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.  Returns a pointer to the first byte of data in the
 239  * attribute, which is left uninitialized. */
 240 void
 241 nl_msg_put_unspec(struct ofpbuf *msg, uint16_t type,
 242                   const void *data, size_t size)
 243 {
 244     memcpy(nl_msg_put_unspec_uninit(msg, type, size), data, size);
 245 }
 246
 247 /* Appends a Netlink attribute of the given 'type' and no payload to 'msg'.
 248  * (Some Netlink protocols use the presence or absence of an attribute as a
 249  * Boolean flag.) */
 250 void
 251 nl_msg_put_flag(struct ofpbuf *msg, uint16_t type)
 252 {
 253     nl_msg_put_unspec(msg, type, NULL, 0);
 254 }
 255
 256 /* Appends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 257  * to 'msg'. */
 258 void
 259 nl_msg_put_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 260 {
 261     nl_msg_put_unspec(msg, type, &value, sizeof value);
 262 }
 263
 264 /* Appends a Netlink attribute of the given 'type' and the given 16-bit host
 265  * byte order 'value' to 'msg'. */
 266 void
 267 nl_msg_put_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 268 {
 269     nl_msg_put_unspec(msg, type, &value, sizeof value);
 270 }
 271
 272 /* Appends a Netlink attribute of the given 'type' and the given 32-bit host
 273  * byte order 'value' to 'msg'. */
 274 void
 275 nl_msg_put_u32(struct ofpbuf *msg, uint16_t type, uint32_t value)
 276 {
 277     nl_msg_put_unspec(msg, type, &value, sizeof value);
 278 }
 279
 280 /* Appends a Netlink attribute of the given 'type' and the given 64-bit host
 281  * byte order 'value' to 'msg'. */
 282 void
 283 nl_msg_put_u64(struct ofpbuf *msg, uint16_t type, uint64_t value)
 284 {
 285     nl_msg_put_unspec(msg, type, &value, sizeof value);
 286 }
 287
 288 /* Appends a Netlink attribute of the given 'type' and the given 16-bit network
 289  * byte order 'value' to 'msg'. */
 290 void
 291 nl_msg_put_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 value)
 292 {
 293     nl_msg_put_unspec(msg, type, &value, sizeof value);
 294 }
 295
 296 /* Appends a Netlink attribute of the given 'type' and the given 32-bit network
 297  * byte order 'value' to 'msg'. */
 298 void
 299 nl_msg_put_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 value)
 300 {
 301     nl_msg_put_unspec(msg, type, &value, sizeof value);
 302 }
 303
 304 /* Appends a Netlink attribute of the given 'type' and the given 64-bit network
 305  * byte order 'value' to 'msg'. */
 306 void
 307 nl_msg_put_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 value)
 308 {
 309     nl_msg_put_unspec(msg, type, &value, sizeof value);
 310 }
 311
 312 /* Appends a Netlink attribute of the given 'type' and the given IPv6
 313  * address order 'value' to 'msg'. */
 314 void
 315 nl_msg_put_in6_addr(struct ofpbuf *msg, uint16_t type,
 316                     const struct in6_addr *value)
 317 {
 318     nl_msg_put_unspec(msg, type, value, sizeof *value);
 319 }
 320
 321 /* Appends a Netlink attribute of the given 'type' and the given odp_port_t
 322  * 'value' to 'msg'. */
 323 void
 324 nl_msg_put_odp_port(struct ofpbuf *msg, uint16_t type, odp_port_t value)
 325 {
 326     nl_msg_put_u32(msg, type, odp_to_u32(value));
 327 }
 328
 329 /* Appends a Netlink attribute of the given 'type' with the 'len' characters
 330  * of 'value', followed by the null byte to 'msg'. */
 331 void
 332 nl_msg_put_string__(struct ofpbuf *msg, uint16_t type, const char *value,
 333                     size_t len)
 334 {
 335     char *data = nl_msg_put_unspec_uninit(msg, type, len + 1);
 336
 337     memcpy(data, value, len);
 338     data[len] = '\0';
 339 }
 340
 341 /* Appends a Netlink attribute of the given 'type' and the given
 342  * null-terminated string 'value' to 'msg'. */
 343 void
 344 nl_msg_put_string(struct ofpbuf *msg, uint16_t type, const char *value)
 345 {
 346     nl_msg_put_unspec(msg, type, value, strlen(value) + 1);
 347 }
 348
 349 /* Prepends a Netlink attribute of the given 'type' and room for 'size' bytes
 350  * of data as its payload, plus Netlink padding if needed, to the head end of
 351  * 'msg', reallocating and copying its data if necessary.  Returns a pointer to
 352  * the first byte of data in the attribute, which is left uninitialized. */
 353 void *
 354 nl_msg_push_unspec_uninit(struct ofpbuf *msg, uint16_t type, size_t size)
 355 {
 356     size_t total_size = NLA_HDRLEN + size;
 357     struct nlattr* nla = nl_msg_push_uninit(msg, total_size);
 358     ovs_assert(!nl_attr_oversized(size));
 359     nla->nla_len = total_size;
 360     nla->nla_type = type;
 361     return nla + 1;
 362 }
 363
 364 /* Prepends a Netlink attribute of the given 'type' and the 'size' bytes of
 365  * 'data' as its payload, to the head end of 'msg', reallocating and copying
 366  * its data if necessary.  Returns a pointer to the first byte of data in the
 367  * attribute, which is left uninitialized. */
 368 void
 369 nl_msg_push_unspec(struct ofpbuf *msg, uint16_t type,
 370                   const void *data, size_t size)
 371 {
 372     memcpy(nl_msg_push_unspec_uninit(msg, type, size), data, size);
 373 }
 374
 375 /* Prepends a Netlink attribute of the given 'type' and no payload to 'msg'.
 376  * (Some Netlink protocols use the presence or absence of an attribute as a
 377  * Boolean flag.) */
 378 void
 379 nl_msg_push_flag(struct ofpbuf *msg, uint16_t type)
 380 {
 381     nl_msg_push_unspec_uninit(msg, type, 0);
 382 }
 383
 384 /* Prepends a Netlink attribute of the given 'type' and the given 8-bit 'value'
 385  * to 'msg'. */
 386 void
 387 nl_msg_push_u8(struct ofpbuf *msg, uint16_t type, uint8_t value)
 388 {
 389     nl_msg_push_unspec(msg, type, &value, sizeof value);
 390 }
 391
 392 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit host
 393  * byte order 'value' to 'msg'. */
 394 void
 395 nl_msg_push_u16(struct ofpbuf *msg, uint16_t type, uint16_t value)
 396 {
 397     nl_msg_push_unspec(msg, type, &value, sizeof value);
 398 }
 399
 400 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit host
 401  * byte order 'value' to 'msg'. */
 402 void
 403 nl_msg_push_u32(struct ofpbuf *msg, uint16_t type, uint32_t value)
 404 {
 405     nl_msg_push_unspec(msg, type, &value, sizeof value);
 406 }
 407
 408 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit host
 409  * byte order 'value' to 'msg'. */
 410 void
 411 nl_msg_push_u64(struct ofpbuf *msg, uint16_t type, uint64_t value)
 412 {
 413     nl_msg_push_unspec(msg, type, &value, sizeof value);
 414 }
 415
 416 /* Prepends a Netlink attribute of the given 'type' and the given 16-bit
 417  * network byte order 'value' to 'msg'. */
 418 void
 419 nl_msg_push_be16(struct ofpbuf *msg, uint16_t type, ovs_be16 value)
 420 {
 421     nl_msg_push_unspec(msg, type, &value, sizeof value);
 422 }
 423
 424 /* Prepends a Netlink attribute of the given 'type' and the given 32-bit
 425  * network byte order 'value' to 'msg'. */
 426 void
 427 nl_msg_push_be32(struct ofpbuf *msg, uint16_t type, ovs_be32 value)
 428 {
 429     nl_msg_push_unspec(msg, type, &value, sizeof value);
 430 }
 431
 432 /* Prepends a Netlink attribute of the given 'type' and the given 64-bit
 433  * network byte order 'value' to 'msg'. */
 434 void
 435 nl_msg_push_be64(struct ofpbuf *msg, uint16_t type, ovs_be64 value)
 436 {
 437     nl_msg_push_unspec(msg, type, &value, sizeof value);
 438 }
 439
 440 /* Prepends a Netlink attribute of the given 'type' and the given
 441  * null-terminated string 'value' to 'msg'. */
 442 void
 443 nl_msg_push_string(struct ofpbuf *msg, uint16_t type, const char *value)
 444 {
 445     nl_msg_push_unspec(msg, type, value, strlen(value) + 1);
 446 }
 447
 448 /* Adds the header for nested Netlink attributes to 'msg', with the specified
 449  * 'type', and returns the header's offset within 'msg'.  The caller should add
 450  * the content for the nested Netlink attribute to 'msg' (e.g. using the other
 451  * nl_msg_*() functions), and then pass the returned offset to
 452  * nl_msg_end_nested() to finish up the nested attributes. */
 453 size_t
 454 nl_msg_start_nested(struct ofpbuf *msg, uint16_t type)
 455 {
 456     size_t offset = msg->size;
 457     nl_msg_put_unspec(msg, type, NULL, 0);
 458     return offset;
 459 }
 460
 461 /* Finalizes a nested Netlink attribute in 'msg'.  'offset' should be the value
 462  * returned by nl_msg_start_nested(). */
 463 void
 464 nl_msg_end_nested(struct ofpbuf *msg, size_t offset)
 465 {
 466     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
 467     attr->nla_len = msg->size - offset;
 468 }
 469
 470 /* Same as nls_msg_end_nested() when the nested Netlink contains non empty
 471  * message. Otherwise, drop the nested message header from 'msg'.    */
 472 void
 473 nl_msg_end_non_empty_nested(struct ofpbuf *msg, size_t offset)
 474 {
 475     nl_msg_end_nested(msg, offset);
 476
 477     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
 478     if (!nl_attr_get_size(attr)) {
 479         msg->size = offset;
 480     }
 481 }
 482
 483 /* Appends a nested Netlink attribute of the given 'type', with the 'size'
 484  * bytes of content starting at 'data', to 'msg'. */
 485 void
 486 nl_msg_put_nested(struct ofpbuf *msg,
 487                   uint16_t type, const void *data, size_t size)
 488 {
 489     size_t offset = nl_msg_start_nested(msg, type);
 490     nl_msg_put(msg, data, size);
 491     nl_msg_end_nested(msg, offset);
 492 }
 493
 494 /* If 'buffer' begins with a valid "struct nlmsghdr", pulls the header and its
 495  * payload off 'buffer', stores header and payload in 'msg->data' and
 496  * 'msg->size', and returns a pointer to the header.
 497  *
 498  * If 'buffer' does not begin with a "struct nlmsghdr" or begins with one that
 499  * is invalid, returns NULL and clears 'buffer' and 'msg'. */
 500 struct nlmsghdr *
 501 nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg)
 502 {
 503     if (buffer->size >= sizeof(struct nlmsghdr)) {
 504         struct nlmsghdr *nlmsghdr = nl_msg_nlmsghdr(buffer);
 505         size_t len = nlmsghdr->nlmsg_len;
 506         if (len >= sizeof *nlmsghdr && len <= buffer->size) {
 507             ofpbuf_use_const(msg, nlmsghdr, len);
 508             ofpbuf_pull(buffer, len);
 509             return nlmsghdr;
 510         }
 511     }
 512
 513     ofpbuf_clear(buffer);
 514     msg->data = NULL;
 515     msg->size = 0;
 516     return NULL;
 517 }
 518
 519 /* Returns true if a Netlink attribute with a payload that is 'payload_size'
 520  * bytes long would be oversized, that is, if it's not possible to create an
 521  * nlattr of that size because its size wouldn't fit in the 16-bit nla_len
 522  * field. */
 523 bool
 524 nl_attr_oversized(size_t payload_size)
 525 {
 526     return payload_size > UINT16_MAX - NLA_HDRLEN;
 527 }
 528 \f
 529 /* Attributes. */
 530
 531 /* Returns the bits of 'nla->nla_type' that are significant for determining its
 532  * type. */
 533 int
 534 nl_attr_type(const struct nlattr *nla)
 535 {
 536     return nla->nla_type & NLA_TYPE_MASK;
 537 }
 538
 539 /* Returns the first byte in the payload of attribute 'nla'. */
 540 const void *
 541 nl_attr_get(const struct nlattr *nla)
 542 {
 543     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 544     return nla + 1;
 545 }
 546
 547 /* Returns the number of bytes in the payload of attribute 'nla'. */
 548 size_t
 549 nl_attr_get_size(const struct nlattr *nla)
 550 {
 551     ovs_assert(nla->nla_len >= NLA_HDRLEN);
 552     return nla->nla_len - NLA_HDRLEN;
 553 }
 554
 555 /* Asserts that 'nla''s payload is at least 'size' bytes long, and returns the
 556  * first byte of the payload. */
 557 const void *
 558 nl_attr_get_unspec(const struct nlattr *nla, size_t size)
 559 {
 560     ovs_assert(nla->nla_len >= NLA_HDRLEN + size);
 561     return nla + 1;
 562 }
 563
 564 /* Returns true if 'nla' is nonnull.  (Some Netlink protocols use the presence
 565  * or absence of an attribute as a Boolean flag.) */
 566 bool
 567 nl_attr_get_flag(const struct nlattr *nla)
 568 {
 569     return nla != NULL;
 570 }
 571
 572 #define NL_ATTR_GET_AS(NLA, TYPE) \
 573         (*(TYPE*) nl_attr_get_unspec(nla, sizeof(TYPE)))
 574
 575 /* Returns the 8-bit value in 'nla''s payload.
 576  *
 577  * Asserts that 'nla''s payload is at least 1 byte long. */
 578 uint8_t
 579 nl_attr_get_u8(const struct nlattr *nla)
 580 {
 581     return NL_ATTR_GET_AS(nla, uint8_t);
 582 }
 583
 584 /* Returns the 16-bit host byte order value in 'nla''s payload.
 585  *
 586  * Asserts that 'nla''s payload is at least 2 bytes long. */
 587 uint16_t
 588 nl_attr_get_u16(const struct nlattr *nla)
 589 {
 590     return NL_ATTR_GET_AS(nla, uint16_t);
 591 }
 592
 593 /* Returns the 32-bit host byte order value in 'nla''s payload.
 594  *
 595  * Asserts that 'nla''s payload is at least 4 bytes long. */
 596 uint32_t
 597 nl_attr_get_u32(const struct nlattr *nla)
 598 {
 599     return NL_ATTR_GET_AS(nla, uint32_t);
 600 }
 601
 602 /* Returns the 64-bit host byte order value in 'nla''s payload.
 603  *
 604  * Asserts that 'nla''s payload is at least 8 bytes long. */
 605 uint64_t
 606 nl_attr_get_u64(const struct nlattr *nla)
 607 {
 608     const ovs_32aligned_u64 *x = nl_attr_get_unspec(nla, sizeof *x);
 609     return get_32aligned_u64(x);
 610 }
 611
 612 /* Returns the 16-bit network byte order value in 'nla''s payload.
 613  *
 614  * Asserts that 'nla''s payload is at least 2 bytes long. */
 615 ovs_be16
 616 nl_attr_get_be16(const struct nlattr *nla)
 617 {
 618     return NL_ATTR_GET_AS(nla, ovs_be16);
 619 }
 620
 621 /* Returns the 32-bit network byte order value in 'nla''s payload.
 622  *
 623  * Asserts that 'nla''s payload is at least 4 bytes long. */
 624 ovs_be32
 625 nl_attr_get_be32(const struct nlattr *nla)
 626 {
 627     return NL_ATTR_GET_AS(nla, ovs_be32);
 628 }
 629
 630 /* Returns the 64-bit network byte order value in 'nla''s payload.
 631  *
 632  * Asserts that 'nla''s payload is at least 8 bytes long. */
 633 ovs_be64
 634 nl_attr_get_be64(const struct nlattr *nla)
 635 {
 636     const ovs_32aligned_be64 *x = nl_attr_get_unspec(nla, sizeof *x);
 637     return get_32aligned_be64(x);
 638 }
 639
 640 /* Returns the IPv6 address value in 'nla''s payload.
 641  *
 642  * Asserts that 'nla''s payload is at least 16 bytes long. */
 643 struct in6_addr
 644 nl_attr_get_in6_addr(const struct nlattr *nla)
 645 {
 646     return NL_ATTR_GET_AS(nla, struct in6_addr);
 647 }
 648
 649 /* Returns the 32-bit odp_port_t value in 'nla''s payload.
 650  *
 651  * Asserts that 'nla''s payload is at least 4 bytes long. */
 652 odp_port_t
 653 nl_attr_get_odp_port(const struct nlattr *nla)
 654 {
 655     return u32_to_odp(nl_attr_get_u32(nla));
 656 }
 657
 658 /* Returns the null-terminated string value in 'nla''s payload.
 659  *
 660  * Asserts that 'nla''s payload contains a null-terminated string. */
 661 const char *
 662 nl_attr_get_string(const struct nlattr *nla)
 663 {
 664     ovs_assert(nla->nla_len > NLA_HDRLEN);
 665     ovs_assert(memchr(nl_attr_get(nla), '\0', nla->nla_len - NLA_HDRLEN));
 666     return nl_attr_get(nla);
 667 }
 668
 669 /* Initializes 'nested' to the payload of 'nla'. */
 670 void
 671 nl_attr_get_nested(const struct nlattr *nla, struct ofpbuf *nested)
 672 {
 673     ofpbuf_use_const(nested, nl_attr_get(nla), nl_attr_get_size(nla));
 674 }
 675
 676 /* Default minimum payload size for each type of attribute. */
 677 static size_t
 678 min_attr_len(enum nl_attr_type type)
 679 {
 680     switch (type) {
 681     case NL_A_NO_ATTR: return 0;
 682     case NL_A_UNSPEC: return 0;
 683     case NL_A_U8: return 1;
 684     case NL_A_U16: return 2;
 685     case NL_A_U32: return 4;
 686     case NL_A_U64: return 8;
 687     case NL_A_STRING: return 1;
 688     case NL_A_FLAG: return 0;
 689     case NL_A_IPV6: return 16;
 690     case NL_A_NESTED: return 0;
 691     case N_NL_ATTR_TYPES: default: OVS_NOT_REACHED();
 692     }
 693 }
 694
 695 /* Default maximum payload size for each type of attribute. */
 696 static size_t
 697 max_attr_len(enum nl_attr_type type)
 698 {
 699     switch (type) {
 700     case NL_A_NO_ATTR: return SIZE_MAX;
 701     case NL_A_UNSPEC: return SIZE_MAX;
 702     case NL_A_U8: return 1;
 703     case NL_A_U16: return 2;
 704     case NL_A_U32: return 4;
 705     case NL_A_U64: return 8;
 706     case NL_A_STRING: return SIZE_MAX;
 707     case NL_A_FLAG: return SIZE_MAX;
 708     case NL_A_IPV6: return 16;
 709     case NL_A_NESTED: return SIZE_MAX;
 710     case N_NL_ATTR_TYPES: default: OVS_NOT_REACHED();
 711     }
 712 }
 713
 714 bool
 715 nl_attr_validate(const struct nlattr *nla, const struct nl_policy *policy)
 716 {
 717     uint16_t type = nl_attr_type(nla);
 718     size_t min_len;
 719     size_t max_len;
 720     size_t len;
 721
 722     if (policy->type == NL_A_NO_ATTR) {
 723         return true;
 724     }
 725
 726     /* Figure out min and max length. */
 727     min_len = policy->min_len;
 728     if (!min_len) {
 729         min_len = min_attr_len(policy->type);
 730     }
 731     max_len = policy->max_len;
 732     if (!max_len) {
 733         max_len = max_attr_len(policy->type);
 734     }
 735
 736     /* Verify length. */
 737     len = nl_attr_get_size(nla);
 738     if (len < min_len || len > max_len) {
 739         VLOG_DBG_RL(&rl, "attr %"PRIu16" length %"PRIuSIZE" not in "
 740                     "allowed range %"PRIuSIZE"...%"PRIuSIZE, type, len, min_len, max_len);
 741         return false;
 742     }
 743
 744     /* Strings must be null terminated and must not have embedded nulls. */
 745     if (policy->type == NL_A_STRING) {
 746         if (((char *) nla)[nla->nla_len - 1]) {
 747             VLOG_DBG_RL(&rl, "attr %"PRIu16" lacks null at end", type);
 748             return false;
 749         }
 750         if (memchr(nla + 1, '\0', len - 1) != NULL) {
 751             VLOG_DBG_RL(&rl, "attr %"PRIu16" has bad length", type);
 752             return false;
 753         }
 754     }
 755
 756     return true;
 757 }
 758
 759 /* Parses the 'msg' starting at the given 'nla_offset' as a sequence of Netlink
 760  * attributes.  'policy[i]', for 0 <= i < n_attrs, specifies how the attribute
 761  * with nla_type == i is parsed; a pointer to attribute i is stored in
 762  * attrs[i].  Returns true if successful, false on failure.
 763  *
 764  * If the Netlink attributes in 'msg' follow a Netlink header and a Generic
 765  * Netlink header, then 'nla_offset' should be NLMSG_HDRLEN + GENL_HDRLEN. */
 766 bool
 767 nl_policy_parse(const struct ofpbuf *msg, size_t nla_offset,
 768                 const struct nl_policy policy[],
 769                 struct nlattr *attrs[], size_t n_attrs)
 770 {
 771     struct nlattr *nla;
 772     size_t left;
 773     size_t i;
 774
 775     memset(attrs, 0, n_attrs * sizeof *attrs);
 776
 777     if (msg->size < nla_offset) {
 778         VLOG_DBG_RL(&rl, "missing headers in nl_policy_parse");
 779         return false;
 780     }
 781
 782     NL_ATTR_FOR_EACH (nla, left, ofpbuf_at(msg, nla_offset, 0),
 783                       msg->size - nla_offset)
 784     {
 785         uint16_t type = nl_attr_type(nla);
 786         if (type < n_attrs && policy[type].type != NL_A_NO_ATTR) {
 787             const struct nl_policy *e = &policy[type];
 788             if (!nl_attr_validate(nla, e)) {
 789                 return false;
 790             }
 791             if (attrs[type]) {
 792                 VLOG_DBG_RL(&rl, "duplicate attr %"PRIu16, type);
 793             }
 794             attrs[type] = nla;
 795         }
 796     }
 797     if (left) {
 798         VLOG_DBG_RL(&rl, "attributes followed by garbage");
 799         return false;
 800     }
 801
 802     for (i = 0; i < n_attrs; i++) {
 803         const struct nl_policy *e = &policy[i];
 804         if (!e->optional && e->type != NL_A_NO_ATTR && !attrs[i]) {
 805             VLOG_DBG_RL(&rl, "required attr %"PRIuSIZE" missing", i);
 806             return false;
 807         }
 808     }
 809     return true;
 810 }
 811
 812 /* Parses the Netlink attributes within 'nla'.  'policy[i]', for 0 <= i <
 813  * n_attrs, specifies how the attribute with nla_type == i is parsed; a pointer
 814  * to attribute i is stored in attrs[i].  Returns true if successful, false on
 815  * failure. */
 816 bool
 817 nl_parse_nested(const struct nlattr *nla, const struct nl_policy policy[],
 818                 struct nlattr *attrs[], size_t n_attrs)
 819 {
 820     struct ofpbuf buf;
 821
 822     nl_attr_get_nested(nla, &buf);
 823     return nl_policy_parse(&buf, 0, policy, attrs, n_attrs);
 824 }
 825
 826 const struct nlattr *
 827 nl_attr_find__(const struct nlattr *attrs, size_t size, uint16_t type)
 828 {
 829     const struct nlattr *nla;
 830     size_t left;
 831
 832     NL_ATTR_FOR_EACH (nla, left, attrs, size) {
 833         if (nl_attr_type(nla) == type) {
 834             return nla;
 835         }
 836     }
 837     return NULL;
 838 }
 839
 840 /* Returns the first Netlink attribute within 'buf' with the specified 'type',
 841  * skipping a header of 'hdr_len' bytes at the beginning of 'buf'.
 842  *
 843  * This function does not validate the attribute's length. */
 844 const struct nlattr *
 845 nl_attr_find(const struct ofpbuf *buf, size_t hdr_len, uint16_t type)
 846 {
 847     return nl_attr_find__(ofpbuf_at(buf, hdr_len, 0), buf->size - hdr_len,
 848                           type);
 849 }
 850
 851 /* Returns the first Netlink attribute within 'nla' with the specified
 852  * 'type'.
 853  *
 854  * This function does not validate the attribute's length. */
 855 const struct nlattr *
 856 nl_attr_find_nested(const struct nlattr *nla, uint16_t type)
 857 {
 858     return nl_attr_find__(nl_attr_get(nla), nl_attr_get_size(nla), type);
 859 }