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  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   7  */
   8
   9 #include "common.h"
  10 #include "dhcpd.h"
  11 #include "options.h"
  12
  13
  14 /* Supported options are easily added here.
  15  * See RFC2132 for more options.
  16  * OPTION_REQ: these options are requested by udhcpc (unless -o).
  17  */
  18 const struct dhcp_option dhcp_options[] = {
  19         /* flags                                    code */
  20         { OPTION_IP                   | OPTION_REQ, 0x01 }, /* DHCP_SUBNET        */
  21         { OPTION_S32                              , 0x02 }, /* DHCP_TIME_OFFSET   */
  22         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x03 }, /* DHCP_ROUTER        */
  23         { OPTION_IP | OPTION_LIST                 , 0x04 }, /* DHCP_TIME_SERVER   */
  24 //      { OPTION_IP | OPTION_LIST                 , 0x05 }, /* DHCP_NAME_SERVER   */
  25         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x06 }, /* DHCP_DNS_SERVER    */
  26         { OPTION_IP | OPTION_LIST                 , 0x07 }, /* DHCP_LOG_SERVER    */
  27 //      { OPTION_IP | OPTION_LIST                 , 0x08 }, /* DHCP_COOKIE_SERVER */
  28         { OPTION_IP | OPTION_LIST                 , 0x09 }, /* DHCP_LPR_SERVER    */
  29         { OPTION_STRING               | OPTION_REQ, 0x0c }, /* DHCP_HOST_NAME     */
  30         { OPTION_U16                              , 0x0d }, /* DHCP_BOOT_SIZE     */
  31         { OPTION_STRING               | OPTION_REQ, 0x0f }, /* DHCP_DOMAIN_NAME   */
  32         { OPTION_IP                               , 0x10 }, /* DHCP_SWAP_SERVER   */
  33         { OPTION_STRING                           , 0x11 }, /* DHCP_ROOT_PATH     */
  34         { OPTION_U8                               , 0x17 }, /* DHCP_IP_TTL        */
  35         { OPTION_U16                              , 0x1a }, /* DHCP_MTU           */
  36         { OPTION_IP                   | OPTION_REQ, 0x1c }, /* DHCP_BROADCAST     */
  37         { OPTION_STRING                           , 0x28 }, /* nisdomain          */
  38         { OPTION_IP | OPTION_LIST                 , 0x29 }, /* nissrv             */
  39         { OPTION_IP | OPTION_LIST     | OPTION_REQ, 0x2a }, /* DHCP_NTP_SERVER    */
  40         { OPTION_IP | OPTION_LIST                 , 0x2c }, /* DHCP_WINS_SERVER   */
  41         { OPTION_U32                              , 0x33 }, /* DHCP_LEASE_TIME    */
  42         { OPTION_IP                               , 0x36 }, /* DHCP_SERVER_ID     */
  43         { OPTION_STRING                           , 0x38 }, /* DHCP_MESSAGE       */
  44         { OPTION_STRING                           , 0x42 }, /* tftp               */
  45         { OPTION_STRING                           , 0x43 }, /* bootfile           */
  46 //TODO: not a string, but a set of LASCII strings:
  47 //      { OPTION_STRING                           , 0x4D }, /* userclass          */
  48 #if ENABLE_FEATURE_UDHCP_RFC3397
  49         { OPTION_STR1035 | OPTION_LIST            , 0x77 }, /* search             */
  50 #endif
  51         { OPTION_STATIC_ROUTES                    , 0x79 }, /* DHCP_STATIC_ROUTES */
  52         /* MSIE's "Web Proxy Autodiscovery Protocol" support */
  53         { OPTION_STRING                           , 0xfc }, /* wpad               */
  54
  55         /* Options below have no match in dhcp_option_strings[],
  56          * are not passed to dhcpc scripts, and cannot be specified
  57          * with "option XXX YYY" syntax in dhcpd config file.
  58          * These entries are only used internally by udhcp[cd]
  59          * to correctly encode options into packets.
  60          */
  61
  62         { OPTION_IP                               , 0x32 }, /* DHCP_REQUESTED_IP  */
  63         { OPTION_U8                               , 0x35 }, /* DHCP_MESSAGE_TYPE  */
  64         { OPTION_U16                              , 0x39 }, /* DHCP_MAX_SIZE      */
  65         { OPTION_STRING                           , 0x3C }, /* DHCP_VENDOR        */
  66         { OPTION_STRING                           , 0x3D }, /* DHCP_CLIENT_ID     */
  67         { 0, 0 } /* zeroed terminating entry */
  68 };
  69
  70 /* Used for converting options from incoming packets to env variables
  71  * for udhcpc stript, and for setting options for udhcpd via
  72  * "opt OPTION_NAME OPTION_VALUE" directives in udhcpd.conf file.
  73  */
  74 /* Must match dhcp_options[] order */
  75 const char dhcp_option_strings[] ALIGN1 =
  76         "subnet" "\0"      /* DHCP_SUBNET         */
  77         "timezone" "\0"    /* DHCP_TIME_OFFSET    */
  78         "router" "\0"      /* DHCP_ROUTER         */
  79         "timesrv" "\0"     /* DHCP_TIME_SERVER    */
  80 //      "namesrv" "\0"     /* DHCP_NAME_SERVER    */
  81         "dns" "\0"         /* DHCP_DNS_SERVER     */
  82         "logsrv" "\0"      /* DHCP_LOG_SERVER     */
  83 //      "cookiesrv" "\0"   /* DHCP_COOKIE_SERVER  */
  84         "lprsrv" "\0"      /* DHCP_LPR_SERVER     */
  85         "hostname" "\0"    /* DHCP_HOST_NAME      */
  86         "bootsize" "\0"    /* DHCP_BOOT_SIZE      */
  87         "domain" "\0"      /* DHCP_DOMAIN_NAME    */
  88         "swapsrv" "\0"     /* DHCP_SWAP_SERVER    */
  89         "rootpath" "\0"    /* DHCP_ROOT_PATH      */
  90         "ipttl" "\0"       /* DHCP_IP_TTL         */
  91         "mtu" "\0"         /* DHCP_MTU            */
  92         "broadcast" "\0"   /* DHCP_BROADCAST      */
  93         "nisdomain" "\0"   /*                     */
  94         "nissrv" "\0"      /*                     */
  95         "ntpsrv" "\0"      /* DHCP_NTP_SERVER     */
  96         "wins" "\0"        /* DHCP_WINS_SERVER    */
  97         "lease" "\0"       /* DHCP_LEASE_TIME     */
  98         "serverid" "\0"    /* DHCP_SERVER_ID      */
  99         "message" "\0"     /* DHCP_MESSAGE        */
 100         "tftp" "\0"
 101         "bootfile" "\0"
 102 //      "userclass" "\0"
 103 #if ENABLE_FEATURE_UDHCP_RFC3397
 104         "search" "\0"
 105 #endif
 106 // "staticroutes" is only used to set udhcpc environment, it doesn't work
 107 // in udhcpd.conf since OPTION_STATIC_ROUTES is not handled yet:
 108         "staticroutes" "\0" /* DHCP_STATIC_ROUTES  */
 109         /* MSIE's "Web Proxy Autodiscovery Protocol" support */
 110         "wpad" "\0"
 111         ;
 112
 113
 114 /* Lengths of the different option types */
 115 const uint8_t dhcp_option_lengths[] ALIGN1 = {
 116         [OPTION_IP] =      4,
 117         [OPTION_IP_PAIR] = 8,
 118         [OPTION_BOOLEAN] = 1,
 119         [OPTION_STRING] =  1,
 120 #if ENABLE_FEATURE_UDHCP_RFC3397
 121         [OPTION_STR1035] = 1,
 122 #endif
 123         [OPTION_U8] =      1,
 124         [OPTION_U16] =     2,
 125         [OPTION_S16] =     2,
 126         [OPTION_U32] =     4,
 127         [OPTION_S32] =     4,
 128         /* Just like OPTION_STRING, we use minimum length here */
 129         [OPTION_STATIC_ROUTES] = 5,
 130 };
 131
 132
 133 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
 134 static void log_option(const char *pfx, const uint8_t *opt)
 135 {
 136         if (dhcp_verbose >= 2) {
 137                 char buf[256 * 2 + 2];
 138                 *bin2hex(buf, (void*) (opt + OPT_DATA), opt[OPT_LEN]) = '\0';
 139                 bb_info_msg("%s: 0x%02x %s", pfx, opt[OPT_CODE], buf);
 140         }
 141 }
 142 #else
 143 # define log_option(pfx, opt) ((void)0)
 144 #endif
 145
 146
 147 /* get an option with bounds checking (warning, result is not aligned). */
 148 uint8_t* FAST_FUNC get_option(struct dhcp_packet *packet, int code)
 149 {
 150         uint8_t *optionptr;
 151         int len;
 152         int rem;
 153         int overload = 0;
 154         enum {
 155                 FILE_FIELD101  = FILE_FIELD  * 0x101,
 156                 SNAME_FIELD101 = SNAME_FIELD * 0x101,
 157         };
 158
 159         /* option bytes: [code][len][data1][data2]..[dataLEN] */
 160         optionptr = packet->options;
 161         rem = sizeof(packet->options);
 162         while (1) {
 163                 if (rem <= 0) {
 164                         bb_error_msg("bogus packet, malformed option field");
 165                         return NULL;
 166                 }
 167                 if (optionptr[OPT_CODE] == DHCP_PADDING) {
 168                         rem--;
 169                         optionptr++;
 170                         continue;
 171                 }
 172                 if (optionptr[OPT_CODE] == DHCP_END) {
 173                         if ((overload & FILE_FIELD101) == FILE_FIELD) {
 174                                 /* can use packet->file, and didn't look at it yet */
 175                                 overload |= FILE_FIELD101; /* "we looked at it" */
 176                                 optionptr = packet->file;
 177                                 rem = sizeof(packet->file);
 178                                 continue;
 179                         }
 180                         if ((overload & SNAME_FIELD101) == SNAME_FIELD) {
 181                                 /* can use packet->sname, and didn't look at it yet */
 182                                 overload |= SNAME_FIELD101; /* "we looked at it" */
 183                                 optionptr = packet->sname;
 184                                 rem = sizeof(packet->sname);
 185                                 continue;
 186                         }
 187                         break;
 188                 }
 189                 len = 2 + optionptr[OPT_LEN];
 190                 rem -= len;
 191                 if (rem < 0)
 192                         continue; /* complain and return NULL */
 193
 194                 if (optionptr[OPT_CODE] == code) {
 195                         log_option("Option found", optionptr);
 196                         return optionptr + OPT_DATA;
 197                 }
 198
 199                 if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD) {
 200                         overload |= optionptr[OPT_DATA];
 201                         /* fall through */
 202                 }
 203                 optionptr += len;
 204         }
 205
 206         /* log3 because udhcpc uses it a lot - very noisy */
 207         log3("Option 0x%02x not found", code);
 208         return NULL;
 209 }
 210
 211
 212 /* return the position of the 'end' option (no bounds checking) */
 213 int FAST_FUNC end_option(uint8_t *optionptr)
 214 {
 215         int i = 0;
 216
 217         while (optionptr[i] != DHCP_END) {
 218                 if (optionptr[i] != DHCP_PADDING)
 219                         i += optionptr[i + OPT_LEN] + 1;
 220                 i++;
 221         }
 222         return i;
 223 }
 224
 225
 226 /* add an option string to the options */
 227 /* option bytes: [code][len][data1][data2]..[dataLEN] */
 228 int FAST_FUNC add_option_string(uint8_t *optionptr, uint8_t *string)
 229 {
 230         int end = end_option(optionptr);
 231
 232         /* end position + string length + option code/length + end option */
 233         if (end + string[OPT_LEN] + 2 + 1 >= DHCP_OPTIONS_BUFSIZE) {
 234                 bb_error_msg("option 0x%02x did not fit into the packet",
 235                                 string[OPT_CODE]);
 236                 return 0;
 237         }
 238         log_option("Adding option", string);
 239         memcpy(optionptr + end, string, string[OPT_LEN] + 2);
 240         optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
 241         return string[OPT_LEN] + 2;
 242 }
 243
 244
 245 /* add a one to four byte option to a packet */
 246 int FAST_FUNC add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
 247 {
 248         const struct dhcp_option *dh;
 249
 250         for (dh = dhcp_options; dh->code; dh++) {
 251                 if (dh->code == code) {
 252                         uint8_t option[6], len;
 253
 254                         option[OPT_CODE] = code;
 255                         len = dhcp_option_lengths[dh->flags & TYPE_MASK];
 256                         option[OPT_LEN] = len;
 257                         if (BB_BIG_ENDIAN)
 258                                 data <<= 8 * (4 - len);
 259                         /* Assignment is unaligned! */
 260                         move_to_unaligned32(&option[OPT_DATA], data);
 261                         return add_option_string(optionptr, option);
 262                 }
 263         }
 264
 265         bb_error_msg("can't add option 0x%02x", code);
 266         return 0;
 267 }