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         if (sk->s_debug_tx_cb)
 196                 sk->s_debug_tx_cb(sk->s_debug_tx_priv, buf, size);
 197
 198         ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *)
 199                      &sk->s_peer, sizeof(sk->s_peer));
 200         if (ret < 0)
 201                 return -nl_syserr2nlerr(errno);
 202
 203         return ret;
 204 }
 205
 206 /**
 207  * Send netlink message with control over sendmsg() message header.
 208  * @arg sk              Netlink socket.
 209  * @arg msg             Netlink message to be sent.
 210  * @arg hdr             Sendmsg() message header.
 211  * @return Number of characters sent on sucess or a negative error code.
 212  */
 213 int nl_sendmsg(struct nl_sock *sk, struct nl_msg *msg, struct msghdr *hdr)
 214 {
 215         struct nl_cb *cb;
 216         int ret;
 217
 218         struct iovec iov = {
 219                 .iov_base = (void *) nlmsg_hdr(msg),
 220                 .iov_len = nlmsg_hdr(msg)->nlmsg_len,
 221         };
 222
 223         hdr->msg_iov = &iov;
 224         hdr->msg_iovlen = 1;
 225
 226         nlmsg_set_src(msg, &sk->s_local);
 227
 228         cb = sk->s_cb;
 229         if (cb->cb_set[NL_CB_MSG_OUT])
 230                 if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK)
 231                         return 0;
 232
 233         if (sk->s_debug_tx_cb)
 234                 sk->s_debug_tx_cb(sk->s_debug_tx_priv, iov.iov_base, iov.iov_len);
 235
 236         ret = sendmsg(sk->s_fd, hdr, 0);
 237         if (ret < 0)
 238                 return -nl_syserr2nlerr(errno);
 239
 240         return ret;
 241 }
 242
 243
 244 /**
 245  * Send netlink message.
 246  * @arg sk              Netlink socket.
 247  * @arg msg             Netlink message to be sent.
 248  * @see nl_sendmsg()
 249  * @return Number of characters sent on success or a negative error code.
 250  */
 251 int nl_send(struct nl_sock *sk, struct nl_msg *msg)
 252 {
 253         struct sockaddr_nl *dst;
 254         struct ucred *creds;
 255
 256         struct msghdr hdr = {
 257                 .msg_name = (void *) &sk->s_peer,
 258                 .msg_namelen = sizeof(struct sockaddr_nl),
 259         };
 260
 261         /* Overwrite destination if specified in the message itself, defaults
 262          * to the peer address of the socket.
 263          */
 264         dst = nlmsg_get_dst(msg);
 265         if (dst->nl_family == AF_NETLINK)
 266                 hdr.msg_name = dst;
 267
 268         /* Add credentials if present. */
 269         creds = nlmsg_get_creds(msg);
 270         if (creds != NULL) {
 271                 char buf[CMSG_SPACE(sizeof(struct ucred))];
 272                 struct cmsghdr *cmsg;
 273
 274                 hdr.msg_control = buf;
 275                 hdr.msg_controllen = sizeof(buf);
 276
 277                 cmsg = CMSG_FIRSTHDR(&hdr);
 278                 cmsg->cmsg_level = SOL_SOCKET;
 279                 cmsg->cmsg_type = SCM_CREDENTIALS;
 280                 cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
 281                 memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred));
 282         }
 283
 284         return nl_sendmsg(sk, msg, &hdr);
 285 }
 286
 287 /**
 288  * Send netlink message and check & extend header values as needed.
 289  * @arg sk              Netlink socket.
 290  * @arg msg             Netlink message to be sent.
 291  *
 292  * Checks the netlink message \c nlh for completness and extends it
 293  * as required before sending it out. Checked fields include pid,
 294  * sequence nr, and flags.
 295  *
 296  * @see nl_send()
 297  * @return Number of characters sent or a negative error code.
 298  */
 299 int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg)
 300 {
 301         struct nlmsghdr *nlh;
 302         struct nl_cb *cb = sk->s_cb;
 303
 304         nlh = nlmsg_hdr(msg);
 305         if (nlh->nlmsg_pid == 0)
 306                 nlh->nlmsg_pid = sk->s_local.nl_pid;
 307
 308         if (nlh->nlmsg_seq == 0)
 309                 nlh->nlmsg_seq = sk->s_seq_next++;
 310
 311         if (msg->nm_protocol == -1)
 312                 msg->nm_protocol = sk->s_proto;
 313
 314         nlh->nlmsg_flags |= NLM_F_REQUEST;
 315
 316         if (!(sk->s_flags & NL_NO_AUTO_ACK))
 317                 nlh->nlmsg_flags |= NLM_F_ACK;
 318
 319         if (cb->cb_send_ow)
 320                 return cb->cb_send_ow(sk, msg);
 321         else
 322                 return nl_send(sk, msg);
 323 }
 324
 325 /**
 326  * Send simple netlink message using nl_send_auto_complete()
 327  * @arg sk              Netlink socket.
 328  * @arg type            Netlink message type.
 329  * @arg flags           Netlink message flags.
 330  * @arg buf             Data buffer.
 331  * @arg size            Size of data buffer.
 332  *
 333  * Builds a netlink message with the specified type and flags and
 334  * appends the specified data as payload to the message.
 335  *
 336  * @see nl_send_auto_complete()
 337  * @return Number of characters sent on success or a negative error code.
 338  */
 339 int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf,
 340                    size_t size)
 341 {
 342         int err;
 343         struct nl_msg *msg;
 344
 345         msg = nlmsg_alloc_simple(type, flags);
 346         if (!msg)
 347                 return -NLE_NOMEM;
 348
 349         if (buf && size) {
 350                 err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO);
 351                 if (err < 0)
 352                         goto errout;
 353         }
 354
 355
 356         err = nl_send_auto_complete(sk, msg);
 357 errout:
 358         nlmsg_free(msg);
 359
 360         return err;
 361 }
 362
 363 /** @} */
 364
 365 /**
 366  * @name Receive
 367  * @{
 368  */
 369
 370 /**
 371  * Receive data from netlink socket
 372  * @arg sk              Netlink socket.
 373  * @arg nla             Destination pointer for peer's netlink address.
 374  * @arg buf             Destination pointer for message content.
 375  * @arg creds           Destination pointer for credentials.
 376  *
 377  * Receives a netlink message, allocates a buffer in \c *buf and
 378  * stores the message content. The peer's netlink address is stored
 379  * in \c *nla. The caller is responsible for freeing the buffer allocated
 380  * in \c *buf if a positive value is returned.  Interrupted system calls
 381  * are handled by repeating the read. The input buffer size is determined
 382  * by peeking before the actual read is done.
 383  *
 384  * A non-blocking sockets causes the function to return immediately with
 385  * a return value of 0 if no data is available.
 386  *
 387  * @return Number of octets read, 0 on EOF or a negative error code.
 388  */
 389 int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla,
 390             unsigned char **buf, struct ucred **creds)
 391 {
 392         int n;
 393         int flags = 0;
 394         static int page_size = 0;
 395         struct iovec iov;
 396         struct msghdr msg = {
 397                 .msg_name = (void *) nla,
 398                 .msg_namelen = sizeof(struct sockaddr_nl),
 399                 .msg_iov = &iov,
 400                 .msg_iovlen = 1,
 401                 .msg_control = NULL,
 402                 .msg_controllen = 0,
 403                 .msg_flags = 0,
 404         };
 405         struct cmsghdr *cmsg;
 406
 407         if (sk->s_flags & NL_MSG_PEEK)
 408                 flags |= MSG_PEEK;
 409
 410         if (page_size == 0)
 411                 page_size = getpagesize() * 4;
 412
 413         iov.iov_len = page_size;
 414         iov.iov_base = *buf = calloc(1, iov.iov_len);
 415         if (!*buf)
 416                 return -nl_syserr2nlerr(errno);
 417
 418         if (sk->s_flags & NL_SOCK_PASSCRED) {
 419                 msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred));
 420                 msg.msg_control = calloc(1, msg.msg_controllen);
 421         }
 422 retry:
 423
 424         n = recvmsg(sk->s_fd, &msg, flags);
 425         if (!n)
 426                 goto abort;
 427         else if (n < 0) {
 428                 if (errno == EINTR) {
 429                         NL_DBG(3, "recvmsg() returned EINTR, retrying\n");
 430                         goto retry;
 431                 } else if (errno == EAGAIN) {
 432                         NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n");
 433                         goto abort;
 434                 } else {
 435                         free(msg.msg_control);
 436                         free(*buf);
 437                         *buf = NULL;
 438                         return -nl_syserr2nlerr(errno);
 439                 }
 440         }
 441
 442         if (iov.iov_len < (size_t) n ||
 443             msg.msg_flags & MSG_TRUNC) {
 444                 /* Provided buffer is not long enough, enlarge it
 445                  * and try again. */
 446                 iov.iov_len *= 2;
 447                 iov.iov_base = *buf = realloc(*buf, iov.iov_len);
 448                 goto retry;
 449         } else if (msg.msg_flags & MSG_CTRUNC) {
 450                 msg.msg_controllen *= 2;
 451                 msg.msg_control = realloc(msg.msg_control, msg.msg_controllen);
 452                 goto retry;
 453         } else if (flags != 0) {
 454                 /* Buffer is big enough, do the actual reading */
 455                 flags = 0;
 456                 goto retry;
 457         }
 458
 459         if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
 460                 free(msg.msg_control);
 461                 free(*buf);
 462                 *buf = NULL;
 463                 return -NLE_NOADDR;
 464         }
 465
 466         for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 467                 if (cmsg->cmsg_level == SOL_SOCKET &&
 468                     cmsg->cmsg_type == SCM_CREDENTIALS) {
 469                         *creds = calloc(1, sizeof(struct ucred));
 470                         memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred));
 471                         break;
 472                 }
 473         }
 474
 475         if (sk->s_debug_rx_cb)
 476                 sk->s_debug_rx_cb(sk->s_debug_rx_priv, *buf, n);
 477
 478         free(msg.msg_control);
 479         return n;
 480
 481 abort:
 482         free(msg.msg_control);
 483         free(*buf);
 484         *buf = NULL;
 485         return 0;
 486 }
 487
 488 #define NL_CB_CALL(cb, type, msg) \
 489 do { \
 490         err = nl_cb_call(cb, type, msg); \
 491         switch (err) { \
 492         case NL_OK: \
 493                 err = 0; \
 494                 break; \
 495         case NL_SKIP: \
 496                 goto skip; \
 497         case NL_STOP: \
 498                 goto stop; \
 499         default: \
 500                 goto out; \
 501         } \
 502 } while (0)
 503
 504 static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
 505 {
 506         int n, err = 0, multipart = 0;
 507         unsigned char *buf = NULL;
 508         struct nlmsghdr *hdr;
 509         struct sockaddr_nl nla = {0};
 510         struct nl_msg *msg = NULL;
 511         struct ucred *creds = NULL;
 512
 513 continue_reading:
 514         NL_DBG(3, "Attempting to read from %p\n", sk);
 515         if (cb->cb_recv_ow)
 516                 n = cb->cb_recv_ow(sk, &nla, &buf, &creds);
 517         else
 518                 n = nl_recv(sk, &nla, &buf, &creds);
 519
 520         if (n <= 0)
 521                 return n;
 522
 523         /* make clang analyzer happy */
 524         assert(n > 0 && buf);
 525
 526         NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", sk, n);
 527
 528         hdr = (struct nlmsghdr *) buf;
 529         while (nlmsg_ok(hdr, n)) {
 530                 NL_DBG(3, "recgmsgs(%p): Processing valid message...\n", sk);
 531
 532                 nlmsg_free(msg);
 533                 msg = nlmsg_convert(hdr);
 534                 if (!msg) {
 535                         err = -NLE_NOMEM;
 536                         goto out;
 537                 }
 538
 539                 nlmsg_set_proto(msg, sk->s_proto);
 540                 nlmsg_set_src(msg, &nla);
 541                 if (creds)
 542                         nlmsg_set_creds(msg, creds);
 543
 544                 /* Raw callback is the first, it gives the most control
 545                  * to the user and he can do his very own parsing. */
 546                 if (cb->cb_set[NL_CB_MSG_IN])
 547                         NL_CB_CALL(cb, NL_CB_MSG_IN, msg);
 548
 549                 /* Sequence number checking. The check may be done by
 550                  * the user, otherwise a very simple check is applied
 551                  * enforcing strict ordering */
 552                 if (cb->cb_set[NL_CB_SEQ_CHECK])
 553                         NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg);
 554                 else if (hdr->nlmsg_seq != sk->s_seq_expect) {
 555                         if (cb->cb_set[NL_CB_INVALID])
 556                                 NL_CB_CALL(cb, NL_CB_INVALID, msg);
 557                         else {
 558                                 err = -NLE_SEQ_MISMATCH;
 559                                 goto out;
 560                         }
 561                 }
 562
 563                 if (hdr->nlmsg_type == NLMSG_DONE ||
 564                     hdr->nlmsg_type == NLMSG_ERROR ||
 565                     hdr->nlmsg_type == NLMSG_NOOP ||
 566                     hdr->nlmsg_type == NLMSG_OVERRUN) {
 567                         /* We can't check for !NLM_F_MULTI since some netlink
 568                          * users in the kernel are broken. */
 569                         sk->s_seq_expect++;
 570                         NL_DBG(3, "recvmsgs(%p): Increased expected " \
 571                                "sequence number to %d\n",
 572                                sk, sk->s_seq_expect);
 573                 }
 574
 575                 if (hdr->nlmsg_flags & NLM_F_MULTI)
 576                         multipart = 1;
 577
 578                 /* Other side wishes to see an ack for this message */
 579                 if (hdr->nlmsg_flags & NLM_F_ACK) {
 580                         if (cb->cb_set[NL_CB_SEND_ACK])
 581                                 NL_CB_CALL(cb, NL_CB_SEND_ACK, msg);
 582                         else {
 583                                 /* FIXME: implement */
 584                         }
 585                 }
 586
 587                 /* messages terminates a multpart message, this is
 588                  * usually the end of a message and therefore we slip
 589                  * out of the loop by default. the user may overrule
 590                  * this action by skipping this packet. */
 591                 if (hdr->nlmsg_type == NLMSG_DONE) {
 592                         multipart = 0;
 593                         if (cb->cb_set[NL_CB_FINISH])
 594                                 NL_CB_CALL(cb, NL_CB_FINISH, msg);
 595                 }
 596
 597                 /* Message to be ignored, the default action is to
 598                  * skip this message if no callback is specified. The
 599                  * user may overrule this action by returning
 600                  * NL_PROCEED. */
 601                 else if (hdr->nlmsg_type == NLMSG_NOOP) {
 602                         if (cb->cb_set[NL_CB_SKIPPED])
 603                                 NL_CB_CALL(cb, NL_CB_SKIPPED, msg);
 604                         else
 605                                 goto skip;
 606                 }
 607
 608                 /* Data got lost, report back to user. The default action is to
 609                  * quit parsing. The user may overrule this action by retuning
 610                  * NL_SKIP or NL_PROCEED (dangerous) */
 611                 else if (hdr->nlmsg_type == NLMSG_OVERRUN) {
 612                         if (cb->cb_set[NL_CB_OVERRUN])
 613                                 NL_CB_CALL(cb, NL_CB_OVERRUN, msg);
 614                         else {
 615                                 err = -NLE_MSG_OVERFLOW;
 616                                 goto out;
 617                         }
 618                 }
 619
 620                 /* Message carries a nlmsgerr */
 621                 else if (hdr->nlmsg_type == NLMSG_ERROR) {
 622                         struct nlmsgerr *e = nlmsg_data(hdr);
 623
 624                         if (hdr->nlmsg_len < (unsigned) nlmsg_msg_size(sizeof(*e))) {
 625                                 /* Truncated error message, the default action
 626                                  * is to stop parsing. The user may overrule
 627                                  * this action by returning NL_SKIP or
 628                                  * NL_PROCEED (dangerous) */
 629                                 if (cb->cb_set[NL_CB_INVALID])
 630                                         NL_CB_CALL(cb, NL_CB_INVALID, msg);
 631                                 else {
 632                                         err = -NLE_MSG_TRUNC;
 633                                         goto out;
 634                                 }
 635                         } else if (e->error) {
 636                                 /* Error message reported back from kernel. */
 637                                 if (cb->cb_err) {
 638                                         err = cb->cb_err(&nla, e,
 639                                                            cb->cb_err_arg);
 640                                         if (err < 0)
 641                                                 goto out;
 642                                         else if (err == NL_SKIP)
 643                                                 goto skip;
 644                                         else if (err == NL_STOP) {
 645                                                 err = -nl_syserr2nlerr(e->error);
 646                                                 goto out;
 647                                         }
 648                                 } else {
 649                                         err = -nl_syserr2nlerr(e->error);
 650                                         goto out;
 651                                 }
 652                         } else if (cb->cb_set[NL_CB_ACK])
 653                                 NL_CB_CALL(cb, NL_CB_ACK, msg);
 654                 } else {
 655                         /* Valid message (not checking for MULTIPART bit to
 656                          * get along with broken kernels. NL_SKIP has no
 657                          * effect on this.  */
 658                         if (cb->cb_set[NL_CB_VALID])
 659                                 NL_CB_CALL(cb, NL_CB_VALID, msg);
 660                 }
 661 skip:
 662                 hdr = nlmsg_next(hdr, &n);
 663         }
 664
 665         nlmsg_free(msg);
 666         free(buf);
 667         free(creds);
 668         buf = NULL;
 669         msg = NULL;
 670         creds = NULL;
 671
 672         if (multipart) {
 673                 /* Multipart message not yet complete, continue reading */
 674                 goto continue_reading;
 675         }
 676 stop:
 677         err = 0;
 678 out:
 679         nlmsg_free(msg);
 680         free(buf);
 681         free(creds);
 682
 683         return err;
 684 }
 685
 686 /**
 687  * Receive a set of messages from a netlink socket.
 688  * @arg sk              Netlink socket.
 689  * @arg cb              set of callbacks to control behaviour.
 690  *
 691  * Repeatedly calls nl_recv() or the respective replacement if provided
 692  * by the application (see nl_cb_overwrite_recv()) and parses the
 693  * received data as netlink messages. Stops reading if one of the
 694  * callbacks returns NL_STOP or nl_recv returns either 0 or a negative error code.
 695  *
 696  * A non-blocking sockets causes the function to return immediately if
 697  * no data is available.
 698  *
 699  * @return 0 on success or a negative error code from nl_recv().
 700  */
 701 int nl_recvmsgs(struct nl_sock *sk, struct nl_cb *cb)
 702 {
 703         if (cb->cb_recvmsgs_ow)
 704                 return cb->cb_recvmsgs_ow(sk, cb);
 705         else
 706                 return recvmsgs(sk, cb);
 707 }
 708
 709
 710 static int ack_wait_handler(struct nl_msg *msg, void *arg)
 711 {
 712         return NL_STOP;
 713 }
 714
 715 /**
 716  * Wait for ACK.
 717  * @arg sk              Netlink socket.
 718  * @pre The netlink socket must be in blocking state.
 719  *
 720  * Waits until an ACK is received for the latest not yet acknowledged
 721  * netlink message.
 722  */
 723 int nl_wait_for_ack(struct nl_sock *sk)
 724 {
 725         int err;
 726         struct nl_cb *cb;
 727
 728         cb = nl_cb_clone(sk->s_cb);
 729         if (cb == NULL)
 730                 return -NLE_NOMEM;
 731
 732         nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL);
 733         err = nl_recvmsgs(sk, cb);
 734         nl_cb_put(cb);
 735
 736         return err;
 737 }
 738
 739 /** @} */
 740
 741 /** @} */