lib/netlink.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "netlink.h"
  19 #include <errno.h>
  20 #include <inttypes.h>
  21 #include <sys/types.h>
  22 #include <unistd.h>
  23 #include "coverage.h"
  24 #include "flow.h"
  25 #include "netlink-protocol.h"
  26 #include "openvswitch/ofpbuf.h"
  27 #include "timeval.h"
  28 #include "unaligned.h"
  29 #include "openvswitch/vlog.h"
  30 #include "util.h"
  31
  32 VLOG_DEFINE_THIS_MODULE(netlink);
  33
  34 /* A single (bad) Netlink message can in theory dump out many, many log
  35  * messages, so the burst size is set quite high here to avoid missing useful
  36  * information.  Also, at high logging levels we log *all* Netlink messages. */
  37 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(60, 600);
  38
  39 /* Returns the nlmsghdr at the head of 'msg'.
  40  *
  41  * 'msg' must be at least as large as a nlmsghdr. */
  42 struct nlmsghdr *
  43 nl_msg_nlmsghdr(const struct ofpbuf *msg)
  44 {
  45     return ofpbuf_at_assert(msg, 0, NLMSG_HDRLEN);
  46 }
  47
  48 /* Returns the genlmsghdr just past 'msg''s nlmsghdr.
  49  *
  50  * Returns a null pointer if 'msg' is not large enough to contain an nlmsghdr
  51  * and a genlmsghdr. */
  52 struct genlmsghdr *
  53 nl_msg_genlmsghdr(const struct ofpbuf *msg)
  54 {
  55     return ofpbuf_at(msg, NLMSG_HDRLEN, GENL_HDRLEN);
  56 }
  57
  58 /* If 'buffer' is a NLMSG_ERROR message, stores 0 in '*errorp' if it is an ACK
  59  * message, otherwise a positive errno value, and returns true.  If 'buffer' is
  60  * not an NLMSG_ERROR message, returns false.
  61  *
  62  * 'msg' must be at least as large as a nlmsghdr. */
  63 bool
  64 nl_msg_nlmsgerr(const struct ofpbuf *msg, int *errorp)
  65 {
  66     if (nl_msg_nlmsghdr(msg)->nlmsg_type == NLMSG_ERROR) {
  67         struct nlmsgerr *err = ofpbuf_at(msg, NLMSG_HDRLEN, sizeof *err);
  68         int code = EPROTO;
  69         if (!err) {
  70             VLOG_ERR_RL(&rl, "received invalid nlmsgerr (%"PRIu32" bytes < %"PRIuSIZE")",
  71                         msg->size, NLMSG_HDRLEN + sizeof *err);
  72         } else if (err->error <= 0 && err->error > INT_MIN) {
  73             code = -err->error;
  74         }
  75         if (errorp) {
  76             *errorp = code;
  77         }
  78         return true;
  79     } else {
  80         return false;
  81     }
  82 }
  83
  84 /* Ensures that 'b' has room for at least 'size' bytes plus netlink padding at
  85  * its tail end, reallocating and copying its data if necessary. */
  86 void
  87 nl_msg_reserve(struct ofpbuf *msg, size_t size)
  88 {
  89     ofpbuf_prealloc_tailroom(msg, NLMSG_ALIGN(size));
  90 }
  91
  92 /* Puts a nlmsghdr at the beginning of 'msg', which must be initially empty.
  93  * Uses the given 'type' and 'flags'.  'expected_payload' should be
  94  * an estimate of the number of payload bytes to be supplied; if the size of
  95  * the payload is unknown a value of 0 is acceptable.
  96  *
  97  * 'type' is ordinarily an enumerated value specific to the Netlink protocol
  98  * (e.g. RTM_NEWLINK, for NETLINK_ROUTE protocol).  For Generic Netlink, 'type'
  99  * is the family number obtained via nl_lookup_genl_family().
 100  *
 101  * 'flags' is a bit-mask that indicates what kind of request is being made.  It
 102  * is often NLM_F_REQUEST indicating that a request is being made, commonly
 103  * or'd with NLM_F_ACK to request an acknowledgement.
 104  *
 105  * Sets the new nlmsghdr's nlmsg_len, nlmsg_seq, and nlmsg_pid fields to 0 for
 106  * now.  Functions that send Netlink messages will fill these in just before
 107  * sending the message.
 108  *
 109  * nl_msg_put_genlmsghdr() is more convenient for composing a Generic Netlink
 110  * message. */
 111 void
 112 nl_msg_put_nlmsghdr(struct ofpbuf *msg,
 113                     size_t expected_payload, uint32_t type, uint32_t flags)
 114 {
 115     struct nlmsghdr *nlmsghdr;
 116
 117     ovs_assert(msg->size == 0);
 118
 119     nl_msg_reserve(msg, NLMSG_HDRLEN + expected_payload);
 120     nlmsghdr = nl_msg_put_uninit(msg, NLMSG_HDRLEN);
 121     nlmsghdr->nlmsg_len = 0;
 122     nlmsghdr->nlmsg_type = type;
 123     nlmsghdr->nlmsg_flags = flags;
 124     nlmsghdr->nlmsg_seq = 0;
 125     nlmsghdr->nlmsg_pid = 0;
 126 }
 127
 128 /* Puts a nlmsghdr and genlmsghdr at the beginning of 'msg', which must be
 129  * initially empty.  'expected_payload' should be an estimate of the number of
 130  * payload bytes to be supplied; if the size of the payload is unknown a value
 131  * of 0 is acceptable.
 132  *
 133  * 'family' is the family number obtained via nl_lookup_genl_family().
 134  *
 135  * 'flags' is a bit-mask that indicates what kind of request is being made.  It
 136  * is often NLM_F_REQUEST indicating that a request is being made, commonly
 137  * or'd with NLM_F_ACK to request an acknowledgement.
 138  *
 139  * 'cmd' is an enumerated value specific to the Generic Netlink family
 140  * (e.g. CTRL_CMD_NEWFAMILY for the GENL_ID_CTRL family).
 141  *
 142  * 'version' is a version number specific to the family and command (often 1).
 143  *
 144  * Sets the new nlmsghdr's nlmsg_pid field to 0 for now.  nl_sock_send() will
 145  * fill it in just before sending the message.
 146  *
 147  * nl_msg_put_nlmsghdr() should be used to compose Netlink messages that are
 148  * not Generic Netlink messages. */
 149 void
 150 nl_msg_put_genlmsghdr(struct ofpbuf *msg, size_t expected_payload,
 151                       int family, uint32_t flags, uint8_t cmd, uint8_t version)
 152 {
 153     struct genlmsghdr *genlmsghdr;
 154
 155     nl_msg_put_nlmsghdr(msg, GENL_HDRLEN + expected_payload, family, flags);
 156     ovs_assert(msg->size == NLMSG_HDRLEN);
 157     genlmsghdr = nl_msg_put_uninit(msg, GENL_HDRLEN);
 158     genlmsghdr->cmd = cmd;
 159     genlmsghdr->version = version;
 160     genlmsghdr->reserved = 0;
 161 }
 162
 163 /* Appends the 'size' bytes of data in 'p', plus Netlink padding if needed, to
 164  * the tail end of 'msg'.  Data in 'msg' is reallocated and copied if
 165  * necessary. */
 166 void
 167 nl_msg_put(struct ofpbuf *msg, const void *data, size_t size)
 168 {
 169     memcpy(nl_msg_put_uninit(msg, size), data, size);
 170 }
 171
 172 /* Appends 'size' bytes of data, plus Netlink padding if needed, to the tail
 173  * end of 'msg', reallocating and copying its data if necessary.  Returns a
 174  * pointer to the first byte of the new data, which is left uninitialized. */
 175 void *
 176 nl_msg_put_uninit(struct ofpbuf *msg, size_t size)
 177 {
 178     size_t pad = PAD_SIZE(size, NLMSG_ALIGNTO);
 179     char *p = ofpbuf_put_uninit(msg, size + pad);
 180     if (pad) {
 181         memset(p + size, 0, pad);
 182     }
 183     return p;
 184 }
 185
 186 /* Prepends the 'size' bytes of data in 'p', plus Netlink padding if needed, to
 187  * the head end of 'msg'.  Data in 'msg' is reallocated and copied if
 188  * necessary. */
 189 void
 190 nl_msg_push(struct ofpbuf *msg, const void *data, size_t size)
 191 {
 192     memcpy(nl_msg_push_uninit(msg, size), data, size);
 193 }
 194
 195 /* Prepends 'size' bytes of data, plus Netlink padding if needed, to the head
 196  * end of 'msg', reallocating and copying its data if necessary.  Returns a
 197  * pointer to the first byte of the new data, which is left uninitialized. */
 198 void *
 199 nl_msg_push_uninit(struct ofpbuf *msg, size_t size)
 200 {
 201     size_t pad = PAD_SIZE(size, NLMSG_ALIGNTO);
 202     char *p = ofpbuf_push_uninit(msg, size + pad);
 203     if (pad) {
 204         memset(p + size, 0, pad);
 205     }
 206     return p;
 207 }
 208
 209 /* Appends a Netlink attribute of the given 'type' and room for 'size' bytes of
 210  * data as its payload, plus Netlink padding if needed, to the tail end of
 211  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 212  * the first byte of data in the attribute, which is left uninitialized. */
 213 void *
 214 nl_msg_put_unspec_uninit(struct ofpbuf *msg, uint16_t type, size_t size)
 215 {
 216     size_t total_size = NLA_HDRLEN + size;
 217     struct nlattr* nla = nl_msg_put_uninit(msg, total_size);
 218     ovs_assert(!nl_attr_oversized(size));
 219     nla->nla_len = total_size;
 220     nla->nla_type = type;
 221     return nla + 1;
 222 }
 223
 224 /* Appends a Netlink attribute of the given 'type' and room for 'size' bytes of
 225  * data as its payload, plus Netlink padding if needed, to the tail end of
 226  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 227  * the first byte of data in the attribute, which is zeroed. */
 228 void *
 229 nl_msg_put_unspec_zero(struct ofpbuf *msg, uint16_t type, size_t size)
 230 {
 231     void *data = nl_msg_put_unspec_uninit(msg, type, size);
 232     memset(data, 0, size);
 233     return data;
 234 }
 235
 236 /* Appends a Netlink attribute of the given 'type' and the 'size' bytes of
 237  * 'data' as its payload, to the tail end of 'msg', reallocating and copying
 238  * its data if necessary. */
 239 void
 240 nl_msg_put_unspec(struct ofpbuf *msg, uint16_t type,
 241                   const void *data, size_t size)
 242 {
 243     void *ptr;
 244
 245     ptr = nl_msg_put_unspec_uninit(msg, type, size);
 246     nullable_memcpy(ptr, data, size);
 247 }
 248
 249 /* Appends a Netlink attribute of the given 'type' and no payload to 'msg'.
 250  * (Some Netlink protocols use the presence or absence of an attribute as a
 251  * Boolean flag.) */
 252 void
 253 nl_msg_put_flag(struct ofpbuf *msg, uint16_t type)
 254 {
 255     nl_msg_put_unspec(msg, type, NULL, 0);
 256 }
 257
 258 /* Appends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 259  * to 'msg'. */
 260 void
 261 nl_msg_put_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 262 {
 263     nl_msg_put_unspec(msg, type, &value, sizeof value);
 264 }
 265
 266 /* Appends a Netlink attribute of the given 'type' and the given 16-bit host
 267  * byte order 'value' to 'msg'. */
 268 void
 269 nl_msg_put_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 270 {
 271     nl_msg_put_unspec(msg, type, &value, sizeof value);
 272 }
 273
 274 /* Appends a Netlink attribute of the given 'type' and the given 32-bit host
 275  * byte order 'value' to 'msg'. */
 276 void
 277 nl_msg_put_u32(struct ofpbuf *msg, uint16_t type, uint32_t value)
 278 {
 279     nl_msg_put_unspec(msg, type, &value, sizeof value);
 280 }
 281
 282 /* Appends a Netlink attribute of the given 'type' and the given 64-bit host
 283  * byte order 'value' to 'msg'. */
 284 void
 285 nl_msg_put_u64(struct ofpbuf *msg, uint16_t type, uint64_t value)
 286 {
 287     nl_msg_put_unspec(msg, type, &value, sizeof value);
 288 }
 289
 290 /* Appends a Netlink attribute of the given 'type' and the given 128-bit host
 291  * byte order 'value' to 'msg'. */
 292 void
 293 nl_msg_put_u128(struct ofpbuf *msg, uint16_t type, ovs_u128 value)
 294 {
 295     nl_msg_put_unspec(msg, type, &value, sizeof value);
 296 }
 297
 298 /* Appends a Netlink attribute of the given 'type' and the given 16-bit network
 299  * byte order 'value' to 'msg'. */
 300 void
 301 nl_msg_put_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 value)
 302 {
 303     nl_msg_put_unspec(msg, type, &value, sizeof value);
 304 }
 305
 306 /* Appends a Netlink attribute of the given 'type' and the given 32-bit network
 307  * byte order 'value' to 'msg'. */
 308 void
 309 nl_msg_put_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 value)
 310 {
 311     nl_msg_put_unspec(msg, type, &value, sizeof value);
 312 }
 313
 314 /* Appends a Netlink attribute of the given 'type' and the given 64-bit network
 315  * byte order 'value' to 'msg'. */
 316 void
 317 nl_msg_put_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 value)
 318 {
 319     nl_msg_put_unspec(msg, type, &value, sizeof value);
 320 }
 321
 322 /* Appends a Netlink attribute of the given 'type' and the given 128-bit
 323  * network byte order 'value' to 'msg'. */
 324 void
 325 nl_msg_put_be128(struct ofpbuf *msg, uint16_t type, ovs_be128 value)
 326 {
 327     nl_msg_put_unspec(msg, type, &value, sizeof value);
 328 }
 329
 330 /* Appends a Netlink attribute of the given 'type' and the given IPv6
 331  * address order 'value' to 'msg'. */
 332 void
 333 nl_msg_put_in6_addr(struct ofpbuf *msg, uint16_t type,
 334                     const struct in6_addr *value)
 335 {
 336     nl_msg_put_unspec(msg, type, value, sizeof *value);
 337 }
 338
 339 /* Appends a Netlink attribute of the given 'type' and the given odp_port_t
 340  * 'value' to 'msg'. */
 341 void
 342 nl_msg_put_odp_port(struct ofpbuf *msg, uint16_t type, odp_port_t value)
 343 {
 344     nl_msg_put_u32(msg, type, odp_to_u32(value));
 345 }
 346
 347 /* Appends a Netlink attribute of the given 'type' with the 'len' characters
 348  * of 'value', followed by the null byte to 'msg'. */
 349 void
 350 nl_msg_put_string__(struct ofpbuf *msg, uint16_t type, const char *value,
 351                     size_t len)
 352 {
 353     char *data = nl_msg_put_unspec_uninit(msg, type, len + 1);
 354
 355     memcpy(data, value, len);
 356     data[len] = '\0';
 357 }
 358
 359 /* Appends a Netlink attribute of the given 'type' and the given
 360  * null-terminated string 'value' to 'msg'. */
 361 void
 362 nl_msg_put_string(struct ofpbuf *msg, uint16_t type, const char *value)
 363 {
 364     nl_msg_put_unspec(msg, type, value, strlen(value) + 1);
 365 }
 366
 367 /* Prepends a Netlink attribute of the given 'type' and room for 'size' bytes
 368  * of data as its payload, plus Netlink padding if needed, to the head end of
 369  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 370  * the first byte of data in the attribute, which is left uninitialized. */
 371 void *
 372 nl_msg_push_unspec_uninit(struct ofpbuf *msg, uint16_t type, size_t size)
 373 {
 374     size_t total_size = NLA_HDRLEN + size;
 375     struct nlattr* nla = nl_msg_push_uninit(msg, total_size);
 376     ovs_assert(!nl_attr_oversized(size));
 377     nla->nla_len = total_size;
 378     nla->nla_type = type;
 379     return nla + 1;
 380 }
 381
 382 /* Prepends a Netlink attribute of the given 'type' and the 'size' bytes of
 383  * 'data' as its payload, to the head end of 'msg', reallocating and copying
 384  * its data if necessary.  Returns a pointer to the first byte of data in the
 385  * attribute, which is left uninitialized. */
 386 void
 387 nl_msg_push_unspec(struct ofpbuf *msg, uint16_t type,
 388                   const void *data, size_t size)
 389 {
 390     memcpy(nl_msg_push_unspec_uninit(msg, type, size), data, size);
 391 }
 392
 393 /* Prepends a Netlink attribute of the given 'type' and no payload to 'msg'.
 394  * (Some Netlink protocols use the presence or absence of an attribute as a
 395  * Boolean flag.) */
 396 void
 397 nl_msg_push_flag(struct ofpbuf *msg, uint16_t type)
 398 {
 399     nl_msg_push_unspec_uninit(msg, type, 0);
 400 }
 401
 402 /* Prepends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 403  * to 'msg'. */
 404 void
 405 nl_msg_push_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 406 {
 407     nl_msg_push_unspec(msg, type, &value, sizeof value);
 408 }
 409
 410 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit host
 411  * byte order 'value' to 'msg'. */
 412 void
 413 nl_msg_push_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 414 {
 415     nl_msg_push_unspec(msg, type, &value, sizeof value);
 416 }
 417
 418 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit host
 419  * byte order 'value' to 'msg'. */
 420 void
 421 nl_msg_push_u32(struct ofpbuf *msg, uint16_t type, uint32_t value)
 422 {
 423     nl_msg_push_unspec(msg, type, &value, sizeof value);
 424 }
 425
 426 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit host
 427  * byte order 'value' to 'msg'. */
 428 void
 429 nl_msg_push_u64(struct ofpbuf *msg, uint16_t type, uint64_t value)
 430 {
 431     nl_msg_push_unspec(msg, type, &value, sizeof value);
 432 }
 433
 434 /* Prepends a Netlink attribute of the given 'type' and the given 128-bit host
 435  * byte order 'value' to 'msg'. */
 436 void
 437 nl_msg_push_u128(struct ofpbuf *msg, uint16_t type, ovs_u128 value)
 438 {
 439     nl_msg_push_unspec(msg, type, &value, sizeof value);
 440 }
 441
 442 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit
 443  * network byte order 'value' to 'msg'. */
 444 void
 445 nl_msg_push_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 value)
 446 {
 447     nl_msg_push_unspec(msg, type, &value, sizeof value);
 448 }
 449
 450 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit
 451  * network byte order 'value' to 'msg'. */
 452 void
 453 nl_msg_push_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 value)
 454 {
 455     nl_msg_push_unspec(msg, type, &value, sizeof value);
 456 }
 457
 458 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit
 459  * network byte order 'value' to 'msg'. */
 460 void
 461 nl_msg_push_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 value)
 462 {
 463     nl_msg_push_unspec(msg, type, &value, sizeof value);
 464 }
 465
 466 /* Prepends a Netlink attribute of the given 'type' and the given 128-bit
 467  * network byte order 'value' to 'msg'. */
 468 void
 469 nl_msg_push_be128(struct ofpbuf *msg, uint16_t type, ovs_be128 value)
 470 {
 471     nl_msg_push_unspec(msg, type, &value, sizeof value);
 472 }
 473
 474 /* Prepends a Netlink attribute of the given 'type' and the given
 475  * null-terminated string 'value' to 'msg'. */
 476 void
 477 nl_msg_push_string(struct ofpbuf *msg, uint16_t type, const char *value)
 478 {
 479     nl_msg_push_unspec(msg, type, value, strlen(value) + 1);
 480 }
 481
 482 /* Adds the header for nested Netlink attributes to 'msg', with the specified
 483  * 'type', and returns the header's offset within 'msg'.  The caller should add
 484  * the content for the nested Netlink attribute to 'msg' (e.g. using the other
 485  * nl_msg_*() functions), and then pass the returned offset to
 486  * nl_msg_end_nested() to finish up the nested attributes. */
 487 size_t
 488 nl_msg_start_nested(struct ofpbuf *msg, uint16_t type)
 489 {
 490     size_t offset = msg->size;
 491     nl_msg_put_unspec_uninit(msg, type, 0);
 492     return offset;
 493 }
 494
 495 /* Finalizes a nested Netlink attribute in 'msg'.  'offset' should be the value
 496  * returned by nl_msg_start_nested(). */
 497 void
 498 nl_msg_end_nested(struct ofpbuf *msg, size_t offset)
 499 {
 500     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
 501     ovs_assert(!nl_attr_oversized(msg->size - offset - NLA_HDRLEN));
 502     attr->nla_len = msg->size - offset;
 503 }
 504
 505 /* Cancel a nested Netlink attribute in 'msg'.  'offset' should be the value
 506  * returned by nl_msg_start_nested(). */
 507 void
 508 nl_msg_cancel_nested(struct ofpbuf *msg, size_t offset)
 509 {
 510     msg->size = offset;
 511 }
 512
 513 /* Same as nls_msg_end_nested() when the nested Netlink contains non empty
 514  * message. Otherwise, drop the nested message header from 'msg'.
 515  *
 516  * Return true if the nested message has been dropped.  */
 517 bool
 518 nl_msg_end_non_empty_nested(struct ofpbuf *msg, size_t offset)
 519 {
 520     nl_msg_end_nested(msg, offset);
 521
 522     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
 523     if (!nl_attr_get_size(attr)) {
 524         nl_msg_cancel_nested(msg, offset);
 525         return true;
 526     } else {
 527         return false;
 528     }
 529 }
 530
 531 /* Appends a nested Netlink attribute of the given 'type', with the 'size'
 532  * bytes of content starting at 'data', to 'msg'. */
 533 void
 534 nl_msg_put_nested(struct ofpbuf *msg,
 535                   uint16_t type, const void *data, size_t size)
 536 {
 537     size_t offset = nl_msg_start_nested(msg, type);
 538     nl_msg_put(msg, data, size);
 539     nl_msg_end_nested(msg, offset);
 540 }
 541
 542 /* If 'buffer' begins with a valid "struct nlmsghdr", pulls the header and its
 543  * payload off 'buffer', stores header and payload in 'msg->data' and
 544  * 'msg->size', and returns a pointer to the header.
 545  *
 546  * If 'buffer' does not begin with a "struct nlmsghdr" or begins with one that
 547  * is invalid, returns NULL and clears 'buffer' and 'msg'. */
 548 struct nlmsghdr *
 549 nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg)
 550 {
 551     if (buffer->size >= sizeof(struct nlmsghdr)) {
 552         struct nlmsghdr *nlmsghdr = nl_msg_nlmsghdr(buffer);
 553         size_t len = nlmsghdr->nlmsg_len;
 554         if (len >= sizeof *nlmsghdr && len <= buffer->size) {
 555             ofpbuf_use_const(msg, nlmsghdr, len);
 556             ofpbuf_pull(buffer, len);
 557             return nlmsghdr;
 558         }
 559     }
 560
 561     ofpbuf_clear(buffer);
 562     msg->data = NULL;
 563     msg->size = 0;
 564     return NULL;
 565 }
 566
 567 /* Returns true if a Netlink attribute with a payload that is 'payload_size'
 568  * bytes long would be oversized, that is, if it's not possible to create an
 569  * nlattr of that size because its size wouldn't fit in the 16-bit nla_len
 570  * field. */
 571 bool
 572 nl_attr_oversized(size_t payload_size)
 573 {
 574     return payload_size > UINT16_MAX - NLA_HDRLEN;
 575 }
 576 \f
 577 /* Attributes. */
 578
 579 /* Returns the bits of 'nla->nla_type' that are significant for determining its
 580  * type. */
 581 int
 582 nl_attr_type(const struct nlattr *nla)
 583 {
 584     return nla->nla_type & NLA_TYPE_MASK;
 585 }
 586
 587 /* Returns the first byte in the payload of attribute 'nla'. */
 588 const void *
 589 nl_attr_get(const struct nlattr *nla)
 590 {
 591     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 592     return nla + 1;
 593 }
 594
 595 /* Returns the number of bytes in the payload of attribute 'nla'. */
 596 size_t
 597 nl_attr_get_size(const struct nlattr *nla)
 598 {
 599     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 600     return nla->nla_len - NLA_HDRLEN;
 601 }
 602
 603 /* Asserts that 'nla''s payload is at least 'size' bytes long, and returns the
 604  * first byte of the payload. */
 605 const void *
 606 nl_attr_get_unspec(const struct nlattr *nla, size_t size)
 607 {
 608     ovs_assert(nla->nla_len >= NLA_HDRLEN + size);
 609     return nla + 1;
 610 }
 611
 612 /* Returns true if 'nla' is nonnull.  (Some Netlink protocols use the presence
 613  * or absence of an attribute as a Boolean flag.) */
 614 bool
 615 nl_attr_get_flag(const struct nlattr *nla)
 616 {
 617     return nla != NULL;
 618 }
 619
 620 #define NL_ATTR_GET_AS(NLA, TYPE) \
 621         (*(TYPE*) nl_attr_get_unspec(nla, sizeof(TYPE)))
 622
 623 /* Returns the 8-bit value in 'nla''s payload.
 624  *
 625  * Asserts that 'nla''s payload is at least 1 byte long. */
 626 uint8_t
 627 nl_attr_get_u8(const struct nlattr *nla)
 628 {
 629     return NL_ATTR_GET_AS(nla, uint8_t);
 630 }
 631
 632 /* Returns the 16-bit host byte order value in 'nla''s payload.
 633  *
 634  * Asserts that 'nla''s payload is at least 2 bytes long. */
 635 uint16_t
 636 nl_attr_get_u16(const struct nlattr *nla)
 637 {
 638     return NL_ATTR_GET_AS(nla, uint16_t);
 639 }
 640
 641 /* Returns the 32-bit host byte order value in 'nla''s payload.
 642  *
 643  * Asserts that 'nla''s payload is at least 4 bytes long. */
 644 uint32_t
 645 nl_attr_get_u32(const struct nlattr *nla)
 646 {
 647     return NL_ATTR_GET_AS(nla, uint32_t);
 648 }
 649
 650 /* Returns the 64-bit host byte order value in 'nla''s payload.
 651  *
 652  * Asserts that 'nla''s payload is at least 8 bytes long. */
 653 uint64_t
 654 nl_attr_get_u64(const struct nlattr *nla)
 655 {
 656     const ovs_32aligned_u64 *x = nl_attr_get_unspec(nla, sizeof *x);
 657     return get_32aligned_u64(x);
 658 }
 659
 660 /* Returns the 128-bit host byte order value in 'nla''s payload.
 661  *
 662  * Asserts that 'nla''s payload is at least 16 bytes long. */
 663 ovs_u128
 664 nl_attr_get_u128(const struct nlattr *nla)
 665 {
 666     const ovs_32aligned_u128 *x = nl_attr_get_unspec(nla, sizeof *x);
 667     return get_32aligned_u128(x);
 668 }
 669
 670 /* Returns the 16-bit network byte order value in 'nla''s payload.
 671  *
 672  * Asserts that 'nla''s payload is at least 2 bytes long. */
 673 ovs_be16
 674 nl_attr_get_be16(const struct nlattr *nla)
 675 {
 676     return NL_ATTR_GET_AS(nla, ovs_be16);
 677 }
 678
 679 /* Returns the 32-bit network byte order value in 'nla''s payload.
 680  *
 681  * Asserts that 'nla''s payload is at least 4 bytes long. */
 682 ovs_be32
 683 nl_attr_get_be32(const struct nlattr *nla)
 684 {
 685     return NL_ATTR_GET_AS(nla, ovs_be32);
 686 }
 687
 688 /* Returns the 64-bit network byte order value in 'nla''s payload.
 689  *
 690  * Asserts that 'nla''s payload is at least 8 bytes long. */
 691 ovs_be64
 692 nl_attr_get_be64(const struct nlattr *nla)
 693 {
 694     const ovs_32aligned_be64 *x = nl_attr_get_unspec(nla, sizeof *x);
 695     return get_32aligned_be64(x);
 696 }
 697
 698 /* Returns the 128-bit network byte order value in 'nla''s payload.
 699  *
 700  * Asserts that 'nla''s payload is at least 16 bytes long. */
 701 ovs_be128
 702 nl_attr_get_be128(const struct nlattr *nla)
 703 {
 704     const ovs_32aligned_be128 *x = nl_attr_get_unspec(nla, sizeof *x);
 705     return get_32aligned_be128(x);
 706 }
 707
 708 /* Returns the IPv6 address value in 'nla''s payload.
 709  *
 710  * Asserts that 'nla''s payload is at least 16 bytes long. */
 711 struct in6_addr
 712 nl_attr_get_in6_addr(const struct nlattr *nla)
 713 {
 714     return NL_ATTR_GET_AS(nla, struct in6_addr);
 715 }
 716
 717 /* Returns the 32-bit odp_port_t value in 'nla''s payload.
 718  *
 719  * Asserts that 'nla''s payload is at least 4 bytes long. */
 720 odp_port_t
 721 nl_attr_get_odp_port(const struct nlattr *nla)
 722 {
 723     return u32_to_odp(nl_attr_get_u32(nla));
 724 }
 725
 726 /* Returns the null-terminated string value in 'nla''s payload.
 727  *
 728  * Asserts that 'nla''s payload contains a null-terminated string. */
 729 const char *
 730 nl_attr_get_string(const struct nlattr *nla)
 731 {
 732     ovs_assert(nla->nla_len > NLA_HDRLEN);
 733     ovs_assert(memchr(nl_attr_get(nla), '\0', nla->nla_len - NLA_HDRLEN));
 734     return nl_attr_get(nla);
 735 }
 736
 737 /* Initializes 'nested' to the payload of 'nla'. */
 738 void
 739 nl_attr_get_nested(const struct nlattr *nla, struct ofpbuf *nested)
 740 {
 741     ofpbuf_use_const(nested, nl_attr_get(nla), nl_attr_get_size(nla));
 742 }
 743
 744 /* Default minimum payload size for each type of attribute. */
 745 static size_t
 746 min_attr_len(enum nl_attr_type type)
 747 {
 748     switch (type) {
 749     case NL_A_NO_ATTR: return 0;
 750     case NL_A_UNSPEC: return 0;
 751     case NL_A_U8: return 1;
 752     case NL_A_U16: return 2;
 753     case NL_A_U32: return 4;
 754     case NL_A_U64: return 8;
 755     case NL_A_U128: return 16;
 756     case NL_A_STRING: return 1;
 757     case NL_A_FLAG: return 0;
 758     case NL_A_IPV6: return 16;
 759     case NL_A_NESTED: return 0;
 760     case N_NL_ATTR_TYPES: default: OVS_NOT_REACHED();
 761     }
 762 }
 763
 764 /* Default maximum payload size for each type of attribute. */
 765 static size_t
 766 max_attr_len(enum nl_attr_type type)
 767 {
 768     switch (type) {
 769     case NL_A_NO_ATTR: return SIZE_MAX;
 770     case NL_A_UNSPEC: return SIZE_MAX;
 771     case NL_A_U8: return 1;
 772     case NL_A_U16: return 2;
 773     case NL_A_U32: return 4;
 774     case NL_A_U64: return 8;
 775     case NL_A_U128: return 16;
 776     case NL_A_STRING: return SIZE_MAX;
 777     case NL_A_FLAG: return SIZE_MAX;
 778     case NL_A_IPV6: return 16;
 779     case NL_A_NESTED: return SIZE_MAX;
 780     case N_NL_ATTR_TYPES: default: OVS_NOT_REACHED();
 781     }
 782 }
 783
 784 bool
 785 nl_attr_validate(const struct nlattr *nla, const struct nl_policy *policy)
 786 {
 787     uint16_t type = nl_attr_type(nla);
 788     size_t min_len;
 789     size_t max_len;
 790     size_t len;
 791
 792     if (policy->type == NL_A_NO_ATTR) {
 793         return true;
 794     }
 795
 796     /* Figure out min and max length. */
 797     min_len = policy->min_len;
 798     if (!min_len) {
 799         min_len = min_attr_len(policy->type);
 800     }
 801     max_len = policy->max_len;
 802     if (!max_len) {
 803         max_len = max_attr_len(policy->type);
 804     }
 805
 806     /* Verify length. */
 807     len = nl_attr_get_size(nla);
 808     if (len < min_len || len > max_len) {
 809         VLOG_DBG_RL(&rl, "attr %"PRIu16" length %"PRIuSIZE" not in "
 810                     "allowed range %"PRIuSIZE"...%"PRIuSIZE, type, len, min_len, max_len);
 811         return false;
 812     }
 813
 814     /* Strings must be null terminated and must not have embedded nulls. */
 815     if (policy->type == NL_A_STRING) {
 816         if (((char *) nla)[nla->nla_len - 1]) {
 817             VLOG_DBG_RL(&rl, "attr %"PRIu16" lacks null at end", type);
 818             return false;
 819         }
 820         if (memchr(nla + 1, '\0', len - 1) != NULL) {
 821             VLOG_DBG_RL(&rl, "attr %"PRIu16" has bad length", type);
 822             return false;
 823         }
 824     }
 825
 826     return true;
 827 }
 828
 829 /* Parses the 'msg' starting at the given 'nla_offset' as a sequence of Netlink
 830  * attributes.  'policy[i]', for 0 <= i < n_attrs, specifies how the attribute
 831  * with nla_type == i is parsed; a pointer to attribute i is stored in
 832  * attrs[i].  Returns true if successful, false on failure.
 833  *
 834  * If the Netlink attributes in 'msg' follow a Netlink header and a Generic
 835  * Netlink header, then 'nla_offset' should be NLMSG_HDRLEN + GENL_HDRLEN. */
 836 bool
 837 nl_policy_parse(const struct ofpbuf *msg, size_t nla_offset,
 838                 const struct nl_policy policy[],
 839                 struct nlattr *attrs[], size_t n_attrs)
 840 {
 841     struct nlattr *nla;
 842     size_t left;
 843     size_t i;
 844
 845     memset(attrs, 0, n_attrs * sizeof *attrs);
 846
 847     if (msg->size < nla_offset) {
 848         VLOG_DBG_RL(&rl, "missing headers in nl_policy_parse");
 849         return false;
 850     }
 851
 852     NL_ATTR_FOR_EACH (nla, left, ofpbuf_at(msg, nla_offset, 0),
 853                       msg->size - nla_offset)
 854     {
 855         uint16_t type = nl_attr_type(nla);
 856         if (type < n_attrs && policy[type].type != NL_A_NO_ATTR) {
 857             const struct nl_policy *e = &policy[type];
 858             if (!nl_attr_validate(nla, e)) {
 859                 return false;
 860             }
 861             if (attrs[type]) {
 862                 VLOG_DBG_RL(&rl, "duplicate attr %"PRIu16, type);
 863             }
 864             attrs[type] = nla;
 865         }
 866     }
 867     if (left) {
 868         VLOG_DBG_RL(&rl, "attributes followed by garbage");
 869         return false;
 870     }
 871
 872     for (i = 0; i < n_attrs; i++) {
 873         const struct nl_policy *e = &policy[i];
 874         if (!e->optional && e->type != NL_A_NO_ATTR && !attrs[i]) {
 875             VLOG_DBG_RL(&rl, "required attr %"PRIuSIZE" missing", i);
 876             return false;
 877         }
 878     }
 879     return true;
 880 }
 881
 882 /* Parses the Netlink attributes within 'nla'.  'policy[i]', for 0 <= i <
 883  * n_attrs, specifies how the attribute with nla_type == i is parsed; a pointer
 884  * to attribute i is stored in attrs[i].  Returns true if successful, false on
 885  * failure. */
 886 bool
 887 nl_parse_nested(const struct nlattr *nla, const struct nl_policy policy[],
 888                 struct nlattr *attrs[], size_t n_attrs)
 889 {
 890     struct ofpbuf buf;
 891
 892     nl_attr_get_nested(nla, &buf);
 893     return nl_policy_parse(&buf, 0, policy, attrs, n_attrs);
 894 }
 895
 896 const struct nlattr *
 897 nl_attr_find__(const struct nlattr *attrs, size_t size, uint16_t type)
 898 {
 899     const struct nlattr *nla;
 900     size_t left;
 901
 902     NL_ATTR_FOR_EACH (nla, left, attrs, size) {
 903         if (nl_attr_type(nla) == type) {
 904             return nla;
 905         }
 906     }
 907     return NULL;
 908 }
 909
 910 /* Returns the first Netlink attribute within 'buf' with the specified 'type',
 911  * skipping a header of 'hdr_len' bytes at the beginning of 'buf'.
 912  *
 913  * This function does not validate the attribute's length. */
 914 const struct nlattr *
 915 nl_attr_find(const struct ofpbuf *buf, size_t hdr_len, uint16_t type)
 916 {
 917     return nl_attr_find__(ofpbuf_at(buf, hdr_len, 0), buf->size - hdr_len,
 918                           type);
 919 }
 920
 921 /* Returns the first Netlink attribute within 'nla' with the specified
 922  * 'type'.
 923  *
 924  * This function does not validate the attribute's length. */
 925 const struct nlattr *
 926 nl_attr_find_nested(const struct nlattr *nla, uint16_t type)
 927 {
 928     return nl_attr_find__(nl_attr_get(nla), nl_attr_get_size(nla), type);
 929 }