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