Resync patch with contrib.

[dragonfly.git] / sys / sys / mbuf.h

/*
 * Copyright (c) 2004 The DragonFly Project.  All rights reserved.
 *
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)mbuf.h      8.5 (Berkeley) 2/19/95
 * $FreeBSD: src/sys/sys/mbuf.h,v 1.44.2.17 2003/04/15 06:15:02 silby Exp $
 * $DragonFly: src/sys/sys/mbuf.h,v 1.41 2007/08/16 20:03:54 dillon Exp $
 */

#ifndef _SYS_MBUF_H_
#define _SYS_MBUF_H_

#if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)

#ifndef _SYS_TYPES_H_
#include <sys/types.h>
#endif
#ifndef _SYS_PARAM_H_
#include <sys/param.h>
#endif
#ifndef _SYS_QUEUE_H_
#include <sys/queue.h>
#endif
#ifndef _NET_NETISR_H_
#include <net/netisr.h>
#endif

/*
 * Mbufs are of a single size, MSIZE (machine/param.h), which
 * includes overhead.  An mbuf may add a single "mbuf cluster" of size
 * MCLBYTES (also in machine/param.h), which has no additional overhead
 * and is used instead of the internal data area; this is done when
 * at least MINCLSIZE of data must be stored.
 */
#define MLEN            (MSIZE - sizeof(struct m_hdr))  /* normal data len */
#define MHLEN           (MLEN - sizeof(struct pkthdr))  /* data len w/pkthdr */
#define MINCLSIZE       (MHLEN + 1)     /* smallest amount to put in cluster */
#define M_MAXCOMPRESS   (MHLEN / 2)     /* max amount to copy for compression */

/*
 * Macros for type conversion:
 * mtod(m, t)   -- Convert mbuf pointer to data pointer of correct type.
 * mtocl(x) -   convert pointer within cluster to cluster index #
 * cltom(x) -   convert cluster # to ptr to beginning of cluster
 */
#define mtod(m, t)      ((t)((m)->m_data))

/*
 * Header present at the beginning of every mbuf.
 */
struct m_hdr {
        struct  mbuf *mh_next;          /* next buffer in chain */
        struct  mbuf *mh_nextpkt;       /* next chain in queue/record */
        caddr_t mh_data;                /* location of data */
        int     mh_len;                 /* amount of data in this mbuf */
        short   mh_type;                /* type of data in this mbuf */
        short   mh_flags;               /* flags; see below */
        struct netmsg_packet mh_netmsg; /* hardware->proto stack msg */
};

/*
 * Packet tag structure (see below for details).
 */
struct m_tag {
        SLIST_ENTRY(m_tag)      m_tag_link;     /* List of packet tags */
        u_int16_t               m_tag_id;       /* Tag ID */
        u_int16_t               m_tag_len;      /* Length of data */
        u_int32_t               m_tag_cookie;   /* ABI/Module ID */
};

SLIST_HEAD(packet_tags, m_tag);

/*
 * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
 *
 * Be careful: The fields have been carefully ordered to avoid hidden padding.
 *             Keep this in mind, when adding or removing fields!
 */
struct pkthdr {
        struct  ifnet *rcvif;           /* rcv interface */
        int     len;                    /* total packet length */
        struct packet_tags tags;        /* list of packet tags */

        /* variables for ip and tcp reassembly */
        void    *header;                /* pointer to packet header */

        /* variables for hardware checksum */
        int     csum_flags;             /* flags regarding checksum */
        int     csum_data;              /* data field used by csum routines */

        /* firewall flags */
        uint32_t fw_flags;              /* flags for PF */

        /* variables for PF processing */
        uint16_t pf_tag;                /* PF tag id */
        uint8_t pf_routed;              /* PF routing counter */

        /* variables for ALTQ processing */
        uint8_t ecn_af;                 /* address family for ECN */
        uint32_t altq_qid;              /* queue id */
};

/*
 * Description of external storage mapped into mbuf; valid only if M_EXT is set.
 */
struct m_ext {
        caddr_t ext_buf;                /* start of buffer */
        void    (*ext_free)(void *);
        u_int   ext_size;               /* size of buffer, for ext_free */
        void    (*ext_ref)(void *);
        void    *ext_arg;
};

/*
 * The core of the mbuf object along with some shortcut defines for
 * practical purposes.
 */
struct mbuf {
        struct  m_hdr m_hdr;
        union {
                struct {
                        struct  pkthdr MH_pkthdr;       /* M_PKTHDR set */
                        union {
                                struct  m_ext MH_ext;   /* M_EXT set */
                                char    MH_databuf[MHLEN];
                        } MH_dat;
                } MH;
                char    M_databuf[MLEN];                /* !M_PKTHDR, !M_EXT */
        } M_dat;
};
#define m_next          m_hdr.mh_next
#define m_len           m_hdr.mh_len
#define m_data          m_hdr.mh_data
#define m_type          m_hdr.mh_type
#define m_flags         m_hdr.mh_flags
#define m_nextpkt       m_hdr.mh_nextpkt
#define m_pkthdr        M_dat.MH.MH_pkthdr
#define m_ext           M_dat.MH.MH_dat.MH_ext
#define m_pktdat        M_dat.MH.MH_dat.MH_databuf
#define m_dat           M_dat.M_databuf

/*
 * Code that uses m_act should be converted to use m_nextpkt
 * instead; m_act is historical and deprecated.
 */
#define m_act           m_nextpkt

/*
 * mbuf flags.
 */
#define M_EXT           0x0001  /* has associated external storage */
#define M_PKTHDR        0x0002  /* start of record */
#define M_EOR           0x0004  /* end of record */
#define M_PROTO1        0x0008  /* protocol-specific */
#define M_PROTO2        0x0010  /* protocol-specific */
#define M_PROTO3        0x0020  /* protocol-specific */
#define M_PROTO4        0x0040  /* protocol-specific */
#define M_PROTO5        0x0080  /* protocol-specific */

/*
 * mbuf pkthdr flags (also stored in m_flags).
 */
#define M_BCAST         0x0100  /* send/received as link-level broadcast */
#define M_MCAST         0x0200  /* send/received as link-level multicast */
#define M_FRAG          0x0400  /* packet is a fragment of a larger packet */
#define M_FIRSTFRAG     0x0800  /* packet is first fragment */
#define M_LASTFRAG      0x1000  /* packet is last fragment */
#define M_CLCACHE       0x2000  /* mbuf allocated from the cluster cache */
#define M_EXT_CLUSTER   0x4000  /* standard cluster else special */
#define M_PHCACHE       0x8000  /* mbuf allocated from the pkt header cache */
#define M_NOTIFICATION  0x10000 /* notification event */

/*
 * Flags copied when copying m_pkthdr.
 */
#define M_COPYFLAGS     (M_PKTHDR|M_EOR|M_PROTO1|M_PROTO1|M_PROTO2|M_PROTO3 | \
                            M_PROTO4|M_PROTO5|M_BCAST|M_MCAST|M_FRAG | \
                            M_FIRSTFRAG|M_LASTFRAG)

/*
 * Flags indicating hw checksum support and sw checksum requirements.
 */
#define CSUM_IP                 0x0001          /* will csum IP */
#define CSUM_TCP                0x0002          /* will csum TCP */
#define CSUM_UDP                0x0004          /* will csum UDP */
#define CSUM_IP_FRAGS           0x0008          /* will csum IP fragments */
#define CSUM_FRAGMENT           0x0010          /* will do IP fragmentation */

#define CSUM_IP_CHECKED         0x0100          /* did csum IP */
#define CSUM_IP_VALID           0x0200          /*   ... the csum is valid */
#define CSUM_DATA_VALID         0x0400          /* csum_data field is valid */
#define CSUM_PSEUDO_HDR         0x0800          /* csum_data has pseudo hdr */
#define CSUM_FRAG_NOT_CHECKED   0x1000          /* did _not_ csum fragment
                                                 * NB: This flag is only used
                                                 * by IP defragmenter.
                                                 */

#define CSUM_DELAY_DATA         (CSUM_TCP | CSUM_UDP)
#define CSUM_DELAY_IP           (CSUM_IP)       /* XXX add ipv6 here too? */

/*
 * Flags indicating PF processing status
 */
#define PF_MBUF_GENERATED       0x00000001
#define PF_MBUF_TAGGED          0x00000002      /* pf_tag field is valid */
#define PF_MBUF_ROUTED          0x00000004      /* pf_routed field is valid */
#define PF_MBUF_TRANSLATE_LOCALHOST                                     \
                                0x00000008
#define PF_MBUF_FRAGCACHE       0x00000010
#define ALTQ_MBUF_TAGGED        0x00000020      /* altq_qid is valid */
#define IPFW_MBUF_SKIP_FIREWALL 0x00000040

/*
 * mbuf types.
 */
#define MT_FREE         0       /* should be on free list */
#define MT_DATA         1       /* dynamic (data) allocation */
#define MT_HEADER       2       /* packet header */
#define MT_SONAME       3       /* socket name */
#define MT_TAG          4       /* volatile metadata associated to pkts */
#define MT_CONTROL      5       /* extra-data protocol message */
#define MT_OOBDATA      6       /* expedited data  */
#define MT_NTYPES       7       /* number of mbuf types for mbtypes[] */

/*
 * General mbuf allocator statistics structure.
 */
struct mbstat {
        u_long  m_mbufs;        /* mbufs obtained from page pool */
        u_long  m_clusters;     /* clusters obtained from page pool */
        u_long  m_spare;        /* spare field */
        u_long  m_clfree;       /* free clusters */
        u_long  m_drops;        /* times failed to find space */
        u_long  m_wait;         /* times waited for space */
        u_long  m_drain;        /* times drained protocols for space */
        u_long  m_mcfail;       /* times m_copym failed */
        u_long  m_mpfail;       /* times m_pullup failed */
        u_long  m_msize;        /* length of an mbuf */
        u_long  m_mclbytes;     /* length of an mbuf cluster */
        u_long  m_minclsize;    /* min length of data to allocate a cluster */
        u_long  m_mlen;         /* length of data in an mbuf */
        u_long  m_mhlen;        /* length of data in a header mbuf */
};

/*
 * Flags specifying how an allocation should be made.
 */

#define MB_DONTWAIT     0x4
#define MB_TRYWAIT      0x8
#define MB_WAIT         MB_TRYWAIT

/*
 * Mbuf to Malloc Flag Conversion.
 */
#define MBTOM(how)      ((how) & MB_TRYWAIT ? M_WAITOK : M_NOWAIT)

/*
 * These are identifying numbers passed to the m_mballoc_wait function,
 * allowing us to determine whether the call came from an MGETHDR or
 * an MGET.
 */
#define MGETHDR_C      1
#define MGET_C         2

/*
 * mbuf allocation/deallocation macros (YYY deprecated, too big):
 *
 *      MGET(struct mbuf *m, int how, int type)
 * allocates an mbuf and initializes it to contain internal data.
 *
 *      MGETHDR(struct mbuf *m, int how, int type)
 * allocates an mbuf and initializes it to contain a packet header
 * and internal data.
 */
#define MGET(m, how, type) do {                                         \
        (m) = m_get((how), (type));                                     \
} while (0)

#define MGETHDR(m, how, type) do {                                      \
        (m) = m_gethdr((how), (type));                                  \
} while (0)

/*
 * MCLGET adds such clusters to a normal mbuf.  The flag M_EXT is set upon
 * success.
 * Deprecated.  Use m_getcl() or m_getl() instead.
 */
#define MCLGET(m, how) do {                                             \
        m_mclget((m), (how));                                           \
} while (0)

/*
 * NB: M_COPY_PKTHDR is deprecated; use either M_MOVE_PKTHDR
 *     or m_dup_pkthdr.
 */
/*
 * Move mbuf pkthdr from "from" to "to".
 * from should have M_PKTHDR set, and to must be empty.
 * from no longer has a pkthdr after this operation.
 */
#define M_MOVE_PKTHDR(_to, _from)       m_move_pkthdr((_to), (_from))

/*
 * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
 * an object of the specified size at the end of the mbuf, longword aligned.
 */
#define M_ALIGN(m, len) do {                                            \
        (m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);            \
} while (0)

/*
 * As above, for mbufs allocated with m_gethdr/MGETHDR
 * or initialized by M_COPY_PKTHDR.
 */
#define MH_ALIGN(m, len) do {                                           \
        (m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);           \
} while (0)

/*
 * Check if we can write to an mbuf.
 */
#define M_EXT_WRITABLE(m)       (m_sharecount(m) == 1)
#define M_WRITABLE(m)           (!((m)->m_flags & M_EXT) || M_EXT_WRITABLE(m))

/*
 * Check if the supplied mbuf has a packet header, or else panic.
 */
#define M_ASSERTPKTHDR(m)                                               \
        KASSERT(m != NULL && m->m_flags & M_PKTHDR,                     \
                ("%s: invalid mbuf or no mbuf packet header!", __func__))

/*
 * Compute the amount of space available before the current start of data.
 * The M_EXT_WRITABLE() is a temporary, conservative safety measure: the burden
 * of checking writability of the mbuf data area rests solely with the caller.
 */
#define M_LEADINGSPACE(m)                                               \
        ((m)->m_flags & M_EXT ?                                         \
            (M_EXT_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0): \
            (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :     \
            (m)->m_data - (m)->m_dat)

/*
 * Compute the amount of space available after the end of data in an mbuf.
 * The M_WRITABLE() is a temporary, conservative safety measure: the burden
 * of checking writability of the mbuf data area rests solely with the caller.
 */
#define M_TRAILINGSPACE(m)                                              \
        ((m)->m_flags & M_EXT ?                                         \
            (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size   \
                - ((m)->m_data + (m)->m_len) : 0) :                     \
            &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))

/*
 * Arrange to prepend space of size plen to mbuf m.
 * If a new mbuf must be allocated, how specifies whether to wait.
 * If how is MB_DONTWAIT and allocation fails, the original mbuf chain
 * is freed and m is set to NULL.
 */
#define M_PREPEND(m, plen, how) do {                                    \
        struct mbuf **_mmp = &(m);                                      \
        struct mbuf *_mm = *_mmp;                                       \
        int _mplen = (plen);                                            \
        int __mhow = (how);                                             \
                                                                        \
        if (M_LEADINGSPACE(_mm) >= _mplen) {                            \
                _mm->m_data -= _mplen;                                  \
                _mm->m_len += _mplen;                                   \
        } else                                                          \
                _mm = m_prepend(_mm, _mplen, __mhow);                   \
        if (_mm != NULL && _mm->m_flags & M_PKTHDR)                     \
                _mm->m_pkthdr.len += _mplen;                            \
        *_mmp = _mm;                                                    \
} while (0)

/* Length to m_copy to copy all. */
#define M_COPYALL       1000000000

/* Compatibility with 4.3 */
#define m_copy(m, o, l) m_copym((m), (o), (l), MB_DONTWAIT)

#ifdef _KERNEL
extern  u_int            m_clalloc_wid; /* mbuf cluster wait count */
extern  u_int            m_mballoc_wid; /* mbuf wait count */
extern  int              max_linkhdr;   /* largest link-level header */
extern  int              max_protohdr;  /* largest protocol header */
extern  int              max_hdr;       /* largest link+protocol header */
extern  int              max_datalen;   /* MHLEN - max_hdr */
extern  int              mbuf_wait;     /* mbuf sleep time */
extern  int              nmbclusters;
extern  int              nmbufs;

struct uio;

void             m_adj(struct mbuf *, int);
void             m_cat(struct mbuf *, struct mbuf *);
u_int            m_countm(struct mbuf *m, struct mbuf **lastm, u_int *mbcnt);
void             m_copyback(struct mbuf *, int, int, caddr_t);
void             m_copydata(const struct mbuf *, int, int, caddr_t);
struct  mbuf    *m_copym(const struct mbuf *, int, int, int);
struct  mbuf    *m_copypacket(struct mbuf *, int);
struct  mbuf    *m_defrag(struct mbuf *, int);
struct  mbuf    *m_defrag_nofree(struct mbuf *, int);
struct  mbuf    *m_devget(char *, int, int, struct ifnet *,
                  void (*copy)(volatile const void *, volatile void *, size_t));
struct  mbuf    *m_dup(struct mbuf *, int);
int              m_dup_pkthdr(struct mbuf *, const struct mbuf *, int);
struct  mbuf    *m_free(struct mbuf *);
void             m_freem(struct mbuf *);
struct  mbuf    *m_get(int, int);
struct  mbuf    *m_getc(int len, int how, int type);
struct  mbuf    *m_getcl(int how, short type, int flags);
struct  mbuf    *m_getclr(int, int);
struct  mbuf    *m_gethdr(int, int);
struct  mbuf    *m_getm(struct mbuf *, int, int, int);
struct  mbuf    *m_last(struct mbuf *m);
u_int            m_lengthm(struct mbuf *m, struct mbuf **lastm);
void             m_move_pkthdr(struct mbuf *, struct mbuf *);
struct  mbuf    *m_prepend(struct mbuf *, int, int);
void             m_print(const struct mbuf *m);
struct  mbuf    *m_pulldown(struct mbuf *, int, int, int *);
struct  mbuf    *m_pullup(struct mbuf *, int);
struct  mbuf    *m_split(struct mbuf *, int, int);
struct  mbuf    *m_uiomove(struct uio *);
void            m_mclget(struct mbuf *m, int how);
int             m_sharecount(struct mbuf *m);
void            m_chtype(struct mbuf *m, int type);

#ifdef MBUF_DEBUG
void            mbuftrackid(struct mbuf *, int);
#else
#define mbuftrackid(m, id)      /* empty */
#endif

/*
 * Allocate the right type of mbuf for the desired total length.
 * The mbuf returned does not necessarily cover the entire requested length.
 * This function follows mbuf chaining policy of allowing MINCLSIZE
 * amount of chained mbufs.
 */
static __inline struct mbuf *
m_getl(int len, int how, int type, int flags, int *psize)
{
        struct mbuf *m;
        int size;

        if (len >= MINCLSIZE) {
                m = m_getcl(how, type, flags);
                size = MCLBYTES;
        } else if (flags & M_PKTHDR) {
                m = m_gethdr(how, type);
                size = MHLEN;
        } else {
                m = m_get(how, type);
                size = MLEN;
        }
        if (psize != NULL)
                *psize = size;
        return (m);
}

/*
 * Get a single mbuf that covers the requested number of bytes.
 * This function does not create mbuf chains.  It explicitly marks
 * places in the code that abuse mbufs for contiguous data buffers.
 */
static __inline struct mbuf *
m_getb(int len, int how, int type, int flags)
{
        struct mbuf *m;
        int mbufsize = (flags & M_PKTHDR) ? MHLEN : MLEN;

        if (len > mbufsize)
                m = m_getcl(how, type, flags);
        else if (flags & M_PKTHDR)
                m = m_gethdr(how, type);
        else
                m = m_get(how, type);
        return (m);
}

/*
 * Packets may have annotations attached by affixing a list
 * of "packet tags" to the pkthdr structure.  Packet tags are
 * dynamically allocated semi-opaque data structures that have
 * a fixed header (struct m_tag) that specifies the size of the
 * memory block and a <cookie,type> pair that identifies it.
 * The cookie is a 32-bit unique unsigned value used to identify
 * a module or ABI.  By convention this value is chose as the
 * date+time that the module is created, expressed as the number of
 * seconds since the epoch (e.g. using date -u +'%s').  The type value
 * is an ABI/module-specific value that identifies a particular annotation
 * and is private to the module.  For compatibility with systems
 * like openbsd that define packet tags w/o an ABI/module cookie,
 * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
 * m_tag_find compatibility shim functions and several tag types are
 * defined below.  Users that do not require compatibility should use
 * a private cookie value so that packet tag-related definitions
 * can be maintained privately.
 *
 * Note that the packet tag returned by m_tag_allocate has the default
 * memory alignment implemented by malloc.  To reference private data
 * one can use a construct like:
 *
 *      struct m_tag *mtag = m_tag_allocate(...);
 *      struct foo *p = (struct foo *)(mtag+1);
 *
 * if the alignment of struct m_tag is sufficient for referencing members
 * of struct foo.  Otherwise it is necessary to embed struct m_tag within
 * the private data structure to insure proper alignment; e.g.
 *
 *      struct foo {
 *              struct m_tag    tag;
 *              ...
 *      };
 *      struct foo *p = (struct foo *) m_tag_allocate(...);
 *      struct m_tag *mtag = &p->tag;
 */

#define PACKET_TAG_NONE                         0  /* Nadda */

/* Packet tag for use with PACKET_ABI_COMPAT */
#define PACKET_TAG_IPSEC_IN_DONE                1  /* IPsec applied, in */
/* struct tdb_indent */
#define PACKET_TAG_IPSEC_OUT_DONE               2  /* IPsec applied, out */
/* struct tdb_indent */
#define PACKET_TAG_IPSEC_IN_CRYPTO_DONE         3  /* NIC IPsec crypto done */
/* struct tdb_indent, never added */
#define PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED      4  /* NIC IPsec crypto req'ed */
/* struct tdb_indent, never added */
#define PACKET_TAG_IPSEC_PENDING_TDB            5  /* Reminder to do IPsec */
/* struct tdb_indent, never added */
#define PACKET_TAG_ENCAP                        6 /* Encap.  processing */
/* struct ifnet *, the GIF interface */
#define PACKET_TAG_IPSEC_HISTORY                7 /* IPSEC history */
/* struct ipsec_history */
#define PACKET_TAG_IPV6_INPUT                   8 /* IPV6 input processing */
/* struct ip6aux */
#define PACKET_TAG_IPFW_DIVERT                  9 /* divert info */
/* uint16_t */
#define PACKET_TAG_CARP                         28 /* CARP info */

/*
 * As a temporary and low impact solution to replace the even uglier
 * approach used so far in some parts of the network stack (which relies
 * on global variables), packet tag-like annotations are stored in MT_TAG
 * mbufs (or lookalikes) prepended to the actual mbuf chain.
 *
 *      m_type  = MT_TAG
 *      m_flags = m_tag_id
 *      m_next  = next buffer in chain.
 *
 * BE VERY CAREFUL not to pass these blocks to the mbuf handling routines.
 */
#define _m_tag_id       m_hdr.mh_flags

/* Packet tags used in the FreeBSD network stack */
#define PACKET_TAG_DUMMYNET                     15 /* dummynet info */
/* struct dn_pkt as fake mbuf */
#define PACKET_TAG_IPFORWARD                    18 /* ipforward info */
/* struct sockaddr_in * as m_data */

/* Packet tag routines */
struct  m_tag   *m_tag_alloc(u_int32_t, int, int, int);
void             m_tag_free(struct m_tag *);
void             m_tag_prepend(struct mbuf *, struct m_tag *);
void             m_tag_unlink(struct mbuf *, struct m_tag *);
void             m_tag_delete(struct mbuf *, struct m_tag *);
void             m_tag_delete_chain(struct mbuf *);
struct  m_tag   *m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
struct  m_tag   *m_tag_copy(struct m_tag *, int);
int              m_tag_copy_chain(struct mbuf *, const struct mbuf *, int);
void             m_tag_init(struct mbuf *);
struct  m_tag   *m_tag_first(struct mbuf *);
struct  m_tag   *m_tag_next(struct mbuf *, struct m_tag *);

/* these are for openbsd compatibility */
#define MTAG_ABI_COMPAT         0               /* compatibility ABI */

static __inline void *
m_tag_data(struct m_tag *tag)
{
        return ((void *)(tag + 1));
}

static __inline struct m_tag *
m_tag_get(int type, int length, int wait)
{
        return m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait);
}

static __inline struct m_tag *
m_tag_find(struct mbuf *m, int type, struct m_tag *start)
{
        return m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
}

#endif  /* _KERNEL */

#endif  /* _KERNEL || _KERNEL_STRUCTURES */
#endif  /* !_SYS_MBUF_H_ */