1 #include <stdio.h> 2 #include <stdlib.h> 3 #include <errno.h> 4 #include <fcntl.h> 5 6 #include "dhcp.h" 7 #include "config.h" 8 9 #ifndef DEFAULT_LEASETIME 10 #define DEFAULT_LEASETIME 3600 /* 1 hour */ 11 #endif 12 13 #define REQUEST (1 << 0) 14 #define UINT8 (1 << 1) 15 #define UINT16 (1 << 2) 16 #define SINT16 (1 << 3) 17 #define UINT32 (1 << 4) 18 #define SINT32 (1 << 5) 19 #define IPV4 (1 << 6) 20 #define STRING (1 << 7) 21 #define PAIR (1 << 8) 22 #define ARRAY (1 << 9) 23 #define RFC3361 (1 << 10) 24 #define RFC3397 (1 << 11) 25 #define RFC3442 (1 << 12) 26 27 struct dhcp_opt { 28 uint8_t option; 29 int type; 30 const char *var; 31 }; 32 33 static const struct dhcp_opt const dhcp_opts[] = { 34 { 1, IPV4 | REQUEST, "subnet_mask" }, 35 { 2, UINT32, "time_offset" }, 36 { 3, IPV4 | ARRAY | REQUEST, "routers" }, 37 { 4, IPV4 | ARRAY, "time_servers" }, 38 { 5, IPV4 | ARRAY, "ien116_name_servers" }, 39 { 6, IPV4 | ARRAY, "domain_name_servers" }, 40 { 7, IPV4 | ARRAY, "log_servers" }, 41 { 8, IPV4 | ARRAY, "cookie_servers" }, 42 { 9, IPV4 | ARRAY, "lpr_servers" }, 43 { 10, IPV4 | ARRAY, "impress_servers" }, 44 { 11, IPV4 | ARRAY, "resource_location_servers" }, 45 { 12, STRING, "host_name" }, 46 { 13, UINT16, "boot_size" }, 47 { 14, STRING, "merit_dump" }, 48 { 15, STRING, "domain_name" }, 49 { 16, IPV4, "swap_server" }, 50 { 17, STRING, "root_path" }, 51 { 18, STRING, "extensions_path" }, 52 { 19, UINT8, "ip_forwarding" }, 53 { 20, UINT8, "non_local_source_routing" }, 54 { 21, IPV4 | ARRAY, "policy_filter" }, 55 { 22, SINT16, "max_dgram_reassembly" }, 56 { 23, UINT16, "default_ip_ttl" }, 57 { 24, UINT32, "path_mtu_aging_timeout" }, 58 { 25, UINT16 | ARRAY, "path_mtu_plateau_table" }, 59 { 26, UINT16, "interface_mtu" }, 60 { 27, UINT8, "all_subnets_local" }, 61 { 28, IPV4 | REQUEST, "broadcast_address" }, 62 { 29, UINT8, "perform_mask_discovery" }, 63 { 30, UINT8, "mask_supplier" }, 64 { 31, UINT8, "router_discovery" }, 65 { 32, IPV4, "router_solicitation_address" }, 66 { 33, IPV4 | ARRAY | REQUEST, "static_routes" }, 67 { 34, UINT8, "trailer_encapsulation" }, 68 { 35, UINT32, "arp_cache_timeout" }, 69 { 36, UINT16, "ieee802_3_encapsulation" }, 70 { 37, UINT8, "default_tcp_ttl" }, 71 { 38, UINT32, "tcp_keepalive_interval" }, 72 { 39, UINT8, "tcp_keepalive_garbage" }, 73 { 40, STRING, "nis_domain" }, 74 { 41, IPV4 | ARRAY, "nis_servers" }, 75 { 42, IPV4 | ARRAY, "ntp_servers" }, 76 { 43, STRING, "vendor_encapsulated_options" }, 77 { 44, IPV4 | ARRAY, "netbios_name_servers" }, 78 { 45, IPV4, "netbios_dd_server" }, 79 { 46, UINT8, "netbios_node_type" }, 80 { 47, STRING, "netbios_scope" }, 81 { 48, IPV4 | ARRAY, "font_servers" }, 82 { 49, IPV4 | ARRAY, "x_display_manager" }, 83 { 50, IPV4, "dhcp_requested_address" }, 84 { 51, UINT32 | REQUEST, "dhcp_lease_time" }, 85 { 52, UINT8, "dhcp_option_overload" }, 86 { 53, UINT8, "dhcp_message_type" }, 87 { 54, IPV4, "dhcp_server_identifier" }, 88 { 55, UINT8 | ARRAY, "dhcp_parameter_request_list" }, 89 { 56, STRING, "dhcp_message" }, 90 { 57, UINT16, "dhcp_max_message_size" }, 91 { 58, UINT32 | REQUEST, "dhcp_renewal_time" }, 92 { 59, UINT32 | REQUEST, "dhcp_rebinding_time" }, 93 { 64, STRING, "nisplus_domain" }, 94 { 65, IPV4 | ARRAY, "nisplus_servers" }, 95 { 66, STRING, "tftp_server_name" }, 96 { 67, STRING, "bootfile_name" }, 97 { 68, IPV4 | ARRAY, "mobile_ip_home_agent" }, 98 { 69, IPV4 | ARRAY, "smtp_server" }, 99 { 70, IPV4 | ARRAY, "pop_server" }, 100 { 71, IPV4 | ARRAY, "nntp_server" }, 101 { 72, IPV4 | ARRAY, "www_server" }, 102 { 73, IPV4 | ARRAY, "finger_server" }, 103 { 74, IPV4 | ARRAY, "irc_server" }, 104 { 75, IPV4 | ARRAY, "streettalk_server" }, 105 { 76, IPV4 | ARRAY, "streettalk_directory_assistance_server" }, 106 { 77, STRING, "user_class" }, 107 { 85, IPV4 | ARRAY, "nds_servers" }, 108 { 86, STRING, "nds_tree_name" }, 109 { 87, STRING, "nds_context" }, 110 { 88, STRING | RFC3397, "bcms_controller_names" }, 111 { 89, IPV4 | ARRAY, "bcms_controller_address" }, 112 { 91, UINT32, "client_last_transaction_time" }, 113 { 92, IPV4 | ARRAY, "associated_ip" }, 114 { 98, STRING, "uap_servers" }, 115 { 112, IPV4 | ARRAY, "netinfo_server_address" }, 116 { 113, STRING, "netinfo_server_tag" }, 117 { 114, STRING, "default_url" }, 118 { 118, IPV4, "subnet_selection" }, 119 { 119, STRING | RFC3397, "domain_search" }, 120 { 121, RFC3442 | REQUEST, "classless_static_routes" }, 121 { 249, RFC3442, "ms-classless_static_routes" }, 122 { 0, 0, NULL } 123 }; 124 125 struct dhcp_message * 126 get_lease_from_file(const char *leasefile) 127 { 128 int fd; 129 struct dhcp_message *dhcp; 130 ssize_t bytes; 131 132 fd = open(leasefile, O_RDONLY); 133 if (fd == -1) 134 return NULL; 135 dhcp = malloc(sizeof(*dhcp)); 136 memset(dhcp, 0, sizeof(*dhcp)); 137 bytes = read(fd, dhcp, sizeof(*dhcp)); 138 close(fd); 139 if (bytes < 0) { 140 free(dhcp); 141 dhcp = NULL; 142 } 143 return dhcp; 144 } 145 146 static uint8_t *dhcp_opt_buffer = NULL; 147 148 static int 149 valid_length(uint8_t option, int dl, int *type) 150 { 151 const struct dhcp_opt *opt; 152 ssize_t sz; 153 154 if (dl == 0) 155 return -1; 156 157 for (opt = dhcp_opts; opt->option; opt++) { 158 if (opt->option != option) 159 continue; 160 161 if (type) 162 *type = opt->type; 163 164 if (opt->type == 0 || opt->type & STRING || opt->type & RFC3442) 165 return 0; 166 167 sz = 0; 168 if (opt->type & UINT32 || opt->type & IPV4) 169 sz = sizeof(uint32_t); 170 if (opt->type & UINT16) 171 sz = sizeof(uint16_t); 172 if (opt->type & UINT8) 173 sz = sizeof(uint8_t); 174 if (opt->type & IPV4 || opt->type & ARRAY) 175 return dl % sz; 176 return (dl == sz ? 0 : -1); 177 } 178 179 /* unknown option, so let it pass */ 180 return 0; 181 } 182 183 static void 184 free_option_buffer(void) 185 { 186 free(dhcp_opt_buffer); 187 } 188 189 190 #define get_option_raw(dhcp, opt) get_option(dhcp, opt, NULL, NULL) 191 static const uint8_t * 192 get_option(const struct dhcp_message *dhcp, uint8_t opt, int *len, int *type) 193 { 194 const uint8_t *p = dhcp->options; 195 const uint8_t *e = p + sizeof(dhcp->options); 196 uint8_t l, ol = 0; 197 uint8_t o = 0; 198 uint8_t overl = 0; 199 uint8_t *bp = NULL; 200 const uint8_t *op = NULL; 201 int bl = 0; 202 203 while (p < e) { 204 o = *p++; 205 if (o == opt) { 206 if (op) { 207 if (!dhcp_opt_buffer) { 208 dhcp_opt_buffer = malloc(sizeof(struct dhcp_message)); 209 atexit(free_option_buffer); 210 } 211 if (!bp) 212 bp = dhcp_opt_buffer; 213 memcpy(bp, op, ol); 214 bp += ol; 215 } 216 ol = *p; 217 op = p + 1; 218 bl += ol; 219 } 220 switch (o) { 221 case DHO_PAD: 222 continue; 223 case DHO_END: 224 if (overl & 1) { 225 /* bit 1 set means parse boot file */ 226 overl &= ~1; 227 p = dhcp->bootfile; 228 e = p + sizeof(dhcp->bootfile); 229 } else if (overl & 2) { 230 /* bit 2 set means parse server name */ 231 overl &= ~2; 232 p = dhcp->servername; 233 e = p + sizeof(dhcp->servername); 234 } else 235 goto exit; 236 break; 237 case DHO_OPTIONSOVERLOADED: 238 /* Ensure we only get this option once */ 239 if (!overl) 240 overl = p[1]; 241 break; 242 } 243 l = *p++; 244 p += l; 245 } 246 247 exit: 248 if (valid_length(o, bl, type) == -1) { 249 errno = EINVAL; 250 return NULL; 251 } 252 if (len) 253 *len = bl; 254 if (bp) { 255 memcpy(bp, op, ol); 256 return (const uint8_t *)&dhcp_opt_buffer; 257 } 258 if (op) 259 return op; 260 errno = ENOENT; 261 return NULL; 262 } 263 264 int 265 get_option_addr32(uint32_t *a, const struct dhcp_message *dhcp, uint8_t option) 266 { 267 const uint8_t *p = get_option_raw(dhcp, option); 268 269 if (!p) 270 return -1; 271 memcpy(a, p, sizeof(*a)); 272 return 0; 273 } 274 275 int 276 get_option_uint32(uint32_t *i, const struct dhcp_message *dhcp, uint8_t option) 277 { 278 uint32_t a; 279 280 if (get_option_addr32(&a, dhcp, option) == -1) 281 return -1; 282 283 *i = ntohl(a); 284 return 0; 285 } 286 287 uint32_t 288 get_netmask(uint32_t addr) 289 { 290 uint32_t dst; 291 292 if (addr == 0) 293 return 0; 294 295 dst = htonl(addr); 296 if (IN_CLASSA(dst)) 297 return ntohl(IN_CLASSA_NET); 298 if (IN_CLASSB (dst)) 299 return ntohl(IN_CLASSB_NET); 300 if (IN_CLASSC (dst)) 301 return ntohl(IN_CLASSC_NET); 302 303 return 0; 304 } 305 306 void showlease(struct dhcp_lease *lease) 307 { 308 printf("addr: %s\n", inet_ntoa(lease->addr)); 309 printf("net: %s\n", inet_ntoa(lease->net)); 310 printf("leasetime: %d\n", lease->leasetime); 311 printf("renew: %d\n", lease->renewaltime); 312 printf("rebind: %d\n", lease->rebindtime); 313 printf("server: %s\n", inet_ntoa(lease->server)); 314 } 315 #define MAX_LEASETIME 2147460 316 317 int 318 main(int argc, char *argv[]) 319 { 320 struct dhcp_message *dhcp; 321 struct dhcp_lease *lease; 322 char leasefile[PATH_MAX]; 323 324 if (argc < 2) { 325 fprintf(stderr, "Usage: %s <interface>\n", argv[0]); 326 exit(1); 327 } 328 snprintf(leasefile, PATH_MAX, LEASEFILE, argv[1]); 329 if ((dhcp = get_lease_from_file(leasefile)) == NULL) { 330 fprintf(stderr, "Couldn't read lease file: %s\n", strerror(errno)); 331 exit(1); 332 } 333 lease = malloc(sizeof(*lease)); 334 lease->frominfo = 0; 335 lease->addr.s_addr = dhcp->yiaddr; 336 337 if (get_option_addr32(&lease->net.s_addr, dhcp, DHO_SUBNETMASK) == -1) 338 lease->net.s_addr = get_netmask(dhcp->yiaddr); 339 if (get_option_uint32(&lease->leasetime, dhcp, DHO_LEASETIME) != 0) 340 lease->leasetime = DEFAULT_LEASETIME; 341 get_option_addr32(&lease->server.s_addr, dhcp, DHO_SERVERID); 342 /* Dm: limit lease time value to avoid negative numbers when 343 converting to milliseconds */ 344 if ((lease->leasetime != ~0U) && (lease->leasetime > MAX_LEASETIME)) 345 lease->leasetime = MAX_LEASETIME; 346 if (get_option_uint32(&lease->renewaltime, dhcp, DHO_RENEWALTIME) != 0) 347 lease->renewaltime = 0; 348 if (get_option_uint32(&lease->rebindtime, dhcp, DHO_REBINDTIME) != 0) 349 lease->rebindtime = 0; 350 showlease(lease); 351 free(lease); 352 return 0; 353 } 354
