src/net/dhcppkt.c

   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., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  *
  19  * You can also choose to distribute this program under the terms of
  20  * the Unmodified Binary Distribution Licence (as given in the file
  21  * COPYING.UBDL), provided that you have satisfied its requirements.
  22  */
  23
  24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  25
  26 #include <stdint.h>
  27 #include <stdlib.h>
  28 #include <stdio.h>
  29 #include <errno.h>
  30 #include <string.h>
  31 #include <ipxe/netdevice.h>
  32 #include <ipxe/dhcp.h>
  33 #include <ipxe/dhcpopts.h>
  34 #include <ipxe/dhcppkt.h>
  35
  36 /** @file
  37  *
  38  * DHCP packets
  39  *
  40  */
  41
  42 /****************************************************************************
  43  *
  44  * DHCP packet raw interface
  45  *
  46  */
  47
  48 /**
  49  * Calculate used length of an IPv4 field within a DHCP packet
  50  *
  51  * @v data              Field data
  52  * @v len               Length of field
  53  * @ret used            Used length of field
  54  */
  55 static size_t used_len_ipv4 ( const void *data, size_t len __unused ) {
  56         const struct in_addr *in = data;
  57
  58         return ( in->s_addr ? sizeof ( *in ) : 0 );
  59 }
  60
  61 /**
  62  * Calculate used length of a string field within a DHCP packet
  63  *
  64  * @v data              Field data
  65  * @v len               Length of field
  66  * @ret used            Used length of field
  67  */
  68 static size_t used_len_string ( const void *data, size_t len ) {
  69         return strnlen ( data, len );
  70 }
  71
  72 /** A dedicated field within a DHCP packet */
  73 struct dhcp_packet_field {
  74         /** Settings tag number */
  75         unsigned int tag;
  76         /** Offset within DHCP packet */
  77         uint16_t offset;
  78         /** Length of field */
  79         uint16_t len;
  80         /** Calculate used length of field
  81          *
  82          * @v data      Field data
  83          * @v len       Length of field
  84          * @ret used    Used length of field
  85          */
  86         size_t ( * used_len ) ( const void *data, size_t len );
  87 };
  88
  89 /** Declare a dedicated field within a DHCP packet
  90  *
  91  * @v _tag              Settings tag number
  92  * @v _field            Field name
  93  * @v _used_len         Function to calculate used length of field
  94  */
  95 #define DHCP_PACKET_FIELD( _tag, _field, _used_len ) {                  \
  96                 .tag = (_tag),                                          \
  97                 .offset = offsetof ( struct dhcphdr, _field ),          \
  98                 .len = sizeof ( ( ( struct dhcphdr * ) 0 )->_field ),   \
  99                 .used_len = _used_len,                                  \
 100         }
 101
 102 /** Dedicated fields within a DHCP packet */
 103 static struct dhcp_packet_field dhcp_packet_fields[] = {
 104         DHCP_PACKET_FIELD ( DHCP_EB_YIADDR, yiaddr, used_len_ipv4 ),
 105         DHCP_PACKET_FIELD ( DHCP_EB_SIADDR, siaddr, used_len_ipv4 ),
 106         DHCP_PACKET_FIELD ( DHCP_TFTP_SERVER_NAME, sname, used_len_string ),
 107         DHCP_PACKET_FIELD ( DHCP_BOOTFILE_NAME, file, used_len_string ),
 108 };
 109
 110 /**
 111  * Get address of a DHCP packet field
 112  *
 113  * @v dhcphdr           DHCP packet header
 114  * @v field             DHCP packet field
 115  * @ret data            Packet field data
 116  */
 117 static inline void * dhcp_packet_field ( struct dhcphdr *dhcphdr,
 118                                          struct dhcp_packet_field *field ) {
 119         return ( ( ( void * ) dhcphdr ) + field->offset );
 120 }
 121
 122 /**
 123  * Find DHCP packet field corresponding to settings tag number
 124  *
 125  * @v tag               Settings tag number
 126  * @ret field           DHCP packet field, or NULL
 127  */
 128 static struct dhcp_packet_field *
 129 find_dhcp_packet_field ( unsigned int tag ) {
 130         struct dhcp_packet_field *field;
 131         unsigned int i;
 132
 133         for ( i = 0 ; i < ( sizeof ( dhcp_packet_fields ) /
 134                             sizeof ( dhcp_packet_fields[0] ) ) ; i++ ) {
 135                 field = &dhcp_packet_fields[i];
 136                 if ( field->tag == tag )
 137                         return field;
 138         }
 139         return NULL;
 140 }
 141
 142 /**
 143  * Check applicability of DHCP setting
 144  *
 145  * @v dhcppkt           DHCP packet
 146  * @v tag               Setting tag number
 147  * @ret applies         Setting applies within this settings block
 148  */
 149 static int dhcppkt_applies ( struct dhcp_packet *dhcppkt __unused,
 150                              unsigned int tag ) {
 151
 152         return dhcpopt_applies ( tag );
 153 }
 154
 155 /**
 156  * Store value of DHCP packet setting
 157  *
 158  * @v dhcppkt           DHCP packet
 159  * @v tag               Setting tag number
 160  * @v data              Setting data, or NULL to clear setting
 161  * @v len               Length of setting data
 162  * @ret rc              Return status code
 163  */
 164 int dhcppkt_store ( struct dhcp_packet *dhcppkt, unsigned int tag,
 165                     const void *data, size_t len ) {
 166         struct dhcp_packet_field *field;
 167         void *field_data;
 168
 169         /* If this is a special field, fill it in */
 170         if ( ( field = find_dhcp_packet_field ( tag ) ) != NULL ) {
 171                 if ( len > field->len )
 172                         return -ENOSPC;
 173                 field_data = dhcp_packet_field ( dhcppkt->dhcphdr, field );
 174                 memset ( field_data, 0, field->len );
 175                 memcpy ( dhcp_packet_field ( dhcppkt->dhcphdr, field ),
 176                          data, len );
 177                 /* Erase any equivalent option from the options block */
 178                 dhcpopt_store ( &dhcppkt->options, tag, NULL, 0 );
 179                 return 0;
 180         }
 181
 182         /* Otherwise, use the generic options block */
 183         return dhcpopt_store ( &dhcppkt->options, tag, data, len );
 184 }
 185
 186 /**
 187  * Fetch value of DHCP packet setting
 188  *
 189  * @v dhcppkt           DHCP packet
 190  * @v tag               Setting tag number
 191  * @v data              Buffer to fill with setting data
 192  * @v len               Length of buffer
 193  * @ret len             Length of setting data, or negative error
 194  */
 195 int dhcppkt_fetch ( struct dhcp_packet *dhcppkt, unsigned int tag,
 196                     void *data, size_t len ) {
 197         struct dhcp_packet_field *field;
 198         void *field_data;
 199         size_t field_len = 0;
 200
 201         /* Identify special field, if any */
 202         if ( ( field = find_dhcp_packet_field ( tag ) ) != NULL ) {
 203                 field_data = dhcp_packet_field ( dhcppkt->dhcphdr, field );
 204                 field_len = field->used_len ( field_data, field->len );
 205         }
 206
 207         /* Return special field, if it exists and is populated */
 208         if ( field_len ) {
 209                 if ( len > field_len )
 210                         len = field_len;
 211                 memcpy ( data, field_data, len );
 212                 return field_len;
 213         }
 214
 215         /* Otherwise, use the generic options block */
 216         return dhcpopt_fetch ( &dhcppkt->options, tag, data, len );
 217 }
 218
 219 /****************************************************************************
 220  *
 221  * DHCP packet settings interface
 222  *
 223  */
 224
 225 /**
 226  * Check applicability of DHCP setting
 227  *
 228  * @v settings          Settings block
 229  * @v setting           Setting
 230  * @ret applies         Setting applies within this settings block
 231  */
 232 static int dhcppkt_settings_applies ( struct settings *settings,
 233                                       const struct setting *setting ) {
 234         struct dhcp_packet *dhcppkt =
 235                 container_of ( settings, struct dhcp_packet, settings );
 236
 237         return ( ( setting->scope == NULL ) &&
 238                  dhcppkt_applies ( dhcppkt, setting->tag ) );
 239 }
 240
 241 /**
 242  * Store value of DHCP setting
 243  *
 244  * @v settings          Settings block
 245  * @v setting           Setting to store
 246  * @v data              Setting data, or NULL to clear setting
 247  * @v len               Length of setting data
 248  * @ret rc              Return status code
 249  */
 250 static int dhcppkt_settings_store ( struct settings *settings,
 251                                     const struct setting *setting,
 252                                     const void *data, size_t len ) {
 253         struct dhcp_packet *dhcppkt =
 254                 container_of ( settings, struct dhcp_packet, settings );
 255
 256         return dhcppkt_store ( dhcppkt, setting->tag, data, len );
 257 }
 258
 259 /**
 260  * Fetch value of DHCP setting
 261  *
 262  * @v settings          Settings block, or NULL to search all blocks
 263  * @v setting           Setting to fetch
 264  * @v data              Buffer to fill with setting data
 265  * @v len               Length of buffer
 266  * @ret len             Length of setting data, or negative error
 267  */
 268 static int dhcppkt_settings_fetch ( struct settings *settings,
 269                                     struct setting *setting,
 270                                     void *data, size_t len ) {
 271         struct dhcp_packet *dhcppkt =
 272                 container_of ( settings, struct dhcp_packet, settings );
 273
 274         return dhcppkt_fetch ( dhcppkt, setting->tag, data, len );
 275 }
 276
 277 /** DHCP settings operations */
 278 static struct settings_operations dhcppkt_settings_operations = {
 279         .applies = dhcppkt_settings_applies,
 280         .store = dhcppkt_settings_store,
 281         .fetch = dhcppkt_settings_fetch,
 282 };
 283
 284 /****************************************************************************
 285  *
 286  * Constructor
 287  *
 288  */
 289
 290 /**
 291  * Initialise DHCP packet
 292  *
 293  * @v dhcppkt           DHCP packet structure to fill in
 294  * @v data              DHCP packet raw data
 295  * @v max_len           Length of raw data buffer
 296  *
 297  * Initialise a DHCP packet structure from a data buffer containing a
 298  * DHCP packet.
 299  */
 300 void dhcppkt_init ( struct dhcp_packet *dhcppkt, struct dhcphdr *data,
 301                     size_t len ) {
 302         ref_init ( &dhcppkt->refcnt, NULL );
 303         dhcppkt->dhcphdr = data;
 304         dhcpopt_init ( &dhcppkt->options, &dhcppkt->dhcphdr->options,
 305                        ( len - offsetof ( struct dhcphdr, options ) ),
 306                        dhcpopt_no_realloc );
 307         settings_init ( &dhcppkt->settings, &dhcppkt_settings_operations,
 308                         &dhcppkt->refcnt, NULL );
 309 }