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