xref: /netbsd-src/sys/nfs/nfs_boot.c (revision 3b01aba77a7a698587faaae455bbfe740923c1f5)
1 /*	$NetBSD: nfs_boot.c,v 1.56 2001/01/19 14:26:01 enami Exp $	*/
2 
3 /*-
4  * Copyright (c) 1995, 1997 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Adam Glass and Gordon W. Ross.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the NetBSD
21  *	Foundation, Inc. and its contributors.
22  * 4. Neither the name of The NetBSD Foundation nor the names of its
23  *    contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36  * POSSIBILITY OF SUCH DAMAGE.
37  */
38 
39 /*
40  * Support for NFS diskless booting, specifically getting information
41  * about where to mount root from, what pathnames, etc.
42  */
43 
44 #include "opt_nfs.h"
45 #include "opt_nfs_boot.h"
46 
47 #include <sys/param.h>
48 #include <sys/systm.h>
49 #include <sys/kernel.h>
50 #include <sys/device.h>
51 #include <sys/ioctl.h>
52 #include <sys/proc.h>
53 #include <sys/mount.h>
54 #include <sys/mbuf.h>
55 #include <sys/reboot.h>
56 #include <sys/socket.h>
57 #include <sys/socketvar.h>
58 
59 #include <net/if.h>
60 #include <net/route.h>
61 #include <net/if_ether.h>
62 #include <net/if_types.h>
63 
64 #include <netinet/in.h>
65 #include <netinet/if_inarp.h>
66 
67 #include <nfs/rpcv2.h>
68 #include <nfs/krpc.h>
69 #include <nfs/xdr_subs.h>
70 
71 #include <nfs/nfsproto.h>
72 #include <nfs/nfs.h>
73 #include <nfs/nfsmount.h>
74 #include <nfs/nfsdiskless.h>
75 
76 /*
77  * There are two implementations of NFS diskless boot.
78  * One implementation uses BOOTP (RFC951, RFC1048),
79  * the other uses Sun RPC/bootparams.  See the files:
80  *    nfs_bootp.c:   BOOTP (RFC951, RFC1048)
81  *    nfs_bootsun.c: Sun RPC/bootparams
82  */
83 #if defined(NFS_BOOT_BOOTP) || defined(NFS_BOOT_DHCP)
84 int nfs_boot_rfc951 = 1; /* BOOTP enabled (default) */
85 #endif
86 #ifdef NFS_BOOT_BOOTPARAM
87 int nfs_boot_bootparam = 1; /* BOOTPARAM enabled (default) */
88 #endif
89 
90 /* mountd RPC */
91 static int md_mount __P((struct sockaddr_in *mdsin, char *path,
92 	struct nfs_args *argp));
93 
94 static void nfs_boot_defrt __P((struct in_addr *));
95 static  int nfs_boot_getfh __P((struct nfs_dlmount *ndm));
96 
97 
98 /*
99  * Called with an empty nfs_diskless struct to be filled in.
100  * Find an interface, determine its ip address (etc.) and
101  * save all the boot parameters in the nfs_diskless struct.
102  */
103 int
104 nfs_boot_init(nd, procp)
105 	struct nfs_diskless *nd;
106 	struct proc *procp;
107 {
108 	struct ifnet *ifp;
109 	int error;
110 
111 	/*
112 	 * Find the network interface.
113 	 */
114 	ifp = ifunit(root_device->dv_xname);
115 	if (ifp == NULL) {
116 		printf("nfs_boot: '%s' not found\n",
117 		       root_device->dv_xname);
118 		return (ENXIO);
119 	}
120 	nd->nd_ifp = ifp;
121 
122 	error = EADDRNOTAVAIL; /* ??? */
123 #if defined(NFS_BOOT_BOOTP) || defined(NFS_BOOT_DHCP)
124 	if (error && nfs_boot_rfc951) {
125 #if defined(NFS_BOOT_DHCP)
126 		printf("nfs_boot: trying DHCP/BOOTP\n");
127 #else
128 		printf("nfs_boot: trying BOOTP\n");
129 #endif
130 		error = nfs_bootdhcp(nd, procp);
131 	}
132 #endif
133 #ifdef NFS_BOOT_BOOTPARAM
134 	if (error && nfs_boot_bootparam) {
135 		printf("nfs_boot: trying RARP (and RPC/bootparam)\n");
136 		error = nfs_bootparam(nd, procp);
137 	}
138 #endif
139 	if (error)
140 		return (error);
141 
142 	/*
143 	 * If the gateway address is set, add a default route.
144 	 * (The mountd RPCs may go across a gateway.)
145 	 */
146 	if (nd->nd_gwip.s_addr)
147 		nfs_boot_defrt(&nd->nd_gwip);
148 
149 	/*
150 	 * Now fetch the NFS file handles as appropriate.
151 	 */
152 	error = nfs_boot_getfh(&nd->nd_root);
153 
154 	if (error)
155 		nfs_boot_cleanup(nd, procp);
156 
157 	return (error);
158 }
159 
160 void
161 nfs_boot_cleanup(nd, procp)
162 	struct nfs_diskless *nd;
163 	struct proc *procp;
164 {
165 
166 	nfs_boot_deladdress(nd->nd_ifp, procp, nd->nd_myip.s_addr);
167 	nfs_boot_ifupdown(nd->nd_ifp, procp, 0);
168 	nfs_boot_flushrt(nd->nd_ifp);
169 }
170 
171 int
172 nfs_boot_ifupdown(ifp, procp, up)
173 	struct ifnet *ifp;
174 	struct proc *procp;
175 	int up;
176 {
177 	struct socket *so;
178 	struct ifreq ireq;
179 	int error;
180 
181 	memset(&ireq, 0, sizeof(ireq));
182 	memcpy(ireq.ifr_name, ifp->if_xname, IFNAMSIZ);
183 
184 	/*
185 	 * Get a socket to use for various things in here.
186 	 * After this, use "goto out" to cleanup and return.
187 	 */
188 	error = socreate(AF_INET, &so, SOCK_DGRAM, 0);
189 	if (error) {
190 		printf("ifupdown: socreate, error=%d\n", error);
191 		return (error);
192 	}
193 
194 	/*
195 	 * Bring up the interface. (just set the "up" flag)
196 	 * Get the old interface flags and or IFF_UP into them so
197 	 * things like media selection flags are not clobbered.
198 	 */
199 	error = ifioctl(so, SIOCGIFFLAGS, (caddr_t)&ireq, procp);
200 	if (error) {
201 		printf("ifupdown: GIFFLAGS, error=%d\n", error);
202 		goto out;
203 	}
204 	if (up)
205 		ireq.ifr_flags |= IFF_UP;
206 	else
207 		ireq.ifr_flags &= ~IFF_UP;
208 	error = ifioctl(so, SIOCSIFFLAGS, (caddr_t)&ireq, procp);
209 	if (error) {
210 		printf("ifupdown: SIFFLAGS, error=%d\n", error);
211 		goto out;
212 	}
213 
214 	if (up)
215 		/* give the link some time to get up */
216 		tsleep(nfs_boot_ifupdown, PZERO, "nfsbif", 3 * hz);
217 out:
218 	soclose(so);
219 	return (error);
220 }
221 
222 int
223 nfs_boot_setaddress(ifp, procp, addr, netmask, braddr)
224 	struct ifnet *ifp;
225 	struct proc *procp;
226 	u_int32_t addr, netmask, braddr;
227 {
228 	struct socket *so;
229 	struct ifaliasreq iareq;
230 	struct sockaddr_in *sin;
231 	int error;
232 
233 	/*
234 	 * Get a socket to use for various things in here.
235 	 * After this, use "goto out" to cleanup and return.
236 	 */
237 	error = socreate(AF_INET, &so, SOCK_DGRAM, 0);
238 	if (error) {
239 		printf("setaddress: socreate, error=%d\n", error);
240 		return (error);
241 	}
242 
243 	memset(&iareq, 0, sizeof(iareq));
244 	memcpy(iareq.ifra_name, ifp->if_xname, IFNAMSIZ);
245 
246 	/* Set the I/F address */
247 	sin = (struct sockaddr_in *)&iareq.ifra_addr;
248 	sin->sin_len = sizeof(*sin);
249 	sin->sin_family = AF_INET;
250 	sin->sin_addr.s_addr = addr;
251 
252 	/* Set the netmask */
253 	if (netmask != INADDR_ANY) {
254 		sin = (struct sockaddr_in *)&iareq.ifra_mask;
255 		sin->sin_len = sizeof(*sin);
256 		sin->sin_family = AF_INET;
257 		sin->sin_addr.s_addr = netmask;
258 	} /* else leave subnetmask unspecified (len=0) */
259 
260 	/* Set the broadcast addr. */
261 	if (braddr != INADDR_ANY) {
262 		sin = (struct sockaddr_in *)&iareq.ifra_broadaddr;
263 		sin->sin_len = sizeof(*sin);
264 		sin->sin_family = AF_INET;
265 		sin->sin_addr.s_addr = braddr;
266 	} /* else leave broadcast addr unspecified (len=0) */
267 
268 	error = ifioctl(so, SIOCAIFADDR, (caddr_t)&iareq, procp);
269 	if (error) {
270 		printf("setaddress, error=%d\n", error);
271 		goto out;
272 	}
273 
274 	/* give the link some time to get up */
275 	tsleep(nfs_boot_setaddress, PZERO, "nfsbtd", 3 * hz);
276 out:
277 	soclose(so);
278 	return (error);
279 }
280 
281 int
282 nfs_boot_deladdress(ifp, procp, addr)
283 	struct ifnet *ifp;
284 	struct proc *procp;
285 	u_int32_t addr;
286 {
287 	struct socket *so;
288 	struct ifreq ireq;
289 	struct sockaddr_in *sin;
290 	int error;
291 
292 	/*
293 	 * Get a socket to use for various things in here.
294 	 * After this, use "goto out" to cleanup and return.
295 	 */
296 	error = socreate(AF_INET, &so, SOCK_DGRAM, 0);
297 	if (error) {
298 		printf("deladdress: socreate, error=%d\n", error);
299 		return (error);
300 	}
301 
302 	memset(&ireq, 0, sizeof(ireq));
303 	memcpy(ireq.ifr_name, ifp->if_xname, IFNAMSIZ);
304 
305 	sin = (struct sockaddr_in *)&ireq.ifr_addr;
306 	sin->sin_len = sizeof(*sin);
307 	sin->sin_family = AF_INET;
308 	sin->sin_addr.s_addr = addr;
309 
310 	error = ifioctl(so, SIOCDIFADDR, (caddr_t)&ireq, procp);
311 	if (error) {
312 		printf("deladdress, error=%d\n", error);
313 		goto out;
314 	}
315 
316 out:
317 	soclose(so);
318 	return (error);
319 }
320 
321 int
322 nfs_boot_setrecvtimo(so)
323 	struct socket *so;
324 {
325 	struct mbuf *m;
326 	struct timeval *tv;
327 
328 	m = m_get(M_WAIT, MT_SOOPTS);
329 	tv = mtod(m, struct timeval *);
330 	m->m_len = sizeof(*tv);
331 	tv->tv_sec = 1;
332 	tv->tv_usec = 0;
333 	return (sosetopt(so, SOL_SOCKET, SO_RCVTIMEO, m));
334 }
335 
336 int
337 nfs_boot_enbroadcast(so)
338 	struct socket *so;
339 {
340 	struct mbuf *m;
341 	int32_t *on;
342 
343 	m = m_get(M_WAIT, MT_SOOPTS);
344 	on = mtod(m, int32_t *);
345 	m->m_len = sizeof(*on);
346 	*on = 1;
347 	return (sosetopt(so, SOL_SOCKET, SO_BROADCAST, m));
348 }
349 
350 int
351 nfs_boot_sobind_ipport(so, port)
352 	struct socket *so;
353 	u_int16_t port;
354 {
355 	struct mbuf *m;
356 	struct sockaddr_in *sin;
357 	int error;
358 
359 	m = m_getclr(M_WAIT, MT_SONAME);
360 	sin = mtod(m, struct sockaddr_in *);
361 	sin->sin_len = m->m_len = sizeof(*sin);
362 	sin->sin_family = AF_INET;
363 	sin->sin_addr.s_addr = INADDR_ANY;
364 	sin->sin_port = htons(port);
365 	error = sobind(so, m, curproc);
366 	m_freem(m);
367 	return (error);
368 }
369 
370 /*
371  * What is the longest we will wait before re-sending a request?
372  * Note this is also the frequency of "timeout" messages.
373  * The re-send loop counts up linearly to this maximum, so the
374  * first complaint will happen after (1+2+3+4+5)=15 seconds.
375  */
376 #define	MAX_RESEND_DELAY 5	/* seconds */
377 #define TOTAL_TIMEOUT   30	/* seconds */
378 
379 int
380 nfs_boot_sendrecv(so, nam, sndproc, snd, rcvproc, rcv, from_p, context)
381 	struct socket *so;
382 	struct mbuf *nam;
383 	int (*sndproc) __P((struct mbuf*, void*, int));
384 	struct mbuf *snd;
385 	int (*rcvproc) __P((struct mbuf*, void*));
386 	struct mbuf **rcv, **from_p;
387 	void *context;
388 {
389 	int error, rcvflg, timo, secs, waited;
390 	struct mbuf *m, *from;
391 	struct uio uio;
392 
393 	/* Free at end if not null. */
394 	from = NULL;
395 
396 	/*
397 	 * Send it, repeatedly, until a reply is received,
398 	 * but delay each re-send by an increasing amount.
399 	 * If the delay hits the maximum, start complaining.
400 	 */
401 	waited = timo = 0;
402 send_again:
403 	waited += timo;
404 	if (waited >= TOTAL_TIMEOUT)
405 		return (ETIMEDOUT);
406 
407 	/* Determine new timeout. */
408 	if (timo < MAX_RESEND_DELAY)
409 		timo++;
410 	else
411 		printf("nfs_boot: timeout...\n");
412 
413 	if (sndproc) {
414 		error = (*sndproc)(snd, context, waited);
415 		if (error)
416 			goto out;
417 	}
418 
419 	/* Send request (or re-send). */
420 	m = m_copypacket(snd, M_WAIT);
421 	if (m == NULL) {
422 		error = ENOBUFS;
423 		goto out;
424 	}
425 	error = (*so->so_send)(so, nam, NULL, m, NULL, 0);
426 	if (error) {
427 		printf("nfs_boot: sosend: %d\n", error);
428 		goto out;
429 	}
430 	m = NULL;
431 
432 	/*
433 	 * Wait for up to timo seconds for a reply.
434 	 * The socket receive timeout was set to 1 second.
435 	 */
436 
437 	secs = timo;
438 	for (;;) {
439 		if (from) {
440 			m_freem(from);
441 			from = NULL;
442 		}
443 		if (m) {
444 			m_freem(m);
445 			m = NULL;
446 		}
447 		uio.uio_resid = 1 << 16; /* ??? */
448 		rcvflg = 0;
449 		error = (*so->so_receive)(so, &from, &uio, &m, NULL, &rcvflg);
450 		if (error == EWOULDBLOCK) {
451 			if (--secs <= 0)
452 				goto send_again;
453 			continue;
454 		}
455 		if (error)
456 			goto out;
457 #ifdef DIAGNOSTIC
458 		if (!m || !(m->m_flags & M_PKTHDR)
459 		    || (1 << 16) - uio.uio_resid != m->m_pkthdr.len)
460 			panic("nfs_boot_sendrecv: return size");
461 #endif
462 
463 		if ((*rcvproc)(m, context))
464 			continue;
465 
466 		if (rcv)
467 			*rcv = m;
468 		else
469 			m_freem(m);
470 		if (from_p) {
471 			*from_p = from;
472 			from = NULL;
473 		}
474 		break;
475 	}
476 out:
477 	if (from) m_freem(from);
478 	return (error);
479 }
480 
481 /*
482  * Install a default route to the passed IP address.
483  */
484 static void
485 nfs_boot_defrt(gw_ip)
486 	struct in_addr *gw_ip;
487 {
488 	struct sockaddr dst, gw, mask;
489 	struct sockaddr_in *sin;
490 	int error;
491 
492 	/* Destination: (default) */
493 	memset((caddr_t)&dst, 0, sizeof(dst));
494 	dst.sa_len = sizeof(dst);
495 	dst.sa_family = AF_INET;
496 	/* Gateway: */
497 	memset((caddr_t)&gw, 0, sizeof(gw));
498 	sin = (struct sockaddr_in *)&gw;
499 	sin->sin_len = sizeof(*sin);
500 	sin->sin_family = AF_INET;
501 	sin->sin_addr.s_addr = gw_ip->s_addr;
502 	/* Mask: (zero length) */
503 	/* XXX - Just pass a null pointer? */
504 	memset(&mask, 0, sizeof(mask));
505 
506 	/* add, dest, gw, mask, flags, 0 */
507 	error = rtrequest(RTM_ADD, &dst, &gw, &mask,
508 			  (RTF_UP | RTF_GATEWAY | RTF_STATIC), NULL);
509 	if (error) {
510 		printf("nfs_boot: add route, error=%d\n", error);
511 		error = 0;
512 	}
513 }
514 
515 static int nfs_boot_delroute __P((struct radix_node *, void *));
516 static int
517 nfs_boot_delroute(rn, w)
518 	struct radix_node *rn;
519 	void *w;
520 {
521 	struct rtentry *rt = (struct rtentry *)rn;
522 	int error;
523 
524 	if (rt->rt_ifp != (struct ifnet *)w)
525 		return (0);
526 
527 	error = rtrequest(RTM_DELETE, rt_key(rt), NULL, rt_mask(rt), 0, NULL);
528 	if (error)
529 		printf("nfs_boot: del route, error=%d\n", error);
530 
531 	return (0);
532 }
533 
534 void
535 nfs_boot_flushrt(ifp)
536 	struct ifnet *ifp;
537 {
538 
539 	rn_walktree(rt_tables[AF_INET], nfs_boot_delroute, ifp);
540 }
541 
542 /*
543  * Get an initial NFS file handle using Sun RPC/mountd.
544  * Separate function because we used to call it twice.
545  * (once for root and once for swap)
546  */
547 static int
548 nfs_boot_getfh(ndm)
549 	struct nfs_dlmount *ndm;	/* output */
550 {
551 	struct nfs_args *args;
552 	struct sockaddr_in *sin;
553 	char *pathname;
554 	int error;
555 	u_int16_t port;
556 
557 	args = &ndm->ndm_args;
558 
559 	/* Initialize mount args. */
560 	memset((caddr_t) args, 0, sizeof(*args));
561 	args->addr     = &ndm->ndm_saddr;
562 	args->addrlen  = args->addr->sa_len;
563 #ifdef NFS_BOOT_TCP
564 	args->sotype   = SOCK_STREAM;
565 #else
566 	args->sotype   = SOCK_DGRAM;
567 #endif
568 	args->fh       = ndm->ndm_fh;
569 	args->hostname = ndm->ndm_host;
570 	args->flags    = NFSMNT_NOCONN | NFSMNT_RESVPORT;
571 
572 #ifndef NFS_V2_ONLY
573 	args->flags    |= NFSMNT_NFSV3;
574 #endif
575 #ifdef	NFS_BOOT_OPTIONS
576 	args->flags    |= NFS_BOOT_OPTIONS;
577 #endif
578 #ifdef	NFS_BOOT_RWSIZE
579 	/*
580 	 * Reduce rsize,wsize for interfaces that consistently
581 	 * drop fragments of long UDP messages.  (i.e. wd8003).
582 	 * You can always change these later via remount.
583 	 */
584 	args->flags   |= NFSMNT_WSIZE | NFSMNT_RSIZE;
585 	args->wsize    = NFS_BOOT_RWSIZE;
586 	args->rsize    = NFS_BOOT_RWSIZE;
587 #endif
588 
589 	/*
590 	 * Find the pathname part of the "server:pathname"
591 	 * string left in ndm->ndm_host by nfs_boot_init.
592 	 */
593 	pathname = strchr(ndm->ndm_host, ':');
594 	if (pathname == 0) {
595 		printf("nfs_boot: getfh - no pathname\n");
596 		return (EIO);
597 	}
598 	pathname++;
599 
600 	/*
601 	 * Get file handle using RPC to mountd/mount
602 	 */
603 	sin = (struct sockaddr_in *)&ndm->ndm_saddr;
604 	error = md_mount(sin, pathname, args);
605 	if (error) {
606 		printf("nfs_boot: mountd `%s', error=%d\n",
607 		       ndm->ndm_host, error);
608 		return (error);
609 	}
610 
611 	/* Set port number for NFS use. */
612 	/* XXX: NFS port is always 2049, right? */
613 #ifdef NFS_BOOT_TCP
614 retry:
615 #endif
616 	error = krpc_portmap(sin, NFS_PROG,
617 		    (args->flags & NFSMNT_NFSV3) ? NFS_VER3 : NFS_VER2,
618 		    (args->sotype == SOCK_STREAM) ? IPPROTO_TCP : IPPROTO_UDP,
619 		    &port);
620 	if (port == htons(0))
621 		error = EIO;
622 	if (error) {
623 #ifdef NFS_BOOT_TCP
624 		if (args->sotype == SOCK_STREAM) {
625 			args->sotype = SOCK_DGRAM;
626 			goto retry;
627 		}
628 #endif
629 		printf("nfs_boot: portmap NFS, error=%d\n", error);
630 		return (error);
631 	}
632 	sin->sin_port = port;
633 	return (0);
634 }
635 
636 
637 /*
638  * RPC: mountd/mount
639  * Given a server pathname, get an NFS file handle.
640  * Also, sets sin->sin_port to the NFS service port.
641  */
642 static int
643 md_mount(mdsin, path, argp)
644 	struct sockaddr_in *mdsin;		/* mountd server address */
645 	char *path;
646 	struct nfs_args *argp;
647 {
648 	/* The RPC structures */
649 	struct rdata {
650 		u_int32_t errno;
651 		union {
652 			u_int8_t  v2fh[NFSX_V2FH];
653 			struct {
654 				u_int32_t fhlen;
655 				u_int8_t  fh[1];
656 			} v3fh;
657 		} fh;
658 	} *rdata;
659 	struct mbuf *m;
660 	u_int8_t *fh;
661 	int minlen, error;
662 	int mntver;
663 
664 	mntver = (argp->flags & NFSMNT_NFSV3) ? 3 : 2;
665 	do {
666 		/*
667 		 * Get port number for MOUNTD.
668 		 */
669 		error = krpc_portmap(mdsin, RPCPROG_MNT, mntver,
670 		                    IPPROTO_UDP, &mdsin->sin_port);
671 		if (error)
672 			continue;
673 
674 		/* This mbuf is consumed by krpc_call. */
675 		m = xdr_string_encode(path, strlen(path));
676 		if (m == NULL)
677 			return ENOMEM;
678 
679 		/* Do RPC to mountd. */
680 		error = krpc_call(mdsin, RPCPROG_MNT, mntver,
681 		                  RPCMNT_MOUNT, &m, NULL);
682 		if (error != EPROGMISMATCH)
683 			break;
684 		/* Try lower version of mountd. */
685 	} while (--mntver >= 1);
686 	if (error) {
687 		printf("nfs_boot: mountd error=%d\n", error);
688 		return error;
689 	}
690 	if (mntver != 3)
691 		argp->flags &= ~NFSMNT_NFSV3;
692 
693 	/* The reply might have only the errno. */
694 	if (m->m_len < 4)
695 		goto bad;
696 	/* Have at least errno, so check that. */
697 	rdata = mtod(m, struct rdata *);
698 	error = fxdr_unsigned(u_int32_t, rdata->errno);
699 	if (error)
700 		goto out;
701 
702 	/* Have errno==0, so the fh must be there. */
703 	if (mntver == 3) {
704 		argp->fhsize   = fxdr_unsigned(u_int32_t, rdata->fh.v3fh.fhlen);
705 		if (argp->fhsize > NFSX_V3FHMAX)
706 			goto bad;
707 		minlen = 2 * sizeof(u_int32_t) + argp->fhsize;
708 	} else {
709 		argp->fhsize   = NFSX_V2FH;
710 		minlen = sizeof(u_int32_t) + argp->fhsize;
711 	}
712 
713 	if (m->m_len < minlen) {
714 		m = m_pullup(m, minlen);
715 		if (m == NULL)
716 			return(EBADRPC);
717 		rdata = mtod(m, struct rdata *);
718 	}
719 
720 	fh = (mntver == 3) ?
721 		rdata->fh.v3fh.fh : rdata->fh.v2fh;
722 	memcpy(argp->fh, fh, argp->fhsize);
723 
724 	goto out;
725 
726 bad:
727 	error = EBADRPC;
728 
729 out:
730 	m_freem(m);
731 	return error;
732 }
733