aboutsummaryrefslogtreecommitdiffstats
path: root/gpxe/src/net/udp/dhcp.c
blob: 3961c61dc92c335223797fb6ddaf171d81832c6b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
/*
 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <gpxe/if_ether.h>
#include <gpxe/netdevice.h>
#include <gpxe/device.h>
#include <gpxe/xfer.h>
#include <gpxe/open.h>
#include <gpxe/job.h>
#include <gpxe/retry.h>
#include <gpxe/tcpip.h>
#include <gpxe/ip.h>
#include <gpxe/uuid.h>
#include <gpxe/dhcp.h>
#include <gpxe/timer.h>
#include <gpxe/settings.h>
#include <gpxe/dhcp.h>
#include <gpxe/dhcpopts.h>
#include <gpxe/dhcppkt.h>

/** @file
 *
 * Dynamic Host Configuration Protocol
 *
 */

/**
 * DHCP operation types
 *
 * This table maps from DHCP message types (i.e. values of the @c
 * DHCP_MESSAGE_TYPE option) to values of the "op" field within a DHCP
 * packet.
 */
static const uint8_t dhcp_op[] = {
	[DHCPDISCOVER]	= BOOTP_REQUEST,
	[DHCPOFFER]	= BOOTP_REPLY,
	[DHCPREQUEST]	= BOOTP_REQUEST,
	[DHCPDECLINE]	= BOOTP_REQUEST,
	[DHCPACK]	= BOOTP_REPLY,
	[DHCPNAK]	= BOOTP_REPLY,
	[DHCPRELEASE]	= BOOTP_REQUEST,
	[DHCPINFORM]	= BOOTP_REQUEST,
};

/** Raw option data for options common to all DHCP requests */
static uint8_t dhcp_request_options_data[] = {
	DHCP_MAX_MESSAGE_SIZE, DHCP_WORD ( ETH_MAX_MTU ),
	DHCP_VENDOR_CLASS_ID,
	DHCP_STRING (  'P', 'X', 'E', 'C', 'l', 'i', 'e', 'n', 't', ':',
		       'A', 'r', 'c', 'h', ':', '0', '0', '0', '0', '0', ':',
		       'U', 'N', 'D', 'I', ':', '0', '0', '2', '0', '0', '1' ),
	DHCP_CLIENT_ARCHITECTURE, DHCP_WORD ( 0 ),
	DHCP_CLIENT_NDI, DHCP_OPTION ( 1 /* UNDI */ , 2, 1 /* v2.1 */ ),
	DHCP_PARAMETER_REQUEST_LIST,
	DHCP_OPTION ( DHCP_SUBNET_MASK, DHCP_ROUTERS, DHCP_DNS_SERVERS,
		      DHCP_LOG_SERVERS, DHCP_HOST_NAME, DHCP_DOMAIN_NAME,
		      DHCP_ROOT_PATH, DHCP_VENDOR_ENCAP, DHCP_VENDOR_CLASS_ID,
		      DHCP_TFTP_SERVER_NAME, DHCP_BOOTFILE_NAME,
		      DHCP_EB_ENCAP, DHCP_ISCSI_INITIATOR_IQN ),
	DHCP_END
};

/** Options common to all DHCP requests */
static struct dhcp_options dhcp_request_options = {
	.data = dhcp_request_options_data,
	.max_len = sizeof ( dhcp_request_options_data ),
	.len = sizeof ( dhcp_request_options_data ),
};

/** DHCP feature codes */
static uint8_t dhcp_features[0] __table_start ( uint8_t, dhcp_features );
static uint8_t dhcp_features_end[0] __table_end ( uint8_t, dhcp_features );

/**
 * Name a DHCP packet type
 *
 * @v msgtype		DHCP message type
 * @ret string		DHCP mesasge type name
 */
static inline const char * dhcp_msgtype_name ( unsigned int msgtype ) {
	switch ( msgtype ) {
	case 0:			return "BOOTP"; /* Non-DHCP packet */
	case DHCPDISCOVER:	return "DHCPDISCOVER";
	case DHCPOFFER:		return "DHCPOFFER";
	case DHCPREQUEST:	return "DHCPREQUEST";
	case DHCPDECLINE:	return "DHCPDECLINE";
	case DHCPACK:		return "DHCPACK";
	case DHCPNAK:		return "DHCPNAK";
	case DHCPRELEASE:	return "DHCPRELEASE";
	case DHCPINFORM:	return "DHCPINFORM";
	default:		return "DHCP<invalid>";
	}
}

/**
 * Calculate DHCP transaction ID for a network device
 *
 * @v netdev		Network device
 * @ret xid		DHCP XID
 *
 * Extract the least significant bits of the hardware address for use
 * as the transaction ID.
 */
static uint32_t dhcp_xid ( struct net_device *netdev ) {
	uint32_t xid;

	memcpy ( &xid, ( netdev->ll_addr + netdev->ll_protocol->ll_addr_len
			 - sizeof ( xid ) ), sizeof ( xid ) );
	return xid;
}

/**
 * Create a DHCP packet
 *
 * @v dhcppkt		DHCP packet structure to fill in
 * @v netdev		Network device
 * @v msgtype		DHCP message type
 * @v options		Initial options to include (or NULL)
 * @v data		Buffer for DHCP packet
 * @v max_len		Size of DHCP packet buffer
 * @ret rc		Return status code
 *
 * Creates a DHCP packet in the specified buffer, and fills out a @c
 * dhcp_packet structure that can be passed to
 * set_dhcp_packet_option() or copy_dhcp_packet_options().
 */
int create_dhcp_packet ( struct dhcp_packet *dhcppkt,
			 struct net_device *netdev, uint8_t msgtype,
			 struct dhcp_options *options, 
			 void *data, size_t max_len ) {
	struct dhcphdr *dhcphdr = data;
	size_t options_len;
	unsigned int hlen;
	int rc;

	/* Sanity check */
	options_len = ( options ? options->len : 0 );
	if ( max_len < ( sizeof ( *dhcphdr ) + options_len ) )
		return -ENOSPC;

	/* Initialise DHCP packet content */
	memset ( dhcphdr, 0, max_len );
	dhcphdr->xid = dhcp_xid ( netdev );
	dhcphdr->magic = htonl ( DHCP_MAGIC_COOKIE );
	dhcphdr->htype = ntohs ( netdev->ll_protocol->ll_proto );
	dhcphdr->op = dhcp_op[msgtype];
	/* If hardware length exceeds the chaddr field length, don't
	 * use the chaddr field.  This is as per RFC4390.
	 */
	hlen = netdev->ll_protocol->ll_addr_len;
	if ( hlen > sizeof ( dhcphdr->chaddr ) ) {
		hlen = 0;
		dhcphdr->flags = htons ( BOOTP_FL_BROADCAST );
	}
	dhcphdr->hlen = hlen;
	memcpy ( dhcphdr->chaddr, netdev->ll_addr, hlen );
	memcpy ( dhcphdr->options, options->data, options_len );

	/* Initialise DHCP packet structure */
	memset ( dhcppkt, 0, sizeof ( *dhcppkt ) );
	dhcppkt_init ( dhcppkt, data, max_len );
	
	/* Set DHCP_MESSAGE_TYPE option */
	if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_MESSAGE_TYPE,
				    &msgtype, sizeof ( msgtype ) ) ) != 0 )
		return rc;

	return 0;
}

/** DHCP network device descriptor */
struct dhcp_netdev_desc {
	/** Bus type ID */
	uint8_t type;
	/** Vendor ID */
	uint16_t vendor;
	/** Device ID */
	uint16_t device;
} __attribute__ (( packed ));

/** DHCP client identifier */
struct dhcp_client_id {
	/** Link-layer protocol */
	uint8_t ll_proto;
	/** Link-layer address */
	uint8_t ll_addr[MAX_LL_ADDR_LEN];
} __attribute__ (( packed ));

/** DHCP client UUID */
struct dhcp_client_uuid {
	/** Identifier type */
	uint8_t type;
	/** UUID */
	union uuid uuid;
} __attribute__ (( packed ));

#define DHCP_CLIENT_UUID_TYPE 0

/**
 * Create DHCP request packet
 *
 * @v dhcppkt		DHCP packet structure to fill in
 * @v netdev		Network device
 * @v dhcpoffer		DHCPOFFER packet received from server
 * @v data		Buffer for DHCP packet
 * @v max_len		Size of DHCP packet buffer
 * @ret rc		Return status code
 */
int create_dhcp_request ( struct dhcp_packet *dhcppkt,
			  struct net_device *netdev,
			  struct dhcp_packet *dhcpoffer,
			  void *data, size_t max_len ) {
	struct device_description *desc = &netdev->dev->desc;
	struct dhcp_netdev_desc dhcp_desc;
	struct dhcp_client_id client_id;
	struct dhcp_client_uuid client_uuid;
	unsigned int msgtype;
	size_t dhcp_features_len;
	size_t ll_addr_len;
	int rc;

	/* Create DHCP packet */
	msgtype = ( dhcpoffer ? DHCPREQUEST : DHCPDISCOVER );
	if ( ( rc = create_dhcp_packet ( dhcppkt, netdev, msgtype,
					 &dhcp_request_options, data,
					 max_len ) ) != 0 ) {
		DBG ( "DHCP could not create DHCP packet: %s\n",
		      strerror ( rc ) );
		return rc;
	}

	/* Copy any required options from previous server repsonse */
	if ( dhcpoffer ) {
		struct in_addr server_id;
		struct in_addr requested_ip;

		if ( dhcppkt_fetch ( dhcpoffer, DHCP_SERVER_IDENTIFIER,
				     &server_id, sizeof ( server_id ) )
		     != sizeof ( server_id ) ) {
			DBG ( "DHCP offer missing server identifier\n" );
			return -EINVAL;
		}
		if ( dhcppkt_fetch ( dhcpoffer, DHCP_EB_YIADDR,
				     &requested_ip, sizeof ( requested_ip ) )
		     != sizeof ( requested_ip ) ) {
			DBG ( "DHCP offer missing IP address\n" );
			return -EINVAL;
		}
		if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_SERVER_IDENTIFIER,
					    &server_id,
					    sizeof ( server_id ) ) ) != 0 ) {
			DBG ( "DHCP could not set server identifier: %s\n ",
			      strerror ( rc ) );
			return rc;
		}
		if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_REQUESTED_ADDRESS,
					    &requested_ip,
					    sizeof ( requested_ip ) ) ) != 0 ){
			DBG ( "DHCP could not set requested address: %s\n",
			      strerror ( rc ) );
			return rc;
		}
	}

	/* Add options to identify the feature list */
	dhcp_features_len = ( dhcp_features_end - dhcp_features );
	if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_EB_ENCAP, dhcp_features,
				    dhcp_features_len ) ) != 0 ) {
		DBG ( "DHCP could not set features list option: %s\n",
		      strerror ( rc ) );
		return rc;
	}

	/* Add options to identify the network device */
	dhcp_desc.type = desc->bus_type;
	dhcp_desc.vendor = htons ( desc->vendor );
	dhcp_desc.device = htons ( desc->device );
	if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_EB_BUS_ID, &dhcp_desc,
				    sizeof ( dhcp_desc ) ) ) != 0 ) {
		DBG ( "DHCP could not set bus ID option: %s\n",
		      strerror ( rc ) );
		return rc;
	}

	/* Add DHCP client identifier.  Required for Infiniband, and
	 * doesn't hurt other link layers.
	 */
	client_id.ll_proto = ntohs ( netdev->ll_protocol->ll_proto );
	ll_addr_len = netdev->ll_protocol->ll_addr_len;
	assert ( ll_addr_len <= sizeof ( client_id.ll_addr ) );
	memcpy ( client_id.ll_addr, netdev->ll_addr, ll_addr_len );
	if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_CLIENT_ID, &client_id,
				    ( ll_addr_len + 1 ) ) ) != 0 ) {
		DBG ( "DHCP could not set client ID: %s\n",
		      strerror ( rc ) );
		return rc;
	}

	/* Add client UUID, if we have one.  Required for PXE. */
	client_uuid.type = DHCP_CLIENT_UUID_TYPE;
	if ( ( rc = get_uuid ( &client_uuid.uuid ) ) == 0 ) {
		if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_CLIENT_UUID,
					    &client_uuid,
					    sizeof ( client_uuid ) ) ) != 0 ) {
			DBG ( "DHCP could not set client UUID: %s\n",
			      strerror ( rc ) );
			return rc;
		}
	}

	return 0;
}

/****************************************************************************
 *
 * DHCP settings
 *
 */

/** A DHCP settings block */
struct dhcp_settings {
	/** Reference counter */
	struct refcnt refcnt;
	/** DHCP packet */
	struct dhcp_packet dhcppkt;
	/** Setting interface */
	struct settings settings;
};

/**
 * Decrement reference count on DHCP settings block
 *
 * @v dhcpset		DHCP settings block
 */
static inline void dhcpset_put ( struct dhcp_settings *dhcpset ) {
	ref_put ( &dhcpset->refcnt );
}

/**
 * Store value of DHCP setting
 *
 * @v settings		Settings block
 * @v setting		Setting to store
 * @v data		Setting data, or NULL to clear setting
 * @v len		Length of setting data
 * @ret rc		Return status code
 */
static int dhcpset_store ( struct settings *settings, struct setting *setting,
			   const void *data, size_t len ) {
	struct dhcp_settings *dhcpset =
		container_of ( settings, struct dhcp_settings, settings );

	return dhcppkt_store ( &dhcpset->dhcppkt, setting->tag, data, len );
}

/**
 * Fetch value of setting
 *
 * @v settings		Settings block, or NULL to search all blocks
 * @v setting		Setting to fetch
 * @v data		Buffer to fill with setting data
 * @v len		Length of buffer
 * @ret len		Length of setting data, or negative error
 */
static int dhcpset_fetch ( struct settings *settings, struct setting *setting,
			   void *data, size_t len ) {
	struct dhcp_settings *dhcpset =
		container_of ( settings, struct dhcp_settings, settings );

	return dhcppkt_fetch ( &dhcpset->dhcppkt, setting->tag, data, len );
}

/** DHCP settings operations */
static struct settings_operations dhcpset_settings_operations = {
	.store = dhcpset_store,
	.fetch = dhcpset_fetch,
};

/**
 * Create DHCP setting block
 *
 * @v dhcphdr		DHCP packet
 * @v len		Length of DHCP packet
 * @ret dhcpset		DHCP settings block
 */
static struct dhcp_settings * dhcpset_create ( const struct dhcphdr *dhcphdr,
					       size_t len ) {
	struct dhcp_settings *dhcpset;
	void *data;

	dhcpset = zalloc ( sizeof ( *dhcpset ) + len );
	if ( dhcpset ) {
		data = ( ( ( void * ) dhcpset ) + sizeof ( *dhcpset ) );
		memcpy ( data, dhcphdr, len );
		dhcppkt_init ( &dhcpset->dhcppkt, data, len );
		settings_init ( &dhcpset->settings,
				&dhcpset_settings_operations, &dhcpset->refcnt,
				DHCP_SETTINGS_NAME );
	}
	return dhcpset;
}

/****************************************************************************
 *
 * DHCP to UDP interface
 *
 */

/** A DHCP session */
struct dhcp_session {
	/** Reference counter */
	struct refcnt refcnt;
	/** Job control interface */
	struct job_interface job;
	/** Data transfer interface */
	struct xfer_interface xfer;

	/** Network device being configured */
	struct net_device *netdev;

	/** State of the session
	 *
	 * This is a value for the @c DHCP_MESSAGE_TYPE option
	 * (e.g. @c DHCPDISCOVER).
	 */
	int state;
	/** Response obtained from DHCP server */
	struct dhcp_settings *response;
	/** Response obtained from ProxyDHCP server */
	struct dhcp_settings *proxy_response;
	/** Retransmission timer */
	struct retry_timer timer;
	/** Session start time (in ticks) */
	unsigned long start;
};

/**
 * Free DHCP session
 *
 * @v refcnt		Reference counter
 */
static void dhcp_free ( struct refcnt *refcnt ) {
	struct dhcp_session *dhcp =
		container_of ( refcnt, struct dhcp_session, refcnt );

	netdev_put ( dhcp->netdev );
	dhcpset_put ( dhcp->response );
	dhcpset_put ( dhcp->proxy_response );
	free ( dhcp );
}

/**
 * Mark DHCP session as complete
 *
 * @v dhcp		DHCP session
 * @v rc		Return status code
 */
static void dhcp_finished ( struct dhcp_session *dhcp, int rc ) {

	/* Block futher incoming messages */
	job_nullify ( &dhcp->job );
	xfer_nullify ( &dhcp->xfer );

	/* Stop retry timer */
	stop_timer ( &dhcp->timer );

	/* Free resources and close interfaces */
	xfer_close ( &dhcp->xfer, rc );
	job_done ( &dhcp->job, rc );
}

/**
 * Register options received via DHCP
 *
 * @v dhcp		DHCP session
 * @ret rc		Return status code
 */
static int dhcp_register_settings ( struct dhcp_session *dhcp ) {
	struct settings *old_settings;
	struct settings *settings;
	struct settings *parent;
	int rc;

	/* Register ProxyDHCP settings, if present */
	if ( dhcp->proxy_response ) {
		settings = &dhcp->proxy_response->settings;
		settings->name = PROXYDHCP_SETTINGS_NAME;
		old_settings = find_settings ( settings->name );
		if ( old_settings )
			unregister_settings ( old_settings );
		if ( ( rc = register_settings ( settings, NULL ) ) != 0 )
			return rc;
	}

	/* Register DHCP settings */
	parent = netdev_settings ( dhcp->netdev );
	settings = &dhcp->response->settings;
	old_settings = find_child_settings ( parent, settings->name );
	if ( old_settings )
		unregister_settings ( old_settings );
	if ( ( rc = register_settings ( settings, parent ) ) != 0 )
		return rc;

	return 0;
}

/****************************************************************************
 *
 * Data transfer interface
 *
 */

/**
 * Transmit DHCP request
 *
 * @v dhcp		DHCP session
 * @ret rc		Return status code
 */
static int dhcp_send_request ( struct dhcp_session *dhcp ) {
	struct xfer_metadata meta = {
		.netdev = dhcp->netdev,
	};
	struct io_buffer *iobuf;
	struct dhcp_packet *dhcpoffer = NULL;
	struct dhcp_packet dhcppkt;
	int rc;
	
	DBGC ( dhcp, "DHCP %p transmitting %s\n",
	       dhcp, dhcp_msgtype_name ( dhcp->state ) );

	assert ( ( dhcp->state == DHCPDISCOVER ) ||
		 ( dhcp->state == DHCPREQUEST ) );

	/* Start retry timer.  Do this first so that failures to
	 * transmit will be retried.
	 */
	start_timer ( &dhcp->timer );

	/* Allocate buffer for packet */
	iobuf = xfer_alloc_iob ( &dhcp->xfer, DHCP_MIN_LEN );
	if ( ! iobuf )
		return -ENOMEM;

	/* Create DHCP packet in temporary buffer */
	if ( dhcp->state == DHCPREQUEST ) {
		assert ( dhcp->response );
		dhcpoffer = &dhcp->response->dhcppkt;
	}
	if ( ( rc = create_dhcp_request ( &dhcppkt, dhcp->netdev,
					  dhcpoffer, iobuf->data,
					  iob_tailroom ( iobuf ) ) ) != 0 ) {
		DBGC ( dhcp, "DHCP %p could not construct DHCP request: %s\n",
		       dhcp, strerror ( rc ) );
		goto done;
	}

	/* Transmit the packet */
	iob_put ( iobuf, dhcppkt.len );
	rc = xfer_deliver_iob_meta ( &dhcp->xfer, iobuf, &meta );
	iobuf = NULL;
	if ( rc != 0 ) {
		DBGC ( dhcp, "DHCP %p could not transmit UDP packet: %s\n",
		       dhcp, strerror ( rc ) );
		goto done;
	}

 done:
	free_iob ( iobuf );
	return rc;
}

/**
 * Handle DHCP retry timer expiry
 *
 * @v timer		DHCP retry timer
 * @v fail		Failure indicator
 */
static void dhcp_timer_expired ( struct retry_timer *timer, int fail ) {
	struct dhcp_session *dhcp =
		container_of ( timer, struct dhcp_session, timer );

	if ( fail ) {
		dhcp_finished ( dhcp, -ETIMEDOUT );
	} else {
		dhcp_send_request ( dhcp );
	}
}

/**
 * Receive new data
 *
 * @v xfer 		Data transfer interface
 * @v iobuf		I/O buffer
 * @v data		Received data
 * @v len		Length of received data
 * @ret rc		Return status code
 */
static int dhcp_deliver_raw ( struct xfer_interface *xfer,
			      const void *data, size_t len ) {
	struct dhcp_session *dhcp =
		container_of ( xfer, struct dhcp_session, xfer );
	struct dhcp_settings *response;
	struct dhcp_settings **store_response;
	struct dhcphdr *dhcphdr;
	uint8_t msgtype = 0;
	uint8_t priority = 0;
	uint8_t existing_priority = 0;
	unsigned long elapsed;
	int is_proxy;
	uint8_t ignore_proxy = 0;
	int rc;

	/* Convert packet into a DHCP settings block */
	response = dhcpset_create ( data, len );
	if ( ! response ) {
		DBGC ( dhcp, "DHCP %p could not store DHCP packet\n", dhcp );
		return -ENOMEM;
	}
	dhcphdr = response->dhcppkt.dhcphdr;

	/* Check for matching transaction ID */
	if ( dhcphdr->xid != dhcp_xid ( dhcp->netdev ) ) {
		DBGC ( dhcp, "DHCP %p wrong transaction ID (wanted %08lx, "
			"got %08lx)\n", dhcp, ntohl ( dhcphdr->xid ),
			ntohl ( dhcp_xid ( dhcp->netdev ) ) );
		goto out_discard;
	};	

	/* Determine and verify message type */
	is_proxy = ( dhcphdr->yiaddr.s_addr == 0 );
	dhcppkt_fetch ( &response->dhcppkt, DHCP_MESSAGE_TYPE, &msgtype,
			sizeof ( msgtype ) );
	DBGC ( dhcp, "DHCP %p received %s%s\n", dhcp,
	       ( is_proxy ? "Proxy" : "" ), dhcp_msgtype_name ( msgtype ) );
	if ( ( ( dhcp->state != DHCPDISCOVER ) || ( msgtype != DHCPOFFER ) ) &&
	     ( ( dhcp->state != DHCPREQUEST ) || ( msgtype != DHCPACK ) ) ) {
		DBGC ( dhcp, "DHCP %p discarding %s while in %s state\n",
		       dhcp, dhcp_msgtype_name ( msgtype ),
		       dhcp_msgtype_name ( dhcp->state ) );
		goto out_discard;
	}

	/* Update stored standard/ProxyDHCP options, if the new
	 * options have equal or higher priority than the
	 * currently-stored options.
	 */
	store_response = ( is_proxy ? &dhcp->proxy_response : &dhcp->response);
	if ( *store_response ) {
		dhcppkt_fetch ( &(*store_response)->dhcppkt, DHCP_EB_PRIORITY,
				&existing_priority,
				sizeof ( existing_priority ) );
	}
	dhcppkt_fetch ( &response->dhcppkt, DHCP_EB_PRIORITY, &priority,
			sizeof ( priority ) );
	if ( priority >= existing_priority ) {
		dhcpset_put ( *store_response );
		*store_response = response;
	} else {
		dhcpset_put ( response );
	}

	/* If we don't yet have a standard DHCP response (i.e. one
	 * with an IP address), then just leave the timer running.
	 */
	if ( ! dhcp->response )
		goto out;

	/* Handle DHCP response */
	dhcppkt_fetch ( &dhcp->response->dhcppkt, DHCP_EB_NO_PROXYDHCP,
			&ignore_proxy, sizeof ( ignore_proxy ) );
	switch ( dhcp->state ) {
	case DHCPDISCOVER:
		/* If we have allowed sufficient time for ProxyDHCP
		 * reponses, then transition to making the DHCPREQUEST.
		 */
		elapsed = ( currticks() - dhcp->start );
		if ( ignore_proxy || ( elapsed > PROXYDHCP_WAIT_TIME ) ) {
			stop_timer ( &dhcp->timer );
			dhcp->state = DHCPREQUEST;
			dhcp_send_request ( dhcp );
		}
		break;
	case DHCPREQUEST:
		/* DHCP finished; register options and exit */
		if ( ignore_proxy && dhcp->proxy_response ) {
			dhcpset_put ( dhcp->proxy_response );
			dhcp->proxy_response = NULL;
		}
		if ( ( rc = dhcp_register_settings ( dhcp ) ) != 0 ) {
			dhcp_finished ( dhcp, rc );
			break;
		}
		dhcp_finished ( dhcp, 0 );
		break;
	default:
		assert ( 0 );
	}

 out:
	return 0;

 out_discard:
	dhcpset_put ( response );
	return 0;
}

/** DHCP data transfer interface operations */
static struct xfer_interface_operations dhcp_xfer_operations = {
	.close		= ignore_xfer_close,
	.vredirect	= xfer_vopen,
	.window		= unlimited_xfer_window,
	.alloc_iob	= default_xfer_alloc_iob,
	.deliver_iob	= xfer_deliver_as_raw,
	.deliver_raw	= dhcp_deliver_raw,
};

/****************************************************************************
 *
 * Job control interface
 *
 */

/**
 * Handle kill() event received via job control interface
 *
 * @v job		DHCP job control interface
 */
static void dhcp_job_kill ( struct job_interface *job ) {
	struct dhcp_session *dhcp =
		container_of ( job, struct dhcp_session, job );

	/* Terminate DHCP session */
	dhcp_finished ( dhcp, -ECANCELED );
}

/** DHCP job control interface operations */
static struct job_interface_operations dhcp_job_operations = {
	.done		= ignore_job_done,
	.kill		= dhcp_job_kill,
	.progress	= ignore_job_progress,
};

/****************************************************************************
 *
 * Instantiator
 *
 */

/**
 * Start DHCP on a network device
 *
 * @v job		Job control interface
 * @v netdev		Network device
 * @v register_options	DHCP option block registration routine
 * @ret rc		Return status code
 *
 * Starts DHCP on the specified network device.  If successful, the @c
 * register_options() routine will be called with the acquired
 * options.
 */
int start_dhcp ( struct job_interface *job, struct net_device *netdev ) {
	static struct sockaddr_in server = {
		.sin_family = AF_INET,
		.sin_addr.s_addr = INADDR_BROADCAST,
		.sin_port = htons ( BOOTPS_PORT ),
	};
	static struct sockaddr_in client = {
		.sin_family = AF_INET,
		.sin_port = htons ( BOOTPC_PORT ),
	};
	struct dhcp_session *dhcp;
	int rc;

	/* Allocate and initialise structure */
	dhcp = zalloc ( sizeof ( *dhcp ) );
	if ( ! dhcp )
		return -ENOMEM;
	dhcp->refcnt.free = dhcp_free;
	job_init ( &dhcp->job, &dhcp_job_operations, &dhcp->refcnt );
	xfer_init ( &dhcp->xfer, &dhcp_xfer_operations, &dhcp->refcnt );
	dhcp->netdev = netdev_get ( netdev );
	dhcp->timer.expired = dhcp_timer_expired;
	dhcp->state = DHCPDISCOVER;
	dhcp->start = currticks();

	/* Instantiate child objects and attach to our interfaces */
	if ( ( rc = xfer_open_socket ( &dhcp->xfer, SOCK_DGRAM,
				       ( struct sockaddr * ) &server,
				       ( struct sockaddr * ) &client ) ) != 0 )
		goto err;

	/* Start timer to initiate initial DHCPREQUEST */
	start_timer_nodelay ( &dhcp->timer );

	/* Attach parent interface, mortalise self, and return */
	job_plug_plug ( &dhcp->job, job );
	ref_put ( &dhcp->refcnt );
	return 0;

 err:
	dhcp_finished ( dhcp, rc );
	ref_put ( &dhcp->refcnt );
	return rc;
}