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

     /*      $OpenBSD: mbuf.h,v 1.255 2022/08/15 16:15:37 bluhm Exp $        */
     /*      $NetBSD: mbuf.h,v 1.19 1996/02/09 18:25:14 christos Exp $       */
     
     /*
      * 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
     */
    
    #ifndef _SYS_MBUF_H_
    #define _SYS_MBUF_H_
    
    #include <sys/queue.h>
    
    /*
     * Constants related to network buffer management.
     * MCLBYTES must be no larger than PAGE_SIZE (the software page size) and,
     * on machines that exchange pages of input or output buffers with mbuf
     * clusters (MAPPED_MBUFS), MCLBYTES must also be an integral multiple
     * of the hardware page size.
     */
    #define MSIZE           256             /* size of an mbuf */
    
    /*
     * Mbufs are of a single size, MSIZE, which includes overhead.  An mbuf may
     * add a single "mbuf cluster" of size MCLBYTES, 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 MAXMCLBYTES     (64 * 1024)             /* largest cluster from the stack */
    #define MINCLSIZE       (MHLEN + MLEN + 1)      /* smallest amount to put in cluster */
    #define M_MAXCOMPRESS   (MHLEN / 2)             /* max amount to copy for compression */
    
    #define MCLSHIFT        11              /* convert bytes to m_buf clusters */
                                            /* 2K cluster can hold Ether frame */
    #define MCLBYTES        (1 << MCLSHIFT) /* size of a m_buf cluster */
    #define MCLOFSET        (MCLBYTES - 1)
    
    /* Packet tags structure */
    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 */
    };
    
    /*
     * Macros for type conversion
     * mtod(m,t) -  convert mbuf pointer to data pointer of correct type
     */
    #define mtod(m,t)       ((t)((m)->m_data))
    
    /* header at beginning of each 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 */
            u_int   mh_len;                 /* amount of data in this mbuf */
            short   mh_type;                /* type of data in this mbuf */
            u_short mh_flags;               /* flags; see below */
    #ifndef __LP64__
            u_int   mh_pad;                 /* pad to 8-byte boundary */
    #endif
    };
    
    /* pf stuff */
    struct pf_state_key;
    struct inpcb;
    
    struct pkthdr_pf {
            struct pf_state_key *statekey;  /* pf stackside statekey */
           struct inpcb    *inp;           /* connected pcb for outgoing packet */
           u_int32_t        qid;           /* queue id */
           u_int16_t        tag;           /* tag id */
           u_int16_t        delay;         /* delay packet by X ms */
           u_int8_t         flags;
           u_int8_t         routed;
           u_int8_t         prio;
           u_int8_t         pad[1];
   };
   
   /* pkthdr_pf.flags */
   #define PF_TAG_GENERATED                0x01
   #define PF_TAG_SYNCOOKIE_RECREATED      0x02
   #define PF_TAG_TRANSLATE_LOCALHOST      0x04
   #define PF_TAG_DIVERTED                 0x08
   #define PF_TAG_DIVERTED_PACKET          0x10
   #define PF_TAG_REROUTE                  0x20
   #define PF_TAG_REFRAGMENTED             0x40    /* refragmented ipv6 packet */
   #define PF_TAG_PROCESSED                0x80    /* packet was checked by pf */
   
   #ifdef _KERNEL
   #define MPF_BITS \
       ("\2\1GENERATED\2SYNCOOKIE_RECREATED\3TRANSLATE_LOCALHOST\4DIVERTED" \
       "\5DIVERTED_PACKET\6REROUTE\7REFRAGMENTED\10PROCESSED")
   #endif
   
   /* record/packet header in first mbuf of chain; valid if M_PKTHDR set */
   struct  pkthdr {
           void                    *ph_cookie;     /* additional data */
           SLIST_HEAD(, m_tag)      ph_tags;       /* list of packet tags */
           int64_t                  ph_timestamp;  /* packet timestamp */
           int                      len;           /* total packet length */
           u_int16_t                ph_tagsset;    /* mtags attached */
           u_int16_t                ph_flowid;     /* pseudo unique flow id */
           u_int16_t                csum_flags;    /* checksum flags */
           u_int16_t                ether_vtag;    /* Ethernet 802.1p+Q vlan tag */
           u_int                    ph_rtableid;   /* routing table id */
           u_int                    ph_ifidx;      /* rcv interface index */
           u_int8_t                 ph_loopcnt;    /* mbuf is looping in kernel */
           u_int8_t                 ph_family;     /* af, used when queueing */
           struct pkthdr_pf         pf;
   };
   
   /* description of external storage mapped into mbuf, valid if M_EXT set */
   struct mbuf_ext {
           caddr_t ext_buf;                /* start of buffer */
           void    *ext_arg;
           u_int   ext_free_fn;            /* index of free function */
           u_int   ext_size;               /* size of buffer, for ext_free_fn */
           struct mbuf *ext_nextref;
           struct mbuf *ext_prevref;
   #ifdef DEBUG
           const char *ext_ofile;
           const char *ext_nfile;
           int ext_oline;
           int ext_nline;
   #endif
   };
   
   struct mbuf {
           struct  m_hdr m_hdr;
           union {
                   struct {
                           struct  pkthdr MH_pkthdr;       /* M_PKTHDR set */
                           union {
                                   struct  mbuf_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
   
   /* 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_EXTWR         0x0008  /* external storage is writable */
   #define M_PROTO1        0x0010  /* protocol-specific */
   
   /* mbuf pkthdr flags, also in m_flags */
   #define M_VLANTAG       0x0020  /* ether_vtag is valid */
   #define M_LOOP          0x0040  /* packet has been sent from local machine */
   #define M_BCAST         0x0100  /* sent/received as link-level broadcast */
   #define M_MCAST         0x0200  /* sent/received as link-level multicast */
   #define M_CONF          0x0400  /* payload was encrypted (ESP-transport) */
   #define M_AUTH          0x0800  /* payload was authenticated (AH or ESP auth) */
   #define M_TUNNEL        0x1000  /* IP-in-IP added by tunnel mode IPsec */
   #define M_ZEROIZE       0x2000  /* Zeroize data part on free */
   #define M_COMP          0x4000  /* header was decompressed */
   #define M_LINK0         0x8000  /* link layer specific flag */
   
   #ifdef _KERNEL
   #define M_BITS \
       ("\2\1M_EXT\2M_PKTHDR\3M_EOR\4M_EXTWR\5M_PROTO1\6M_VLANTAG\7M_LOOP" \
       "\11M_BCAST\12M_MCAST\13M_CONF\14M_AUTH\15M_TUNNEL" \
       "\16M_ZEROIZE\17M_COMP\20M_LINK0")
   #endif
   
   /* flags copied when copying m_pkthdr */
   #define M_COPYFLAGS     (M_PKTHDR|M_EOR|M_PROTO1|M_BCAST|M_MCAST|M_CONF|M_COMP|\
                            M_AUTH|M_LOOP|M_TUNNEL|M_LINK0|M_VLANTAG|M_ZEROIZE)
   
   /* Checksumming flags */
   #define M_IPV4_CSUM_OUT         0x0001  /* IPv4 checksum needed */
   #define M_TCP_CSUM_OUT          0x0002  /* TCP checksum needed */
   #define M_UDP_CSUM_OUT          0x0004  /* UDP checksum needed */
   #define M_IPV4_CSUM_IN_OK       0x0008  /* IPv4 checksum verified */
   #define M_IPV4_CSUM_IN_BAD      0x0010  /* IPv4 checksum bad */
   #define M_TCP_CSUM_IN_OK        0x0020  /* TCP checksum verified */
   #define M_TCP_CSUM_IN_BAD       0x0040  /* TCP checksum bad */
   #define M_UDP_CSUM_IN_OK        0x0080  /* UDP checksum verified */
   #define M_UDP_CSUM_IN_BAD       0x0100  /* UDP checksum bad */
   #define M_ICMP_CSUM_OUT         0x0200  /* ICMP/ICMPv6 checksum needed */
   #define M_ICMP_CSUM_IN_OK       0x0400  /* ICMP/ICMPv6 checksum verified */
   #define M_ICMP_CSUM_IN_BAD      0x0800  /* ICMP/ICMPv6 checksum bad */
   #define M_IPV6_DF_OUT           0x1000  /* don't fragment outgoing IPv6 */
   #define M_TIMESTAMP             0x2000  /* ph_timestamp is set */
   #define M_FLOWID                0x4000  /* ph_flowid is set */
   
   #ifdef _KERNEL
   #define MCS_BITS \
       ("\2\1IPV4_CSUM_OUT\2TCP_CSUM_OUT\3UDP_CSUM_OUT\4IPV4_CSUM_IN_OK" \
       "\5IPV4_CSUM_IN_BAD\6TCP_CSUM_IN_OK\7TCP_CSUM_IN_BAD\10UDP_CSUM_IN_OK" \
       "\11UDP_CSUM_IN_BAD\12ICMP_CSUM_OUT\13ICMP_CSUM_IN_OK\14ICMP_CSUM_IN_BAD" \
       "\15IPV6_NODF_OUT" "\16TIMESTAMP" "\17FLOWID")
   #endif
   
   /* 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_SOOPTS       4       /* socket options */
   #define MT_FTABLE       5       /* fragment reassembly header */
   #define MT_CONTROL      6       /* extra-data protocol message */
   #define MT_OOBDATA      7       /* expedited data  */
   #define MT_NTYPES       8
   
   /* flags to m_get/MGET */
   #include <sys/malloc.h>
   #define M_DONTWAIT      M_NOWAIT
   #define M_WAIT          M_WAITOK
   
   /*
    * mbuf allocation/deallocation macros:
    *
    *      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) m = m_get((how), (type))
   
   #define MGETHDR(m, how, type) m = m_gethdr((how), (type))
   
   /*
    * Macros for tracking external storage associated with an mbuf.
    */
   #ifdef DEBUG
   #define MCLREFDEBUGN(m, file, line) do {                                \
                   (m)->m_ext.ext_nfile = (file);                          \
                   (m)->m_ext.ext_nline = (line);                          \
           } while (/* CONSTCOND */ 0)
   #define MCLREFDEBUGO(m, file, line) do {                                \
                   (m)->m_ext.ext_ofile = (file);                          \
                   (m)->m_ext.ext_oline = (line);                          \
           } while (/* CONSTCOND */ 0)
   #else
   #define MCLREFDEBUGN(m, file, line)
   #define MCLREFDEBUGO(m, file, line)
   #endif
   
   #define MCLISREFERENCED(m)      ((m)->m_ext.ext_nextref != (m))
   
   #define MCLADDREFERENCE(o, n)   m_extref((o), (n))
   
   #define MCLINITREFERENCE(m)     do {                                    \
                   (m)->m_ext.ext_prevref = (m);                           \
                   (m)->m_ext.ext_nextref = (m);                           \
                   MCLREFDEBUGO((m), __FILE__, __LINE__);                  \
                   MCLREFDEBUGN((m), NULL, 0);                             \
           } while (/* CONSTCOND */ 0)
   
   /*
    * Macros for mbuf external storage.
    *
    * MEXTADD adds pre-allocated external storage to
    * a normal mbuf; the flag M_EXT is set.
    *
    * MCLGET allocates and adds an mbuf cluster to a normal mbuf;
    * the flag M_EXT is set upon success.
    */
   #define MEXTADD(m, buf, size, mflags, freefn, arg) do {                 \
           (m)->m_data = (m)->m_ext.ext_buf = (caddr_t)(buf);              \
           (m)->m_flags |= M_EXT | (mflags & M_EXTWR);                     \
           (m)->m_ext.ext_size = (size);                                   \
           (m)->m_ext.ext_free_fn = (freefn);                                      \
           (m)->m_ext.ext_arg = (arg);                                     \
           MCLINITREFERENCE(m);                                            \
   } while (/* CONSTCOND */ 0)
   
   #define MCLGET(m, how) (void) m_clget((m), (how), MCLBYTES)
   #define MCLGETL(m, how, l) m_clget((m), (how), (l))
   
   u_int mextfree_register(void (*)(caddr_t, u_int, void *));
   #define MEXTFREE_POOL 0
   
   /*
    * Move just m_pkthdr from from to to,
    * remove M_PKTHDR and clean flags/tags for from.
    */
   #define M_MOVE_HDR(to, from) do {                                       \
           (to)->m_pkthdr = (from)->m_pkthdr;                              \
           (from)->m_flags &= ~M_PKTHDR;                                   \
           SLIST_INIT(&(from)->m_pkthdr.ph_tags);                          \
           (from)->m_pkthdr.pf.statekey = NULL;                            \
   } while (/* CONSTCOND */ 0)
   
   /*
    * MOVE mbuf pkthdr from from to to.
    * from must have M_PKTHDR set, and to must be empty.
    */
   #define M_MOVE_PKTHDR(to, from) do {                                    \
           (to)->m_flags = ((to)->m_flags & (M_EXT | M_EXTWR));            \
           (to)->m_flags |= (from)->m_flags & M_COPYFLAGS;                 \
           M_MOVE_HDR((to), (from));                                       \
           if (((to)->m_flags & M_EXT) == 0)                               \
                   (to)->m_data = (to)->m_pktdat;                          \
   } while (/* CONSTCOND */ 0)
   
   /*
    * Determine if an mbuf's data area is read-only. This is true for
    * non-cluster external storage and for clusters that are being
    * referenced by more than one mbuf.
    */
   #define M_READONLY(m)                                                   \
           (((m)->m_flags & M_EXT) != 0 &&                                 \
             (((m)->m_flags & M_EXTWR) == 0 || MCLISREFERENCED(m)))
   
   /*
    * 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 M_DONTWAIT and allocation fails, the original mbuf chain
    * is freed and m is set to NULL.
    */
   #define M_PREPEND(m, plen, how) \
                   (m) = m_prepend((m), (plen), (how))
   
   /* length to m_copy to copy all */
   #define M_COPYALL       1000000000
   
   /*
    * Mbuf statistics.
    * For statistics related to mbuf and cluster allocations, see also the
    * pool headers (mbpool and mclpool).
    */
   struct mbstat {
           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_short m_mtypes[256];  /* type specific mbuf allocations */
   };
   
   #define MBSTAT_TYPES           MT_NTYPES
   #define MBSTAT_DROPS           (MBSTAT_TYPES + 0)
   #define MBSTAT_WAIT            (MBSTAT_TYPES + 1)
   #define MBSTAT_DRAIN           (MBSTAT_TYPES + 2)
   #define MBSTAT_COUNT           (MBSTAT_TYPES + 3)
   
   #include <sys/mutex.h>
   
   struct mbuf_list {
           struct mbuf             *ml_head;
           struct mbuf             *ml_tail;
           u_int                   ml_len;
   };
   
   struct mbuf_queue {
           struct mutex            mq_mtx;
           struct mbuf_list        mq_list;
           u_int                   mq_maxlen;
           u_int                   mq_drops;
   };
   
   #ifdef  _KERNEL
   struct pool;
   
   extern  long nmbclust;                  /* limit on the # of clusters */
   extern  int mblowat;                    /* mbuf low water mark */
   extern  int mcllowat;                   /* mbuf cluster low water mark */
   extern  int max_linkhdr;                /* largest link-level header */
   extern  int max_protohdr;               /* largest protocol header */
   extern  int max_hdr;                    /* largest link+protocol header */
   
   void    mbinit(void);
   void    mbcpuinit(void);
   int     nmbclust_update(long);
   struct  mbuf *m_copym(struct mbuf *, int, int, int);
   struct  mbuf *m_free(struct mbuf *);
   struct  mbuf *m_get(int, int);
   struct  mbuf *m_getclr(int, int);
   struct  mbuf *m_gethdr(int, int);
   struct  mbuf *m_inithdr(struct mbuf *);
   void    m_removehdr(struct mbuf *);
   void    m_resethdr(struct mbuf *);
   void    m_calchdrlen(struct mbuf *);
   int     m_defrag(struct mbuf *, int);
   struct  mbuf *m_prepend(struct mbuf *, int, int);
   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_makespace(struct mbuf *, int, int, int *);
   struct  mbuf *m_getptr(struct mbuf *, int, int *);
   int     m_leadingspace(struct mbuf *);
   int     m_trailingspace(struct mbuf *);
   void    m_align(struct mbuf *, int);
   struct mbuf *m_clget(struct mbuf *, int, u_int);
   void    m_extref(struct mbuf *, struct mbuf *);
   void    m_pool_init(struct pool *, u_int, u_int, const char *);
   u_int   m_pool_used(void);
   void    m_extfree_pool(caddr_t, u_int, void *);
   void    m_adj(struct mbuf *, int);
   int     m_copyback(struct mbuf *, int, int, const void *, int);
   struct mbuf *m_freem(struct mbuf *);
   void    m_purge(struct mbuf *);
   void    m_reclaim(void *, int);
   void    m_copydata(struct mbuf *, int, int, void *);
   void    m_cat(struct mbuf *, struct mbuf *);
   struct mbuf *m_devget(char *, int, int);
   int     m_apply(struct mbuf *, int, int,
               int (*)(caddr_t, caddr_t, unsigned int), caddr_t);
   struct mbuf *m_dup_pkt(struct mbuf *, unsigned int, int);
   int     m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
   
   void    m_microtime(const struct mbuf *, struct timeval *);
   
   static inline struct mbuf *
   m_freemp(struct mbuf **mp)
   {
           struct mbuf *m = *mp;
   
           *mp = NULL;
           return m_freem(m);
   }
   
   /* Packet tag routines */
   struct m_tag *m_tag_get(int, int, int);
   void    m_tag_prepend(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_find(struct mbuf *, 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_init(struct mbuf *);
   struct m_tag *m_tag_first(struct mbuf *);
   struct m_tag *m_tag_next(struct mbuf *, struct m_tag *);
   
   /* Packet tag types */
   #define PACKET_TAG_IPSEC_IN_DONE        0x0001  /* IPsec applied, in */
   #define PACKET_TAG_IPSEC_OUT_DONE       0x0002  /* IPsec applied, out */
   #define PACKET_TAG_IPSEC_FLOWINFO       0x0004  /* IPsec flowinfo */
   #define PACKET_TAG_WIREGUARD            0x0040  /* WireGuard data */
   #define PACKET_TAG_GRE                  0x0080  /* GRE processing done */
   #define PACKET_TAG_DLT                  0x0100 /* data link layer type */
   #define PACKET_TAG_PF_DIVERT            0x0200 /* pf(4) diverted packet */
   #define PACKET_TAG_PF_REASSEMBLED       0x0800 /* pf reassembled ipv6 packet */
   #define PACKET_TAG_SRCROUTE             0x1000 /* IPv4 source routing options */
   #define PACKET_TAG_TUNNEL               0x2000  /* Tunnel endpoint address */
   #define PACKET_TAG_CARP_BAL_IP          0x4000  /* carp(4) ip balanced marker */
   #define PACKET_TAG_IP6_OFFNXT           0x8000  /* IPv6 offset and next proto */
   
   #define MTAG_BITS \
       ("\2\1IPSEC_IN_DONE\2IPSEC_OUT_DONE\3IPSEC_FLOWINFO" \
       "\4IPSEC_OUT_CRYPTO_NEEDED\5IPSEC_PENDING_TDB\6BRIDGE\7WG\10GRE\11DLT" \
       "\12PF_DIVERT\14PF_REASSEMBLED\15SRCROUTE\16TUNNEL\17CARP_BAL_IP")
   
   /*
    * Maximum tag payload length (that is excluding the m_tag structure).
    * Please make sure to update this value when increasing the payload
    * length for an existing packet tag type or when adding a new one that
    * has payload larger than the value below.
    */
   #define PACKET_TAG_MAXSIZE              80
   
   /* Detect mbufs looping in the kernel when spliced too often. */
   #define M_MAXLOOP       128
   
   /*
    * mbuf lists
    */
   
   #define MBUF_LIST_INITIALIZER() { NULL, NULL, 0 }
   
   void                    ml_init(struct mbuf_list *);
   void                    ml_enqueue(struct mbuf_list *, struct mbuf *);
   struct mbuf *           ml_dequeue(struct mbuf_list *);
   void                    ml_enlist(struct mbuf_list *, struct mbuf_list *);
   struct mbuf *           ml_dechain(struct mbuf_list *);
   unsigned int            ml_purge(struct mbuf_list *);
   unsigned int            ml_hdatalen(struct mbuf_list *);
   
   #define ml_len(_ml)             ((_ml)->ml_len)
   #define ml_empty(_ml)           ((_ml)->ml_len == 0)
   
   #define MBUF_LIST_FIRST(_ml)    ((_ml)->ml_head)
   #define MBUF_LIST_NEXT(_m)      ((_m)->m_nextpkt)
   
   #define MBUF_LIST_FOREACH(_ml, _m)                                      \
           for ((_m) = MBUF_LIST_FIRST(_ml);                               \
               (_m) != NULL;                                               \
               (_m) = MBUF_LIST_NEXT(_m))
   
   /*
    * mbuf queues
    */
   
   #define MBUF_QUEUE_INITIALIZER(_maxlen, _ipl) \
       { MUTEX_INITIALIZER(_ipl), MBUF_LIST_INITIALIZER(), (_maxlen), 0 }
   
   void                    mq_init(struct mbuf_queue *, u_int, int);
   int                     mq_push(struct mbuf_queue *, struct mbuf *);
   int                     mq_enqueue(struct mbuf_queue *, struct mbuf *);
   struct mbuf *           mq_dequeue(struct mbuf_queue *);
   int                     mq_enlist(struct mbuf_queue *, struct mbuf_list *);
   void                    mq_delist(struct mbuf_queue *, struct mbuf_list *);
   struct mbuf *           mq_dechain(struct mbuf_queue *);
   unsigned int            mq_purge(struct mbuf_queue *);
   unsigned int            mq_hdatalen(struct mbuf_queue *);
   
   #define mq_len(_mq)             ml_len(&(_mq)->mq_list)
   #define mq_empty(_mq)           ml_empty(&(_mq)->mq_list)
   #define mq_full(_mq)            (mq_len((_mq)) >= (_mq)->mq_maxlen)
   #define mq_drops(_mq)           ((_mq)->mq_drops)
   #define mq_set_maxlen(_mq, _l)  ((_mq)->mq_maxlen = (_l))
   
   #endif /* _KERNEL */
   #endif /* _SYS_MBUF_H_ */

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