networking/udhcp/options.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * options.c -- DHCP server option packet tools
   4  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   5  */
   6
   7 #include <stdlib.h>
   8 #include <string.h>
   9
  10 #include "common.h"
  11 #include "dhcpd.h"
  12 #include "options.h"
  13 #include "files.h"
  14
  15
  16 /* supported options are easily added here */
  17 struct dhcp_option dhcp_options[] = {
  18         /* name[10]     flags                                   code */
  19         {"subnet",      OPTION_IP | OPTION_REQ,                 0x01},
  20         {"timezone",    OPTION_S32,                             0x02},
  21         {"router",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x03},
  22         {"timesvr",     OPTION_IP | OPTION_LIST,                0x04},
  23         {"namesvr",     OPTION_IP | OPTION_LIST,                0x05},
  24         {"dns",         OPTION_IP | OPTION_LIST | OPTION_REQ,   0x06},
  25         {"logsvr",      OPTION_IP | OPTION_LIST,                0x07},
  26         {"cookiesvr",   OPTION_IP | OPTION_LIST,                0x08},
  27         {"lprsvr",      OPTION_IP | OPTION_LIST,                0x09},
  28         {"hostname",    OPTION_STRING | OPTION_REQ,             0x0c},
  29         {"bootsize",    OPTION_U16,                             0x0d},
  30         {"domain",      OPTION_STRING | OPTION_REQ,             0x0f},
  31         {"swapsvr",     OPTION_IP,                              0x10},
  32         {"rootpath",    OPTION_STRING,                          0x11},
  33         {"ipttl",       OPTION_U8,                              0x17},
  34         {"mtu",         OPTION_U16,                             0x1a},
  35         {"broadcast",   OPTION_IP | OPTION_REQ,                 0x1c},
  36         {"nisdomain",   OPTION_STRING | OPTION_REQ,             0x28},
  37         {"nissrv",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x29},
  38         {"ntpsrv",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x2a},
  39         {"wins",        OPTION_IP | OPTION_LIST,                0x2c},
  40         {"requestip",   OPTION_IP,                              0x32},
  41         {"lease",       OPTION_U32,                             0x33},
  42         {"dhcptype",    OPTION_U8,                              0x35},
  43         {"serverid",    OPTION_IP,                              0x36},
  44         {"message",     OPTION_STRING,                          0x38},
  45         {"vendorclass", OPTION_STRING,                          0x3C},
  46         {"clientid",    OPTION_STRING,                          0x3D},
  47         {"tftp",        OPTION_STRING,                          0x42},
  48         {"bootfile",    OPTION_STRING,                          0x43},
  49         {"userclass",   OPTION_STRING,                          0x4D},
  50         {"",            0x00,                           0x00}
  51 };
  52
  53 /* Lengths of the different option types */
  54 int option_lengths[] = {
  55         [OPTION_IP] =           4,
  56         [OPTION_IP_PAIR] =      8,
  57         [OPTION_BOOLEAN] =      1,
  58         [OPTION_STRING] =       1,
  59         [OPTION_U8] =           1,
  60         [OPTION_U16] =          2,
  61         [OPTION_S16] =          2,
  62         [OPTION_U32] =          4,
  63         [OPTION_S32] =          4
  64 };
  65
  66
  67 /* get an option with bounds checking (warning, not aligned). */
  68 uint8_t *get_option(struct dhcpMessage *packet, int code)
  69 {
  70         int i, length;
  71         uint8_t *optionptr;
  72         int over = 0, done = 0, curr = OPTION_FIELD;
  73
  74         optionptr = packet->options;
  75         i = 0;
  76         length = 308;
  77         while (!done) {
  78                 if (i >= length) {
  79                         bb_error_msg("bogus packet, option fields too long");
  80                         return NULL;
  81                 }
  82                 if (optionptr[i + OPT_CODE] == code) {
  83                         if (i + 1 + optionptr[i + OPT_LEN] >= length) {
  84                                 bb_error_msg("bogus packet, option fields too long");
  85                                 return NULL;
  86                         }
  87                         return optionptr + i + 2;
  88                 }
  89                 switch (optionptr[i + OPT_CODE]) {
  90                 case DHCP_PADDING:
  91                         i++;
  92                         break;
  93                 case DHCP_OPTION_OVER:
  94                         if (i + 1 + optionptr[i + OPT_LEN] >= length) {
  95                                 bb_error_msg("bogus packet, option fields too long");
  96                                 return NULL;
  97                         }
  98                         over = optionptr[i + 3];
  99                         i += optionptr[OPT_LEN] + 2;
 100                         break;
 101                 case DHCP_END:
 102                         if (curr == OPTION_FIELD && over & FILE_FIELD) {
 103                                 optionptr = packet->file;
 104                                 i = 0;
 105                                 length = 128;
 106                                 curr = FILE_FIELD;
 107                         } else if (curr == FILE_FIELD && over & SNAME_FIELD) {
 108                                 optionptr = packet->sname;
 109                                 i = 0;
 110                                 length = 64;
 111                                 curr = SNAME_FIELD;
 112                         } else done = 1;
 113                         break;
 114                 default:
 115                         i += optionptr[OPT_LEN + i] + 2;
 116                 }
 117         }
 118         return NULL;
 119 }
 120
 121
 122 /* return the position of the 'end' option (no bounds checking) */
 123 int end_option(uint8_t *optionptr)
 124 {
 125         int i = 0;
 126
 127         while (optionptr[i] != DHCP_END) {
 128                 if (optionptr[i] == DHCP_PADDING) i++;
 129                 else i += optionptr[i + OPT_LEN] + 2;
 130         }
 131         return i;
 132 }
 133
 134
 135 /* add an option string to the options (an option string contains an option code,
 136  * length, then data) */
 137 int add_option_string(uint8_t *optionptr, uint8_t *string)
 138 {
 139         int end = end_option(optionptr);
 140
 141         /* end position + string length + option code/length + end option */
 142         if (end + string[OPT_LEN] + 2 + 1 >= 308) {
 143                 bb_error_msg("option 0x%02x did not fit into the packet",
 144                                 string[OPT_CODE]);
 145                 return 0;
 146         }
 147         DEBUG("adding option 0x%02x", string[OPT_CODE]);
 148         memcpy(optionptr + end, string, string[OPT_LEN] + 2);
 149         optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
 150         return string[OPT_LEN] + 2;
 151 }
 152
 153
 154 /* add a one to four byte option to a packet */
 155 int add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
 156 {
 157         struct dhcp_option *dh;
 158
 159         for (dh=dhcp_options; dh->code; dh++) {
 160                 if (dh->code == code) {
 161                         uint8_t option[6], len;
 162
 163                         option[OPT_CODE] = code;
 164                         len = option_lengths[dh->flags & TYPE_MASK];
 165                         option[OPT_LEN] = len;
 166                         if (BB_BIG_ENDIAN) data <<= 8 * (4 - len);
 167                         /* This memcpy is for broken processors which can't
 168                          * handle a simple unaligned 32-bit assignment */
 169                         memcpy(&option[OPT_DATA], &data, 4);
 170                         return add_option_string(optionptr, option);
 171                 }
 172         }
 173
 174         bb_error_msg("cannot add option 0x%02x", code);
 175         return 0;
 176 }