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