sys/sys/mbuf.h

   1 /*
   2  * Copyright (c) 2004 The DragonFly Project.  All rights reserved.
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  *      @(#)mbuf.h      8.5 (Berkeley) 2/19/95
  36  * $FreeBSD: src/sys/sys/mbuf.h,v 1.44.2.17 2003/04/15 06:15:02 silby Exp $
  37  * $DragonFly: src/sys/sys/mbuf.h,v 1.48 2008/05/02 07:40:32 sephe Exp $
  38  */
  39
  40 #ifndef _SYS_MBUF_H_
  41 #define _SYS_MBUF_H_
  42
  43 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
  44
  45 #ifndef _SYS_TYPES_H_
  46 #include <sys/types.h>
  47 #endif
  48 #ifndef _SYS_PARAM_H_
  49 #include <sys/param.h>
  50 #endif
  51 #ifndef _SYS_QUEUE_H_
  52 #include <sys/queue.h>
  53 #endif
  54 #ifndef _NET_NETISR_H_
  55 #include <net/netisr.h>
  56 #endif
  57
  58 /*
  59  * Mbufs are of a single size, MSIZE (machine/param.h), which
  60  * includes overhead.  An mbuf may add a single "mbuf cluster" of size
  61  * MCLBYTES (also in machine/param.h), which has no additional overhead
  62  * and is used instead of the internal data area; this is done when
  63  * at least MINCLSIZE of data must be stored.
  64  */
  65 #define MLEN            (MSIZE - sizeof(struct m_hdr))  /* normal data len */
  66 #define MHLEN           (MLEN - sizeof(struct pkthdr))  /* data len w/pkthdr */
  67 #define MINCLSIZE       (MHLEN + 1)     /* smallest amount to put in cluster */
  68 #define M_MAXCOMPRESS   (MHLEN / 2)     /* max amount to copy for compression */
  69
  70 /*
  71  * Macros for type conversion:
  72  * mtod(m, t)   -- Convert mbuf pointer to data pointer of correct type.
  73  * mtocl(x) -   convert pointer within cluster to cluster index #
  74  * cltom(x) -   convert cluster # to ptr to beginning of cluster
  75  */
  76 #define mtod(m, t)      ((t)((m)->m_data))
  77
  78 /*
  79  * Header present at the beginning of every mbuf.
  80  */
  81 struct m_hdr {
  82         struct  mbuf *mh_next;          /* next buffer in chain */
  83         struct  mbuf *mh_nextpkt;       /* next chain in queue/record */
  84         caddr_t mh_data;                /* location of data */
  85         int     mh_len;                 /* amount of data in this mbuf */
  86         int     mh_flags;               /* flags; see below */
  87         short   mh_type;                /* type of data in this mbuf */
  88         short   mh_pad;                 /* padding */
  89         struct netmsg_packet mh_netmsg; /* hardware->proto stack msg */
  90 };
  91
  92 /*
  93  * Packet tag structure (see below for details).
  94  */
  95 struct m_tag {
  96         SLIST_ENTRY(m_tag)      m_tag_link;     /* List of packet tags */
  97         u_int16_t               m_tag_id;       /* Tag ID */
  98         u_int16_t               m_tag_len;      /* Length of data */
  99         u_int32_t               m_tag_cookie;   /* ABI/Module ID */
 100 };
 101
 102 SLIST_HEAD(packet_tags, m_tag);
 103
 104 /*
 105  * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
 106  *
 107  * Be careful: The fields have been carefully ordered to avoid hidden padding.
 108  *             Keep this in mind, when adding or removing fields!
 109  */
 110 struct pkthdr {
 111         struct  ifnet *rcvif;           /* rcv interface */
 112         int     len;                    /* total packet length */
 113         struct packet_tags tags;        /* list of packet tags */
 114
 115         /* variables for ip and tcp reassembly */
 116         void    *header;                /* pointer to packet header */
 117
 118         /* variables for hardware checksum */
 119         int     csum_flags;             /* flags regarding checksum */
 120         int     csum_data;              /* data field used by csum routines */
 121
 122         /* firewall flags */
 123         uint32_t fw_flags;              /* flags for PF */
 124
 125         /* variables for PF processing */
 126         uint16_t pf_tag;                /* PF tag id */
 127         uint8_t pf_routed;              /* PF routing counter */
 128
 129         /* variables for ALTQ processing */
 130         uint8_t ecn_af;                 /* address family for ECN */
 131         uint32_t altq_qid;              /* queue id */
 132         uint32_t altq_state_hash;       /* identifies 'connections' */
 133
 134         uint16_t ether_vlantag;         /* ethernet 802.1p+q vlan tag */
 135         uint16_t pad;                   /* explicit padding */
 136 };
 137
 138 /*
 139  * Description of external storage mapped into mbuf; valid only if M_EXT is set.
 140  */
 141 struct m_ext {
 142         caddr_t ext_buf;                /* start of buffer */
 143         void    (*ext_free)(void *);
 144         u_int   ext_size;               /* size of buffer, for ext_free */
 145         void    (*ext_ref)(void *);
 146         void    *ext_arg;
 147 };
 148
 149 /*
 150  * The core of the mbuf object along with some shortcut defines for
 151  * practical purposes.
 152  */
 153 struct mbuf {
 154         struct  m_hdr m_hdr;
 155         union {
 156                 struct {
 157                         struct  pkthdr MH_pkthdr;       /* M_PKTHDR set */
 158                         union {
 159                                 struct  m_ext MH_ext;   /* M_EXT set */
 160                                 char    MH_databuf[MHLEN];
 161                         } MH_dat;
 162                 } MH;
 163                 char    M_databuf[MLEN];                /* !M_PKTHDR, !M_EXT */
 164         } M_dat;
 165 };
 166 #define m_next          m_hdr.mh_next
 167 #define m_len           m_hdr.mh_len
 168 #define m_data          m_hdr.mh_data
 169 #define m_type          m_hdr.mh_type
 170 #define m_flags         m_hdr.mh_flags
 171 #define m_nextpkt       m_hdr.mh_nextpkt
 172 #define m_pkthdr        M_dat.MH.MH_pkthdr
 173 #define m_ext           M_dat.MH.MH_dat.MH_ext
 174 #define m_pktdat        M_dat.MH.MH_dat.MH_databuf
 175 #define m_dat           M_dat.M_databuf
 176
 177 /*
 178  * Code that uses m_act should be converted to use m_nextpkt
 179  * instead; m_act is historical and deprecated.
 180  */
 181 #define m_act           m_nextpkt
 182
 183 /*
 184  * mbuf flags.
 185  */
 186 #define M_EXT           0x0001  /* has associated external storage */
 187 #define M_PKTHDR        0x0002  /* start of record */
 188 #define M_EOR           0x0004  /* end of record */
 189 #define M_PROTO1        0x0008  /* protocol-specific */
 190 #define M_PROTO2        0x0010  /* protocol-specific */
 191 #define M_PROTO3        0x0020  /* protocol-specific */
 192 #define M_PROTO4        0x0040  /* protocol-specific */
 193 #define M_PROTO5        0x0080  /* protocol-specific */
 194
 195 /*
 196  * mbuf pkthdr flags (also stored in m_flags).
 197  */
 198 #define M_BCAST         0x0100  /* send/received as link-level broadcast */
 199 #define M_MCAST         0x0200  /* send/received as link-level multicast */
 200 #define M_FRAG          0x0400  /* packet is a fragment of a larger packet */
 201 #define M_FIRSTFRAG     0x0800  /* packet is first fragment */
 202 #define M_LASTFRAG      0x1000  /* packet is last fragment */
 203 #define M_CLCACHE       0x2000  /* mbuf allocated from the cluster cache */
 204 #define M_EXT_CLUSTER   0x4000  /* standard cluster else special */
 205 #define M_PHCACHE       0x8000  /* mbuf allocated from the pkt header cache */
 206 #define M_NOTIFICATION  0x10000 /* notification event */
 207 #define M_VLANTAG       0x20000 /* ether_vlantag is valid */
 208
 209 /*
 210  * Flags copied when copying m_pkthdr.
 211  */
 212 #define M_COPYFLAGS     (M_PKTHDR|M_EOR|M_PROTO1|M_PROTO1|M_PROTO2|M_PROTO3 | \
 213                             M_PROTO4|M_PROTO5|M_BCAST|M_MCAST|M_FRAG | \
 214                             M_FIRSTFRAG|M_LASTFRAG|M_VLANTAG)
 215
 216 /*
 217  * Flags indicating hw checksum support and sw checksum requirements.
 218  */
 219 #define CSUM_IP                 0x0001          /* will csum IP */
 220 #define CSUM_TCP                0x0002          /* will csum TCP */
 221 #define CSUM_UDP                0x0004          /* will csum UDP */
 222 #define CSUM_IP_FRAGS           0x0008          /* will csum IP fragments */
 223 #define CSUM_FRAGMENT           0x0010          /* will do IP fragmentation */
 224
 225 #define CSUM_IP_CHECKED         0x0100          /* did csum IP */
 226 #define CSUM_IP_VALID           0x0200          /*   ... the csum is valid */
 227 #define CSUM_DATA_VALID         0x0400          /* csum_data field is valid */
 228 #define CSUM_PSEUDO_HDR         0x0800          /* csum_data has pseudo hdr */
 229 #define CSUM_FRAG_NOT_CHECKED   0x1000          /* did _not_ csum fragment
 230                                                  * NB: This flag is only used
 231                                                  * by IP defragmenter.
 232                                                  */
 233
 234 #define CSUM_DELAY_DATA         (CSUM_TCP | CSUM_UDP)
 235 #define CSUM_DELAY_IP           (CSUM_IP)       /* XXX add ipv6 here too? */
 236
 237 /*
 238  * Flags indicating PF processing status
 239  */
 240 #define FW_MBUF_GENERATED       0x00000001
 241 #define PF_MBUF_TAGGED          0x00000002      /* pf_tag field is valid */
 242 #define PF_MBUF_ROUTED          0x00000004      /* pf_routed field is valid */
 243 #define PF_MBUF_TRANSLATE_LOCALHOST                                     \
 244                                 0x00000008
 245 #define PF_MBUF_FRAGCACHE       0x00000010
 246 #define ALTQ_MBUF_TAGGED        0x00000020      /* altq_qid is valid */
 247 #define PF_MBUF_GENERATED       FW_MBUF_GENERATED
 248 #define IPFW_MBUF_GENERATED     FW_MBUF_GENERATED
 249 #define DUMMYNET_MBUF_TAGGED    0x00000080
 250 #define ALTQ_MBUF_STATE_HASHED  0x00000100
 251
 252 /*
 253  * mbuf types.
 254  */
 255 #define MT_FREE         0       /* should be on free list */
 256 #define MT_DATA         1       /* dynamic (data) allocation */
 257 #define MT_HEADER       2       /* packet header */
 258 #define MT_SONAME       3       /* socket name */
 259 #define MT_TAG          4       /* volatile metadata associated to pkts */
 260 #define MT_CONTROL      5       /* extra-data protocol message */
 261 #define MT_OOBDATA      6       /* expedited data  */
 262 #define MT_NTYPES       7       /* number of mbuf types for mbtypes[] */
 263
 264 struct mbuf_chain {
 265         struct mbuf     *mc_head;
 266         struct mbuf     *mc_tail;
 267 };
 268
 269 /*
 270  * General mbuf allocator statistics structure.
 271  */
 272 struct mbstat {
 273         u_long  m_mbufs;        /* mbufs obtained from page pool */
 274         u_long  m_clusters;     /* clusters obtained from page pool */
 275         u_long  m_spare;        /* spare field */
 276         u_long  m_clfree;       /* free clusters */
 277         u_long  m_drops;        /* times failed to find space */
 278         u_long  m_wait;         /* times waited for space */
 279         u_long  m_drain;        /* times drained protocols for space */
 280         u_long  m_mcfail;       /* times m_copym failed */
 281         u_long  m_mpfail;       /* times m_pullup failed */
 282         u_long  m_msize;        /* length of an mbuf */
 283         u_long  m_mclbytes;     /* length of an mbuf cluster */
 284         u_long  m_minclsize;    /* min length of data to allocate a cluster */
 285         u_long  m_mlen;         /* length of data in an mbuf */
 286         u_long  m_mhlen;        /* length of data in a header mbuf */
 287 };
 288
 289 /*
 290  * Flags specifying how an allocation should be made.
 291  */
 292
 293 #define MB_DONTWAIT     0x4
 294 #define MB_TRYWAIT      0x8
 295 #define MB_WAIT         MB_TRYWAIT
 296
 297 /*
 298  * Mbuf to Malloc Flag Conversion.
 299  */
 300 #define MBTOM(how)      ((how) & MB_TRYWAIT ? M_WAITOK : M_NOWAIT)
 301
 302 /*
 303  * These are identifying numbers passed to the m_mballoc_wait function,
 304  * allowing us to determine whether the call came from an MGETHDR or
 305  * an MGET.
 306  */
 307 #define MGETHDR_C      1
 308 #define MGET_C         2
 309
 310 /*
 311  * mbuf allocation/deallocation macros (YYY deprecated, too big):
 312  *
 313  *      MGET(struct mbuf *m, int how, int type)
 314  * allocates an mbuf and initializes it to contain internal data.
 315  *
 316  *      MGETHDR(struct mbuf *m, int how, int type)
 317  * allocates an mbuf and initializes it to contain a packet header
 318  * and internal data.
 319  */
 320 #define MGET(m, how, type) do {                                         \
 321         (m) = m_get((how), (type));                                     \
 322 } while (0)
 323
 324 #define MGETHDR(m, how, type) do {                                      \
 325         (m) = m_gethdr((how), (type));                                  \
 326 } while (0)
 327
 328 /*
 329  * MCLGET adds such clusters to a normal mbuf.  The flag M_EXT is set upon
 330  * success.
 331  * Deprecated.  Use m_getcl() or m_getl() instead.
 332  */
 333 #define MCLGET(m, how) do {                                             \
 334         m_mclget((m), (how));                                           \
 335 } while (0)
 336
 337 /*
 338  * NB: M_COPY_PKTHDR is deprecated; use either M_MOVE_PKTHDR
 339  *     or m_dup_pkthdr.
 340  */
 341 /*
 342  * Move mbuf pkthdr from "from" to "to".
 343  * from should have M_PKTHDR set, and to must be empty.
 344  * from no longer has a pkthdr after this operation.
 345  */
 346 #define M_MOVE_PKTHDR(_to, _from)       m_move_pkthdr((_to), (_from))
 347
 348 /*
 349  * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
 350  * an object of the specified size at the end of the mbuf, longword aligned.
 351  */
 352 #define M_ALIGN(m, len) do {                                            \
 353         (m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);            \
 354 } while (0)
 355
 356 /*
 357  * As above, for mbufs allocated with m_gethdr/MGETHDR
 358  * or initialized by M_COPY_PKTHDR.
 359  */
 360 #define MH_ALIGN(m, len) do {                                           \
 361         (m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);           \
 362 } while (0)
 363
 364 /*
 365  * Check if we can write to an mbuf.
 366  */
 367 #define M_EXT_WRITABLE(m)       (m_sharecount(m) == 1)
 368 #define M_WRITABLE(m)           (!((m)->m_flags & M_EXT) || M_EXT_WRITABLE(m))
 369
 370 /*
 371  * Check if the supplied mbuf has a packet header, or else panic.
 372  */
 373 #define M_ASSERTPKTHDR(m)                                               \
 374         KASSERT(m != NULL && m->m_flags & M_PKTHDR,                     \
 375                 ("%s: invalid mbuf or no mbuf packet header!", __func__))
 376
 377 /*
 378  * Compute the amount of space available before the current start of data.
 379  * The M_EXT_WRITABLE() is a temporary, conservative safety measure: the burden
 380  * of checking writability of the mbuf data area rests solely with the caller.
 381  */
 382 #define M_LEADINGSPACE(m)                                               \
 383         ((m)->m_flags & M_EXT ?                                         \
 384             (M_EXT_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0): \
 385             (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :     \
 386             (m)->m_data - (m)->m_dat)
 387
 388 /*
 389  * Compute the amount of space available after the end of data in an mbuf.
 390  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
 391  * of checking writability of the mbuf data area rests solely with the caller.
 392  */
 393 #define M_TRAILINGSPACE(m)                                              \
 394         ((m)->m_flags & M_EXT ?                                         \
 395             (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size   \
 396                 - ((m)->m_data + (m)->m_len) : 0) :                     \
 397             &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))
 398
 399 /*
 400  * Arrange to prepend space of size plen to mbuf m.
 401  * If a new mbuf must be allocated, how specifies whether to wait.
 402  * If how is MB_DONTWAIT and allocation fails, the original mbuf chain
 403  * is freed and m is set to NULL.
 404  */
 405 #define M_PREPEND(m, plen, how) do {                                    \
 406         struct mbuf **_mmp = &(m);                                      \
 407         struct mbuf *_mm = *_mmp;                                       \
 408         int _mplen = (plen);                                            \
 409         int __mhow = (how);                                             \
 410                                                                         \
 411         if (M_LEADINGSPACE(_mm) >= _mplen) {                            \
 412                 _mm->m_data -= _mplen;                                  \
 413                 _mm->m_len += _mplen;                                   \
 414         } else                                                          \
 415                 _mm = m_prepend(_mm, _mplen, __mhow);                   \
 416         if (_mm != NULL && _mm->m_flags & M_PKTHDR)                     \
 417                 _mm->m_pkthdr.len += _mplen;                            \
 418         *_mmp = _mm;                                                    \
 419 } while (0)
 420
 421 /* Length to m_copy to copy all. */
 422 #define M_COPYALL       1000000000
 423
 424 /* Compatibility with 4.3 */
 425 #define m_copy(m, o, l) m_copym((m), (o), (l), MB_DONTWAIT)
 426
 427 #ifdef _KERNEL
 428 extern  u_int            m_clalloc_wid; /* mbuf cluster wait count */
 429 extern  u_int            m_mballoc_wid; /* mbuf wait count */
 430 extern  int              max_linkhdr;   /* largest link-level header */
 431 extern  int              max_protohdr;  /* largest protocol header */
 432 extern  int              max_hdr;       /* largest link+protocol header */
 433 extern  int              max_datalen;   /* MHLEN - max_hdr */
 434 extern  int              mbuf_wait;     /* mbuf sleep time */
 435 extern  int              nmbclusters;
 436 extern  int              nmbufs;
 437
 438 struct uio;
 439
 440 void             m_adj(struct mbuf *, int);
 441 void             m_cat(struct mbuf *, struct mbuf *);
 442 u_int            m_countm(struct mbuf *m, struct mbuf **lastm, u_int *mbcnt);
 443 void             m_copyback(struct mbuf *, int, int, caddr_t);
 444 void             m_copydata(const struct mbuf *, int, int, caddr_t);
 445 struct  mbuf    *m_copym(const struct mbuf *, int, int, int);
 446 struct  mbuf    *m_copypacket(struct mbuf *, int);
 447 struct  mbuf    *m_defrag(struct mbuf *, int);
 448 struct  mbuf    *m_defrag_nofree(struct mbuf *, int);
 449 struct  mbuf    *m_devget(char *, int, int, struct ifnet *,
 450                   void (*copy)(volatile const void *, volatile void *, size_t));
 451 struct  mbuf    *m_dup(struct mbuf *, int);
 452 int              m_dup_pkthdr(struct mbuf *, const struct mbuf *, int);
 453 struct  mbuf    *m_free(struct mbuf *);
 454 void             m_freem(struct mbuf *);
 455 struct  mbuf    *m_get(int, int);
 456 struct  mbuf    *m_getc(int len, int how, int type);
 457 struct  mbuf    *m_getcl(int how, short type, int flags);
 458 struct  mbuf    *m_getclr(int, int);
 459 struct  mbuf    *m_gethdr(int, int);
 460 struct  mbuf    *m_getm(struct mbuf *, int, int, int);
 461 struct  mbuf    *m_last(struct mbuf *m);
 462 u_int            m_lengthm(struct mbuf *m, struct mbuf **lastm);
 463 void             m_move_pkthdr(struct mbuf *, struct mbuf *);
 464 struct  mbuf    *m_prepend(struct mbuf *, int, int);
 465 void             m_print(const struct mbuf *m);
 466 struct  mbuf    *m_pulldown(struct mbuf *, int, int, int *);
 467 struct  mbuf    *m_pullup(struct mbuf *, int);
 468 struct  mbuf    *m_split(struct mbuf *, int, int);
 469 struct  mbuf    *m_uiomove(struct uio *);
 470 void            m_mclget(struct mbuf *m, int how);
 471 int             m_sharecount(struct mbuf *m);
 472 void            m_chtype(struct mbuf *m, int type);
 473
 474 #ifdef MBUF_DEBUG
 475 void            mbuftrackid(struct mbuf *, int);
 476 #else
 477 #define mbuftrackid(m, id)      /* empty */
 478 #endif
 479
 480 /*
 481  * Allocate the right type of mbuf for the desired total length.
 482  * The mbuf returned does not necessarily cover the entire requested length.
 483  * This function follows mbuf chaining policy of allowing MINCLSIZE
 484  * amount of chained mbufs.
 485  */
 486 static __inline struct mbuf *
 487 m_getl(int len, int how, int type, int flags, int *psize)
 488 {
 489         struct mbuf *m;
 490         int size;
 491
 492         if (len >= MINCLSIZE) {
 493                 m = m_getcl(how, type, flags);
 494                 size = MCLBYTES;
 495         } else if (flags & M_PKTHDR) {
 496                 m = m_gethdr(how, type);
 497                 size = MHLEN;
 498         } else {
 499                 m = m_get(how, type);
 500                 size = MLEN;
 501         }
 502         if (psize != NULL)
 503                 *psize = size;
 504         return (m);
 505 }
 506
 507 /*
 508  * Get a single mbuf that covers the requested number of bytes.
 509  * This function does not create mbuf chains.  It explicitly marks
 510  * places in the code that abuse mbufs for contiguous data buffers.
 511  */
 512 static __inline struct mbuf *
 513 m_getb(int len, int how, int type, int flags)
 514 {
 515         struct mbuf *m;
 516         int mbufsize = (flags & M_PKTHDR) ? MHLEN : MLEN;
 517
 518         if (len > mbufsize)
 519                 m = m_getcl(how, type, flags);
 520         else if (flags & M_PKTHDR)
 521                 m = m_gethdr(how, type);
 522         else
 523                 m = m_get(how, type);
 524         return (m);
 525 }
 526
 527 /*
 528  * Packets may have annotations attached by affixing a list
 529  * of "packet tags" to the pkthdr structure.  Packet tags are
 530  * dynamically allocated semi-opaque data structures that have
 531  * a fixed header (struct m_tag) that specifies the size of the
 532  * memory block and a <cookie,type> pair that identifies it.
 533  * The cookie is a 32-bit unique unsigned value used to identify
 534  * a module or ABI.  By convention this value is chose as the
 535  * date+time that the module is created, expressed as the number of
 536  * seconds since the epoch (e.g. using date -u +'%s').  The type value
 537  * is an ABI/module-specific value that identifies a particular annotation
 538  * and is private to the module.  For compatibility with systems
 539  * like openbsd that define packet tags w/o an ABI/module cookie,
 540  * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
 541  * m_tag_find compatibility shim functions and several tag types are
 542  * defined below.  Users that do not require compatibility should use
 543  * a private cookie value so that packet tag-related definitions
 544  * can be maintained privately.
 545  *
 546  * Note that the packet tag returned by m_tag_alloc has the default
 547  * memory alignment implemented by kmalloc.  To reference private data
 548  * one can use a construct like:
 549  *
 550  *      struct m_tag *mtag = m_tag_alloc(...);
 551  *      struct foo *p = m_tag_data(mtag);
 552  *
 553  * if the alignment of struct m_tag is sufficient for referencing members
 554  * of struct foo.  Otherwise it is necessary to embed struct m_tag within
 555  * the private data structure to insure proper alignment; e.g.
 556  *
 557  *      struct foo {
 558  *              struct m_tag    tag;
 559  *              ...
 560  *      };
 561  *      struct foo *p = (struct foo *)m_tag_alloc(...);
 562  *      struct m_tag *mtag = &p->tag;
 563  */
 564
 565 #define PACKET_TAG_NONE                         0  /* Nadda */
 566
 567 /* Packet tag for use with PACKET_ABI_COMPAT */
 568 #define PACKET_TAG_IPSEC_IN_DONE                1  /* IPsec applied, in */
 569 /* struct tdb_indent */
 570 #define PACKET_TAG_IPSEC_OUT_DONE               2  /* IPsec applied, out */
 571 /* struct tdb_indent */
 572 #define PACKET_TAG_IPSEC_IN_CRYPTO_DONE         3  /* NIC IPsec crypto done */
 573 /* struct tdb_indent, never added */
 574 #define PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED      4  /* NIC IPsec crypto req'ed */
 575 /* struct tdb_indent, never added */
 576 #define PACKET_TAG_IPSEC_PENDING_TDB            5  /* Reminder to do IPsec */
 577 /* struct tdb_indent, never added */
 578 #define PACKET_TAG_ENCAP                        6 /* Encap.  processing */
 579 /* struct ifnet *, the GIF interface */
 580 #define PACKET_TAG_IPSEC_HISTORY                7 /* IPSEC history */
 581 /* struct ipsec_history */
 582 #define PACKET_TAG_IPV6_INPUT                   8 /* IPV6 input processing */
 583 /* struct ip6aux */
 584 #define PACKET_TAG_IPFW_DIVERT                  9 /* divert info */
 585 /* uint16_t */
 586 #define PACKET_TAG_DUMMYNET                     15 /* dummynet info */
 587 /* struct dn_pkt */
 588 #define PACKET_TAG_CARP                         28 /* CARP info */
 589
 590 /*
 591  * As a temporary and low impact solution to replace the even uglier
 592  * approach used so far in some parts of the network stack (which relies
 593  * on global variables), packet tag-like annotations are stored in MT_TAG
 594  * mbufs (or lookalikes) prepended to the actual mbuf chain.
 595  *
 596  *      m_type  = MT_TAG
 597  *      m_flags = m_tag_id
 598  *      m_next  = next buffer in chain.
 599  *
 600  * BE VERY CAREFUL not to pass these blocks to the mbuf handling routines.
 601  */
 602 #define _m_tag_id       m_hdr.mh_flags
 603
 604 /* Packet tags used in the FreeBSD network stack */
 605 #define PACKET_TAG_IPFORWARD                    18 /* ipforward info */
 606 /* struct sockaddr_in * as m_data */
 607
 608 /* Packet tag routines */
 609 struct  m_tag   *m_tag_alloc(u_int32_t, int, int, int);
 610 void             m_tag_free(struct m_tag *);
 611 void             m_tag_prepend(struct mbuf *, struct m_tag *);
 612 void             m_tag_unlink(struct mbuf *, struct m_tag *);
 613 void             m_tag_delete(struct mbuf *, struct m_tag *);
 614 void             m_tag_delete_chain(struct mbuf *);
 615 struct  m_tag   *m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
 616 struct  m_tag   *m_tag_copy(struct m_tag *, int);
 617 int              m_tag_copy_chain(struct mbuf *, const struct mbuf *, int);
 618 void             m_tag_init(struct mbuf *);
 619 struct  m_tag   *m_tag_first(struct mbuf *);
 620 struct  m_tag   *m_tag_next(struct mbuf *, struct m_tag *);
 621
 622 /* these are for openbsd compatibility */
 623 #define MTAG_ABI_COMPAT         0               /* compatibility ABI */
 624
 625 static __inline void *
 626 m_tag_data(struct m_tag *tag)
 627 {
 628         return ((void *)(tag + 1));
 629 }
 630
 631 static __inline struct m_tag *
 632 m_tag_get(int type, int length, int wait)
 633 {
 634         return m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait);
 635 }
 636
 637 static __inline struct m_tag *
 638 m_tag_find(struct mbuf *m, int type, struct m_tag *start)
 639 {
 640         return m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
 641 }
 642
 643 #endif  /* _KERNEL */
 644
 645 #endif  /* _KERNEL || _KERNEL_STRUCTURES */
 646 #endif  /* !_SYS_MBUF_H_ */