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
19 FILE_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 */
used_len_ipv4(const void * data,size_t len __unused)50 static 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 */
used_len_string(const void * data,size_t len)63 static 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 */
68 struct 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 */
98 static 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 */
dhcp_packet_field(struct dhcphdr * dhcphdr,struct dhcp_packet_field * field)112 static 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 */
123 static struct dhcp_packet_field *
find_dhcp_packet_field(unsigned int tag)124 find_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 */
dhcppkt_store(struct dhcp_packet * dhcppkt,unsigned int tag,const void * data,size_t len)146 int 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 */
dhcppkt_fetch(struct dhcp_packet * dhcppkt,unsigned int tag,void * data,size_t len)184 int 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 */
dhcppkt_settings_store(struct settings * settings,struct setting * setting,const void * data,size_t len)223 static 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 */
dhcppkt_settings_fetch(struct settings * settings,struct setting * setting,void * data,size_t len)241 static 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 */
251 static 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 */
dhcppkt_init(struct dhcp_packet * dhcppkt,struct dhcphdr * data,size_t len)272 void 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