usr/src/sys/deprecated/netimp/if_imphost.h

/*      if_imphost.h    4.5     82/03/09        */

/*
 * Host structure used with IMP's.
 * Used to hold outgoing packets which
 * would exceed allowed RFNM count.
 *
 * These structures are packed into
 * mbuf's and kept as small as possible.
 */
struct host {
        struct  mbuf *h_q;              /* holding queue */
        struct  in_addr h_addr;         /* host's address */
        short   h_qcnt;                 /* size of holding q */
        u_char  h_rfnm;                 /* # outstanding rfnm's */
        u_char  h_refcnt;               /* reference count */
};

/*
 * Host structures, as seen inside an mbuf.
 * Hashing on the host address is used to
 * select an index into the first mbuf.  Collisions
 * are then resolved by searching successive
 * mbuf's at the same index.  Reclamation is done
 * automatically at the time a structure is free'd.
 */
#define HPMBUF  ((MLEN - sizeof(int)) / sizeof(struct host))
#if vax
#define HOSTHASH(a)     ((((a).s_addr>>8)+(a).s_net) % HPMBUF)
#endif

/*
 * In-line expansions for queuing operations on
 * host message holding queue.  Queue is maintained
 * as circular list with the head pointing to the
 * last message in the queue.
 */
#define HOST_ENQUE(hp, m) { \
        register struct mbuf *n; \
        (hp)->h_qcnt++; \
        if ((n = (hp)->h_q) == 0) \
                (hp)->h_q = (m)->m_act = (m); \
        else { \
                (m)->m_act = n->m_act; \
                (hp)->h_q = n->m_act = (m); \
        } \
}
#define HOST_DEQUE(hp, m) { \
        if ((m) = (hp)->h_q) { \
                if ((m)->m_act == (m)) \
                        (hp)->h_q = 0; \
                else { \
                        (m) = (m)->m_act; \
                        (hp)->h_q->m_act = (m)->m_act; \
                } \
                (hp)->h_qcnt--; \
                (m)->m_act = 0; \
        } \
}

struct hmbuf {
        int     hm_count;               /* # of struct's in use */
        struct  host hm_hosts[HPMBUF];  /* data structures proper */
};

#ifdef KERNEL
struct host *hostlookup();
struct host *hostenter();
struct mbuf *hostdeque();
#endif