
* @return The number of messages processed or a negative error code.
*/
int nl_cache_mngr_data_ready(struct nl_cache_mngr *mngr)
{
int err, nread = 0;
struct nl_cb *cb;
NL_DBG(2, "Cache manager %p, reading new data from fd %d\n",
mngr, nl_socket_get_fd(mngr->cm_sock));
cb = nl_cb_clone(mngr->cm_sock->s_cb);
if (cb == NULL)
return -NLE_NOMEM;
nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, event_input, mngr);
while ((err = nl_recvmsgs_report(mngr->cm_sock, cb)) > 0) {
NL_DBG(2, "Cache manager %p, recvmsgs read %d messages\n",
mngr, err);
nread += err;
}
nl_cb_put(cb);
if (err < 0 && err != -NLE_AGAIN)
return err;
return nread;
}
