FreeBSD/Linux Kernel Cross Reference
sys/sys/mbuf.h

     /*-
      * 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. 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: releng/10.0/sys/sys/mbuf.h 255047 2013-08-29 23:46:38Z np $
     */
    
    #ifndef _SYS_MBUF_H_
    #define _SYS_MBUF_H_
    
    /* XXX: These includes suck. Sorry! */
    #include <sys/queue.h>
    #ifdef _KERNEL
    #include <sys/systm.h>
    #include <vm/uma.h>
    #ifdef WITNESS
    #include <sys/lock.h>
    #endif
    #endif
    
    /*
     * Mbufs are of a single size, MSIZE (sys/param.h), which includes overhead.
     * An mbuf may add a single "mbuf cluster" of size MCLBYTES (also in
     * sys/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.  Additionally, it is possible to allocate a separate buffer
     * externally and attach it to the mbuf in a way similar to that of mbuf
     * clusters.
     *
     * NB: These calculation do not take actual compiler-induced alignment and
     * padding inside the complete struct mbuf into account.  Appropriate
     * attention is required when changing members of struct mbuf.
     *
     * MLEN is data length in a normal mbuf.
     * MHLEN is data length in an mbuf with pktheader.
     * MINCLSIZE is a smallest amount of data that should be put into cluster.
     */
    #define MLEN            ((int)(MSIZE - sizeof(struct m_hdr)))
    #define MHLEN           ((int)(MLEN - sizeof(struct pkthdr)))
    #define MINCLSIZE       (MHLEN + 1)
    
    #ifdef _KERNEL
    /*-
     * Macro for type conversion: convert mbuf pointer to data pointer of correct
     * type:
     *
     * mtod(m, t)   -- Convert mbuf pointer to data pointer of correct type.
     * mtodo(m, o) -- Same as above but with offset 'o' into data.
     */
    #define mtod(m, t)      ((t)((m)->m_data))
    #define mtodo(m, o)     ((void *)(((m)->m_data) + (o)))
    
    /*
     * Argument structure passed to UMA routines during mbuf and packet
     * allocations.
     */
    struct mb_args {
            int     flags;  /* Flags for mbuf being allocated */
            short   type;   /* Type of mbuf being allocated */
    };
    #endif /* _KERNEL */
    
    /*
     * Header present at the beginning of every mbuf.
     * Size ILP32: 24
     *       LP64: 32
     */
    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 */
            int32_t          mh_len;        /* amount of data in this mbuf */
            uint32_t         mh_type:8,     /* type of data in this mbuf */
                            mh_flags:24;   /* flags; see below */
   #if !defined(__LP64__)
           uint32_t         mh_pad;        /* pad for 64bit alignment */
   #endif
   };
   
   /*
    * 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 */
           void                    (*m_tag_free)(struct m_tag *);
   };
   
   /*
    * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
    * Size ILP32: 48
    *       LP64: 56
    */
   struct pkthdr {
           struct ifnet    *rcvif;         /* rcv interface */
           SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
           int32_t          len;           /* total packet length */
   
           /* Layer crossing persistent information. */
           uint32_t         flowid;        /* packet's 4-tuple system */
           uint64_t         csum_flags;    /* checksum and offload features */
           uint16_t         fibnum;        /* this packet should use this fib */
           uint8_t          cosqos;        /* class/quality of service */
           uint8_t          rsstype;       /* hash type */
           uint8_t          l2hlen;        /* layer 2 header length */
           uint8_t          l3hlen;        /* layer 3 header length */
           uint8_t          l4hlen;        /* layer 4 header length */
           uint8_t          l5hlen;        /* layer 5 header length */
           union {
                   uint8_t  eigth[8];
                   uint16_t sixteen[4];
                   uint32_t thirtytwo[2];
                   uint64_t sixtyfour[1];
                   uintptr_t unintptr[1];
                   void    *ptr;
           } PH_per;
   
           /* Layer specific non-persistent local storage for reassembly, etc. */
           union {
                   uint8_t  eigth[8];
                   uint16_t sixteen[4];
                   uint32_t thirtytwo[2];
                   uint64_t sixtyfour[1];
                   uintptr_t unintptr[1];
                   void    *ptr;
           } PH_loc;
   };
   #define ether_vtag      PH_per.sixteen[0]
   #define PH_vt           PH_per
   #define vt_nrecs        sixteen[0]
   #define tso_segsz       PH_per.sixteen[1]
   #define csum_phsum      PH_per.sixteen[2]
   #define csum_data       PH_per.thirtytwo[1]
   
   /*
    * Description of external storage mapped into mbuf; valid only if M_EXT is
    * set.
    * Size ILP32: 28
    *       LP64: 48
    */
   struct m_ext {
           volatile u_int  *ref_cnt;       /* pointer to ref count info */
           caddr_t          ext_buf;       /* start of buffer */
           uint32_t         ext_size;      /* size of buffer, for ext_free */
           uint32_t         ext_type:8,    /* type of external storage */
                            ext_flags:24;  /* external storage mbuf flags */
           int             (*ext_free)     /* free routine if not the usual */
                               (struct mbuf *, void *, void *);
           void            *ext_arg1;      /* optional argument pointer */
           void            *ext_arg2;      /* optional argument pointer */
   };
   
   /*
    * 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_act           m_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
   
   /*
    * mbuf flags of global significance and layer crossing.
    * Those of only protocol/layer specific significance are to be mapped
    * to M_PROTO[1-12] and cleared at layer handoff boundaries.
    * NB: Limited to the lower 24 bits.
    */
   #define M_EXT           0x00000001 /* has associated external storage */
   #define M_PKTHDR        0x00000002 /* start of record */
   #define M_EOR           0x00000004 /* end of record */
   #define M_RDONLY        0x00000008 /* associated data is marked read-only */
   #define M_BCAST         0x00000010 /* send/received as link-level broadcast */
   #define M_MCAST         0x00000020 /* send/received as link-level multicast */
   #define M_PROMISC       0x00000040 /* packet was not for us */
   #define M_VLANTAG       0x00000080 /* ether_vtag is valid */
   #define M_FLOWID        0x00000100 /* deprecated: flowid is valid */
   #define M_NOFREE        0x00000200 /* do not free mbuf, embedded in cluster */
   
   #define M_PROTO1        0x00001000 /* protocol-specific */
   #define M_PROTO2        0x00002000 /* protocol-specific */
   #define M_PROTO3        0x00004000 /* protocol-specific */
   #define M_PROTO4        0x00008000 /* protocol-specific */
   #define M_PROTO5        0x00010000 /* protocol-specific */
   #define M_PROTO6        0x00020000 /* protocol-specific */
   #define M_PROTO7        0x00040000 /* protocol-specific */
   #define M_PROTO8        0x00080000 /* protocol-specific */
   #define M_PROTO9        0x00100000 /* protocol-specific */
   #define M_PROTO10       0x00200000 /* protocol-specific */
   #define M_PROTO11       0x00400000 /* protocol-specific */
   #define M_PROTO12       0x00800000 /* protocol-specific */
   
   /*
    * Flags to purge when crossing layers.
    */
   #define M_PROTOFLAGS \
       (M_PROTO1|M_PROTO2|M_PROTO3|M_PROTO4|M_PROTO5|M_PROTO6|M_PROTO7|M_PROTO8|\
        M_PROTO9|M_PROTO10|M_PROTO11|M_PROTO12)
   
   /*
    * Flags preserved when copying m_pkthdr.
    */
   #define M_COPYFLAGS \
       (M_PKTHDR|M_EOR|M_RDONLY|M_BCAST|M_MCAST|M_VLANTAG|M_PROMISC| \
        M_PROTOFLAGS)
   
   /*
    * Mbuf flag description for use with printf(9) %b identifier.
    */
   #define M_FLAG_BITS \
       "\2\1M_EXT\2M_PKTHDR\3M_EOR\4M_RDONLY\5M_BCAST\6M_MCAST" \
       "\7M_PROMISC\10M_VLANTAG\11M_FLOWID"
   #define M_FLAG_PROTOBITS \
       "\15M_PROTO1\16M_PROTO2\17M_PROTO3\20M_PROTO4\21M_PROTO5" \
       "\22M_PROTO6\23M_PROTO7\24M_PROTO8\25M_PROTO9\26M_PROTO10" \
       "\27M_PROTO11\30M_PROTO12"
   #define M_FLAG_PRINTF (M_FLAG_BITS M_FLAG_PROTOBITS)
   
   /*
    * Network interface cards are able to hash protocol fields (such as IPv4
    * addresses and TCP port numbers) classify packets into flows.  These flows
    * can then be used to maintain ordering while delivering packets to the OS
    * via parallel input queues, as well as to provide a stateless affinity
    * model.  NIC drivers can pass up the hash via m->m_pkthdr.flowid, and set
    * m_flag fields to indicate how the hash should be interpreted by the
    * network stack.
    *
    * Most NICs support RSS, which provides ordering and explicit affinity, and
    * use the hash m_flag bits to indicate what header fields were covered by
    * the hash.  M_HASHTYPE_OPAQUE can be set by non-RSS cards or configurations
    * that provide an opaque flow identifier, allowing for ordering and
    * distribution without explicit affinity.
    */
   #define M_HASHTYPE_NONE                 0
   #define M_HASHTYPE_RSS_IPV4             1       /* IPv4 2-tuple */
   #define M_HASHTYPE_RSS_TCP_IPV4         2       /* TCPv4 4-tuple */
   #define M_HASHTYPE_RSS_IPV6             3       /* IPv6 2-tuple */
   #define M_HASHTYPE_RSS_TCP_IPV6         4       /* TCPv6 4-tuple */
   #define M_HASHTYPE_RSS_IPV6_EX          5       /* IPv6 2-tuple + ext hdrs */
   #define M_HASHTYPE_RSS_TCP_IPV6_EX      6       /* TCPv6 4-tiple + ext hdrs */
   #define M_HASHTYPE_OPAQUE               255     /* ordering, not affinity */
   
   #define M_HASHTYPE_CLEAR(m)     ((m)->m_pkthdr.rsstype = 0)
   #define M_HASHTYPE_GET(m)       ((m)->m_pkthdr.rsstype)
   #define M_HASHTYPE_SET(m, v)    ((m)->m_pkthdr.rsstype = (v))
   #define M_HASHTYPE_TEST(m, v)   (M_HASHTYPE_GET(m) == (v))
   
   /*
    * COS/QOS class and quality of service tags.
    * It uses DSCP code points as base.
    */
   #define QOS_DSCP_CS0            0x00
   #define QOS_DSCP_DEF            QOS_DSCP_CS0
   #define QOS_DSCP_CS1            0x20
   #define QOS_DSCP_AF11           0x28
   #define QOS_DSCP_AF12           0x30
   #define QOS_DSCP_AF13           0x38
   #define QOS_DSCP_CS2            0x40
   #define QOS_DSCP_AF21           0x48
   #define QOS_DSCP_AF22           0x50
   #define QOS_DSCP_AF23           0x58
   #define QOS_DSCP_CS3            0x60
   #define QOS_DSCP_AF31           0x68
   #define QOS_DSCP_AF32           0x70
   #define QOS_DSCP_AF33           0x78
   #define QOS_DSCP_CS4            0x80
   #define QOS_DSCP_AF41           0x88
   #define QOS_DSCP_AF42           0x90
   #define QOS_DSCP_AF43           0x98
   #define QOS_DSCP_CS5            0xa0
   #define QOS_DSCP_EF             0xb8
   #define QOS_DSCP_CS6            0xc0
   #define QOS_DSCP_CS7            0xe0
   
   /*
    * External mbuf storage buffer types.
    */
   #define EXT_CLUSTER     1       /* mbuf cluster */
   #define EXT_SFBUF       2       /* sendfile(2)'s sf_bufs */
   #define EXT_JUMBOP      3       /* jumbo cluster 4096 bytes */
   #define EXT_JUMBO9      4       /* jumbo cluster 9216 bytes */
   #define EXT_JUMBO16     5       /* jumbo cluster 16184 bytes */
   #define EXT_PACKET      6       /* mbuf+cluster from packet zone */
   #define EXT_MBUF        7       /* external mbuf reference (M_IOVEC) */
   
   #define EXT_VENDOR1     224     /* for vendor-internal use */
   #define EXT_VENDOR2     225     /* for vendor-internal use */
   #define EXT_VENDOR3     226     /* for vendor-internal use */
   #define EXT_VENDOR4     227     /* for vendor-internal use */
   
   #define EXT_EXP1        244     /* for experimental use */
   #define EXT_EXP2        245     /* for experimental use */
   #define EXT_EXP3        246     /* for experimental use */
   #define EXT_EXP4        247     /* for experimental use */
   
   #define EXT_NET_DRV     252     /* custom ext_buf provided by net driver(s) */
   #define EXT_MOD_TYPE    253     /* custom module's ext_buf type */
   #define EXT_DISPOSABLE  254     /* can throw this buffer away w/page flipping */
   #define EXT_EXTREF      255     /* has externally maintained ref_cnt ptr */
   
   /*
    * Flags for external mbuf buffer types.
    * NB: limited to the lower 24 bits.
    */
   #define EXT_FLAG_EMBREF         0x000001        /* embedded ref_cnt, notyet */
   #define EXT_FLAG_EXTREF         0x000002        /* external ref_cnt, notyet */
   #define EXT_FLAG_NOFREE         0x000010        /* don't free mbuf to pool, notyet */
   
   #define EXT_FLAG_VENDOR1        0x010000        /* for vendor-internal use */
   #define EXT_FLAG_VENDOR2        0x020000        /* for vendor-internal use */
   #define EXT_FLAG_VENDOR3        0x040000        /* for vendor-internal use */
   #define EXT_FLAG_VENDOR4        0x080000        /* for vendor-internal use */
   
   #define EXT_FLAG_EXP1           0x100000        /* for experimental use */
   #define EXT_FLAG_EXP2           0x200000        /* for experimental use */
   #define EXT_FLAG_EXP3           0x400000        /* for experimental use */
   #define EXT_FLAG_EXP4           0x800000        /* for experimental use */
   
   /*
    * EXT flag description for use with printf(9) %b identifier.
    */
   #define EXT_FLAG_BITS \
       "\2\1EXT_FLAG_EMBREF\2EXT_FLAG_EXTREF\5EXT_FLAG_NOFREE" \
       "\21EXT_FLAG_VENDOR1\22EXT_FLAG_VENDOR2\23EXT_FLAG_VENDOR3" \
       "\24EXT_FLAG_VENDOR4\25EXT_FLAG_EXP1\26EXT_FLAG_EXP2\27EXT_FLAG_EXP3" \
       "\30EXT_FLAG_EXP4"
   
   /*
    * Return values for (*ext_free).
    */
   #define EXT_FREE_OK     0       /* Normal return */
   
   /*
    * Flags indicating checksum, segmentation and other offload work to be
    * done, or already done, by hardware or lower layers.  It is split into
    * separate inbound and outbound flags.
    *
    * Outbound flags that are set by upper protocol layers requesting lower
    * layers, or ideally the hardware, to perform these offloading tasks.
    * For outbound packets this field and its flags can be directly tested
    * against if_data.ifi_hwassist.
    */
   #define CSUM_IP                 0x00000001      /* IP header checksum offload */
   #define CSUM_IP_UDP             0x00000002      /* UDP checksum offload */
   #define CSUM_IP_TCP             0x00000004      /* TCP checksum offload */
   #define CSUM_IP_SCTP            0x00000008      /* SCTP checksum offload */
   #define CSUM_IP_TSO             0x00000010      /* TCP segmentation offload */
   #define CSUM_IP_ISCSI           0x00000020      /* iSCSI checksum offload */
   
   #define CSUM_IP6_UDP            0x00000200      /* UDP checksum offload */
   #define CSUM_IP6_TCP            0x00000400      /* TCP checksum offload */
   #define CSUM_IP6_SCTP           0x00000800      /* SCTP checksum offload */
   #define CSUM_IP6_TSO            0x00001000      /* TCP segmentation offload */
   #define CSUM_IP6_ISCSI          0x00002000      /* iSCSI checksum offload */
   
   /* Inbound checksum support where the checksum was verified by hardware. */
   #define CSUM_L3_CALC            0x01000000      /* calculated layer 3 csum */
   #define CSUM_L3_VALID           0x02000000      /* checksum is correct */
   #define CSUM_L4_CALC            0x04000000      /* calculated layer 4 csum */
   #define CSUM_L4_VALID           0x08000000      /* checksum is correct */
   #define CSUM_L5_CALC            0x10000000      /* calculated layer 5 csum */
   #define CSUM_L5_VALID           0x20000000      /* checksum is correct */
   #define CSUM_COALESED           0x40000000      /* contains merged segments */
   
   /*
    * CSUM flag description for use with printf(9) %b identifier.
    */
   #define CSUM_BITS \
       "\2\1CSUM_IP\2CSUM_IP_UDP\3CSUM_IP_TCP\4CSUM_IP_SCTP\5CSUM_IP_TSO" \
       "\6CSUM_IP_ISCSI" \
       "\12CSUM_IP6_UDP\13CSUM_IP6_TCP\14CSUM_IP6_SCTP\15CSUM_IP6_TSO" \
       "\16CSUM_IP6_ISCSI" \
       "\31CSUM_L3_CALC\32CSUM_L3_VALID\33CSUM_L4_CALC\34CSUM_L4_VALID" \
       "\35CSUM_L5_CALC\36CSUM_L5_VALID\37CSUM_COALESED"
   
   /* CSUM flags compatibility mappings. */
   #define CSUM_IP_CHECKED         CSUM_L3_CALC
   #define CSUM_IP_VALID           CSUM_L3_VALID
   #define CSUM_DATA_VALID         CSUM_L4_VALID
   #define CSUM_PSEUDO_HDR         CSUM_L4_CALC
   #define CSUM_SCTP_VALID         CSUM_L4_VALID
   #define CSUM_DELAY_DATA         (CSUM_TCP|CSUM_UDP)
   #define CSUM_DELAY_IP           CSUM_IP         /* Only v4, no v6 IP hdr csum */
   #define CSUM_DELAY_DATA_IPV6    (CSUM_TCP_IPV6|CSUM_UDP_IPV6)
   #define CSUM_DATA_VALID_IPV6    CSUM_DATA_VALID
   #define CSUM_TCP                CSUM_IP_TCP
   #define CSUM_UDP                CSUM_IP_UDP
   #define CSUM_SCTP               CSUM_IP_SCTP
   #define CSUM_TSO                (CSUM_IP_TSO|CSUM_IP6_TSO)
   #define CSUM_UDP_IPV6           CSUM_IP6_UDP
   #define CSUM_TCP_IPV6           CSUM_IP6_TCP
   #define CSUM_SCTP_IPV6          CSUM_IP6_SCTP
   #define CSUM_FRAGMENT           0x0             /* Unused */
   
   /*
    * mbuf types describing the content of the mbuf (including external storage).
    */
   #define MT_NOTMBUF      0       /* USED INTERNALLY ONLY! Object is not mbuf */
   #define MT_DATA         1       /* dynamic (data) allocation */
   #define MT_HEADER       MT_DATA /* packet header, use M_PKTHDR instead */
   
   #define MT_VENDOR1      4       /* for vendor-internal use */
   #define MT_VENDOR2      5       /* for vendor-internal use */
   #define MT_VENDOR3      6       /* for vendor-internal use */
   #define MT_VENDOR4      7       /* for vendor-internal use */
   
   #define MT_SONAME       8       /* socket name */
   
   #define MT_EXP1         9       /* for experimental use */
   #define MT_EXP2         10      /* for experimental use */
   #define MT_EXP3         11      /* for experimental use */
   #define MT_EXP4         12      /* for experimental use */
   
   #define MT_CONTROL      14      /* extra-data protocol message */
   #define MT_OOBDATA      15      /* expedited data  */
   #define MT_NTYPES       16      /* number of mbuf types for mbtypes[] */
   
   #define MT_NOINIT       255     /* Not a type but a flag to allocate
                                      a non-initialized mbuf */
   
   /*
    * Compatibility with historic mbuf allocator.
    */
   #define MBTOM(how)      (how)
   #define M_DONTWAIT      M_NOWAIT
   #define M_TRYWAIT       M_WAITOK
   #define M_WAIT          M_WAITOK
   
   /*
    * String names of mbuf-related UMA(9) and malloc(9) types.  Exposed to
    * !_KERNEL so that monitoring tools can look up the zones with
    * libmemstat(3).
    */
   #define MBUF_MEM_NAME           "mbuf"
   #define MBUF_CLUSTER_MEM_NAME   "mbuf_cluster"
   #define MBUF_PACKET_MEM_NAME    "mbuf_packet"
   #define MBUF_JUMBOP_MEM_NAME    "mbuf_jumbo_page"
   #define MBUF_JUMBO9_MEM_NAME    "mbuf_jumbo_9k"
   #define MBUF_JUMBO16_MEM_NAME   "mbuf_jumbo_16k"
   #define MBUF_TAG_MEM_NAME       "mbuf_tag"
   #define MBUF_EXTREFCNT_MEM_NAME "mbuf_ext_refcnt"
   
   #ifdef _KERNEL
   
   #ifdef WITNESS
   #define MBUF_CHECKSLEEP(how) do {                                       \
           if (how == M_WAITOK)                                            \
                   WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,         \
                       "Sleeping in \"%s\"", __func__);                    \
   } while (0)
   #else
   #define MBUF_CHECKSLEEP(how)
   #endif
   
   /*
    * Network buffer allocation API
    *
    * The rest of it is defined in kern/kern_mbuf.c
    */
   extern uma_zone_t       zone_mbuf;
   extern uma_zone_t       zone_clust;
   extern uma_zone_t       zone_pack;
   extern uma_zone_t       zone_jumbop;
   extern uma_zone_t       zone_jumbo9;
   extern uma_zone_t       zone_jumbo16;
   extern uma_zone_t       zone_ext_refcnt;
   
   void             mb_free_ext(struct mbuf *);
   int              m_pkthdr_init(struct mbuf *, int);
   
   static __inline int
   m_gettype(int size)
   {
           int type;
   
           switch (size) {
           case MSIZE:
                   type = EXT_MBUF;
                   break;
           case MCLBYTES:
                   type = EXT_CLUSTER;
                   break;
   #if MJUMPAGESIZE != MCLBYTES
           case MJUMPAGESIZE:
                   type = EXT_JUMBOP;
                   break;
   #endif
           case MJUM9BYTES:
                   type = EXT_JUMBO9;
                   break;
           case MJUM16BYTES:
                   type = EXT_JUMBO16;
                   break;
           default:
                   panic("%s: invalid cluster size", __func__);
           }
   
           return (type);
   }
   
   /*
    * Associated an external reference counted buffer with an mbuf.
    */
   static __inline void
   m_extaddref(struct mbuf *m, caddr_t buf, u_int size, u_int *ref_cnt,
       int (*freef)(struct mbuf *, void *, void *), void *arg1, void *arg2)
   {
   
           KASSERT(ref_cnt != NULL, ("%s: ref_cnt not provided", __func__));
   
           atomic_add_int(ref_cnt, 1);
           m->m_flags |= M_EXT;
           m->m_ext.ext_buf = buf;
           m->m_ext.ref_cnt = ref_cnt;
           m->m_data = m->m_ext.ext_buf;
           m->m_ext.ext_size = size;
           m->m_ext.ext_free = freef;
           m->m_ext.ext_arg1 = arg1;
           m->m_ext.ext_arg2 = arg2;
           m->m_ext.ext_type = EXT_EXTREF;
   }
   
   static __inline uma_zone_t
   m_getzone(int size)
   {
           uma_zone_t zone;
   
           switch (size) {
           case MCLBYTES:
                   zone = zone_clust;
                   break;
   #if MJUMPAGESIZE != MCLBYTES
           case MJUMPAGESIZE:
                   zone = zone_jumbop;
                   break;
   #endif
           case MJUM9BYTES:
                   zone = zone_jumbo9;
                   break;
           case MJUM16BYTES:
                   zone = zone_jumbo16;
                   break;
           default:
                   panic("%s: invalid cluster size", __func__);
           }
   
           return (zone);
   }
   
   /*
    * Initialize an mbuf with linear storage.
    *
    * Inline because the consumer text overhead will be roughly the same to
    * initialize or call a function with this many parameters and M_PKTHDR
    * should go away with constant propagation for !MGETHDR.
    */
   static __inline int
   m_init(struct mbuf *m, uma_zone_t zone, int size, int how, short type,
       int flags)
   {
           int error;
   
           m->m_next = NULL;
           m->m_nextpkt = NULL;
           m->m_data = m->m_dat;
           m->m_len = 0;
           m->m_flags = flags;
           m->m_type = type;
           if (flags & M_PKTHDR) {
                   if ((error = m_pkthdr_init(m, how)) != 0)
                           return (error);
           }
   
           return (0);
   }
   
   static __inline struct mbuf *
   m_get(int how, short type)
   {
           struct mb_args args;
   
           args.flags = 0;
           args.type = type;
           return (uma_zalloc_arg(zone_mbuf, &args, how));
   }
   
   /*
    * XXX This should be deprecated, very little use.
    */
   static __inline struct mbuf *
   m_getclr(int how, short type)
   {
           struct mbuf *m;
           struct mb_args args;
   
           args.flags = 0;
           args.type = type;
           m = uma_zalloc_arg(zone_mbuf, &args, how);
           if (m != NULL)
                   bzero(m->m_data, MLEN);
           return (m);
   }
   
   static __inline struct mbuf *
   m_gethdr(int how, short type)
   {
           struct mb_args args;
   
           args.flags = M_PKTHDR;
           args.type = type;
           return (uma_zalloc_arg(zone_mbuf, &args, how));
   }
   
   static __inline struct mbuf *
   m_getcl(int how, short type, int flags)
   {
           struct mb_args args;
   
           args.flags = flags;
           args.type = type;
           return (uma_zalloc_arg(zone_pack, &args, how));
   }
   
   static __inline void
   m_clget(struct mbuf *m, int how)
   {
   
           if (m->m_flags & M_EXT)
                   printf("%s: %p mbuf already has cluster\n", __func__, m);
           m->m_ext.ext_buf = (char *)NULL;
           uma_zalloc_arg(zone_clust, m, how);
           /*
            * On a cluster allocation failure, drain the packet zone and retry,
            * we might be able to loosen a few clusters up on the drain.
            */
           if ((how & M_NOWAIT) && (m->m_ext.ext_buf == NULL)) {
                   zone_drain(zone_pack);
                   uma_zalloc_arg(zone_clust, m, how);
           }
   }
   
   /*
    * m_cljget() is different from m_clget() as it can allocate clusters without
    * attaching them to an mbuf.  In that case the return value is the pointer
    * to the cluster of the requested size.  If an mbuf was specified, it gets
    * the cluster attached to it and the return value can be safely ignored.
    * For size it takes MCLBYTES, MJUMPAGESIZE, MJUM9BYTES, MJUM16BYTES.
    */
   static __inline void *
   m_cljget(struct mbuf *m, int how, int size)
   {
           uma_zone_t zone;
   
           if (m && m->m_flags & M_EXT)
                   printf("%s: %p mbuf already has cluster\n", __func__, m);
           if (m != NULL)
                   m->m_ext.ext_buf = NULL;
   
           zone = m_getzone(size);
           return (uma_zalloc_arg(zone, m, how));
   }
   
   static __inline void
   m_cljset(struct mbuf *m, void *cl, int type)
   {
           uma_zone_t zone;
           int size;
   
           switch (type) {
           case EXT_CLUSTER:
                   size = MCLBYTES;
                   zone = zone_clust;
                   break;
   #if MJUMPAGESIZE != MCLBYTES
           case EXT_JUMBOP:
                   size = MJUMPAGESIZE;
                   zone = zone_jumbop;
                   break;
   #endif
           case EXT_JUMBO9:
                   size = MJUM9BYTES;
                   zone = zone_jumbo9;
                   break;
           case EXT_JUMBO16:
                   size = MJUM16BYTES;
                   zone = zone_jumbo16;
                   break;
           default:
                   panic("%s: unknown cluster type", __func__);
                   break;
           }
   
           m->m_data = m->m_ext.ext_buf = cl;
           m->m_ext.ext_free = m->m_ext.ext_arg1 = m->m_ext.ext_arg2 = NULL;
           m->m_ext.ext_size = size;
           m->m_ext.ext_type = type;
           m->m_ext.ext_flags = 0;
           m->m_ext.ref_cnt = uma_find_refcnt(zone, cl);
           m->m_flags |= M_EXT;
   
   }
   
   static __inline void
   m_chtype(struct mbuf *m, short new_type)
   {
   
           m->m_type = new_type;
   }
   
   static __inline void
   m_clrprotoflags(struct mbuf *m)
   {
   
           m->m_flags &= ~M_PROTOFLAGS;
   }
   
   static __inline struct mbuf *
   m_last(struct mbuf *m)
   {
   
           while (m->m_next)
                   m = m->m_next;
           return (m);
   }
   
   /*
    * mbuf, cluster, and external object allocation macros (for compatibility
    * purposes).
    */
   #define M_MOVE_PKTHDR(to, from) m_move_pkthdr((to), (from))
   #define MGET(m, how, type)      ((m) = m_get((how), (type)))
   #define MGETHDR(m, how, type)   ((m) = m_gethdr((how), (type)))
   #define MCLGET(m, how)          m_clget((m), (how))
   #define MEXTADD(m, buf, size, free, arg1, arg2, flags, type)            \
       (void )m_extadd((m), (caddr_t)(buf), (size), (free), (arg1), (arg2),\
       (flags), (type), M_NOWAIT)
   #define m_getm(m, len, how, type)                                       \
       m_getm2((m), (len), (how), (type), M_PKTHDR)
   
   /*
    * Evaluate TRUE if it's safe to write to the mbuf m's data region (this can
    * be both the local data payload, or an external buffer area, depending on
    * whether M_EXT is set).
    */
   #define M_WRITABLE(m)   (!((m)->m_flags & M_RDONLY) &&                  \
                            (!(((m)->m_flags & M_EXT)) ||                  \
                            (*((m)->m_ext.ref_cnt) == 1)) )                \
   
   /* 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: no mbuf packet header!", __func__))
   
   /*
    * Ensure that the supplied mbuf is a valid, non-free mbuf.
    *
    * XXX: Broken at the moment.  Need some UMA magic to make it work again.
    */
   #define M_ASSERTVALID(m)                                                \
           KASSERT((((struct mbuf *)m)->m_flags & 0) == 0,                 \
               ("%s: attempted use of a free mbuf!", __func__))
   
   /*
    * 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 {                                            \
           KASSERT(!((m)->m_flags & (M_PKTHDR|M_EXT)),                     \
                   ("%s: M_ALIGN not normal mbuf", __func__));             \
           KASSERT((m)->m_data == (m)->m_dat,                              \
                   ("%s: M_ALIGN not a virgin mbuf", __func__));           \
           (m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);            \
   } while (0)
   
   /*
    * As above, for mbufs allocated with m_gethdr/MGETHDR or initialized by
    * M_DUP/MOVE_PKTHDR.
    */
   #define MH_ALIGN(m, len) do {                                           \
           KASSERT((m)->m_flags & M_PKTHDR && !((m)->m_flags & M_EXT),     \
                   ("%s: MH_ALIGN not PKTHDR mbuf", __func__));            \
           KASSERT((m)->m_data == (m)->m_pktdat,                           \
                   ("%s: MH_ALIGN not a virgin mbuf", __func__));          \
           (m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);           \
   } while (0)
   
   /*
    * As above, for mbuf with external storage.
    */
   #define MEXT_ALIGN(m, len) do {                                         \
           KASSERT((m)->m_flags & M_EXT,                                   \
                   ("%s: MEXT_ALIGN not an M_EXT mbuf", __func__));        \
           KASSERT((m)->m_data == (m)->m_ext.ext_buf,                      \
                   ("%s: MEXT_ALIGN not a virgin mbuf", __func__));        \
           (m)->m_data += ((m)->m_ext.ext_size - (len)) &                  \
               ~(sizeof(long) - 1);                                        \
   } while (0)
   
   /*
    * Compute the amount of space available before the current start 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_LEADINGSPACE(m)                                               \
           ((m)->m_flags & M_EXT ?                                         \
               (M_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 the 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);                                             \
                                                                           \
           MBUF_CHECKSLEEP(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)
   
   /*
    * Change mbuf to new type.  This is a relatively expensive operation and
    * should be avoided.
    */
   #define MCHTYPE(m, t)   m_chtype((m), (t))
   
   /* 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), M_NOWAIT)
   
   extern int              max_datalen;    /* MHLEN - max_hdr */
   extern int              max_hdr;        /* Largest link + protocol header */
   extern int              max_linkhdr;    /* Largest link-level header */
   extern int              max_protohdr;   /* Largest protocol header */
   extern int              nmbclusters;    /* Maximum number of clusters */
   
   struct uio;
   
   void             m_adj(struct mbuf *, int);
   void             m_align(struct mbuf *, int);
   int              m_apply(struct mbuf *, int, int,
                       int (*)(void *, void *, u_int), void *);
   int              m_append(struct mbuf *, int, c_caddr_t);
   void             m_cat(struct mbuf *, struct mbuf *);
   int              m_extadd(struct mbuf *, caddr_t, u_int,
                       int (*)(struct mbuf *, void *, void *), void *, void *,
                       int, int, int);
   struct mbuf     *m_collapse(struct mbuf *, int, int);
   void             m_copyback(struct mbuf *, int, int, c_caddr_t);
   void             m_copydata(const struct mbuf *, int, int, caddr_t);
   struct mbuf     *m_copym(struct mbuf *, int, int, int);
   struct mbuf     *m_copymdata(struct mbuf *, struct mbuf *,
                       int, int, int, int);
   struct mbuf     *m_copypacket(struct mbuf *, int);
   void             m_copy_pkthdr(struct mbuf *, struct mbuf *);
   struct mbuf     *m_copyup(struct mbuf *, int, int);
   struct mbuf     *m_defrag(struct mbuf *, int);
   void             m_demote(struct mbuf *, int);
   struct mbuf     *m_devget(char *, int, int, struct ifnet *,
                       void (*)(char *, caddr_t, u_int));
   struct mbuf     *m_dup(struct mbuf *, int);
   int              m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
   u_int            m_fixhdr(struct mbuf *);
   struct mbuf     *m_fragment(struct mbuf *, int, int);
   void             m_freem(struct mbuf *);
   struct mbuf     *m_get2(int, int, short, int);
   struct mbuf     *m_getjcl(int, short, int, int);
   struct mbuf     *m_getm2(struct mbuf *, int, int, short, int);
   struct mbuf     *m_getptr(struct mbuf *, int, int *);
   u_int            m_length(struct mbuf *, struct mbuf **);
   int              m_mbuftouio(struct uio *, struct mbuf *, int);
   void             m_move_pkthdr(struct mbuf *, struct mbuf *);
   struct mbuf     *m_prepend(struct mbuf *, int, int);
   void             m_print(const struct mbuf *, int);
   struct mbuf     *m_pulldown(struct mbuf *, int, int, int *);
   struct mbuf     *m_pullup(struct mbuf *, int);
   int              m_sanity(struct mbuf *, int);
   struct mbuf     *m_split(struct mbuf *, int, int);
   struct mbuf     *m_uiotombuf(struct uio *, int, int, int, int);
   struct mbuf     *m_unshare(struct mbuf *, int);
   
   /*-
    * Network 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 chosen 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_alloc has the default memory
    * alignment implemented by malloc.  To reference private data one can use a
    * construct like:
    *
    *      struct m_tag *mtag = m_tag_alloc(...);
    *      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_alloc(...);
    *      struct m_tag *mtag = &p->tag;
    */
   
   /*
    * Persistent tags stay with an mbuf until the mbuf is reclaimed.  Otherwise
    * tags are expected to ``vanish'' when they pass through a network
    * interface.  For most interfaces this happens normally as the tags are
    * reclaimed when the mbuf is free'd.  However in some special cases
    * reclaiming must be done manually.  An example is packets that pass through
    * the loopback interface.  Also, one must be careful to do this when
    * ``turning around'' packets (e.g., icmp_reflect).
   *
   * To mark a tag persistent bit-or this flag in when defining the tag id.
   * The tag will then be treated as described above.
   */
  #define MTAG_PERSISTENT                         0x800
  
  #define PACKET_TAG_NONE                         0  /* Nadda */
  
  /* Packet tags for use with PACKET_ABI_COMPAT. */
  #define PACKET_TAG_IPSEC_IN_DONE                1  /* IPsec applied, in */
  #define PACKET_TAG_IPSEC_OUT_DONE               2  /* IPsec applied, out */
  #define PACKET_TAG_IPSEC_IN_CRYPTO_DONE         3  /* NIC IPsec crypto done */
  #define PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED      4  /* NIC IPsec crypto req'ed */
  #define PACKET_TAG_IPSEC_IN_COULD_DO_CRYPTO     5  /* NIC notifies IPsec */
  #define PACKET_TAG_IPSEC_PENDING_TDB            6  /* Reminder to do IPsec */
  #define PACKET_TAG_BRIDGE                       7  /* Bridge processing done */
  #define PACKET_TAG_GIF                          8  /* GIF processing done */
  #define PACKET_TAG_GRE                          9  /* GRE processing done */
  #define PACKET_TAG_IN_PACKET_CHECKSUM           10 /* NIC checksumming done */
  #define PACKET_TAG_ENCAP                        11 /* Encap.  processing */
  #define PACKET_TAG_IPSEC_SOCKET                 12 /* IPSEC socket ref */
  #define PACKET_TAG_IPSEC_HISTORY                13 /* IPSEC history */
  #define PACKET_TAG_IPV6_INPUT                   14 /* IPV6 input processing */
  #define PACKET_TAG_DUMMYNET                     15 /* dummynet info */
  #define PACKET_TAG_DIVERT                       17 /* divert info */
  #define PACKET_TAG_IPFORWARD                    18 /* ipforward info */
  #define PACKET_TAG_MACLABEL     (19 | MTAG_PERSISTENT) /* MAC label */
  #define PACKET_TAG_PF           (21 | MTAG_PERSISTENT) /* PF/ALTQ information */
  #define PACKET_TAG_RTSOCKFAM                    25 /* rtsock sa family */
  #define PACKET_TAG_IPOPTIONS                    27 /* Saved IP options */
  #define PACKET_TAG_CARP                         28 /* CARP info */
  #define PACKET_TAG_IPSEC_NAT_T_PORTS            29 /* two uint16_t */
  #define PACKET_TAG_ND_OUTGOING                  30 /* ND outgoing */
  
  /* Specific cookies and tags. */
  
  /* Packet tag routines. */
  struct m_tag    *m_tag_alloc(u_int32_t, int, int, int);
  void             m_tag_delete(struct mbuf *, struct m_tag *);
  void             m_tag_delete_chain(struct mbuf *, struct m_tag *);
  void             m_tag_free_default(struct m_tag *);
  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 *, struct mbuf *, int);
  void             m_tag_delete_nonpersistent(struct mbuf *);
  
  /*
   * Initialize the list of tags associated with an mbuf.
   */
  static __inline void
  m_tag_init(struct mbuf *m)
  {
  
          SLIST_INIT(&m->m_pkthdr.tags);
  }
  
  /*
   * Set up the contents of a tag.  Note that this does not fill in the free
   * method; the caller is expected to do that.
   *
   * XXX probably should be called m_tag_init, but that was already taken.
   */
  static __inline void
  m_tag_setup(struct m_tag *t, u_int32_t cookie, int type, int len)
  {
  
          t->m_tag_id = type;
          t->m_tag_len = len;
          t->m_tag_cookie = cookie;
  }
  
  /*
   * Reclaim resources associated with a tag.
   */
  static __inline void
  m_tag_free(struct m_tag *t)
  {
  
          (*t->m_tag_free)(t);
  }
  
  /*
   * Return the first tag associated with an mbuf.
   */
  static __inline struct m_tag *
  m_tag_first(struct mbuf *m)
  {
  
          return (SLIST_FIRST(&m->m_pkthdr.tags));
  }
  
  /*
   * Return the next tag in the list of tags associated with an mbuf.
   */
  static __inline struct m_tag *
  m_tag_next(struct mbuf *m, struct m_tag *t)
  {
  
          return (SLIST_NEXT(t, m_tag_link));
  }
  
  /*
   * Prepend a tag to the list of tags associated with an mbuf.
   */
  static __inline void
  m_tag_prepend(struct mbuf *m, struct m_tag *t)
  {
  
          SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
  }
  
  /*
   * Unlink a tag from the list of tags associated with an mbuf.
   */
  static __inline void
  m_tag_unlink(struct mbuf *m, struct m_tag *t)
  {
  
          SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
  }
  
  /* These are for OpenBSD compatibility. */
  #define MTAG_ABI_COMPAT         0               /* compatibility ABI */
  
  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 (SLIST_EMPTY(&m->m_pkthdr.tags) ? (struct m_tag *)NULL :
              m_tag_locate(m, MTAG_ABI_COMPAT, type, start));
  }
  
  static __inline struct mbuf *
  m_free(struct mbuf *m)
  {
          struct mbuf *n = m->m_next;
  
          if ((m->m_flags & (M_PKTHDR|M_NOFREE)) == (M_PKTHDR|M_NOFREE))
                  m_tag_delete_chain(m, NULL);
          if (m->m_flags & M_EXT)
                  mb_free_ext(m);
          else if ((m->m_flags & M_NOFREE) == 0)
                  uma_zfree(zone_mbuf, m);
          return (n);
  }
  
  static int inline
  rt_m_getfib(struct mbuf *m)
  {
          KASSERT(m->m_flags & M_PKTHDR , ("Attempt to get FIB from non header mbuf."));
          return (m->m_pkthdr.fibnum);
  }
  
  #define M_GETFIB(_m)   rt_m_getfib(_m)
  
  #define M_SETFIB(_m, _fib) do {                                         \
          KASSERT((_m)->m_flags & M_PKTHDR, ("Attempt to set FIB on non header mbuf."));  \
          ((_m)->m_pkthdr.fibnum) = (_fib);                               \
  } while (0)
  
  #endif /* _KERNEL */
  
  #ifdef MBUF_PROFILING
   void m_profile(struct mbuf *m);
   #define M_PROFILE(m) m_profile(m)
  #else
   #define M_PROFILE(m)
  #endif
  
  
  #endif /* !_SYS_MBUF_H_ */

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