The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/sys/mbuf.h

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)mbuf.h      8.5 (Berkeley) 2/19/95
   30  * $FreeBSD: releng/6.0/sys/sys/mbuf.h 148937 2005-08-10 17:02:29Z sam $
   31  */
   32 
   33 #ifndef _SYS_MBUF_H_
   34 #define _SYS_MBUF_H_
   35 
   36 /* XXX: These includes suck. Sorry! */
   37 #include <sys/queue.h>
   38 #ifdef _KERNEL
   39 #include <sys/systm.h>
   40 #include <vm/uma.h>
   41 #ifdef WITNESS
   42 #include <sys/lock.h>
   43 #endif
   44 #endif
   45 
   46 /*
   47  * Mbufs are of a single size, MSIZE (sys/param.h), which
   48  * includes overhead.  An mbuf may add a single "mbuf cluster" of size
   49  * MCLBYTES (also in sys/param.h), which has no additional overhead
   50  * and is used instead of the internal data area; this is done when
   51  * at least MINCLSIZE of data must be stored.  Additionally, it is possible
   52  * to allocate a separate buffer externally and attach it to the mbuf in
   53  * a way similar to that of mbuf clusters.
   54  */
   55 #define MLEN            (MSIZE - sizeof(struct m_hdr))  /* normal data len */
   56 #define MHLEN           (MLEN - sizeof(struct pkthdr))  /* data len w/pkthdr */
   57 #define MINCLSIZE       (MHLEN + 1)     /* smallest amount to put in cluster */
   58 #define M_MAXCOMPRESS   (MHLEN / 2)     /* max amount to copy for compression */
   59 
   60 #ifdef _KERNEL
   61 /*-
   62  * Macros for type conversion:
   63  * mtod(m, t)   -- Convert mbuf pointer to data pointer of correct type.
   64  * dtom(x)      -- Convert data pointer within mbuf to mbuf pointer (XXX).
   65  */
   66 #define mtod(m, t)      ((t)((m)->m_data))
   67 #define dtom(x)         ((struct mbuf *)((intptr_t)(x) & ~(MSIZE-1)))
   68 
   69 /*
   70  * Argument structure passed to UMA routines during mbuf and packet
   71  * allocations.
   72  */
   73 struct mb_args {
   74         int     flags;  /* Flags for mbuf being allocated */
   75         short   type;   /* Type of mbuf being allocated */
   76 };
   77 #endif /* _KERNEL */
   78 
   79 /*
   80  * Header present at the beginning of every mbuf.
   81  */
   82 struct m_hdr {
   83         struct  mbuf *mh_next;          /* next buffer in chain */
   84         struct  mbuf *mh_nextpkt;       /* next chain in queue/record */
   85         caddr_t mh_data;                /* location of data */
   86         int     mh_len;                 /* amount of data in this mbuf */
   87         int     mh_flags;               /* flags; see below */
   88         short   mh_type;                /* type of data in this mbuf */
   89 };
   90 
   91 /*
   92  * Packet tag structure (see below for details).
   93  */
   94 struct m_tag {
   95         SLIST_ENTRY(m_tag)      m_tag_link;     /* List of packet tags */
   96         u_int16_t               m_tag_id;       /* Tag ID */
   97         u_int16_t               m_tag_len;      /* Length of data */
   98         u_int32_t               m_tag_cookie;   /* ABI/Module ID */
   99         void                    (*m_tag_free)(struct m_tag *);
  100 };
  101 
  102 /*
  103  * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
  104  */
  105 struct pkthdr {
  106         struct  ifnet *rcvif;           /* rcv interface */
  107         int     len;                    /* total packet length */
  108         /* variables for ip and tcp reassembly */
  109         void    *header;                /* pointer to packet header */
  110         /* variables for hardware checksum */
  111         int     csum_flags;             /* flags regarding checksum */
  112         int     csum_data;              /* data field used by csum routines */
  113         SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
  114 };
  115 
  116 /*
  117  * Description of external storage mapped into mbuf; valid only if M_EXT is set.
  118  */
  119 struct m_ext {
  120         caddr_t ext_buf;                /* start of buffer */
  121         void    (*ext_free)             /* free routine if not the usual */
  122                     (void *, void *);
  123         void    *ext_args;              /* optional argument pointer */
  124         u_int   ext_size;               /* size of buffer, for ext_free */
  125         volatile u_int *ref_cnt;        /* pointer to ref count info */
  126         int     ext_type;               /* type of external storage */
  127 };
  128 
  129 /*
  130  * The core of the mbuf object along with some shortcut defines for
  131  * practical purposes.
  132  */
  133 struct mbuf {
  134         struct  m_hdr m_hdr;
  135         union {
  136                 struct {
  137                         struct  pkthdr MH_pkthdr;       /* M_PKTHDR set */
  138                         union {
  139                                 struct  m_ext MH_ext;   /* M_EXT set */
  140                                 char    MH_databuf[MHLEN];
  141                         } MH_dat;
  142                 } MH;
  143                 char    M_databuf[MLEN];                /* !M_PKTHDR, !M_EXT */
  144         } M_dat;
  145 };
  146 #define m_next          m_hdr.mh_next
  147 #define m_len           m_hdr.mh_len
  148 #define m_data          m_hdr.mh_data
  149 #define m_type          m_hdr.mh_type
  150 #define m_flags         m_hdr.mh_flags
  151 #define m_nextpkt       m_hdr.mh_nextpkt
  152 #define m_act           m_nextpkt
  153 #define m_pkthdr        M_dat.MH.MH_pkthdr
  154 #define m_ext           M_dat.MH.MH_dat.MH_ext
  155 #define m_pktdat        M_dat.MH.MH_dat.MH_databuf
  156 #define m_dat           M_dat.M_databuf
  157 
  158 /*
  159  * mbuf flags.
  160  */
  161 #define M_EXT           0x0001  /* has associated external storage */
  162 #define M_PKTHDR        0x0002  /* start of record */
  163 #define M_EOR           0x0004  /* end of record */
  164 #define M_RDONLY        0x0008  /* associated data is marked read-only */
  165 #define M_PROTO1        0x0010  /* protocol-specific */
  166 #define M_PROTO2        0x0020  /* protocol-specific */
  167 #define M_PROTO3        0x0040  /* protocol-specific */
  168 #define M_PROTO4        0x0080  /* protocol-specific */
  169 #define M_PROTO5        0x0100  /* protocol-specific */
  170 #define M_SKIP_FIREWALL 0x4000  /* skip firewall processing */
  171 #define M_FREELIST      0x8000  /* mbuf is on the free list */
  172 
  173 /*
  174  * mbuf pkthdr flags (also stored in m_flags).
  175  */
  176 #define M_BCAST         0x0200  /* send/received as link-level broadcast */
  177 #define M_MCAST         0x0400  /* send/received as link-level multicast */
  178 #define M_FRAG          0x0800  /* packet is a fragment of a larger packet */
  179 #define M_FIRSTFRAG     0x1000  /* packet is first fragment */
  180 #define M_LASTFRAG      0x2000  /* packet is last fragment */
  181 #define M_VLANTAG       0x10000 /* packet has VLAN tag attached */
  182 
  183 /*
  184  * External buffer types: identify ext_buf type.
  185  */
  186 #define EXT_CLUSTER     1       /* mbuf cluster */
  187 #define EXT_SFBUF       2       /* sendfile(2)'s sf_bufs */
  188 #define EXT_PACKET      3       /* came out of Packet zone */
  189 #define EXT_NET_DRV     100     /* custom ext_buf provided by net driver(s) */
  190 #define EXT_MOD_TYPE    200     /* custom module's ext_buf type */
  191 #define EXT_DISPOSABLE  300     /* can throw this buffer away w/page flipping */
  192 #define EXT_EXTREF      400     /* has externally maintained ref_cnt ptr */
  193 
  194 /*
  195  * Flags copied when copying m_pkthdr.
  196  */
  197 #define M_COPYFLAGS     (M_PKTHDR|M_EOR|M_RDONLY|M_PROTO1|M_PROTO1|M_PROTO2|\
  198                             M_PROTO3|M_PROTO4|M_PROTO5|M_SKIP_FIREWALL|\
  199                             M_BCAST|M_MCAST|M_FRAG|M_FIRSTFRAG|M_LASTFRAG|\
  200                             M_VLANTAG)
  201 
  202 /*
  203  * Flags indicating hw checksum support and sw checksum requirements.
  204  */
  205 #define CSUM_IP                 0x0001          /* will csum IP */
  206 #define CSUM_TCP                0x0002          /* will csum TCP */
  207 #define CSUM_UDP                0x0004          /* will csum UDP */
  208 #define CSUM_IP_FRAGS           0x0008          /* will csum IP fragments */
  209 #define CSUM_FRAGMENT           0x0010          /* will do IP fragmentation */
  210 
  211 #define CSUM_IP_CHECKED         0x0100          /* did csum IP */
  212 #define CSUM_IP_VALID           0x0200          /*   ... the csum is valid */
  213 #define CSUM_DATA_VALID         0x0400          /* csum_data field is valid */
  214 #define CSUM_PSEUDO_HDR         0x0800          /* csum_data has pseudo hdr */
  215 
  216 #define CSUM_DELAY_DATA         (CSUM_TCP | CSUM_UDP)
  217 #define CSUM_DELAY_IP           (CSUM_IP)       /* XXX add ipv6 here too? */
  218 
  219 /*
  220  * mbuf types.
  221  */
  222 #define MT_NOTMBUF      0       /* USED INTERNALLY ONLY! Object is not mbuf */
  223 #define MT_DATA         1       /* dynamic (data) allocation */
  224 #define MT_HEADER       2       /* packet header */
  225 #if 0
  226 #define MT_SOCKET       3       /* socket structure */
  227 #define MT_PCB          4       /* protocol control block */
  228 #define MT_RTABLE       5       /* routing tables */
  229 #define MT_HTABLE       6       /* IMP host tables */
  230 #define MT_ATABLE       7       /* address resolution tables */
  231 #endif
  232 #define MT_SONAME       8       /* socket name */
  233 #if 0
  234 #define MT_SOOPTS       10      /* socket options */
  235 #endif
  236 #define MT_FTABLE       11      /* fragment reassembly header */
  237 #if 0
  238 #define MT_RIGHTS       12      /* access rights */
  239 #define MT_IFADDR       13      /* interface address */
  240 #endif
  241 #define MT_CONTROL      14      /* extra-data protocol message */
  242 #define MT_OOBDATA      15      /* expedited data  */
  243 #define MT_NTYPES       16      /* number of mbuf types for mbtypes[] */
  244 
  245 /*
  246  * General mbuf allocator statistics structure.
  247  */
  248 struct mbstat {
  249         u_long  m_mbufs;        /* XXX */
  250         u_long  m_mclusts;      /* XXX */
  251 
  252         u_long  m_drain;        /* times drained protocols for space */
  253         u_long  m_mcfail;       /* XXX: times m_copym failed */
  254         u_long  m_mpfail;       /* XXX: times m_pullup failed */
  255         u_long  m_msize;        /* length of an mbuf */
  256         u_long  m_mclbytes;     /* length of an mbuf cluster */
  257         u_long  m_minclsize;    /* min length of data to allocate a cluster */
  258         u_long  m_mlen;         /* length of data in an mbuf */
  259         u_long  m_mhlen;        /* length of data in a header mbuf */
  260 
  261         /* Number of mbtypes (gives # elems in mbtypes[] array: */
  262         short   m_numtypes;
  263 
  264         /* XXX: Sendfile stats should eventually move to their own struct */
  265         u_long  sf_iocnt;       /* times sendfile had to do disk I/O */
  266         u_long  sf_allocfail;   /* times sfbuf allocation failed */
  267         u_long  sf_allocwait;   /* times sfbuf allocation had to wait */
  268 };
  269 
  270 /*
  271  * Flags specifying how an allocation should be made.
  272  *
  273  * The flag to use is as follows:
  274  * - M_DONTWAIT or M_NOWAIT from an interrupt handler to not block allocation.
  275  * - M_WAIT or M_WAITOK or M_TRYWAIT from wherever it is safe to block.
  276  *
  277  * M_DONTWAIT/M_NOWAIT means that we will not block the thread explicitly
  278  * and if we cannot allocate immediately we may return NULL,
  279  * whereas M_WAIT/M_WAITOK/M_TRYWAIT means that if we cannot allocate
  280  * resources we will block until they are available, and thus never
  281  * return NULL.
  282  *
  283  * XXX Eventually just phase this out to use M_WAITOK/M_NOWAIT.
  284  */
  285 #define MBTOM(how)      (how)
  286 #define M_DONTWAIT      M_NOWAIT
  287 #define M_TRYWAIT       M_WAITOK
  288 #define M_WAIT          M_WAITOK
  289 
  290 /*
  291  * String names of mbuf-related UMA(9) and malloc(9) types.  Exposed to
  292  * !_KERNEL so that monitoring tools can look up the zones with
  293  * libmemstat(3).
  294  */
  295 #define MBUF_MEM_NAME           "mbuf"
  296 #define MBUF_CLUSTER_MEM_NAME   "mbuf_cluster"
  297 #define MBUF_PACKET_MEM_NAME    "mbuf_packet"
  298 #define MBUF_TAG_MEM_NAME       "mbuf_tag"
  299 
  300 #ifdef _KERNEL
  301 /*-
  302  * mbuf external reference count management macros.
  303  *
  304  * MEXT_IS_REF(m): true if (m) is not the only mbuf referencing
  305  *     the external buffer ext_buf.
  306  *
  307  * MEXT_REM_REF(m): remove reference to m_ext object.
  308  *
  309  * MEXT_ADD_REF(m): add reference to m_ext object already
  310  *     referred to by (m).  XXX Note that it is VERY important that you
  311  *     always set the second mbuf's m_ext.ref_cnt to point to the first
  312  *     one's (i.e., n->m_ext.ref_cnt = m->m_ext.ref_cnt) AFTER you run
  313  *     MEXT_ADD_REF(m).  This is because m might have a lazy initialized
  314  *     ref_cnt (NULL) before this is run and it will only be looked up
  315  *     from here.  We should make MEXT_ADD_REF() always take two mbufs
  316  *     as arguments so that it can take care of this itself.
  317  */
  318 #define MEXT_IS_REF(m)  (((m)->m_ext.ref_cnt != NULL)                   \
  319     && (*((m)->m_ext.ref_cnt) > 1))
  320 
  321 #define MEXT_REM_REF(m) do {                                            \
  322         KASSERT((m)->m_ext.ref_cnt != NULL, ("m_ext refcnt lazy NULL")); \
  323         KASSERT(*((m)->m_ext.ref_cnt) > 0, ("m_ext refcnt < 0"));       \
  324         atomic_subtract_int((m)->m_ext.ref_cnt, 1);                     \
  325 } while(0)
  326 
  327 #define MEXT_ADD_REF(m) do {                                            \
  328         if ((m)->m_ext.ref_cnt == NULL) {                               \
  329                 KASSERT((m)->m_ext.ext_type == EXT_CLUSTER ||           \
  330                     (m)->m_ext.ext_type == EXT_PACKET,                  \
  331                     ("Unexpected mbuf type has lazy refcnt"));          \
  332                 (m)->m_ext.ref_cnt = (u_int *)uma_find_refcnt(          \
  333                     zone_clust, (m)->m_ext.ext_buf);                    \
  334                 *((m)->m_ext.ref_cnt) = 2;                              \
  335         } else                                                          \
  336                 atomic_add_int((m)->m_ext.ref_cnt, 1);                  \
  337 } while (0)
  338 
  339 #ifdef WITNESS
  340 #define MBUF_CHECKSLEEP(how) do {                                       \
  341         if (how == M_WAITOK)                                            \
  342                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,         \
  343                     "Sleeping in \"%s\"", __func__);                    \
  344 } while(0)
  345 #else
  346 #define MBUF_CHECKSLEEP(how)
  347 #endif
  348 
  349 /*
  350  * Network buffer allocation API
  351  *
  352  * The rest of it is defined in kern/kern_mbuf.c
  353  */
  354 
  355 extern uma_zone_t       zone_mbuf;
  356 extern uma_zone_t       zone_clust;
  357 extern uma_zone_t       zone_pack;
  358 
  359 static __inline struct mbuf     *m_get(int how, short type);
  360 static __inline struct mbuf     *m_gethdr(int how, short type);
  361 static __inline struct mbuf     *m_getcl(int how, short type, int flags);
  362 static __inline struct mbuf     *m_getclr(int how, short type); /* XXX */
  363 static __inline struct mbuf     *m_free(struct mbuf *m);
  364 static __inline void             m_clget(struct mbuf *m, int how);
  365 static __inline void             m_chtype(struct mbuf *m, short new_type);
  366 void                             mb_free_ext(struct mbuf *);
  367 
  368 static __inline
  369 struct mbuf *
  370 m_get(int how, short type)
  371 {
  372         struct mb_args args;
  373 
  374         args.flags = 0;
  375         args.type = type;
  376         return (uma_zalloc_arg(zone_mbuf, &args, how));
  377 }
  378 
  379 /* XXX This should be depracated, very little use */
  380 static __inline
  381 struct mbuf *
  382 m_getclr(int how, short type)
  383 {
  384         struct mbuf *m;
  385         struct mb_args args;
  386 
  387         args.flags = 0;
  388         args.type = type;
  389         m = uma_zalloc_arg(zone_mbuf, &args, how);
  390         if (m != NULL)
  391                 bzero(m->m_data, MLEN);
  392         return m;
  393 }
  394 
  395 static __inline
  396 struct mbuf *
  397 m_gethdr(int how, short type)
  398 {
  399         struct mb_args args;
  400 
  401         args.flags = M_PKTHDR;
  402         args.type = type;
  403         return (uma_zalloc_arg(zone_mbuf, &args, how));
  404 }
  405 
  406 static __inline
  407 struct mbuf *
  408 m_getcl(int how, short type, int flags)
  409 {
  410         struct mb_args args;
  411 
  412         args.flags = flags;
  413         args.type = type;
  414         return (uma_zalloc_arg(zone_pack, &args, how));
  415 }
  416 
  417 static __inline
  418 struct mbuf *
  419 m_free(struct mbuf *m)
  420 {
  421         struct mbuf *n = m->m_next;
  422 
  423 #ifdef INVARIANTS
  424         m->m_flags |= M_FREELIST;
  425 #endif
  426         if (m->m_flags & M_EXT)
  427                 mb_free_ext(m);
  428         else
  429                 uma_zfree(zone_mbuf, m);
  430         return n;
  431 }
  432 
  433 static __inline
  434 void
  435 m_clget(struct mbuf *m, int how)
  436 {
  437 
  438         m->m_ext.ext_buf = NULL;
  439         uma_zalloc_arg(zone_clust, m, how);
  440 }
  441 
  442 static __inline
  443 void
  444 m_chtype(struct mbuf *m, short new_type)
  445 {
  446         m->m_type = new_type;
  447 }
  448 
  449 /*
  450  * mbuf, cluster, and external object allocation macros
  451  * (for compatibility purposes).
  452  */
  453 /* NB: M_COPY_PKTHDR is deprecated.  Use M_MOVE_PKTHDR or m_dup_pktdr. */
  454 #define M_MOVE_PKTHDR(to, from) m_move_pkthdr((to), (from))
  455 #define MGET(m, how, type)      ((m) = m_get((how), (type)))
  456 #define MGETHDR(m, how, type)   ((m) = m_gethdr((how), (type)))
  457 #define MCLGET(m, how)          m_clget((m), (how))
  458 #define MEXTADD(m, buf, size, free, args, flags, type)                  \
  459     m_extadd((m), (caddr_t)(buf), (size), (free), (args), (flags), (type))
  460 
  461 /*
  462  * Evaluate TRUE if it's safe to write to the mbuf m's data region (this
  463  * can be both the local data payload, or an external buffer area,
  464  * depending on whether M_EXT is set).
  465  */
  466 #define M_WRITABLE(m)   (!((m)->m_flags & M_RDONLY) && (!((m)->m_flags  \
  467                             & M_EXT) || !MEXT_IS_REF(m)))
  468 
  469 /* Check if the supplied mbuf has a packet header, or else panic. */
  470 #define M_ASSERTPKTHDR(m)                                               \
  471         KASSERT(m != NULL && m->m_flags & M_PKTHDR,                     \
  472             ("%s: no mbuf packet header!", __func__))
  473 
  474 /* Ensure that the supplied mbuf is a valid, non-free mbuf. */
  475 #define M_ASSERTVALID(m)                                                \
  476         KASSERT((((struct mbuf *)m)->m_flags & M_FREELIST) == 0,        \
  477             ("%s: attempted use of a free mbuf!", __func__))
  478 
  479 /*
  480  * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
  481  * an object of the specified size at the end of the mbuf, longword aligned.
  482  */
  483 #define M_ALIGN(m, len) do {                                            \
  484         (m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);            \
  485 } while (0)
  486 
  487 /*
  488  * As above, for mbufs allocated with m_gethdr/MGETHDR
  489  * or initialized by M_COPY_PKTHDR.
  490  */
  491 #define MH_ALIGN(m, len) do {                                           \
  492         (m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);           \
  493 } while (0)
  494 
  495 /*
  496  * Compute the amount of space available
  497  * before the current start of data in an mbuf.
  498  *
  499  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
  500  * of checking writability of the mbuf data area rests solely with the caller.
  501  */
  502 #define M_LEADINGSPACE(m)                                               \
  503         ((m)->m_flags & M_EXT ?                                         \
  504             (M_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0):     \
  505             (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :     \
  506             (m)->m_data - (m)->m_dat)
  507 
  508 /*
  509  * Compute the amount of space available
  510  * after the end of data in an mbuf.
  511  *
  512  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
  513  * of checking writability of the mbuf data area rests solely with the caller.
  514  */
  515 #define M_TRAILINGSPACE(m)                                              \
  516         ((m)->m_flags & M_EXT ?                                         \
  517             (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size   \
  518                 - ((m)->m_data + (m)->m_len) : 0) :                     \
  519             &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))
  520 
  521 /*
  522  * Arrange to prepend space of size plen to mbuf m.
  523  * If a new mbuf must be allocated, how specifies whether to wait.
  524  * If the allocation fails, the original mbuf chain is freed and m is
  525  * set to NULL.
  526  */
  527 #define M_PREPEND(m, plen, how) do {                                    \
  528         struct mbuf **_mmp = &(m);                                      \
  529         struct mbuf *_mm = *_mmp;                                       \
  530         int _mplen = (plen);                                            \
  531         int __mhow = (how);                                             \
  532                                                                         \
  533         MBUF_CHECKSLEEP(how);                                           \
  534         if (M_LEADINGSPACE(_mm) >= _mplen) {                            \
  535                 _mm->m_data -= _mplen;                                  \
  536                 _mm->m_len += _mplen;                                   \
  537         } else                                                          \
  538                 _mm = m_prepend(_mm, _mplen, __mhow);                   \
  539         if (_mm != NULL && _mm->m_flags & M_PKTHDR)                     \
  540                 _mm->m_pkthdr.len += _mplen;                            \
  541         *_mmp = _mm;                                                    \
  542 } while (0)
  543 
  544 /*
  545  * Change mbuf to new type.
  546  * This is a relatively expensive operation and should be avoided.
  547  */
  548 #define MCHTYPE(m, t)   m_chtype((m), (t))
  549 
  550 /* Length to m_copy to copy all. */
  551 #define M_COPYALL       1000000000
  552 
  553 /* Compatibility with 4.3. */
  554 #define m_copy(m, o, l) m_copym((m), (o), (l), M_DONTWAIT)
  555 
  556 extern  int max_datalen;                /* MHLEN - max_hdr */
  557 extern  int max_hdr;                    /* Largest link + protocol header */
  558 extern  int max_linkhdr;                /* Largest link-level header */
  559 extern  int max_protohdr;               /* Largest protocol header */
  560 extern  struct mbstat mbstat;           /* General mbuf stats/infos */
  561 extern  int nmbclusters;                /* Maximum number of clusters */
  562 
  563 struct uio;
  564 
  565 void             m_adj(struct mbuf *, int);
  566 void             m_align(struct mbuf *, int);
  567 int              m_apply(struct mbuf *, int, int,
  568                     int (*)(void *, void *, u_int), void *);
  569 int              m_append(struct mbuf *, int, c_caddr_t);
  570 void             m_cat(struct mbuf *, struct mbuf *);
  571 void             m_extadd(struct mbuf *, caddr_t, u_int,
  572                     void (*)(void *, void *), void *, int, int);
  573 void             m_copyback(struct mbuf *, int, int, c_caddr_t);
  574 void             m_copydata(const struct mbuf *, int, int, caddr_t);
  575 struct  mbuf    *m_copym(struct mbuf *, int, int, int);
  576 struct  mbuf    *m_copypacket(struct mbuf *, int);
  577 void             m_copy_pkthdr(struct mbuf *, struct mbuf *);
  578 struct  mbuf    *m_copyup(struct mbuf *n, int len, int dstoff);
  579 struct  mbuf    *m_defrag(struct mbuf *, int);
  580 struct  mbuf    *m_devget(char *, int, int, struct ifnet *,
  581                     void (*)(char *, caddr_t, u_int));
  582 struct  mbuf    *m_dup(struct mbuf *, int);
  583 int              m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
  584 u_int            m_fixhdr(struct mbuf *);
  585 struct  mbuf    *m_fragment(struct mbuf *, int, int);
  586 void             m_freem(struct mbuf *);
  587 struct  mbuf    *m_getm(struct mbuf *, int, int, short);
  588 struct  mbuf    *m_getptr(struct mbuf *, int, int *);
  589 u_int            m_length(struct mbuf *, struct mbuf **);
  590 void             m_move_pkthdr(struct mbuf *, struct mbuf *);
  591 struct  mbuf    *m_prepend(struct mbuf *, int, int);
  592 void             m_print(const struct mbuf *, int);
  593 struct  mbuf    *m_pulldown(struct mbuf *, int, int, int *);
  594 struct  mbuf    *m_pullup(struct mbuf *, int);
  595 struct  mbuf    *m_split(struct mbuf *, int, int);
  596 struct  mbuf    *m_uiotombuf(struct uio *, int, int, int);
  597 
  598 /*-
  599  * Network packets may have annotations attached by affixing a list
  600  * of "packet tags" to the pkthdr structure.  Packet tags are
  601  * dynamically allocated semi-opaque data structures that have
  602  * a fixed header (struct m_tag) that specifies the size of the
  603  * memory block and a <cookie,type> pair that identifies it.
  604  * The cookie is a 32-bit unique unsigned value used to identify
  605  * a module or ABI.  By convention this value is chose as the
  606  * date+time that the module is created, expressed as the number of
  607  * seconds since the epoch (e.g., using date -u +'%s').  The type value
  608  * is an ABI/module-specific value that identifies a particular annotation
  609  * and is private to the module.  For compatibility with systems
  610  * like OpenBSD that define packet tags w/o an ABI/module cookie,
  611  * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
  612  * m_tag_find compatibility shim functions and several tag types are
  613  * defined below.  Users that do not require compatibility should use
  614  * a private cookie value so that packet tag-related definitions
  615  * can be maintained privately.
  616  *
  617  * Note that the packet tag returned by m_tag_alloc has the default
  618  * memory alignment implemented by malloc.  To reference private data
  619  * one can use a construct like:
  620  *
  621  *      struct m_tag *mtag = m_tag_alloc(...);
  622  *      struct foo *p = (struct foo *)(mtag+1);
  623  *
  624  * if the alignment of struct m_tag is sufficient for referencing members
  625  * of struct foo.  Otherwise it is necessary to embed struct m_tag within
  626  * the private data structure to insure proper alignment; e.g.,
  627  *
  628  *      struct foo {
  629  *              struct m_tag    tag;
  630  *              ...
  631  *      };
  632  *      struct foo *p = (struct foo *) m_tag_alloc(...);
  633  *      struct m_tag *mtag = &p->tag;
  634  */
  635 
  636 /*
  637  * Persistent tags stay with an mbuf until the mbuf is reclaimed.
  638  * Otherwise tags are expected to ``vanish'' when they pass through
  639  * a network interface.  For most interfaces this happens normally
  640  * as the tags are reclaimed when the mbuf is free'd.  However in
  641  * some special cases reclaiming must be done manually.  An example
  642  * is packets that pass through the loopback interface.  Also, one
  643  * must be careful to do this when ``turning around'' packets (e.g.,
  644  * icmp_reflect).
  645  *
  646  * To mark a tag persistent bit-or this flag in when defining the
  647  * tag id.  The tag will then be treated as described above.
  648  */
  649 #define MTAG_PERSISTENT                         0x800
  650 
  651 #define PACKET_TAG_NONE                         0  /* Nadda */
  652 
  653 /* Packet tags for use with PACKET_ABI_COMPAT. */
  654 #define PACKET_TAG_IPSEC_IN_DONE                1  /* IPsec applied, in */
  655 #define PACKET_TAG_IPSEC_OUT_DONE               2  /* IPsec applied, out */
  656 #define PACKET_TAG_IPSEC_IN_CRYPTO_DONE         3  /* NIC IPsec crypto done */
  657 #define PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED      4  /* NIC IPsec crypto req'ed */
  658 #define PACKET_TAG_IPSEC_IN_COULD_DO_CRYPTO     5  /* NIC notifies IPsec */
  659 #define PACKET_TAG_IPSEC_PENDING_TDB            6  /* Reminder to do IPsec */
  660 #define PACKET_TAG_BRIDGE                       7  /* Bridge processing done */
  661 #define PACKET_TAG_GIF                          8  /* GIF processing done */
  662 #define PACKET_TAG_GRE                          9  /* GRE processing done */
  663 #define PACKET_TAG_IN_PACKET_CHECKSUM           10 /* NIC checksumming done */
  664 #define PACKET_TAG_ENCAP                        11 /* Encap.  processing */
  665 #define PACKET_TAG_IPSEC_SOCKET                 12 /* IPSEC socket ref */
  666 #define PACKET_TAG_IPSEC_HISTORY                13 /* IPSEC history */
  667 #define PACKET_TAG_IPV6_INPUT                   14 /* IPV6 input processing */
  668 #define PACKET_TAG_DUMMYNET                     15 /* dummynet info */
  669 #define PACKET_TAG_DIVERT                       17 /* divert info */
  670 #define PACKET_TAG_IPFORWARD                    18 /* ipforward info */
  671 #define PACKET_TAG_MACLABEL     (19 | MTAG_PERSISTENT) /* MAC label */
  672 #define PACKET_TAG_PF_ROUTED                    21 /* PF routed, avoid loops */
  673 #define PACKET_TAG_PF_FRAGCACHE                 22 /* PF fragment cached */
  674 #define PACKET_TAG_PF_QID                       23 /* PF ALTQ queue id */
  675 #define PACKET_TAG_PF_TAG                       24 /* PF tagged */
  676 #define PACKET_TAG_RTSOCKFAM                    25 /* rtsock sa family */
  677 #define PACKET_TAG_PF_TRANSLATE_LOCALHOST       26 /* PF translate localhost */
  678 #define PACKET_TAG_IPOPTIONS                    27 /* Saved IP options */
  679 #define PACKET_TAG_CARP                         28 /* CARP info */
  680 
  681 /* Packet tag routines. */
  682 struct  m_tag   *m_tag_alloc(u_int32_t, int, int, int);
  683 void             m_tag_delete(struct mbuf *, struct m_tag *);
  684 void             m_tag_delete_chain(struct mbuf *, struct m_tag *);
  685 void             m_tag_free_default(struct m_tag *);
  686 struct  m_tag   *m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
  687 struct  m_tag   *m_tag_copy(struct m_tag *, int);
  688 int              m_tag_copy_chain(struct mbuf *, struct mbuf *, int);
  689 void             m_tag_delete_nonpersistent(struct mbuf *);
  690 
  691 /*
  692  * Initialize the list of tags associated with an mbuf.
  693  */
  694 static __inline void
  695 m_tag_init(struct mbuf *m)
  696 {
  697         SLIST_INIT(&m->m_pkthdr.tags);
  698 }
  699 
  700 /*
  701  * Set up the contents of a tag.  Note that this does not
  702  * fill in the free method; the caller is expected to do that.
  703  *
  704  * XXX probably should be called m_tag_init, but that was
  705  * already taken.
  706  */
  707 static __inline void
  708 m_tag_setup(struct m_tag *t, u_int32_t cookie, int type, int len)
  709 {
  710         t->m_tag_id = type;
  711         t->m_tag_len = len;
  712         t->m_tag_cookie = cookie;
  713 }
  714 
  715 /*
  716  * Reclaim resources associated with a tag.
  717  */
  718 static __inline void
  719 m_tag_free(struct m_tag *t)
  720 {
  721         (*t->m_tag_free)(t);
  722 }
  723 
  724 /*
  725  * Return the first tag associated with an mbuf.
  726  */
  727 static __inline struct m_tag *
  728 m_tag_first(struct mbuf *m)
  729 {
  730         return (SLIST_FIRST(&m->m_pkthdr.tags));
  731 }
  732 
  733 /*
  734  * Return the next tag in the list of tags associated with an mbuf.
  735  */
  736 static __inline struct m_tag *
  737 m_tag_next(struct mbuf *m, struct m_tag *t)
  738 {
  739         return (SLIST_NEXT(t, m_tag_link));
  740 }
  741 
  742 /*
  743  * Prepend a tag to the list of tags associated with an mbuf.
  744  */
  745 static __inline void
  746 m_tag_prepend(struct mbuf *m, struct m_tag *t)
  747 {
  748         SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
  749 }
  750 
  751 /*
  752  * Unlink a tag from the list of tags associated with an mbuf.
  753  */
  754 static __inline void
  755 m_tag_unlink(struct mbuf *m, struct m_tag *t)
  756 {
  757         SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
  758 }
  759 
  760 /* These are for OpenBSD compatibility. */
  761 #define MTAG_ABI_COMPAT         0               /* compatibility ABI */
  762 
  763 static __inline struct m_tag *
  764 m_tag_get(int type, int length, int wait)
  765 {
  766         return (m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait));
  767 }
  768 
  769 static __inline struct m_tag *
  770 m_tag_find(struct mbuf *m, int type, struct m_tag *start)
  771 {
  772         return (SLIST_EMPTY(&m->m_pkthdr.tags) ?
  773             NULL : m_tag_locate(m, MTAG_ABI_COMPAT, type, start));
  774 }
  775 
  776 #endif /* _KERNEL */
  777 
  778 #endif /* !_SYS_MBUF_H_ */

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