ceph/src/spdk/dpdk/test/bpf/mbuf.h

   1 /* SPDX-License-Identifier: BSD-3-Clause
   2  * Copyright(c) 2010-2014 Intel Corporation.
   3  * Copyright 2014 6WIND S.A.
   4  */
   5
   6 /*
   7  * Snipper from dpdk.org rte_mbuf.h.
   8  * used to provide BPF programs information about rte_mbuf layout.
   9  */
  10
  11 #ifndef _MBUF_H_
  12 #define _MBUF_H_
  13
  14 #include <stdint.h>
  15 #include <rte_common.h>
  16 #include <rte_memory.h>
  17
  18 #ifdef __cplusplus
  19 extern "C" {
  20 #endif
  21
  22 /*
  23  * Packet Offload Features Flags. It also carry packet type information.
  24  * Critical resources. Both rx/tx shared these bits. Be cautious on any change
  25  *
  26  * - RX flags start at bit position zero, and get added to the left of previous
  27  *   flags.
  28  * - The most-significant 3 bits are reserved for generic mbuf flags
  29  * - TX flags therefore start at bit position 60 (i.e. 63-3), and new flags get
  30  *   added to the right of the previously defined flags i.e. they should count
  31  *   downwards, not upwards.
  32  *
  33  * Keep these flags synchronized with rte_get_rx_ol_flag_name() and
  34  * rte_get_tx_ol_flag_name().
  35  */
  36
  37 /**
  38  * RX packet is a 802.1q VLAN packet. This flag was set by PMDs when
  39  * the packet is recognized as a VLAN, but the behavior between PMDs
  40  * was not the same. This flag is kept for some time to avoid breaking
  41  * applications and should be replaced by PKT_RX_VLAN_STRIPPED.
  42  */
  43 #define PKT_RX_VLAN_PKT      (1ULL << 0)
  44
  45 #define PKT_RX_RSS_HASH      (1ULL << 1)
  46 /**< RX packet with RSS hash result. */
  47 #define PKT_RX_FDIR          (1ULL << 2)
  48 /**< RX packet with FDIR match indicate. */
  49
  50 /**
  51  * Deprecated.
  52  * Checking this flag alone is deprecated: check the 2 bits of
  53  * PKT_RX_L4_CKSUM_MASK.
  54  * This flag was set when the L4 checksum of a packet was detected as
  55  * wrong by the hardware.
  56  */
  57 #define PKT_RX_L4_CKSUM_BAD  (1ULL << 3)
  58
  59 /**
  60  * Deprecated.
  61  * Checking this flag alone is deprecated: check the 2 bits of
  62  * PKT_RX_IP_CKSUM_MASK.
  63  * This flag was set when the IP checksum of a packet was detected as
  64  * wrong by the hardware.
  65  */
  66 #define PKT_RX_IP_CKSUM_BAD  (1ULL << 4)
  67
  68 #define PKT_RX_EIP_CKSUM_BAD (1ULL << 5)
  69 /**< External IP header checksum error. */
  70
  71 /**
  72  * A vlan has been stripped by the hardware and its tci is saved in
  73  * mbuf->vlan_tci. This can only happen if vlan stripping is enabled
  74  * in the RX configuration of the PMD.
  75  */
  76 #define PKT_RX_VLAN_STRIPPED (1ULL << 6)
  77
  78 /**
  79  * Mask of bits used to determine the status of RX IP checksum.
  80  * - PKT_RX_IP_CKSUM_UNKNOWN: no information about the RX IP checksum
  81  * - PKT_RX_IP_CKSUM_BAD: the IP checksum in the packet is wrong
  82  * - PKT_RX_IP_CKSUM_GOOD: the IP checksum in the packet is valid
  83  * - PKT_RX_IP_CKSUM_NONE: the IP checksum is not correct in the packet
  84  *   data, but the integrity of the IP header is verified.
  85  */
  86 #define PKT_RX_IP_CKSUM_MASK ((1ULL << 4) | (1ULL << 7))
  87
  88 #define PKT_RX_IP_CKSUM_UNKNOWN 0
  89 #define PKT_RX_IP_CKSUM_BAD     (1ULL << 4)
  90 #define PKT_RX_IP_CKSUM_GOOD    (1ULL << 7)
  91 #define PKT_RX_IP_CKSUM_NONE    ((1ULL << 4) | (1ULL << 7))
  92
  93 /**
  94  * Mask of bits used to determine the status of RX L4 checksum.
  95  * - PKT_RX_L4_CKSUM_UNKNOWN: no information about the RX L4 checksum
  96  * - PKT_RX_L4_CKSUM_BAD: the L4 checksum in the packet is wrong
  97  * - PKT_RX_L4_CKSUM_GOOD: the L4 checksum in the packet is valid
  98  * - PKT_RX_L4_CKSUM_NONE: the L4 checksum is not correct in the packet
  99  *   data, but the integrity of the L4 data is verified.
 100  */
 101 #define PKT_RX_L4_CKSUM_MASK ((1ULL << 3) | (1ULL << 8))
 102
 103 #define PKT_RX_L4_CKSUM_UNKNOWN 0
 104 #define PKT_RX_L4_CKSUM_BAD     (1ULL << 3)
 105 #define PKT_RX_L4_CKSUM_GOOD    (1ULL << 8)
 106 #define PKT_RX_L4_CKSUM_NONE    ((1ULL << 3) | (1ULL << 8))
 107
 108 #define PKT_RX_IEEE1588_PTP  (1ULL << 9)
 109 /**< RX IEEE1588 L2 Ethernet PT Packet. */
 110 #define PKT_RX_IEEE1588_TMST (1ULL << 10)
 111 /**< RX IEEE1588 L2/L4 timestamped packet.*/
 112 #define PKT_RX_FDIR_ID       (1ULL << 13)
 113 /**< FD id reported if FDIR match. */
 114 #define PKT_RX_FDIR_FLX      (1ULL << 14)
 115 /**< Flexible bytes reported if FDIR match. */
 116
 117 /**
 118  * The 2 vlans have been stripped by the hardware and their tci are
 119  * saved in mbuf->vlan_tci (inner) and mbuf->vlan_tci_outer (outer).
 120  * This can only happen if vlan stripping is enabled in the RX
 121  * configuration of the PMD. If this flag is set, PKT_RX_VLAN_STRIPPED
 122  * must also be set.
 123  */
 124 #define PKT_RX_QINQ_STRIPPED (1ULL << 15)
 125
 126 /**
 127  * Deprecated.
 128  * RX packet with double VLAN stripped.
 129  * This flag is replaced by PKT_RX_QINQ_STRIPPED.
 130  */
 131 #define PKT_RX_QINQ_PKT      PKT_RX_QINQ_STRIPPED
 132
 133 /**
 134  * When packets are coalesced by a hardware or virtual driver, this flag
 135  * can be set in the RX mbuf, meaning that the m->tso_segsz field is
 136  * valid and is set to the segment size of original packets.
 137  */
 138 #define PKT_RX_LRO           (1ULL << 16)
 139
 140 /**
 141  * Indicate that the timestamp field in the mbuf is valid.
 142  */
 143 #define PKT_RX_TIMESTAMP     (1ULL << 17)
 144
 145 /* add new RX flags here */
 146
 147 /* add new TX flags here */
 148
 149 /**
 150  * Offload the MACsec. This flag must be set by the application to enable
 151  * this offload feature for a packet to be transmitted.
 152  */
 153 #define PKT_TX_MACSEC        (1ULL << 44)
 154
 155 /**
 156  * Bits 45:48 used for the tunnel type.
 157  * When doing Tx offload like TSO or checksum, the HW needs to configure the
 158  * tunnel type into the HW descriptors.
 159  */
 160 #define PKT_TX_TUNNEL_VXLAN   (0x1ULL << 45)
 161 #define PKT_TX_TUNNEL_GRE     (0x2ULL << 45)
 162 #define PKT_TX_TUNNEL_IPIP    (0x3ULL << 45)
 163 #define PKT_TX_TUNNEL_GENEVE  (0x4ULL << 45)
 164 /**< TX packet with MPLS-in-UDP RFC 7510 header. */
 165 #define PKT_TX_TUNNEL_MPLSINUDP (0x5ULL << 45)
 166 /* add new TX TUNNEL type here */
 167 #define PKT_TX_TUNNEL_MASK    (0xFULL << 45)
 168
 169 /**
 170  * Second VLAN insertion (QinQ) flag.
 171  */
 172 #define PKT_TX_QINQ_PKT    (1ULL << 49)
 173 /**< TX packet with double VLAN inserted. */
 174
 175 /**
 176  * TCP segmentation offload. To enable this offload feature for a
 177  * packet to be transmitted on hardware supporting TSO:
 178  *  - set the PKT_TX_TCP_SEG flag in mbuf->ol_flags (this flag implies
 179  *    PKT_TX_TCP_CKSUM)
 180  *  - set the flag PKT_TX_IPV4 or PKT_TX_IPV6
 181  *  - if it's IPv4, set the PKT_TX_IP_CKSUM flag and write the IP checksum
 182  *    to 0 in the packet
 183  *  - fill the mbuf offload information: l2_len, l3_len, l4_len, tso_segsz
 184  *  - calculate the pseudo header checksum without taking ip_len in account,
 185  *    and set it in the TCP header. Refer to rte_ipv4_phdr_cksum() and
 186  *    rte_ipv6_phdr_cksum() that can be used as helpers.
 187  */
 188 #define PKT_TX_TCP_SEG       (1ULL << 50)
 189
 190 #define PKT_TX_IEEE1588_TMST (1ULL << 51)
 191 /**< TX IEEE1588 packet to timestamp. */
 192
 193 /**
 194  * Bits 52+53 used for L4 packet type with checksum enabled: 00: Reserved,
 195  * 01: TCP checksum, 10: SCTP checksum, 11: UDP checksum. To use hardware
 196  * L4 checksum offload, the user needs to:
 197  *  - fill l2_len and l3_len in mbuf
 198  *  - set the flags PKT_TX_TCP_CKSUM, PKT_TX_SCTP_CKSUM or PKT_TX_UDP_CKSUM
 199  *  - set the flag PKT_TX_IPV4 or PKT_TX_IPV6
 200  *  - calculate the pseudo header checksum and set it in the L4 header (only
 201  *    for TCP or UDP). See rte_ipv4_phdr_cksum() and rte_ipv6_phdr_cksum().
 202  *    For SCTP, set the crc field to 0.
 203  */
 204 #define PKT_TX_L4_NO_CKSUM   (0ULL << 52)
 205 /**< Disable L4 cksum of TX pkt. */
 206 #define PKT_TX_TCP_CKSUM     (1ULL << 52)
 207 /**< TCP cksum of TX pkt. computed by NIC. */
 208 #define PKT_TX_SCTP_CKSUM    (2ULL << 52)
 209 /**< SCTP cksum of TX pkt. computed by NIC. */
 210 #define PKT_TX_UDP_CKSUM     (3ULL << 52)
 211 /**< UDP cksum of TX pkt. computed by NIC. */
 212 #define PKT_TX_L4_MASK       (3ULL << 52)
 213 /**< Mask for L4 cksum offload request. */
 214
 215 /**
 216  * Offload the IP checksum in the hardware. The flag PKT_TX_IPV4 should
 217  * also be set by the application, although a PMD will only check
 218  * PKT_TX_IP_CKSUM.
 219  *  - set the IP checksum field in the packet to 0
 220  *  - fill the mbuf offload information: l2_len, l3_len
 221  */
 222 #define PKT_TX_IP_CKSUM      (1ULL << 54)
 223
 224 /**
 225  * Packet is IPv4. This flag must be set when using any offload feature
 226  * (TSO, L3 or L4 checksum) to tell the NIC that the packet is an IPv4
 227  * packet. If the packet is a tunneled packet, this flag is related to
 228  * the inner headers.
 229  */
 230 #define PKT_TX_IPV4          (1ULL << 55)
 231
 232 /**
 233  * Packet is IPv6. This flag must be set when using an offload feature
 234  * (TSO or L4 checksum) to tell the NIC that the packet is an IPv6
 235  * packet. If the packet is a tunneled packet, this flag is related to
 236  * the inner headers.
 237  */
 238 #define PKT_TX_IPV6          (1ULL << 56)
 239
 240 #define PKT_TX_VLAN_PKT      (1ULL << 57)
 241 /**< TX packet is a 802.1q VLAN packet. */
 242
 243 /**
 244  * Offload the IP checksum of an external header in the hardware. The
 245  * flag PKT_TX_OUTER_IPV4 should also be set by the application, alto ugh
 246  * a PMD will only check PKT_TX_IP_CKSUM.  The IP checksum field in the
 247  * packet must be set to 0.
 248  *  - set the outer IP checksum field in the packet to 0
 249  *  - fill the mbuf offload information: outer_l2_len, outer_l3_len
 250  */
 251 #define PKT_TX_OUTER_IP_CKSUM   (1ULL << 58)
 252
 253 /**
 254  * Packet outer header is IPv4. This flag must be set when using any
 255  * outer offload feature (L3 or L4 checksum) to tell the NIC that the
 256  * outer header of the tunneled packet is an IPv4 packet.
 257  */
 258 #define PKT_TX_OUTER_IPV4   (1ULL << 59)
 259
 260 /**
 261  * Packet outer header is IPv6. This flag must be set when using any
 262  * outer offload feature (L4 checksum) to tell the NIC that the outer
 263  * header of the tunneled packet is an IPv6 packet.
 264  */
 265 #define PKT_TX_OUTER_IPV6    (1ULL << 60)
 266
 267 /**
 268  * Bitmask of all supported packet Tx offload features flags,
 269  * which can be set for packet.
 270  */
 271 #define PKT_TX_OFFLOAD_MASK (    \
 272                 PKT_TX_IP_CKSUM |        \
 273                 PKT_TX_L4_MASK |         \
 274                 PKT_TX_OUTER_IP_CKSUM |  \
 275                 PKT_TX_TCP_SEG |         \
 276                 PKT_TX_IEEE1588_TMST |   \
 277                 PKT_TX_QINQ_PKT |        \
 278                 PKT_TX_VLAN_PKT |        \
 279                 PKT_TX_TUNNEL_MASK |     \
 280                 PKT_TX_MACSEC)
 281
 282 #define __RESERVED           (1ULL << 61) /**< reserved for future mbuf use */
 283
 284 #define IND_ATTACHED_MBUF    (1ULL << 62) /**< Indirect attached mbuf */
 285
 286 /* Use final bit of flags to indicate a control mbuf */
 287 #define CTRL_MBUF_FLAG       (1ULL << 63) /**< Mbuf contains control data */
 288
 289 /** Alignment constraint of mbuf private area. */
 290 #define RTE_MBUF_PRIV_ALIGN 8
 291
 292 /**
 293  * Get the name of a RX offload flag
 294  *
 295  * @param mask
 296  *   The mask describing the flag.
 297  * @return
 298  *   The name of this flag, or NULL if it's not a valid RX flag.
 299  */
 300 const char *rte_get_rx_ol_flag_name(uint64_t mask);
 301
 302 /**
 303  * Dump the list of RX offload flags in a buffer
 304  *
 305  * @param mask
 306  *   The mask describing the RX flags.
 307  * @param buf
 308  *   The output buffer.
 309  * @param buflen
 310  *   The length of the buffer.
 311  * @return
 312  *   0 on success, (-1) on error.
 313  */
 314 int rte_get_rx_ol_flag_list(uint64_t mask, char *buf, size_t buflen);
 315
 316 /**
 317  * Get the name of a TX offload flag
 318  *
 319  * @param mask
 320  *   The mask describing the flag. Usually only one bit must be set.
 321  *   Several bits can be given if they belong to the same mask.
 322  *   Ex: PKT_TX_L4_MASK.
 323  * @return
 324  *   The name of this flag, or NULL if it's not a valid TX flag.
 325  */
 326 const char *rte_get_tx_ol_flag_name(uint64_t mask);
 327
 328 /**
 329  * Dump the list of TX offload flags in a buffer
 330  *
 331  * @param mask
 332  *   The mask describing the TX flags.
 333  * @param buf
 334  *   The output buffer.
 335  * @param buflen
 336  *   The length of the buffer.
 337  * @return
 338  *   0 on success, (-1) on error.
 339  */
 340 int rte_get_tx_ol_flag_list(uint64_t mask, char *buf, size_t buflen);
 341
 342 /**
 343  * Some NICs need at least 2KB buffer to RX standard Ethernet frame without
 344  * splitting it into multiple segments.
 345  * So, for mbufs that planned to be involved into RX/TX, the recommended
 346  * minimal buffer length is 2KB + RTE_PKTMBUF_HEADROOM.
 347  */
 348 #define RTE_MBUF_DEFAULT_DATAROOM       2048
 349 #define RTE_MBUF_DEFAULT_BUF_SIZE       \
 350         (RTE_MBUF_DEFAULT_DATAROOM + RTE_PKTMBUF_HEADROOM)
 351
 352 /* define a set of marker types that can be used to refer to set points in the
 353  * mbuf.
 354  */
 355 __extension__
 356 typedef void    *MARKER[0];   /**< generic marker for a point in a structure */
 357 __extension__
 358 typedef uint8_t  MARKER8[0];  /**< generic marker with 1B alignment */
 359 __extension__
 360 typedef uint64_t MARKER64[0];
 361 /**< marker that allows us to overwrite 8 bytes with a single assignment */
 362
 363 typedef struct {
 364         volatile int16_t cnt; /**< An internal counter value. */
 365 } rte_atomic16_t;
 366
 367 /**
 368  * The generic rte_mbuf, containing a packet mbuf.
 369  */
 370 struct rte_mbuf {
 371         MARKER cacheline0;
 372
 373         void *buf_addr;           /**< Virtual address of segment buffer. */
 374         /**
 375          * Physical address of segment buffer.
 376          * Force alignment to 8-bytes, so as to ensure we have the exact
 377          * same mbuf cacheline0 layout for 32-bit and 64-bit. This makes
 378          * working on vector drivers easier.
 379          */
 380         phys_addr_t buf_physaddr __rte_aligned(sizeof(phys_addr_t));
 381
 382         /* next 8 bytes are initialised on RX descriptor rearm */
 383         MARKER64 rearm_data;
 384         uint16_t data_off;
 385
 386         /**
 387          * Reference counter. Its size should at least equal to the size
 388          * of port field (16 bits), to support zero-copy broadcast.
 389          * It should only be accessed using the following functions:
 390          * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and
 391          * rte_mbuf_refcnt_set(). The functionality of these functions (atomic,
 392          * or non-atomic) is controlled by the CONFIG_RTE_MBUF_REFCNT_ATOMIC
 393          * config option.
 394          */
 395         RTE_STD_C11
 396         union {
 397                 rte_atomic16_t refcnt_atomic; /**< Atomically accessed refcnt */
 398                 uint16_t refcnt;
 399                 /**< Non-atomically accessed refcnt */
 400         };
 401         uint16_t nb_segs;         /**< Number of segments. */
 402
 403         /** Input port (16 bits to support more than 256 virtual ports). */
 404         uint16_t port;
 405
 406         uint64_t ol_flags;        /**< Offload features. */
 407
 408         /* remaining bytes are set on RX when pulling packet from descriptor */
 409         MARKER rx_descriptor_fields1;
 410
 411         /*
 412          * The packet type, which is the combination of outer/inner L2, L3, L4
 413          * and tunnel types. The packet_type is about data really present in the
 414          * mbuf. Example: if vlan stripping is enabled, a received vlan packet
 415          * would have RTE_PTYPE_L2_ETHER and not RTE_PTYPE_L2_VLAN because the
 416          * vlan is stripped from the data.
 417          */
 418         RTE_STD_C11
 419         union {
 420                 uint32_t packet_type; /**< L2/L3/L4 and tunnel information. */
 421                 struct {
 422                         uint32_t l2_type:4; /**< (Outer) L2 type. */
 423                         uint32_t l3_type:4; /**< (Outer) L3 type. */
 424                         uint32_t l4_type:4; /**< (Outer) L4 type. */
 425                         uint32_t tun_type:4; /**< Tunnel type. */
 426                         uint32_t inner_l2_type:4; /**< Inner L2 type. */
 427                         uint32_t inner_l3_type:4; /**< Inner L3 type. */
 428                         uint32_t inner_l4_type:4; /**< Inner L4 type. */
 429                 };
 430         };
 431
 432         uint32_t pkt_len;         /**< Total pkt len: sum of all segments. */
 433         uint16_t data_len;        /**< Amount of data in segment buffer. */
 434         /** VLAN TCI (CPU order), valid if PKT_RX_VLAN_STRIPPED is set. */
 435         uint16_t vlan_tci;
 436
 437         union {
 438                 uint32_t rss;     /**< RSS hash result if RSS enabled */
 439                 struct {
 440                         RTE_STD_C11
 441                         union {
 442                                 struct {
 443                                         uint16_t hash;
 444                                         uint16_t id;
 445                                 };
 446                                 uint32_t lo;
 447                                 /**< Second 4 flexible bytes */
 448                         };
 449                         uint32_t hi;
 450                         /**< First 4 flexible bytes or FD ID, dependent on
 451                          *   PKT_RX_FDIR_* flag in ol_flags.
 452                          */
 453                 } fdir;           /**< Filter identifier if FDIR enabled */
 454                 struct {
 455                         uint32_t lo;
 456                         uint32_t hi;
 457                 } sched;          /**< Hierarchical scheduler */
 458                 uint32_t usr;
 459                 /**< User defined tags. See rte_distributor_process() */
 460         } hash;                   /**< hash information */
 461
 462         /** Outer VLAN TCI (CPU order), valid if PKT_RX_QINQ_STRIPPED is set. */
 463         uint16_t vlan_tci_outer;
 464
 465         uint16_t buf_len;         /**< Length of segment buffer. */
 466
 467         /** Valid if PKT_RX_TIMESTAMP is set. The unit and time reference
 468          * are not normalized but are always the same for a given port.
 469          */
 470         uint64_t timestamp;
 471
 472         /* second cache line - fields only used in slow path or on TX */
 473         MARKER cacheline1 __rte_cache_min_aligned;
 474
 475         RTE_STD_C11
 476         union {
 477                 void *userdata;   /**< Can be used for external metadata */
 478                 uint64_t udata64; /**< Allow 8-byte userdata on 32-bit */
 479         };
 480
 481         struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
 482         struct rte_mbuf *next;    /**< Next segment of scattered packet. */
 483
 484         /* fields to support TX offloads */
 485         RTE_STD_C11
 486         union {
 487                 uint64_t tx_offload;       /**< combined for easy fetch */
 488                 __extension__
 489                 struct {
 490                         uint64_t l2_len:7;
 491                         /**< L2 (MAC) Header Length for non-tunneling pkt.
 492                          * Outer_L4_len + ... + Inner_L2_len for tunneling pkt.
 493                          */
 494                         uint64_t l3_len:9; /**< L3 (IP) Header Length. */
 495                         uint64_t l4_len:8; /**< L4 (TCP/UDP) Header Length. */
 496                         uint64_t tso_segsz:16; /**< TCP TSO segment size */
 497
 498                         /* fields for TX offloading of tunnels */
 499                         uint64_t outer_l3_len:9;
 500                         /**< Outer L3 (IP) Hdr Length. */
 501                         uint64_t outer_l2_len:7;
 502                         /**< Outer L2 (MAC) Hdr Length. */
 503
 504                         /* uint64_t unused:8; */
 505                 };
 506         };
 507
 508         /** Size of the application private data. In case of an indirect
 509          * mbuf, it stores the direct mbuf private data size.
 510          */
 511         uint16_t priv_size;
 512
 513         /** Timesync flags for use with IEEE1588. */
 514         uint16_t timesync;
 515
 516         /** Sequence number. See also rte_reorder_insert(). */
 517         uint32_t seqn;
 518
 519 } __rte_cache_aligned;
 520
 521
 522 /**
 523  * Returns TRUE if given mbuf is indirect, or FALSE otherwise.
 524  */
 525 #define RTE_MBUF_INDIRECT(mb)   ((mb)->ol_flags & IND_ATTACHED_MBUF)
 526
 527 /**
 528  * Returns TRUE if given mbuf is direct, or FALSE otherwise.
 529  */
 530 #define RTE_MBUF_DIRECT(mb)     (!RTE_MBUF_INDIRECT(mb))
 531
 532 /**
 533  * Private data in case of pktmbuf pool.
 534  *
 535  * A structure that contains some pktmbuf_pool-specific data that are
 536  * appended after the mempool structure (in private data).
 537  */
 538 struct rte_pktmbuf_pool_private {
 539         uint16_t mbuf_data_room_size; /**< Size of data space in each mbuf. */
 540         uint16_t mbuf_priv_size;      /**< Size of private area in each mbuf. */
 541 };
 542
 543 /**
 544  * A macro that points to an offset into the data in the mbuf.
 545  *
 546  * The returned pointer is cast to type t. Before using this
 547  * function, the user must ensure that the first segment is large
 548  * enough to accommodate its data.
 549  *
 550  * @param m
 551  *   The packet mbuf.
 552  * @param o
 553  *   The offset into the mbuf data.
 554  * @param t
 555  *   The type to cast the result into.
 556  */
 557 #define rte_pktmbuf_mtod_offset(m, t, o)        \
 558         ((t)((char *)(m)->buf_addr + (m)->data_off + (o)))
 559
 560 /**
 561  * A macro that points to the start of the data in the mbuf.
 562  *
 563  * The returned pointer is cast to type t. Before using this
 564  * function, the user must ensure that the first segment is large
 565  * enough to accommodate its data.
 566  *
 567  * @param m
 568  *   The packet mbuf.
 569  * @param t
 570  *   The type to cast the result into.
 571  */
 572 #define rte_pktmbuf_mtod(m, t) rte_pktmbuf_mtod_offset(m, t, 0)
 573
 574 #ifdef __cplusplus
 575 }
 576 #endif
 577
 578 #endif /* _MBUF_H_ */