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Sources/libnl-tiny/nl.c

  1 /*
  2  * lib/nl.c             Core Netlink Interface
  3  *
  4  *      This library is free software; you can redistribute it and/or
  5  *      modify it under the terms of the GNU Lesser General Public
  6  *      License as published by the Free Software Foundation version 2.1
  7  *      of the License.
  8  *
  9  * Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
 10  */
 11 
 12 /**
 13  * @defgroup core Core
 14  *
 15  * @details
 16  * @par 1) Connecting the socket
 17  * @code
 18  * // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
 19  * nl_connect(sk, NETLINK_ROUTE);
 20  * @endcode
 21  *
 22  * @par 2) Sending data
 23  * @code
 24  * // The most rudimentary method is to use nl_sendto() simply pushing
 25  * // a piece of data to the other netlink peer. This method is not
 26  * // recommended.
 27  * const char buf[] = { 0x01, 0x02, 0x03, 0x04 };
 28  * nl_sendto(sk, buf, sizeof(buf));
 29  *
 30  * // A more comfortable interface is nl_send() taking a pointer to
 31  * // a netlink message.
 32  * struct nl_msg *msg = my_msg_builder();
 33  * nl_send(sk, nlmsg_hdr(msg));
 34  *
 35  * // nl_sendmsg() provides additional control over the sendmsg() message
 36  * // header in order to allow more specific addressing of multiple peers etc.
 37  * struct msghdr hdr = { ... };
 38  * nl_sendmsg(sk, nlmsg_hdr(msg), &hdr);
 39  *
 40  * // You're probably too lazy to fill out the netlink pid, sequence number
 41  * // and message flags all the time. nl_send_auto_complete() automatically
 42  * // extends your message header as needed with an appropriate sequence
 43  * // number, the netlink pid stored in the netlink socket and the message
 44  * // flags NLM_F_REQUEST and NLM_F_ACK (if not disabled in the socket)
 45  * nl_send_auto_complete(sk, nlmsg_hdr(msg));
 46  *
 47  * // Simple protocols don't require the complex message construction interface
 48  * // and may favour nl_send_simple() to easly send a bunch of payload
 49  * // encapsulated in a netlink message header.
 50  * nl_send_simple(sk, MY_MSG_TYPE, 0, buf, sizeof(buf));
 51  * @endcode
 52  *
 53  * @par 3) Receiving data
 54  * @code
 55  * // nl_recv() receives a single message allocating a buffer for the message
 56  * // content and gives back the pointer to you.
 57  * struct sockaddr_nl peer;
 58  * unsigned char *msg;
 59  * nl_recv(sk, &peer, &msg);
 60  *
 61  * // nl_recvmsgs() receives a bunch of messages until the callback system
 62  * // orders it to state, usually after receving a compolete multi part
 63  * // message series.
 64  * nl_recvmsgs(sk, my_callback_configuration);
 65  *
 66  * // nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback
 67  * // configuration stored in the socket.
 68  * nl_recvmsgs_default(sk);
 69  *
 70  * // In case you want to wait for the ACK to be recieved that you requested
 71  * // with your latest message, you can call nl_wait_for_ack()
 72  * nl_wait_for_ack(sk);
 73  * @endcode
 74  *
 75  * @par 4) Closing
 76  * @code
 77  * // Close the socket first to release kernel memory
 78  * nl_close(sk);
 79  * @endcode
 80  * 
 81  * @{
 82  */
 83 
 84 #include <netlink-local.h>
 85 #include <netlink/netlink.h>
 86 #include <netlink/utils.h>
 87 #include <netlink/handlers.h>
 88 #include <netlink/msg.h>
 89 #include <netlink/attr.h>
 90 
 91 /**
 92  * @name Connection Management
 93  * @{
 94  */
 95 
 96 /**
 97  * Create and connect netlink socket.
 98  * @arg sk              Netlink socket.
 99  * @arg protocol        Netlink protocol to use.
100  *
101  * Creates a netlink socket using the specified protocol, binds the socket
102  * and issues a connection attempt.
103  *
104  * @return 0 on success or a negative error code.
105  */
106 int nl_connect(struct nl_sock *sk, int protocol)
107 {
108         int err;
109         int flags = 0;
110         socklen_t addrlen;
111 
112 #ifdef SOCK_CLOEXEC
113         flags = SOCK_CLOEXEC;
114 #endif
115 
116         sk->s_fd = socket(AF_NETLINK, SOCK_RAW | flags, protocol);
117         if (sk->s_fd < 0) {
118                 err = -nl_syserr2nlerr(errno);
119                 goto errout;
120         }
121 
122         if (!(sk->s_flags & NL_SOCK_BUFSIZE_SET)) {
123                 err = nl_socket_set_buffer_size(sk, 0, 0);
124                 if (err < 0)
125                         goto errout;
126         }
127 
128         err = bind(sk->s_fd, (struct sockaddr*) &sk->s_local,
129                    sizeof(sk->s_local));
130         if (err < 0) {
131                 err = -nl_syserr2nlerr(errno);
132                 goto errout;
133         }
134 
135         addrlen = sizeof(sk->s_local);
136         err = getsockname(sk->s_fd, (struct sockaddr *) &sk->s_local,
137                           &addrlen);
138         if (err < 0) {
139                 err = -nl_syserr2nlerr(errno);
140                 goto errout;
141         }
142 
143         if (addrlen != sizeof(sk->s_local)) {
144                 err = -NLE_NOADDR;
145                 goto errout;
146         }
147 
148         if (sk->s_local.nl_family != AF_NETLINK) {
149                 err = -NLE_AF_NOSUPPORT;
150                 goto errout;
151         }
152 
153         sk->s_proto = protocol;
154 
155         return 0;
156 errout:
157         close(sk->s_fd);
158         sk->s_fd = -1;
159 
160         return err;
161 }
162 
163 /**
164  * Close/Disconnect netlink socket.
165  * @arg sk              Netlink socket.
166  */
167 void nl_close(struct nl_sock *sk)
168 {
169         if (sk->s_fd >= 0) {
170                 close(sk->s_fd);
171                 sk->s_fd = -1;
172         }
173 
174         sk->s_proto = 0;
175 }
176 
177 /** @} */
178 
179 /**
180  * @name Send
181  * @{
182  */
183 
184 /**
185  * Send raw data over netlink socket.
186  * @arg sk              Netlink socket.
187  * @arg buf             Data buffer.
188  * @arg size            Size of data buffer.
189  * @return Number of characters written on success or a negative error code.
190  */
191 int nl_sendto(struct nl_sock *sk, void *buf, size_t size)
192 {
193         int ret;
194 
195         ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *)
196                      &sk->s_peer, sizeof(sk->s_peer));
197         if (ret < 0)
198                 return -nl_syserr2nlerr(errno);
199 
200         return ret;
201 }
202 
203 /**
204  * Send netlink message with control over sendmsg() message header.
205  * @arg sk              Netlink socket.
206  * @arg msg             Netlink message to be sent.
207  * @arg hdr             Sendmsg() message header.
208  * @return Number of characters sent on sucess or a negative error code.
209  */
210 int nl_sendmsg(struct nl_sock *sk, struct nl_msg *msg, struct msghdr *hdr)
211 {
212         struct nl_cb *cb;
213         int ret;
214 
215         struct iovec iov = {
216                 .iov_base = (void *) nlmsg_hdr(msg),
217                 .iov_len = nlmsg_hdr(msg)->nlmsg_len,
218         };
219 
220         hdr->msg_iov = &iov;
221         hdr->msg_iovlen = 1;
222 
223         nlmsg_set_src(msg, &sk->s_local);
224 
225         cb = sk->s_cb;
226         if (cb->cb_set[NL_CB_MSG_OUT])
227                 if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK)
228                         return 0;
229 
230         ret = sendmsg(sk->s_fd, hdr, 0);
231         if (ret < 0)
232                 return -nl_syserr2nlerr(errno);
233 
234         return ret;
235 }
236 
237 
238 /**
239  * Send netlink message.
240  * @arg sk              Netlink socket.
241  * @arg msg             Netlink message to be sent.
242  * @see nl_sendmsg()
243  * @return Number of characters sent on success or a negative error code.
244  */
245 int nl_send(struct nl_sock *sk, struct nl_msg *msg)
246 {
247         struct sockaddr_nl *dst;
248         struct ucred *creds;
249         
250         struct msghdr hdr = {
251                 .msg_name = (void *) &sk->s_peer,
252                 .msg_namelen = sizeof(struct sockaddr_nl),
253         };
254 
255         /* Overwrite destination if specified in the message itself, defaults
256          * to the peer address of the socket.
257          */
258         dst = nlmsg_get_dst(msg);
259         if (dst->nl_family == AF_NETLINK)
260                 hdr.msg_name = dst;
261 
262         /* Add credentials if present. */
263         creds = nlmsg_get_creds(msg);
264         if (creds != NULL) {
265                 char buf[CMSG_SPACE(sizeof(struct ucred))];
266                 struct cmsghdr *cmsg;
267 
268                 hdr.msg_control = buf;
269                 hdr.msg_controllen = sizeof(buf);
270 
271                 cmsg = CMSG_FIRSTHDR(&hdr);
272                 cmsg->cmsg_level = SOL_SOCKET;
273                 cmsg->cmsg_type = SCM_CREDENTIALS;
274                 cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
275                 memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred));
276         }
277 
278         return nl_sendmsg(sk, msg, &hdr);
279 }
280 
281 /**
282  * Send netlink message and check & extend header values as needed.
283  * @arg sk              Netlink socket.
284  * @arg msg             Netlink message to be sent.
285  *
286  * Checks the netlink message \c nlh for completness and extends it
287  * as required before sending it out. Checked fields include pid,
288  * sequence nr, and flags.
289  *
290  * @see nl_send()
291  * @return Number of characters sent or a negative error code.
292  */
293 int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
294 {
295         struct nlmsghdr *nlh;
296         struct nl_cb *cb = sk->s_cb;
297 
298         nlh = nlmsg_hdr(msg);
299         if (nlh->nlmsg_pid == 0)
300                 nlh->nlmsg_pid = sk->s_local.nl_pid;
301 
302         if (nlh->nlmsg_seq == 0)
303                 nlh->nlmsg_seq = sk->s_seq_next++;
304 
305         if (msg->nm_protocol == -1)
306                 msg->nm_protocol = sk->s_proto;
307         
308         nlh->nlmsg_flags |= NLM_F_REQUEST;
309 
310         if (!(sk->s_flags & NL_NO_AUTO_ACK))
311                 nlh->nlmsg_flags |= NLM_F_ACK;
312 
313         if (cb->cb_send_ow)
314                 return cb->cb_send_ow(sk, msg);
315         else
316                 return nl_send(sk, msg);
317 }
318 
319 /**
320  * Send simple netlink message using nl_send_auto_complete()
321  * @arg sk              Netlink socket.
322  * @arg type            Netlink message type.
323  * @arg flags           Netlink message flags.
324  * @arg buf             Data buffer.
325  * @arg size            Size of data buffer.
326  *
327  * Builds a netlink message with the specified type and flags and
328  * appends the specified data as payload to the message.
329  *
330  * @see nl_send_auto_complete()
331  * @return Number of characters sent on success or a negative error code.
332  */
333 int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf,
334                    size_t size)
335 {
336         int err;
337         struct nl_msg *msg;
338 
339         msg = nlmsg_alloc_simple(type, flags);
340         if (!msg)
341                 return -NLE_NOMEM;
342 
343         if (buf && size) {
344                 err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO);
345                 if (err < 0)
346                         goto errout;
347         }
348         
349 
350         err = nl_send_auto_complete(sk, msg);
351 errout:
352         nlmsg_free(msg);
353 
354         return err;
355 }
356 
357 /** @} */
358 
359 /**
360  * @name Receive
361  * @{
362  */
363 
364 /**
365  * Receive data from netlink socket
366  * @arg sk              Netlink socket.
367  * @arg nla             Destination pointer for peer's netlink address.
368  * @arg buf             Destination pointer for message content.
369  * @arg creds           Destination pointer for credentials.
370  *
371  * Receives a netlink message, allocates a buffer in \c *buf and
372  * stores the message content. The peer's netlink address is stored
373  * in \c *nla. The caller is responsible for freeing the buffer allocated
374  * in \c *buf if a positive value is returned.  Interrupted system calls
375  * are handled by repeating the read. The input buffer size is determined
376  * by peeking before the actual read is done.
377  *
378  * A non-blocking sockets causes the function to return immediately with
379  * a return value of 0 if no data is available.
380  *
381  * @return Number of octets read, 0 on EOF or a negative error code.
382  */
383 int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla,
384             unsigned char **buf, struct ucred **creds)
385 {
386         int n;
387         int flags = 0;
388         static int page_size = 0;
389         struct iovec iov;
390         struct msghdr msg = {
391                 .msg_name = (void *) nla,
392                 .msg_namelen = sizeof(struct sockaddr_nl),
393                 .msg_iov = &iov,
394                 .msg_iovlen = 1,
395                 .msg_control = NULL,
396                 .msg_controllen = 0,
397                 .msg_flags = 0,
398         };
399         struct cmsghdr *cmsg;
400 
401         if (sk->s_flags & NL_MSG_PEEK)
402                 flags |= MSG_PEEK;
403 
404         if (page_size == 0)
405                 page_size = getpagesize() * 4;
406 
407         iov.iov_len = page_size;
408         iov.iov_base = *buf = calloc(1, iov.iov_len);
409         if (!*buf)
410                 return -nl_syserr2nlerr(errno);
411 
412         if (sk->s_flags & NL_SOCK_PASSCRED) {
413                 msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred));
414                 msg.msg_control = calloc(1, msg.msg_controllen);
415         }
416 retry:
417 
418         n = recvmsg(sk->s_fd, &msg, flags);
419         if (!n)
420                 goto abort;
421         else if (n < 0) {
422                 if (errno == EINTR) {
423                         NL_DBG(3, "recvmsg() returned EINTR, retrying\n");
424                         goto retry;
425                 } else if (errno == EAGAIN) {
426                         NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n");
427                         goto abort;
428                 } else {
429                         free(msg.msg_control);
430                         free(*buf);
431                         *buf = NULL;
432                         return -nl_syserr2nlerr(errno);
433                 }
434         }
435 
436         if (iov.iov_len < (size_t) n ||
437             msg.msg_flags & MSG_TRUNC) {
438                 /* Provided buffer is not long enough, enlarge it
439                  * and try again. */
440                 iov.iov_len *= 2;
441                 iov.iov_base = *buf = realloc(*buf, iov.iov_len);
442                 goto retry;
443         } else if (msg.msg_flags & MSG_CTRUNC) {
444                 msg.msg_controllen *= 2;
445                 msg.msg_control = realloc(msg.msg_control, msg.msg_controllen);
446                 goto retry;
447         } else if (flags != 0) {
448                 /* Buffer is big enough, do the actual reading */
449                 flags = 0;
450                 goto retry;
451         }
452 
453         if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
454                 free(msg.msg_control);
455                 free(*buf);
456                 *buf = NULL;
457                 return -NLE_NOADDR;
458         }
459 
460         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
461                 if (cmsg->cmsg_level == SOL_SOCKET &&
462                     cmsg->cmsg_type == SCM_CREDENTIALS) {
463                         *creds = calloc(1, sizeof(struct ucred));
464                         memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred));
465                         break;
466                 }
467         }
468 
469         free(msg.msg_control);
470         return n;
471 
472 abort:
473         free(msg.msg_control);
474         free(*buf);
475         *buf = NULL;
476         return 0;
477 }
478 
479 #define NL_CB_CALL(cb, type, msg) \
480 do { \
481         err = nl_cb_call(cb, type, msg); \
482         switch (err) { \
483         case NL_OK: \
484                 err = 0; \
485                 break; \
486         case NL_SKIP: \
487                 goto skip; \
488         case NL_STOP: \
489                 goto stop; \
490         default: \
491                 goto out; \
492         } \
493 } while (0)
494 
495 static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
496 {
497         int n, err = 0, multipart = 0;
498         unsigned char *buf = NULL;
499         struct nlmsghdr *hdr;
500         struct sockaddr_nl nla = {0};
501         struct nl_msg *msg = NULL;
502         struct ucred *creds = NULL;
503 
504 continue_reading:
505         NL_DBG(3, "Attempting to read from %p\n", sk);
506         if (cb->cb_recv_ow)
507                 n = cb->cb_recv_ow(sk, &nla, &buf, &creds);
508         else
509                 n = nl_recv(sk, &nla, &buf, &creds);
510 
511         if (n <= 0)
512                 return n;
513 
514         /* make clang analyzer happy */
515         assert(n > 0 && buf);
516 
517         NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", sk, n);
518 
519         hdr = (struct nlmsghdr *) buf;
520         while (nlmsg_ok(hdr, n)) {
521                 NL_DBG(3, "recgmsgs(%p): Processing valid message...\n", sk);
522 
523                 nlmsg_free(msg);
524                 msg = nlmsg_convert(hdr);
525                 if (!msg) {
526                         err = -NLE_NOMEM;
527                         goto out;
528                 }
529 
530                 nlmsg_set_proto(msg, sk->s_proto);
531                 nlmsg_set_src(msg, &nla);
532                 if (creds)
533                         nlmsg_set_creds(msg, creds);
534 
535                 /* Raw callback is the first, it gives the most control
536                  * to the user and he can do his very own parsing. */
537                 if (cb->cb_set[NL_CB_MSG_IN])
538                         NL_CB_CALL(cb, NL_CB_MSG_IN, msg);
539 
540                 /* Sequence number checking. The check may be done by
541                  * the user, otherwise a very simple check is applied
542                  * enforcing strict ordering */
543                 if (cb->cb_set[NL_CB_SEQ_CHECK])
544                         NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg);
545                 else if (hdr->nlmsg_seq != sk->s_seq_expect) {
546                         if (cb->cb_set[NL_CB_INVALID])
547                                 NL_CB_CALL(cb, NL_CB_INVALID, msg);
548                         else {
549                                 err = -NLE_SEQ_MISMATCH;
550                                 goto out;
551                         }
552                 }
553 
554                 if (hdr->nlmsg_type == NLMSG_DONE ||
555                     hdr->nlmsg_type == NLMSG_ERROR ||
556                     hdr->nlmsg_type == NLMSG_NOOP ||
557                     hdr->nlmsg_type == NLMSG_OVERRUN) {
558                         /* We can't check for !NLM_F_MULTI since some netlink
559                          * users in the kernel are broken. */
560                         sk->s_seq_expect++;
561                         NL_DBG(3, "recvmsgs(%p): Increased expected " \
562                                "sequence number to %d\n",
563                                sk, sk->s_seq_expect);
564                 }
565 
566                 if (hdr->nlmsg_flags & NLM_F_MULTI)
567                         multipart = 1;
568         
569                 /* Other side wishes to see an ack for this message */
570                 if (hdr->nlmsg_flags & NLM_F_ACK) {
571                         if (cb->cb_set[NL_CB_SEND_ACK])
572                                 NL_CB_CALL(cb, NL_CB_SEND_ACK, msg);
573                         else {
574                                 /* FIXME: implement */
575                         }
576                 }
577 
578                 /* messages terminates a multpart message, this is
579                  * usually the end of a message and therefore we slip
580                  * out of the loop by default. the user may overrule
581                  * this action by skipping this packet. */
582                 if (hdr->nlmsg_type == NLMSG_DONE) {
583                         multipart = 0;
584                         if (cb->cb_set[NL_CB_FINISH])
585                                 NL_CB_CALL(cb, NL_CB_FINISH, msg);
586                 }
587 
588                 /* Message to be ignored, the default action is to
589                  * skip this message if no callback is specified. The
590                  * user may overrule this action by returning
591                  * NL_PROCEED. */
592                 else if (hdr->nlmsg_type == NLMSG_NOOP) {
593                         if (cb->cb_set[NL_CB_SKIPPED])
594                                 NL_CB_CALL(cb, NL_CB_SKIPPED, msg);
595                         else
596                                 goto skip;
597                 }
598 
599                 /* Data got lost, report back to user. The default action is to
600                  * quit parsing. The user may overrule this action by retuning
601                  * NL_SKIP or NL_PROCEED (dangerous) */
602                 else if (hdr->nlmsg_type == NLMSG_OVERRUN) {
603                         if (cb->cb_set[NL_CB_OVERRUN])
604                                 NL_CB_CALL(cb, NL_CB_OVERRUN, msg);
605                         else {
606                                 err = -NLE_MSG_OVERFLOW;
607                                 goto out;
608                         }
609                 }
610 
611                 /* Message carries a nlmsgerr */
612                 else if (hdr->nlmsg_type == NLMSG_ERROR) {
613                         struct nlmsgerr *e = nlmsg_data(hdr);
614 
615                         if (hdr->nlmsg_len < (unsigned) nlmsg_msg_size(sizeof(*e))) {
616                                 /* Truncated error message, the default action
617                                  * is to stop parsing. The user may overrule
618                                  * this action by returning NL_SKIP or
619                                  * NL_PROCEED (dangerous) */
620                                 if (cb->cb_set[NL_CB_INVALID])
621                                         NL_CB_CALL(cb, NL_CB_INVALID, msg);
622                                 else {
623                                         err = -NLE_MSG_TRUNC;
624                                         goto out;
625                                 }
626                         } else if (e->error) {
627                                 /* Error message reported back from kernel. */
628                                 if (cb->cb_err) {
629                                         err = cb->cb_err(&nla, e,
630                                                            cb->cb_err_arg);
631                                         if (err < 0)
632                                                 goto out;
633                                         else if (err == NL_SKIP)
634                                                 goto skip;
635                                         else if (err == NL_STOP) {
636                                                 err = -nl_syserr2nlerr(e->error);
637                                                 goto out;
638                                         }
639                                 } else {
640                                         err = -nl_syserr2nlerr(e->error);
641                                         goto out;
642                                 }
643                         } else if (cb->cb_set[NL_CB_ACK])
644                                 NL_CB_CALL(cb, NL_CB_ACK, msg);
645                 } else {
646                         /* Valid message (not checking for MULTIPART bit to
647                          * get along with broken kernels. NL_SKIP has no
648                          * effect on this.  */
649                         if (cb->cb_set[NL_CB_VALID])
650                                 NL_CB_CALL(cb, NL_CB_VALID, msg);
651                 }
652 skip:
653                 hdr = nlmsg_next(hdr, &n);
654         }
655         
656         nlmsg_free(msg);
657         free(buf);
658         free(creds);
659         buf = NULL;
660         msg = NULL;
661         creds = NULL;
662 
663         if (multipart) {
664                 /* Multipart message not yet complete, continue reading */
665                 goto continue_reading;
666         }
667 stop:
668         err = 0;
669 out:
670         nlmsg_free(msg);
671         free(buf);
672         free(creds);
673 
674         return err;
675 }
676 
677 /**
678  * Receive a set of messages from a netlink socket.
679  * @arg sk              Netlink socket.
680  * @arg cb              set of callbacks to control behaviour.
681  *
682  * Repeatedly calls nl_recv() or the respective replacement if provided
683  * by the application (see nl_cb_overwrite_recv()) and parses the
684  * received data as netlink messages. Stops reading if one of the
685  * callbacks returns NL_STOP or nl_recv returns either 0 or a negative error code.
686  *
687  * A non-blocking sockets causes the function to return immediately if
688  * no data is available.
689  *
690  * @return 0 on success or a negative error code from nl_recv().
691  */
692 int nl_recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
693 {
694         if (cb->cb_recvmsgs_ow)
695                 return cb->cb_recvmsgs_ow(sk, cb);
696         else
697                 return recvmsgs(sk, cb);
698 }
699 
700 
701 static int ack_wait_handler(struct nl_msg *msg, void *arg)
702 {
703         return NL_STOP;
704 }
705 
706 /**
707  * Wait for ACK.
708  * @arg sk              Netlink socket.
709  * @pre The netlink socket must be in blocking state.
710  *
711  * Waits until an ACK is received for the latest not yet acknowledged
712  * netlink message.
713  */
714 int nl_wait_for_ack(struct nl_sock *sk)
715 {
716         int err;
717         struct nl_cb *cb;
718 
719         cb = nl_cb_clone(sk->s_cb);
720         if (cb == NULL)
721                 return -NLE_NOMEM;
722 
723         nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);
724         err = nl_recvmsgs(sk, cb);
725         nl_cb_put(cb);
726 
727         return err;
728 }
729 
730 /** @} */
731 
732 /** @} */
733 

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