xref: /csrg-svn/sys/deprecated/netimp/if_imp.c (revision 18132)
1 /*	if_imp.c	6.3	85/02/28	*/
2 
3 #include "imp.h"
4 #if NIMP > 0
5 /*
6  * ARPANET IMP interface driver.
7  *
8  * The IMP-host protocol is handled here, leaving
9  * hardware specifics to the lower level interface driver.
10  */
11 #include "../machine/pte.h"
12 
13 #include "param.h"
14 #include "systm.h"
15 #include "mbuf.h"
16 #include "buf.h"
17 #include "protosw.h"
18 #include "socket.h"
19 #include "vmmac.h"
20 #include "time.h"
21 #include "kernel.h"
22 #include "errno.h"
23 #include "ioctl.h"
24 
25 #include "../vax/cpu.h"
26 #include "../vax/mtpr.h"
27 #include "../vaxuba/ubareg.h"
28 #include "../vaxuba/ubavar.h"
29 
30 #include "../net/if.h"
31 #include "../net/route.h"
32 
33 #include "../net/netisr.h"
34 #include "../netinet/in.h"
35 #include "../netinet/in_systm.h"
36 #include "../netinet/ip.h"
37 #include "../netinet/ip_var.h"
38 /* define IMPLEADERS here to get leader printing code */
39 #include "if_imp.h"
40 #include "if_imphost.h"
41 
42 /*
43  * IMP software status per interface.
44  * (partially shared with the hardware specific module)
45  *
46  * Each interface is referenced by a network interface structure,
47  * imp_if, which the routing code uses to locate the interface.
48  * This structure contains the output queue for the interface, its
49  * address, ...  IMP specific structures used in connecting the
50  * IMP software modules to the hardware specific interface routines
51  * are stored here.  The common structures are made visible to the
52  * interface driver by passing a pointer to the hardware routine
53  * at "attach" time.
54  *
55  * NOTE: imp_if and imp_cb are assumed adjacent in hardware code.
56  */
57 struct imp_softc {
58 	struct	ifnet imp_if;		/* network visible interface */
59 	struct	impcb imp_cb;		/* hooks to hardware module */
60 	u_char	imp_state;		/* current state of IMP */
61 	char	imp_dropcnt;		/* used during initialization */
62 } imp_softc[NIMP];
63 
64 /*
65  * Messages from IMP regarding why
66  * it's going down.
67  */
68 static char *impmessage[] = {
69 	"in 30 seconds",
70 	"for hardware PM",
71 	"to reload software",
72 	"for emergency reset"
73 };
74 
75 #define HOSTDEADTIMER	10		/* How long to wait when down */
76 
77 int	impdown(), impinit(), impioctl(), impoutput();
78 
79 /*
80  * IMP attach routine.  Called from hardware device attach routine
81  * at configuration time with a pointer to the UNIBUS device structure.
82  * Sets up local state and returns pointer to base of ifnet+impcb
83  * structures.  This is then used by the device's attach routine
84  * set up its back pointers.
85  */
86 impattach(ui, reset)
87 	struct uba_device *ui;
88 	int (*reset)();
89 {
90 	struct imp_softc *sc = &imp_softc[ui->ui_unit];
91 	register struct ifnet *ifp = &sc->imp_if;
92 
93 	/* UNIT COULD BE AMBIGUOUS */
94 	ifp->if_unit = ui->ui_unit;
95 	ifp->if_name = "imp";
96 	ifp->if_mtu = IMPMTU - sizeof(struct imp_leader);
97 	ifp->if_reset = reset;
98 	ifp->if_init = impinit;
99 	ifp->if_ioctl = impioctl;
100 	ifp->if_output = impoutput;
101 	/* reset is handled at the hardware level */
102 	if_attach(ifp);
103 	return ((int)&sc->imp_if);
104 }
105 
106 /*
107  * IMP initialization routine: call hardware module to
108  * setup UNIBUS resources, init state and get ready for
109  * NOOPs the IMP should send us, and that we want to drop.
110  */
111 impinit(unit)
112 	int unit;
113 {
114 	int s = splimp();
115 	register struct imp_softc *sc = &imp_softc[unit];
116 	struct sockaddr_in *sin;
117 
118 	sin = (struct sockaddr_in *)&sc->imp_if.if_addr;
119 	if (in_netof(sin->sin_addr) == 0)
120 		return;
121 	if ((*sc->imp_cb.ic_init)(unit) == 0) {
122 		sc->imp_state = IMPS_DOWN;
123 		sc->imp_if.if_flags &= ~IFF_UP;
124 		splx(s);
125 		return;
126 	}
127 	sc->imp_if.if_flags |= IFF_RUNNING;
128 	sc->imp_state = IMPS_INIT;
129 	impnoops(sc);
130 	splx(s);
131 }
132 
133 struct sockproto impproto = { PF_IMPLINK };
134 struct sockaddr_in impdst = { AF_IMPLINK };
135 struct sockaddr_in impsrc = { AF_IMPLINK };
136 #ifdef IMPLEADERS
137 int	impprintfs = 0;
138 #endif
139 
140 /*
141  * ARPAnet 1822 input routine.
142  * Called from hardware input interrupt routine to handle 1822
143  * IMP-host messages.  Type 0 messages (non-control) are
144  * passed to higher level protocol processors on the basis
145  * of link number.  Other type messages (control) are handled here.
146  */
147 impinput(unit, m)
148 	int unit;
149 	register struct mbuf *m;
150 {
151 	register struct imp_leader *ip;
152 	register struct imp_softc *sc = &imp_softc[unit];
153 	register struct host *hp;
154 	register struct ifqueue *inq;
155 	struct control_leader *cp;
156 	struct in_addr addr;
157 	struct mbuf *next;
158 	struct sockaddr_in *sin;
159 
160 	/* verify leader length. */
161 	if (m->m_len < sizeof(struct control_leader) &&
162 	    (m = m_pullup(m, sizeof(struct control_leader))) == 0)
163 		return;
164 	cp = mtod(m, struct control_leader *);
165 	if (cp->dl_mtype == IMPTYPE_DATA)
166 		if (m->m_len < sizeof(struct imp_leader) &&
167 		    (m = m_pullup(m, sizeof(struct imp_leader))) == 0)
168 			return;
169 	ip = mtod(m, struct imp_leader *);
170 #ifdef IMPLEADERS
171 	if (impprintfs)
172 		printleader("impinput", ip);
173 #endif
174 
175 	/* check leader type */
176 	if (ip->il_format != IMP_NFF) {
177 		sc->imp_if.if_collisions++;	/* XXX */
178 		goto drop;
179 	}
180 
181 	if (ip->il_mtype != IMPTYPE_DATA) {
182 		/* If not data packet, build IP addr from leader (BRL) */
183 		imp_leader_to_addr( &addr, ip, &sc->imp_if );
184 	}
185 	switch (ip->il_mtype) {
186 
187 	case IMPTYPE_DATA:
188 		break;
189 
190 	/*
191 	 * IMP leader error.  Reset the IMP and discard the packet.
192 	 */
193 	case IMPTYPE_BADLEADER:
194 		/*
195 		 * According to 1822 document, this message
196 		 * will be generated in response to the
197 		 * first noop sent to the IMP after
198 		 * the host resets the IMP interface.
199 		 */
200 		if (sc->imp_state != IMPS_INIT) {
201 			impmsg(sc, "leader error");
202 			hostreset(sc->imp_if.if_net);
203 			impnoops(sc);
204 		}
205 		goto drop;
206 
207 	/*
208 	 * IMP going down.  Print message, and if not immediate,
209 	 * set off a timer to insure things will be reset at the
210 	 * appropriate time.
211 	 */
212 	case IMPTYPE_DOWN:
213 		if (sc->imp_state < IMPS_INIT)
214 			goto drop;
215 		if ((ip->il_link & IMP_DMASK) == 0) {
216 			sc->imp_state = IMPS_GOINGDOWN;
217 			timeout(impdown, (caddr_t)sc, 30 * hz);
218 		}
219 		impmsg(sc, "going down %s",
220 			(u_int)impmessage[ip->il_link&IMP_DMASK]);
221 		goto drop;
222 
223 	/*
224 	 * A NOP usually seen during the initialization sequence.
225 	 * Compare the local address with that in the message.
226 	 * Reset the local address notion if it doesn't match.
227 	 */
228 	case IMPTYPE_NOOP:
229 		if (sc->imp_state == IMPS_DOWN) {
230 			sc->imp_state = IMPS_INIT;
231 			sc->imp_dropcnt = IMP_DROPCNT;
232 		}
233 		if (sc->imp_state == IMPS_INIT && --sc->imp_dropcnt > 0)
234 			goto drop;
235 		sin = (struct sockaddr_in *)&sc->imp_if.if_addr;
236 		if( ip->il_imp != 0 )  {	/* BRL */
237 			struct in_addr leader_addr;
238 			imp_leader_to_addr( &leader_addr, ip, &sc->imp_if );
239 			if( sin->sin_addr.s_addr != leader_addr.s_addr )  {
240 				impmsg(sc, "address x%x (%d/%d)",
241 					htonl( leader_addr.s_addr ),
242 					(u_int)ip->il_host,
243 					htons(ip->il_imp) );
244 				sin->sin_addr.s_addr = leader_addr.s_addr;
245 				sc->imp_if.if_host[0] = in_lnaof( leader_addr.s_addr );
246 			}
247 		}
248 		sc->imp_state = IMPS_UP;
249 		sc->imp_if.if_flags |= IFF_UP;
250 		if_rtinit(&sc->imp_if, RTF_UP);
251 		goto drop;
252 
253 	/*
254 	 * RFNM or INCOMPLETE message, send next
255 	 * message on the q.  We could pass incomplete's
256 	 * up to the next level, but this currently isn't
257 	 * needed.
258 	 */
259 	case IMPTYPE_RFNM:
260 	case IMPTYPE_INCOMPLETE:
261 		if (hp = hostlookup(addr)) {
262 			if (hp->h_rfnm == 0)
263 				hp->h_flags &= ~HF_INUSE;
264 			else if (next = hostdeque(hp))
265 				(void) impsnd(&sc->imp_if, next);
266 		}
267 		goto drop;
268 
269 	/*
270 	 * Host or IMP can't be reached.  Flush any packets
271 	 * awaiting transmission and release the host structure.
272 	 */
273 	case IMPTYPE_HOSTDEAD:
274 	case IMPTYPE_HOSTUNREACH:
275 		impnotify((int)ip->il_mtype, (struct control_leader *)ip,
276 		    hostlookup(addr), sc->imp_if);
277 		goto rawlinkin;
278 
279 	/*
280 	 * Error in data.  Clear RFNM status for this host and send
281 	 * noops to the IMP to clear the interface.
282 	 */
283 	case IMPTYPE_BADDATA:
284 		impmsg(sc, "data error");
285 		if (hp = hostlookup(addr))
286 			hp->h_rfnm = 0;
287 		impnoops(sc);
288 		goto drop;
289 
290 	/*
291 	 * Interface reset.
292 	 */
293 	case IMPTYPE_RESET:
294 		impmsg(sc, "interface reset");
295 		hostreset(sc->imp_if.if_net);	/* clear RFNM counts */
296 		impnoops(sc);
297 		goto drop;
298 
299 	default:
300 		sc->imp_if.if_collisions++;		/* XXX */
301 		goto drop;
302 	}
303 
304 	/*
305 	 * Data for a protocol.  Dispatch to the appropriate
306 	 * protocol routine (running at software interrupt).
307 	 * If this isn't a raw interface, advance pointer
308 	 * into mbuf past leader.
309 	 */
310 	switch (ip->il_link) {
311 
312 #ifdef INET
313 	case IMPLINK_IP:
314 		m->m_len -= sizeof(struct imp_leader);
315 		m->m_off += sizeof(struct imp_leader);
316 		schednetisr(NETISR_IP);
317 		inq = &ipintrq;
318 		break;
319 #endif
320 
321 	default:
322 	rawlinkin:
323 		impproto.sp_protocol = ip->il_link;
324 		sin = (struct sockaddr_in *)&sc->imp_if.if_addr;
325 		impdst.sin_addr = sin->sin_addr;
326 		imp_leader_to_addr( &impsrc.sin_addr, ip, &sc->imp_if );
327 		raw_input(m, &impproto, (struct sockaddr *)&impsrc,
328 		  (struct sockaddr *)&impdst);
329 		return;
330 	}
331 	if (IF_QFULL(inq)) {
332 		IF_DROP(inq);
333 		goto drop;
334 	}
335 	IF_ENQUEUE(inq, m);
336 	return;
337 
338 drop:
339 	m_freem(m);
340 }
341 
342 /*
343  * Bring the IMP down after notification.
344  */
345 impdown(sc)
346 	struct imp_softc *sc;
347 {
348 	int s = splimp();
349 
350 	sc->imp_state = IMPS_DOWN;
351 	impmsg(sc, "marked down");
352 	hostreset(sc->imp_if.if_net);
353 	if_down(&sc->imp_if);
354 	splx(s);
355 }
356 
357 /*VARARGS*/
358 impmsg(sc, fmt, a1, a2, a3)
359 	struct imp_softc *sc;
360 	char *fmt;
361 	u_int a1;
362 {
363 
364 	printf("imp%d: ", sc->imp_if.if_unit);
365 	printf(fmt, a1, a2, a3);
366 	printf("\n");
367 }
368 
369 /*
370  * Process an IMP "error" message, passing this
371  * up to the higher level protocol.
372  */
373 impnotify(what, cp, hp, ifp)
374 	int what;
375 	struct control_leader *cp;
376 	struct host *hp;
377 	struct ifnet *ifp;		/* BRL */
378 {
379 	struct in_addr in;
380 
381 	imp_leader_to_addr( &in, (struct imp_leader *) cp, ifp );  /* BRL */
382 
383 	if (cp->dl_link != IMPLINK_IP)
384 		raw_ctlinput(what, (caddr_t)&in);
385 	else
386 		ip_ctlinput(what, (caddr_t)&in);
387 	if (hp) {
388 		hp->h_flags |= (1 << what);
389 		hostfree(hp);
390 		hp->h_timer = HOSTDEADTIMER;
391 	}
392 }
393 
394 /*
395  * ARPAnet 1822 output routine.
396  * Called from higher level protocol routines to set up messages for
397  * transmission to the imp.  Sets up the header and calls impsnd to
398  * enqueue the message for this IMP's hardware driver.
399  */
400 impoutput(ifp, m0, dst)
401 	register struct ifnet *ifp;
402 	struct mbuf *m0;
403 	struct sockaddr *dst;
404 {
405 	register struct imp_leader *imp;
406 	register struct mbuf *m = m0;
407 	int dhost, dimp, dlink, len, dnet;
408 	int error = 0;
409 
410 	/*
411 	 * Don't even try if the IMP is unavailable.
412 	 */
413 	if (imp_softc[ifp->if_unit].imp_state != IMPS_UP) {
414 		error = ENETDOWN;
415 		goto drop;
416 	}
417 
418 	switch (dst->sa_family) {
419 
420 #ifdef INET
421 	case AF_INET: {
422 		struct ip *ip = mtod(m0, struct ip *);
423 		struct sockaddr_in *sin = (struct sockaddr_in *)dst;
424 
425 		dhost = sin->sin_addr.s_host;
426 		dimp = sin->sin_addr.s_impno;
427 		dlink = IMPLINK_IP;
428 		dnet = 0;
429 		len = ntohs((u_short)ip->ip_len);
430 		break;
431 	}
432 #endif
433 	case AF_IMPLINK:
434 		goto leaderexists;
435 
436 	default:
437 		printf("imp%d: can't handle af%d\n", ifp->if_unit,
438 			dst->sa_family);
439 		error = EAFNOSUPPORT;
440 		goto drop;
441 	}
442 
443 	/*
444 	 * Add IMP leader.  If there's not enough space in the
445 	 * first mbuf, allocate another.  If that should fail, we
446 	 * drop this sucker.
447 	 */
448 	if (m->m_off > MMAXOFF ||
449 	    MMINOFF + sizeof(struct imp_leader) > m->m_off) {
450 		m = m_get(M_DONTWAIT, MT_HEADER);
451 		if (m == 0) {
452 			error = ENOBUFS;
453 			goto drop;
454 		}
455 		m->m_next = m0;
456 		m->m_len = sizeof(struct imp_leader);
457 	} else {
458 		m->m_off -= sizeof(struct imp_leader);
459 		m->m_len += sizeof(struct imp_leader);
460 	}
461 	imp = mtod(m, struct imp_leader *);
462 	imp->il_format = IMP_NFF;
463 	imp->il_mtype = IMPTYPE_DATA;
464 	imp_addr_to_leader(imp,
465 		((struct sockaddr_in *) dst)->sin_addr.s_addr ); /* BRL */
466 	imp->il_length = htons( (u_short) len << 3 );		/* BRL */
467 	imp->il_link = dlink;
468 	imp->il_flags = imp->il_htype = imp->il_subtype = 0;
469 
470 leaderexists:
471 	return (impsnd(ifp, m));
472 drop:
473 	m_freem(m0);
474 	return (error);
475 }
476 
477 /*
478  * Put a message on an interface's output queue.
479  * Perform RFNM counting: no more than 8 message may be
480  * in flight to any one host.
481  */
482 impsnd(ifp, m)
483 	struct ifnet *ifp;
484 	struct mbuf *m;
485 {
486 	register struct imp_leader *ip;
487 	register struct host *hp;
488 	struct impcb *icp;
489 	int s, error;
490 
491 	ip = mtod(m, struct imp_leader *);
492 
493 	/*
494 	 * Do RFNM counting for data messages
495 	 * (no more than 8 outstanding to any host)
496 	 */
497 	s = splimp();
498 	if (ip->il_mtype == IMPTYPE_DATA) {
499 		struct in_addr addr;
500 
501 		imp_leader_to_addr( &addr, ip, ifp );	/* BRL */
502 		if ((hp = hostlookup(addr)) == 0)
503 			hp = hostenter(addr);
504 		if (hp && (hp->h_flags & (HF_DEAD|HF_UNREACH))) {
505 			error = hp->h_flags&HF_DEAD ? EHOSTDOWN : EHOSTUNREACH;
506 			hp->h_timer = HOSTDEADTIMER;
507 			hp->h_flags &= ~HF_INUSE;
508 			goto bad;
509 		}
510 
511 		/*
512 		 * If IMP would block, queue until RFNM
513 		 */
514 		if (hp) {
515 #ifndef NORFNM					/* BRL */
516 			if (hp->h_rfnm < 8)
517 #endif
518 			{
519 				hp->h_rfnm++;
520 				goto enque;
521 			}
522 			if (hp->h_qcnt < 8) {	/* high water mark */
523 				HOST_ENQUE(hp, m);
524 				goto start;
525 			}
526 		}
527 		error = ENOBUFS;
528 		goto bad;
529 	}
530 enque:
531 	if (IF_QFULL(&ifp->if_snd)) {
532 		IF_DROP(&ifp->if_snd);
533 		error = ENOBUFS;
534 bad:
535 		m_freem(m);
536 		splx(s);
537 		return (error);
538 	}
539 	IF_ENQUEUE(&ifp->if_snd, m);
540 start:
541 	icp = &imp_softc[ifp->if_unit].imp_cb;
542 	if (icp->ic_oactive == 0)
543 		(*icp->ic_start)(ifp->if_unit);
544 	splx(s);
545 	return (0);
546 }
547 
548 /*
549  * Put three 1822 NOOPs at the head of the output queue.
550  * Part of host-IMP initialization procedure.
551  * (Should return success/failure, but noone knows
552  * what to do with this, so why bother?)
553  * This routine is always called at splimp, so we don't
554  * protect the call to IF_PREPEND.
555  */
556 impnoops(sc)
557 	register struct imp_softc *sc;
558 {
559 	register i;
560 	register struct mbuf *m;
561 	register struct control_leader *cp;
562 
563 	sc->imp_dropcnt = IMP_DROPCNT;
564 	for (i = 0; i < IMP_DROPCNT + 1; i++ ) {
565 		if ((m = m_getclr(M_DONTWAIT, MT_HEADER)) == 0)
566 			return;
567 		m->m_len = sizeof(struct control_leader);
568 		cp = mtod(m, struct control_leader *);
569 		cp->dl_format = IMP_NFF;
570                 cp->dl_link = i;
571                 cp->dl_mtype = IMPTYPE_NOOP;
572 		IF_PREPEND(&sc->imp_if.if_snd, m);
573 	}
574 	if (sc->imp_cb.ic_oactive == 0)
575 		(*sc->imp_cb.ic_start)(sc->imp_if.if_unit);
576 }
577 
578 /*
579  * Process an ioctl request.
580  */
581 impioctl(ifp, cmd, data)
582 	register struct ifnet *ifp;
583 	int cmd;
584 	caddr_t data;
585 {
586 	struct ifreq *ifr = (struct ifreq *)data;
587 	struct sockaddr_in *sin;
588 	int s = splimp(), error = 0;
589 
590 	switch (cmd) {
591 
592 	case SIOCSIFADDR:
593 		if (ifp->if_flags & IFF_RUNNING)
594 			if_rtinit(ifp, -1);	/* delete previous route */
595 		sin = (struct sockaddr_in *)&ifr->ifr_addr;
596 		ifp->if_net = in_netof(sin->sin_addr);
597 		sin = (struct sockaddr_in *)&ifp->if_addr;
598 		sin->sin_family = AF_INET;
599 		/* host number filled in already, or filled in later */
600 		sin->sin_addr = if_makeaddr(ifp->if_net, ifp->if_host[0]);
601 		if (ifp->if_flags & IFF_RUNNING)
602 			if_rtinit(ifp, RTF_UP);
603 		else
604 			impinit(ifp->if_unit);
605 		break;
606 
607 	default:
608 		error = EINVAL;
609 	}
610 	splx(s);
611 	return (error);
612 }
613 
614 #ifdef IMPLEADERS
615 printleader(routine, ip)
616 	char *routine;
617 	register struct imp_leader *ip;
618 {
619 	printf("%s: ", routine);
620 	printbyte((char *)ip, 12);
621 	printf("<fmt=%x,net=%x,flags=%x,mtype=", ip->il_format, ip->il_network,
622 		ip->il_flags);
623 	if (ip->il_mtype <= IMPTYPE_READY)
624 		printf("%s,", impleaders[ip->il_mtype]);
625 	else
626 		printf("%x,", ip->il_mtype);
627 	printf("htype=%x,host=%x,imp=%x,link=", ip->il_htype, ip->il_host,
628 		ntohs(ip->il_imp));
629 	if (ip->il_link == IMPLINK_IP)
630 		printf("ip,");
631 	else
632 		printf("%x,", ip->il_link);
633 	printf("subtype=%x,len=%x>\n",ip->il_subtype,ntohs(ip->il_length)>>3);
634 }
635 
636 printbyte(cp, n)
637 	register char *cp;
638 	int n;
639 {
640 	register i, j, c;
641 
642 	for (i=0; i<n; i++) {
643 		c = *cp++;
644 		for (j=0; j<2; j++)
645 			putchar("0123456789abcdef"[(c>>((1-j)*4))&0xf]);
646 		putchar(' ');
647 	}
648 	putchar('\n');
649 }
650 #endif
651 
652 /*
653  * Routine to convert from IMP Leader to InterNet Address.
654  *
655  * This procedure is necessary because IMPs may be assigned Class A, B, or C
656  * network numbers, but only have 8 bits in the leader to reflect the
657  * IMP "network number".  The strategy is to take the network number from
658  * the ifnet structure, and blend in the host-on-imp and imp-on-net numbers
659  * from the leader.
660  *
661  * There is no support for "Logical Hosts".
662  *
663  * Class A:	Net.Host.0.Imp
664  * Class B:	Net.net.Host.Imp
665  * Class C:	Net.net.net.(Host4|Imp4)
666  */
667 imp_leader_to_addr( ap, ip, ifp )
668 register struct in_addr *ap;
669 register struct imp_leader *ip;
670 register struct ifnet *ifp;
671 {
672 	register long final;
673 	register struct sockaddr_in *sin;
674 	int imp = htons(ip->il_imp);
675 
676 	sin = (struct sockaddr_in *) (&ifp->if_addr);
677 	final = htonl( sin->sin_addr.s_addr );		/* host order */
678 
679 	if( IN_CLASSA( final ) )  {
680 		final &= IN_CLASSA_NET;
681 		final |= (imp & 0xFF) | ((ip->il_host & 0xFF)<<16);
682 	} else if( IN_CLASSB( final ) )  {
683 		final &= IN_CLASSB_NET;
684 		final |= (imp & 0xFF) | ((ip->il_host & 0xFF)<<8);
685 	} else {
686 		final &= IN_CLASSC_NET;
687 		final |= (imp & 0x0F) | ((ip->il_host & 0x0F)<<4);
688 	}
689 	ap->s_addr = htonl( final );
690 }
691 
692 /*
693  * Function to take InterNet address and fill in IMP leader fields.
694  */
695 imp_addr_to_leader( imp, a )
696 register struct imp_leader *imp;
697 long a;
698 {
699 	register long addr = htonl( a );		/* host order */
700 
701 	imp->il_network = 0;	/* !! */
702 
703 	if( IN_CLASSA( addr ) )  {
704 		imp->il_host = ((addr>>16) & 0xFF);
705 		imp->il_imp = addr & 0xFF;
706 	} else if ( IN_CLASSB( addr ) )  {
707 		imp->il_host = ((addr>>8) & 0xFF);
708 		imp->il_imp = addr & 0xFF;
709 	} else {
710 		imp->il_host = ((addr>>4) & 0xF);
711 		imp->il_imp = addr & 0xF;
712 	}
713 	imp->il_imp = htons(imp->il_imp);	/* network order! */
714 }
715 #endif
716