lib/netlink.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012 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 "netlink-protocol.h"
  25 #include "ofpbuf.h"
  26 #include "timeval.h"
  27 #include "unaligned.h"
  28 #include "vlog.h"
  29
  30 VLOG_DEFINE_THIS_MODULE(netlink);
  31
  32 /* A single (bad) Netlink message can in theory dump out many, many log
  33  * messages, so the burst size is set quite high here to avoid missing useful
  34  * information.  Also, at high logging levels we log *all* Netlink messages. */
  35 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(60, 600);
  36
  37 /* Returns the nlmsghdr at the head of 'msg'.
  38  *
  39  * 'msg' must be at least as large as a nlmsghdr. */
  40 struct nlmsghdr *
  41 nl_msg_nlmsghdr(const struct ofpbuf *msg)
  42 {
  43     return ofpbuf_at_assert(msg, 0, NLMSG_HDRLEN);
  44 }
  45
  46 /* Returns the genlmsghdr just past 'msg''s nlmsghdr.
  47  *
  48  * Returns a null pointer if 'msg' is not large enough to contain an nlmsghdr
  49  * and a genlmsghdr. */
  50 struct genlmsghdr *
  51 nl_msg_genlmsghdr(const struct ofpbuf *msg)
  52 {
  53     return ofpbuf_at(msg, NLMSG_HDRLEN, GENL_HDRLEN);
  54 }
  55
  56 /* If 'buffer' is a NLMSG_ERROR message, stores 0 in '*errorp' if it is an ACK
  57  * message, otherwise a positive errno value, and returns true.  If 'buffer' is
  58  * not an NLMSG_ERROR message, returns false.
  59  *
  60  * 'msg' must be at least as large as a nlmsghdr. */
  61 bool
  62 nl_msg_nlmsgerr(const struct ofpbuf *msg, int *errorp)
  63 {
  64     if (nl_msg_nlmsghdr(msg)->nlmsg_type == NLMSG_ERROR) {
  65         struct nlmsgerr *err = ofpbuf_at(msg, NLMSG_HDRLEN, sizeof *err);
  66         int code = EPROTO;
  67         if (!err) {
  68             VLOG_ERR_RL(&rl, "received invalid nlmsgerr (%zd bytes < %zd)",
  69                         msg->size, NLMSG_HDRLEN + sizeof *err);
  70         } else if (err->error <= 0 && err->error > INT_MIN) {
  71             code = -err->error;
  72         }
  73         if (errorp) {
  74             *errorp = code;
  75         }
  76         return true;
  77     } else {
  78         return false;
  79     }
  80 }
  81
  82 /* Ensures that 'b' has room for at least 'size' bytes plus netlink padding at
  83  * its tail end, reallocating and copying its data if necessary. */
  84 void
  85 nl_msg_reserve(struct ofpbuf *msg, size_t size)
  86 {
  87     ofpbuf_prealloc_tailroom(msg, NLMSG_ALIGN(size));
  88 }
  89
  90 /* Puts a nlmsghdr at the beginning of 'msg', which must be initially empty.
  91  * Uses the given 'type' and 'flags'.  'expected_payload' should be
  92  * an estimate of the number of payload bytes to be supplied; if the size of
  93  * the payload is unknown a value of 0 is acceptable.
  94  *
  95  * 'type' is ordinarily an enumerated value specific to the Netlink protocol
  96  * (e.g. RTM_NEWLINK, for NETLINK_ROUTE protocol).  For Generic Netlink, 'type'
  97  * is the family number obtained via nl_lookup_genl_family().
  98  *
  99  * 'flags' is a bit-mask that indicates what kind of request is being made.  It
 100  * is often NLM_F_REQUEST indicating that a request is being made, commonly
 101  * or'd with NLM_F_ACK to request an acknowledgement.
 102  *
 103  * Sets the new nlmsghdr's nlmsg_len, nlmsg_seq, and nlmsg_pid fields to 0 for
 104  * now.  Functions that send Netlink messages will fill these in just before
 105  * sending the message.
 106  *
 107  * nl_msg_put_genlmsghdr() is more convenient for composing a Generic Netlink
 108  * message. */
 109 void
 110 nl_msg_put_nlmsghdr(struct ofpbuf *msg,
 111                     size_t expected_payload, uint32_t type, uint32_t flags)
 112 {
 113     struct nlmsghdr *nlmsghdr;
 114
 115     ovs_assert(msg->size == 0);
 116
 117     nl_msg_reserve(msg, NLMSG_HDRLEN + expected_payload);
 118     nlmsghdr = nl_msg_put_uninit(msg, NLMSG_HDRLEN);
 119     nlmsghdr->nlmsg_len = 0;
 120     nlmsghdr->nlmsg_type = type;
 121     nlmsghdr->nlmsg_flags = flags;
 122     nlmsghdr->nlmsg_seq = 0;
 123     nlmsghdr->nlmsg_pid = 0;
 124 }
 125
 126 /* Puts a nlmsghdr and genlmsghdr at the beginning of 'msg', which must be
 127  * initially empty.  'expected_payload' should be an estimate of the number of
 128  * payload bytes to be supplied; if the size of the payload is unknown a value
 129  * of 0 is acceptable.
 130  *
 131  * 'family' is the family number obtained via nl_lookup_genl_family().
 132  *
 133  * 'flags' is a bit-mask that indicates what kind of request is being made.  It
 134  * is often NLM_F_REQUEST indicating that a request is being made, commonly
 135  * or'd with NLM_F_ACK to request an acknowledgement.
 136  *
 137  * 'cmd' is an enumerated value specific to the Generic Netlink family
 138  * (e.g. CTRL_CMD_NEWFAMILY for the GENL_ID_CTRL family).
 139  *
 140  * 'version' is a version number specific to the family and command (often 1).
 141  *
 142  * Sets the new nlmsghdr's nlmsg_pid field to 0 for now.  nl_sock_send() will
 143  * fill it in just before sending the message.
 144  *
 145  * nl_msg_put_nlmsghdr() should be used to compose Netlink messages that are
 146  * not Generic Netlink messages. */
 147 void
 148 nl_msg_put_genlmsghdr(struct ofpbuf *msg, size_t expected_payload,
 149                       int family, uint32_t flags, uint8_t cmd, uint8_t version)
 150 {
 151     struct genlmsghdr *genlmsghdr;
 152
 153     nl_msg_put_nlmsghdr(msg, GENL_HDRLEN + expected_payload, family, flags);
 154     ovs_assert(msg->size == NLMSG_HDRLEN);
 155     genlmsghdr = nl_msg_put_uninit(msg, GENL_HDRLEN);
 156     genlmsghdr->cmd = cmd;
 157     genlmsghdr->version = version;
 158     genlmsghdr->reserved = 0;
 159 }
 160
 161 /* Appends the 'size' bytes of data in 'p', plus Netlink padding if needed, to
 162  * the tail end of 'msg'.  Data in 'msg' is reallocated and copied if
 163  * necessary. */
 164 void
 165 nl_msg_put(struct ofpbuf *msg, const void *data, size_t size)
 166 {
 167     memcpy(nl_msg_put_uninit(msg, size), data, size);
 168 }
 169
 170 /* Appends 'size' bytes of data, plus Netlink padding if needed, to the tail
 171  * end of 'msg', reallocating and copying its data if necessary.  Returns a
 172  * pointer to the first byte of the new data, which is left uninitialized. */
 173 void *
 174 nl_msg_put_uninit(struct ofpbuf *msg, size_t size)
 175 {
 176     size_t pad = NLMSG_ALIGN(size) - size;
 177     char *p = ofpbuf_put_uninit(msg, size + pad);
 178     if (pad) {
 179         memset(p + size, 0, pad);
 180     }
 181     return p;
 182 }
 183
 184 /* Prepends the 'size' bytes of data in 'p', plus Netlink padding if needed, to
 185  * the head end of 'msg'.  Data in 'msg' is reallocated and copied if
 186  * necessary. */
 187 void
 188 nl_msg_push(struct ofpbuf *msg, const void *data, size_t size)
 189 {
 190     memcpy(nl_msg_push_uninit(msg, size), data, size);
 191 }
 192
 193 /* Prepends 'size' bytes of data, plus Netlink padding if needed, to the head
 194  * end of 'msg', reallocating and copying its data if necessary.  Returns a
 195  * pointer to the first byte of the new data, which is left uninitialized. */
 196 void *
 197 nl_msg_push_uninit(struct ofpbuf *msg, size_t size)
 198 {
 199     size_t pad = NLMSG_ALIGN(size) - size;
 200     char *p = ofpbuf_push_uninit(msg, size + pad);
 201     if (pad) {
 202         memset(p + size, 0, pad);
 203     }
 204     return p;
 205 }
 206
 207 /* Appends a Netlink attribute of the given 'type' and room for 'size' bytes of
 208  * data as its payload, plus Netlink padding if needed, to the tail end of
 209  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 210  * the first byte of data in the attribute, which is left uninitialized. */
 211 void *
 212 nl_msg_put_unspec_uninit(struct ofpbuf *msg, uint16_t type, size_t size)
 213 {
 214     size_t total_size = NLA_HDRLEN + size;
 215     struct nlattr* nla = nl_msg_put_uninit(msg, total_size);
 216     ovs_assert(NLA_ALIGN(total_size) <= UINT16_MAX);
 217     nla->nla_len = total_size;
 218     nla->nla_type = type;
 219     return nla + 1;
 220 }
 221
 222 /* Appends a Netlink attribute of the given 'type' and the 'size' bytes of
 223  * 'data' as its payload, to the tail end of 'msg', reallocating and copying
 224  * its data if necessary.  Returns a pointer to the first byte of data in the
 225  * attribute, which is left uninitialized. */
 226 void
 227 nl_msg_put_unspec(struct ofpbuf *msg, uint16_t type,
 228                   const void *data, size_t size)
 229 {
 230     memcpy(nl_msg_put_unspec_uninit(msg, type, size), data, size);
 231 }
 232
 233 /* Appends a Netlink attribute of the given 'type' and no payload to 'msg'.
 234  * (Some Netlink protocols use the presence or absence of an attribute as a
 235  * Boolean flag.) */
 236 void
 237 nl_msg_put_flag(struct ofpbuf *msg, uint16_t type)
 238 {
 239     nl_msg_put_unspec(msg, type, NULL, 0);
 240 }
 241
 242 /* Appends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 243  * to 'msg'. */
 244 void
 245 nl_msg_put_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 246 {
 247     nl_msg_put_unspec(msg, type, &value, sizeof value);
 248 }
 249
 250 /* Appends a Netlink attribute of the given 'type' and the given 16-bit host
 251  * byte order 'value' to 'msg'. */
 252 void
 253 nl_msg_put_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 254 {
 255     nl_msg_put_unspec(msg, type, &value, sizeof value);
 256 }
 257
 258 /* Appends a Netlink attribute of the given 'type' and the given 32-bit host
 259  * byte order 'value' to 'msg'. */
 260 void
 261 nl_msg_put_u32(struct ofpbuf *msg, uint16_t type, uint32_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 64-bit host
 267  * byte order 'value' to 'msg'. */
 268 void
 269 nl_msg_put_u64(struct ofpbuf *msg, uint16_t type, uint64_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 16-bit network
 275  * byte order 'value' to 'msg'. */
 276 void
 277 nl_msg_put_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 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 32-bit network
 283  * byte order 'value' to 'msg'. */
 284 void
 285 nl_msg_put_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 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 64-bit network
 291  * byte order 'value' to 'msg'. */
 292 void
 293 nl_msg_put_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 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
 299  * null-terminated string 'value' to 'msg'. */
 300 void
 301 nl_msg_put_string(struct ofpbuf *msg, uint16_t type, const char *value)
 302 {
 303     nl_msg_put_unspec(msg, type, value, strlen(value) + 1);
 304 }
 305
 306 /* Prepends a Netlink attribute of the given 'type' and room for 'size' bytes
 307  * of data as its payload, plus Netlink padding if needed, to the head end of
 308  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 309  * the first byte of data in the attribute, which is left uninitialized. */
 310 void *
 311 nl_msg_push_unspec_uninit(struct ofpbuf *msg, uint16_t type, size_t size)
 312 {
 313     size_t total_size = NLA_HDRLEN + size;
 314     struct nlattr* nla = nl_msg_push_uninit(msg, total_size);
 315     ovs_assert(NLA_ALIGN(total_size) <= UINT16_MAX);
 316     nla->nla_len = total_size;
 317     nla->nla_type = type;
 318     return nla + 1;
 319 }
 320
 321 /* Prepends a Netlink attribute of the given 'type' and the 'size' bytes of
 322  * 'data' as its payload, to the head end of 'msg', reallocating and copying
 323  * its data if necessary.  Returns a pointer to the first byte of data in the
 324  * attribute, which is left uninitialized. */
 325 void
 326 nl_msg_push_unspec(struct ofpbuf *msg, uint16_t type,
 327                   const void *data, size_t size)
 328 {
 329     memcpy(nl_msg_push_unspec_uninit(msg, type, size), data, size);
 330 }
 331
 332 /* Prepends a Netlink attribute of the given 'type' and no payload to 'msg'.
 333  * (Some Netlink protocols use the presence or absence of an attribute as a
 334  * Boolean flag.) */
 335 void
 336 nl_msg_push_flag(struct ofpbuf *msg, uint16_t type)
 337 {
 338     nl_msg_push_unspec(msg, type, NULL, 0);
 339 }
 340
 341 /* Prepends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 342  * to 'msg'. */
 343 void
 344 nl_msg_push_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 345 {
 346     nl_msg_push_unspec(msg, type, &value, sizeof value);
 347 }
 348
 349 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit host
 350  * byte order 'value' to 'msg'. */
 351 void
 352 nl_msg_push_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 353 {
 354     nl_msg_push_unspec(msg, type, &value, sizeof value);
 355 }
 356
 357 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit host
 358  * byte order 'value' to 'msg'. */
 359 void
 360 nl_msg_push_u32(struct ofpbuf *msg, uint16_t type, uint32_t value)
 361 {
 362     nl_msg_push_unspec(msg, type, &value, sizeof value);
 363 }
 364
 365 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit host
 366  * byte order 'value' to 'msg'. */
 367 void
 368 nl_msg_push_u64(struct ofpbuf *msg, uint16_t type, uint64_t value)
 369 {
 370     nl_msg_push_unspec(msg, type, &value, sizeof value);
 371 }
 372
 373 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit
 374  * network byte order 'value' to 'msg'. */
 375 void
 376 nl_msg_push_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 value)
 377 {
 378     nl_msg_push_unspec(msg, type, &value, sizeof value);
 379 }
 380
 381 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit
 382  * network byte order 'value' to 'msg'. */
 383 void
 384 nl_msg_push_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 value)
 385 {
 386     nl_msg_push_unspec(msg, type, &value, sizeof value);
 387 }
 388
 389 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit
 390  * network byte order 'value' to 'msg'. */
 391 void
 392 nl_msg_push_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 value)
 393 {
 394     nl_msg_push_unspec(msg, type, &value, sizeof value);
 395 }
 396
 397 /* Prepends a Netlink attribute of the given 'type' and the given
 398  * null-terminated string 'value' to 'msg'. */
 399 void
 400 nl_msg_push_string(struct ofpbuf *msg, uint16_t type, const char *value)
 401 {
 402     nl_msg_push_unspec(msg, type, value, strlen(value) + 1);
 403 }
 404
 405 /* Adds the header for nested Netlink attributes to 'msg', with the specified
 406  * 'type', and returns the header's offset within 'msg'.  The caller should add
 407  * the content for the nested Netlink attribute to 'msg' (e.g. using the other
 408  * nl_msg_*() functions), and then pass the returned offset to
 409  * nl_msg_end_nested() to finish up the nested attributes. */
 410 size_t
 411 nl_msg_start_nested(struct ofpbuf *msg, uint16_t type)
 412 {
 413     size_t offset = msg->size;
 414     nl_msg_put_unspec(msg, type, NULL, 0);
 415     return offset;
 416 }
 417
 418 /* Finalizes a nested Netlink attribute in 'msg'.  'offset' should be the value
 419  * returned by nl_msg_start_nested(). */
 420 void
 421 nl_msg_end_nested(struct ofpbuf *msg, size_t offset)
 422 {
 423     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
 424     attr->nla_len = msg->size - offset;
 425 }
 426
 427 /* Appends a nested Netlink attribute of the given 'type', with the 'size'
 428  * bytes of content starting at 'data', to 'msg'. */
 429 void
 430 nl_msg_put_nested(struct ofpbuf *msg,
 431                   uint16_t type, const void *data, size_t size)
 432 {
 433     size_t offset = nl_msg_start_nested(msg, type);
 434     nl_msg_put(msg, data, size);
 435     nl_msg_end_nested(msg, offset);
 436 }
 437
 438 /* If 'buffer' begins with a valid "struct nlmsghdr", pulls the header and its
 439  * payload off 'buffer', stores header and payload in 'msg->data' and
 440  * 'msg->size', and returns a pointer to the header.
 441  *
 442  * If 'buffer' does not begin with a "struct nlmsghdr" or begins with one that
 443  * is invalid, returns NULL without modifying 'buffer'. */
 444 struct nlmsghdr *
 445 nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg)
 446 {
 447     if (buffer->size >= sizeof(struct nlmsghdr)) {
 448         struct nlmsghdr *nlmsghdr = nl_msg_nlmsghdr(buffer);
 449         size_t len = nlmsghdr->nlmsg_len;
 450         if (len >= sizeof *nlmsghdr && len <= buffer->size) {
 451             ofpbuf_use_const(msg, nlmsghdr, len);
 452             ofpbuf_pull(buffer, len);
 453             return nlmsghdr;
 454         }
 455     }
 456
 457     msg->data = NULL;
 458     msg->size = 0;
 459     return NULL;
 460 }
 461 \f
 462 /* Attributes. */
 463
 464 /* Returns the bits of 'nla->nla_type' that are significant for determining its
 465  * type. */
 466 int
 467 nl_attr_type(const struct nlattr *nla)
 468 {
 469     return nla->nla_type & NLA_TYPE_MASK;
 470 }
 471
 472 /* Returns the first byte in the payload of attribute 'nla'. */
 473 const void *
 474 nl_attr_get(const struct nlattr *nla)
 475 {
 476     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 477     return nla + 1;
 478 }
 479
 480 /* Returns the number of bytes in the payload of attribute 'nla'. */
 481 size_t
 482 nl_attr_get_size(const struct nlattr *nla)
 483 {
 484     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 485     return nla->nla_len - NLA_HDRLEN;
 486 }
 487
 488 /* Asserts that 'nla''s payload is at least 'size' bytes long, and returns the
 489  * first byte of the payload. */
 490 const void *
 491 nl_attr_get_unspec(const struct nlattr *nla, size_t size)
 492 {
 493     ovs_assert(nla->nla_len >= NLA_HDRLEN + size);
 494     return nla + 1;
 495 }
 496
 497 /* Returns true if 'nla' is nonnull.  (Some Netlink protocols use the presence
 498  * or absence of an attribute as a Boolean flag.) */
 499 bool
 500 nl_attr_get_flag(const struct nlattr *nla)
 501 {
 502     return nla != NULL;
 503 }
 504
 505 #define NL_ATTR_GET_AS(NLA, TYPE) \
 506         (*(TYPE*) nl_attr_get_unspec(nla, sizeof(TYPE)))
 507
 508 /* Returns the 8-bit value in 'nla''s payload.
 509  *
 510  * Asserts that 'nla''s payload is at least 1 byte long. */
 511 uint8_t
 512 nl_attr_get_u8(const struct nlattr *nla)
 513 {
 514     return NL_ATTR_GET_AS(nla, uint8_t);
 515 }
 516
 517 /* Returns the 16-bit host byte order value in 'nla''s payload.
 518  *
 519  * Asserts that 'nla''s payload is at least 2 bytes long. */
 520 uint16_t
 521 nl_attr_get_u16(const struct nlattr *nla)
 522 {
 523     return NL_ATTR_GET_AS(nla, uint16_t);
 524 }
 525
 526 /* Returns the 32-bit host byte order value in 'nla''s payload.
 527  *
 528  * Asserts that 'nla''s payload is at least 4 bytes long. */
 529 uint32_t
 530 nl_attr_get_u32(const struct nlattr *nla)
 531 {
 532     return NL_ATTR_GET_AS(nla, uint32_t);
 533 }
 534
 535 /* Returns the 64-bit host byte order value in 'nla''s payload.
 536  *
 537  * Asserts that 'nla''s payload is at least 8 bytes long. */
 538 uint64_t
 539 nl_attr_get_u64(const struct nlattr *nla)
 540 {
 541     const ovs_32aligned_u64 *x = nl_attr_get_unspec(nla, sizeof *x);
 542     return get_32aligned_u64(x);
 543 }
 544
 545 /* Returns the 16-bit network byte order value in 'nla''s payload.
 546  *
 547  * Asserts that 'nla''s payload is at least 2 bytes long. */
 548 ovs_be16
 549 nl_attr_get_be16(const struct nlattr *nla)
 550 {
 551     return NL_ATTR_GET_AS(nla, ovs_be16);
 552 }
 553
 554 /* Returns the 32-bit network byte order value in 'nla''s payload.
 555  *
 556  * Asserts that 'nla''s payload is at least 4 bytes long. */
 557 ovs_be32
 558 nl_attr_get_be32(const struct nlattr *nla)
 559 {
 560     return NL_ATTR_GET_AS(nla, ovs_be32);
 561 }
 562
 563 /* Returns the 64-bit network byte order value in 'nla''s payload.
 564  *
 565  * Asserts that 'nla''s payload is at least 8 bytes long. */
 566 ovs_be64
 567 nl_attr_get_be64(const struct nlattr *nla)
 568 {
 569     const ovs_32aligned_be64 *x = nl_attr_get_unspec(nla, sizeof *x);
 570     return get_32aligned_be64(x);
 571 }
 572
 573 /* Returns the null-terminated string value in 'nla''s payload.
 574  *
 575  * Asserts that 'nla''s payload contains a null-terminated string. */
 576 const char *
 577 nl_attr_get_string(const struct nlattr *nla)
 578 {
 579     ovs_assert(nla->nla_len > NLA_HDRLEN);
 580     ovs_assert(memchr(nl_attr_get(nla), '\0', nla->nla_len - NLA_HDRLEN));
 581     return nl_attr_get(nla);
 582 }
 583
 584 /* Initializes 'nested' to the payload of 'nla'. */
 585 void
 586 nl_attr_get_nested(const struct nlattr *nla, struct ofpbuf *nested)
 587 {
 588     ofpbuf_use_const(nested, nl_attr_get(nla), nl_attr_get_size(nla));
 589 }
 590
 591 /* Default minimum and maximum payload sizes for each type of attribute. */
 592 static const size_t attr_len_range[][2] = {
 593     [0 ... N_NL_ATTR_TYPES - 1] = { 0, SIZE_MAX },
 594     [NL_A_U8] = { 1, 1 },
 595     [NL_A_U16] = { 2, 2 },
 596     [NL_A_U32] = { 4, 4 },
 597     [NL_A_U64] = { 8, 8 },
 598     [NL_A_STRING] = { 1, SIZE_MAX },
 599     [NL_A_FLAG] = { 0, SIZE_MAX },
 600     [NL_A_NESTED] = { 0, SIZE_MAX },
 601 };
 602
 603 bool
 604 nl_attr_validate(const struct nlattr *nla, const struct nl_policy *policy)
 605 {
 606     uint16_t type = nl_attr_type(nla);
 607     size_t min_len;
 608     size_t max_len;
 609     size_t len;
 610
 611     if (policy->type == NL_A_NO_ATTR) {
 612         return true;
 613     }
 614
 615     /* Figure out min and max length. */
 616     min_len = policy->min_len;
 617     if (!min_len) {
 618         min_len = attr_len_range[policy->type][0];
 619     }
 620     max_len = policy->max_len;
 621     if (!max_len) {
 622         max_len = attr_len_range[policy->type][1];
 623     }
 624
 625     /* Verify length. */
 626     len = nl_attr_get_size(nla);
 627     if (len < min_len || len > max_len) {
 628         VLOG_DBG_RL(&rl, "attr %"PRIu16" length %zu not in "
 629                     "allowed range %zu...%zu", type, len, min_len, max_len);
 630         return false;
 631     }
 632
 633     /* Strings must be null terminated and must not have embedded nulls. */
 634     if (policy->type == NL_A_STRING) {
 635         if (((char *) nla)[nla->nla_len - 1]) {
 636             VLOG_DBG_RL(&rl, "attr %"PRIu16" lacks null at end", type);
 637             return false;
 638         }
 639         if (memchr(nla + 1, '\0', len - 1) != NULL) {
 640             VLOG_DBG_RL(&rl, "attr %"PRIu16" has bad length", type);
 641             return false;
 642         }
 643     }
 644
 645     return true;
 646 }
 647
 648 /* Parses the 'msg' starting at the given 'nla_offset' as a sequence of Netlink
 649  * attributes.  'policy[i]', for 0 <= i < n_attrs, specifies how the attribute
 650  * with nla_type == i is parsed; a pointer to attribute i is stored in
 651  * attrs[i].  Returns true if successful, false on failure.
 652  *
 653  * If the Netlink attributes in 'msg' follow a Netlink header and a Generic
 654  * Netlink header, then 'nla_offset' should be NLMSG_HDRLEN + GENL_HDRLEN. */
 655 bool
 656 nl_policy_parse(const struct ofpbuf *msg, size_t nla_offset,
 657                 const struct nl_policy policy[],
 658                 struct nlattr *attrs[], size_t n_attrs)
 659 {
 660     struct nlattr *nla;
 661     size_t left;
 662     size_t i;
 663
 664     memset(attrs, 0, n_attrs * sizeof *attrs);
 665
 666     if (msg->size < nla_offset) {
 667         VLOG_DBG_RL(&rl, "missing headers in nl_policy_parse");
 668         return false;
 669     }
 670
 671     NL_ATTR_FOR_EACH (nla, left,
 672                       (struct nlattr *) ((char *) msg->data + nla_offset),
 673                       msg->size - nla_offset)
 674     {
 675         uint16_t type = nl_attr_type(nla);
 676         if (type < n_attrs && policy[type].type != NL_A_NO_ATTR) {
 677             const struct nl_policy *e = &policy[type];
 678             if (!nl_attr_validate(nla, e)) {
 679                 return false;
 680             }
 681             if (attrs[type]) {
 682                 VLOG_DBG_RL(&rl, "duplicate attr %"PRIu16, type);
 683             }
 684             attrs[type] = nla;
 685         }
 686     }
 687     if (left) {
 688         VLOG_DBG_RL(&rl, "attributes followed by garbage");
 689         return false;
 690     }
 691
 692     for (i = 0; i < n_attrs; i++) {
 693         const struct nl_policy *e = &policy[i];
 694         if (!e->optional && e->type != NL_A_NO_ATTR && !attrs[i]) {
 695             VLOG_DBG_RL(&rl, "required attr %zu missing", i);
 696             return false;
 697         }
 698     }
 699     return true;
 700 }
 701
 702 /* Parses the Netlink attributes within 'nla'.  'policy[i]', for 0 <= i <
 703  * n_attrs, specifies how the attribute with nla_type == i is parsed; a pointer
 704  * to attribute i is stored in attrs[i].  Returns true if successful, false on
 705  * failure. */
 706 bool
 707 nl_parse_nested(const struct nlattr *nla, const struct nl_policy policy[],
 708                 struct nlattr *attrs[], size_t n_attrs)
 709 {
 710     struct ofpbuf buf;
 711
 712     nl_attr_get_nested(nla, &buf);
 713     return nl_policy_parse(&buf, 0, policy, attrs, n_attrs);
 714 }
 715
 716 const struct nlattr *
 717 nl_attr_find__(const struct nlattr *attrs, size_t size, uint16_t type)
 718 {
 719     const struct nlattr *nla;
 720     size_t left;
 721
 722     NL_ATTR_FOR_EACH (nla, left, attrs, size) {
 723         if (nl_attr_type(nla) == type) {
 724             return nla;
 725         }
 726     }
 727     return NULL;
 728 }
 729
 730 /* Returns the first Netlink attribute within 'buf' with the specified 'type',
 731  * skipping a header of 'hdr_len' bytes at the beginning of 'buf'.
 732  *
 733  * This function does not validate the attribute's length. */
 734 const struct nlattr *
 735 nl_attr_find(const struct ofpbuf *buf, size_t hdr_len, uint16_t type)
 736 {
 737     const uint8_t *start = (const uint8_t *) buf->data + hdr_len;
 738     return nl_attr_find__((const struct nlattr *) start, buf->size - hdr_len,
 739                           type);
 740 }
 741
 742 /* Returns the first Netlink attribute within 'nla' with the specified
 743  * 'type'.
 744  *
 745  * This function does not validate the attribute's length. */
 746 const struct nlattr *
 747 nl_attr_find_nested(const struct nlattr *nla, uint16_t type)
 748 {
 749     return nl_attr_find__(nl_attr_get(nla), nl_attr_get_size(nla), type);
 750 }