sys/netimp/if_imphost.h

/*
 * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *      @(#)if_imphost.h        7.6 (Berkeley) 6/29/88
 */

/*
 * 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 */
        u_short h_timer;                /* used to stay off deletion */
        u_short h_imp;                  /* host's imp number */
        u_char  h_host;                 /* host's number on imp */
        u_char  h_qcnt;                 /* size of holding q */
        u_char  h_rfnm;                 /* # outstanding rfnm's */
        u_char  h_flags;                /* see below */
};

/*
 * A host structure is kept around (even when there are no
 * references to it) for a spell to avoid constant reallocation
 * and also to reflect IMP status back to sites which aren't
 * directly connected to the IMP.  When structures are marked
 * idle, a timer is started; when the timer expires the structure
 * is deallocated.  A structure may be reused before the timer expires.
 * A structure holds a reference on the containing mbuf when it is marked
 * HF_INUSE.
 */
#define HF_INUSE        0x1
#define HF_DEAD         (1<<IMPTYPE_HOSTDEAD)
#define HF_UNREACH      (1<<IMPTYPE_HOSTUNREACH)

#define HOSTTIMER       128             /* keep structure around awhile */

/*
 * Mark a host structure free; used if host entry returned by hostlookup
 * isn't needed.  h_rfnm must be zero.
 */
#define hostfree(hp) { \
        if ((hp)->h_timer == 0 && (hp)->h_qcnt == 0 && \
            (hp)->h_flags & HF_INUSE) \
                hostrelease(hp); \
}

/*
 * Release a host entry when last rfnm is received.
 */
#define hostidle(hp)    { (hp)->h_timer = HOSTTIMER; }

/*
 * Host structures, as seen inside an mbuf.
 * Hashing on the host and imp 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 freed.
 */
#define HPMBUF  ((MLEN - sizeof(int)) / sizeof(struct host))
/* don't need to swab as long as HPMBUF is odd */
#if defined(notdef) && BYTE_ORDER == BIG_ENDIAN
#define HOSTHASH(imp, host)     ((unsigned)(ntohs(imp)+(host)) % HPMBUF)
#else
#define HOSTHASH(imp, host)     ((unsigned)((imp)+(host)) % 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();
#endif