1/*
2 * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19FILE_LICENCE ( GPL2_OR_LATER );
20
21#include <stdint.h>
22#include <stdlib.h>
23#include <stdio.h>
24#include <errno.h>
25#include <string.h>
26#include <gpxe/netdevice.h>
27#include <gpxe/dhcp.h>
28#include <gpxe/dhcpopts.h>
29#include <gpxe/dhcppkt.h>
30
31/** @file
32 *
33 * DHCP packets
34 *
35 */
36
37/****************************************************************************
38 *
39 * DHCP packet raw interface
40 *
41 */
42
43/**
44 * Calculate used length of an IPv4 field within a DHCP packet
45 *
46 * @v data		Field data
47 * @v len		Length of field
48 * @ret used		Used length of field
49 */
50static size_t used_len_ipv4 ( const void *data, size_t len __unused ) {
51	const struct in_addr *in = data;
52
53	return ( in->s_addr ? sizeof ( *in ) : 0 );
54}
55
56/**
57 * Calculate used length of a string field within a DHCP packet
58 *
59 * @v data		Field data
60 * @v len		Length of field
61 * @ret used		Used length of field
62 */
63static size_t used_len_string ( const void *data, size_t len ) {
64	return strnlen ( data, len );
65}
66
67/** A dedicated field within a DHCP packet */
68struct dhcp_packet_field {
69	/** Settings tag number */
70	unsigned int tag;
71	/** Offset within DHCP packet */
72	uint16_t offset;
73	/** Length of field */
74	uint16_t len;
75	/** Calculate used length of field
76	 *
77	 * @v data	Field data
78	 * @v len	Length of field
79	 * @ret used	Used length of field
80	 */
81	size_t ( * used_len ) ( const void *data, size_t len );
82};
83
84/** Declare a dedicated field within a DHCP packet
85 *
86 * @v _tag		Settings tag number
87 * @v _field		Field name
88 * @v _used_len		Function to calculate used length of field
89 */
90#define DHCP_PACKET_FIELD( _tag, _field, _used_len ) {			\
91		.tag = (_tag),						\
92		.offset = offsetof ( struct dhcphdr, _field ),		\
93		.len = sizeof ( ( ( struct dhcphdr * ) 0 )->_field ),	\
94		.used_len = _used_len,					\
95	}
96
97/** Dedicated fields within a DHCP packet */
98static struct dhcp_packet_field dhcp_packet_fields[] = {
99	DHCP_PACKET_FIELD ( DHCP_EB_YIADDR, yiaddr, used_len_ipv4 ),
100	DHCP_PACKET_FIELD ( DHCP_EB_SIADDR, siaddr, used_len_ipv4 ),
101	DHCP_PACKET_FIELD ( DHCP_TFTP_SERVER_NAME, sname, used_len_string ),
102	DHCP_PACKET_FIELD ( DHCP_BOOTFILE_NAME, file, used_len_string ),
103};
104
105/**
106 * Get address of a DHCP packet field
107 *
108 * @v dhcphdr		DHCP packet header
109 * @v field		DHCP packet field
110 * @ret data		Packet field data
111 */
112static inline void * dhcp_packet_field ( struct dhcphdr *dhcphdr,
113					 struct dhcp_packet_field *field ) {
114	return ( ( ( void * ) dhcphdr ) + field->offset );
115}
116
117/**
118 * Find DHCP packet field corresponding to settings tag number
119 *
120 * @v tag		Settings tag number
121 * @ret field		DHCP packet field, or NULL
122 */
123static struct dhcp_packet_field *
124find_dhcp_packet_field ( unsigned int tag ) {
125	struct dhcp_packet_field *field;
126	unsigned int i;
127
128	for ( i = 0 ; i < ( sizeof ( dhcp_packet_fields ) /
129			    sizeof ( dhcp_packet_fields[0] ) ) ; i++ ) {
130		field = &dhcp_packet_fields[i];
131		if ( field->tag == tag )
132			return field;
133	}
134	return NULL;
135}
136
137/**
138 * Store value of DHCP packet setting
139 *
140 * @v dhcppkt		DHCP packet
141 * @v tag		Setting tag number
142 * @v data		Setting data, or NULL to clear setting
143 * @v len		Length of setting data
144 * @ret rc		Return status code
145 */
146int dhcppkt_store ( struct dhcp_packet *dhcppkt, unsigned int tag,
147		    const void *data, size_t len ) {
148	struct dhcp_packet_field *field;
149	void *field_data;
150	int rc;
151
152	/* If this is a special field, fill it in */
153	if ( ( field = find_dhcp_packet_field ( tag ) ) != NULL ) {
154		if ( len > field->len )
155			return -ENOSPC;
156		field_data = dhcp_packet_field ( dhcppkt->dhcphdr, field );
157		memset ( field_data, 0, field->len );
158		memcpy ( dhcp_packet_field ( dhcppkt->dhcphdr, field ),
159			 data, len );
160		/* Erase any equivalent option from the options block */
161		dhcpopt_store ( &dhcppkt->options, tag, NULL, 0 );
162		return 0;
163	}
164
165	/* Otherwise, use the generic options block */
166	rc = dhcpopt_store ( &dhcppkt->options, tag, data, len );
167
168	/* Update our used-length field */
169	dhcppkt->len = ( offsetof ( struct dhcphdr, options ) +
170			 dhcppkt->options.len );
171
172	return rc;
173}
174
175/**
176 * Fetch value of DHCP packet setting
177 *
178 * @v dhcppkt		DHCP packet
179 * @v tag		Setting tag number
180 * @v data		Buffer to fill with setting data
181 * @v len		Length of buffer
182 * @ret len		Length of setting data, or negative error
183 */
184int dhcppkt_fetch ( struct dhcp_packet *dhcppkt, unsigned int tag,
185		    void *data, size_t len ) {
186	struct dhcp_packet_field *field;
187	void *field_data;
188	size_t field_len = 0;
189
190	/* Identify special field, if any */
191	if ( ( field = find_dhcp_packet_field ( tag ) ) != NULL ) {
192		field_data = dhcp_packet_field ( dhcppkt->dhcphdr, field );
193		field_len = field->used_len ( field_data, field->len );
194	}
195
196	/* Return special field, if it exists and is populated */
197	if ( field_len ) {
198		if ( len > field_len )
199			len = field_len;
200		memcpy ( data, field_data, len );
201		return field_len;
202	}
203
204	/* Otherwise, use the generic options block */
205	return dhcpopt_fetch ( &dhcppkt->options, tag, data, len );
206}
207
208/****************************************************************************
209 *
210 * DHCP packet settings interface
211 *
212 */
213
214/**
215 * Store value of DHCP setting
216 *
217 * @v settings		Settings block
218 * @v setting		Setting to store
219 * @v data		Setting data, or NULL to clear setting
220 * @v len		Length of setting data
221 * @ret rc		Return status code
222 */
223static int dhcppkt_settings_store ( struct settings *settings,
224				    struct setting *setting,
225				    const void *data, size_t len ) {
226	struct dhcp_packet *dhcppkt =
227		container_of ( settings, struct dhcp_packet, settings );
228
229	return dhcppkt_store ( dhcppkt, setting->tag, data, len );
230}
231
232/**
233 * Fetch value of DHCP setting
234 *
235 * @v settings		Settings block, or NULL to search all blocks
236 * @v setting		Setting to fetch
237 * @v data		Buffer to fill with setting data
238 * @v len		Length of buffer
239 * @ret len		Length of setting data, or negative error
240 */
241static int dhcppkt_settings_fetch ( struct settings *settings,
242				    struct setting *setting,
243				    void *data, size_t len ) {
244	struct dhcp_packet *dhcppkt =
245		container_of ( settings, struct dhcp_packet, settings );
246
247	return dhcppkt_fetch ( dhcppkt, setting->tag, data, len );
248}
249
250/** DHCP settings operations */
251static struct settings_operations dhcppkt_settings_operations = {
252	.store = dhcppkt_settings_store,
253	.fetch = dhcppkt_settings_fetch,
254};
255
256/****************************************************************************
257 *
258 * Constructor
259 *
260 */
261
262/**
263 * Initialise DHCP packet
264 *
265 * @v dhcppkt		DHCP packet structure to fill in
266 * @v data		DHCP packet raw data
267 * @v max_len		Length of raw data buffer
268 *
269 * Initialise a DHCP packet structure from a data buffer containing a
270 * DHCP packet.
271 */
272void dhcppkt_init ( struct dhcp_packet *dhcppkt, struct dhcphdr *data,
273		    size_t len ) {
274	dhcppkt->dhcphdr = data;
275	dhcppkt->max_len = len;
276	dhcpopt_init ( &dhcppkt->options, &dhcppkt->dhcphdr->options,
277		       ( len - offsetof ( struct dhcphdr, options ) ) );
278	dhcppkt->len = ( offsetof ( struct dhcphdr, options ) +
279			 dhcppkt->options.len );
280	settings_init ( &dhcppkt->settings,
281			&dhcppkt_settings_operations, &dhcppkt->refcnt,
282			DHCP_SETTINGS_NAME, 0 );
283}
284