src/dns.cpp

   1 /*
   2 dns.cpp - based on the dns library Copyright (C) 2002 Ian Gulliver
   3
   4 This program is free software; you can redistribute it and/or modify
   5 it under the terms of version 2 of the GNU General Public License as
   6 published by the Free Software Foundation.
   7
   8 This program is distributed in the hope that it will be useful,
   9 but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 GNU General Public License for more details.
  12
  13 You should have received a copy of the GNU General Public License
  14 along with this program; if not, write to the Free Software
  15 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  16 */
  17
  18 #define _DNS_C
  19
  20 #include <string>
  21 #include <stdlib.h>
  22 #include <time.h>
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <sys/time.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <stdio.h>
  29 #include <errno.h>
  30 #include <fcntl.h>
  31 #include <poll.h>
  32 #include "dns.h"
  33
  34 static const char tagstring[] = "$Id$";
  35
  36 #define max(a,b) (a > b ? a : b)
  37 #define DNS_MAX              8                    /* max number of nameservers used */
  38 #define DNS_CONFIG_FBCK     "/etc/resolv.conf"    /* fallback config file */
  39 #define DNS_PORT            53                    /* DNS well known port */
  40 #define DNS_QRY_A            1                    /* name to IP address */
  41 #define DNS_QRY_AAAA        28                    /* name to IP6 address */
  42 #define DNS_QRY_PTR         12                    /* IP address to name */
  43 #define DNS_QRY_MX          15                    /* name to MX */
  44 #define DNS_QRY_TXT         16                    /* name to TXT */
  45 #define DNS_QRY_CNAME       5
  46
  47 #define DNS_ALIGN (sizeof(void *) > sizeof(long) ? sizeof(void *) : sizeof(long))
  48 #define DNS_TRIES 3
  49 #define RESULTSIZE 1024
  50 #define min(a,b) (a < b ? a : b)
  51
  52 static struct in_addr servers4[DNS_MAX]; /* up to DNS_MAX nameservers; populated by dns_init() */
  53 static int i4; /* actual count of nameservers; set by dns_init() */
  54
  55 static int initdone = 0; /* to ensure dns_init() only runs once (on the first call) */
  56 static int wantclose = 0;
  57 static int lastcreate = -1;
  58
  59 struct s_connection { /* open DNS query */
  60         struct s_connection *next; /* next in list */
  61         unsigned char id[2];
  62         unsigned int _class;
  63         unsigned int type;
  64         int want_list;
  65         int fd; /* file descriptor returned from sockets */
  66 };
  67
  68 struct s_rr_middle {
  69         unsigned int type;
  70         unsigned int _class;
  71         unsigned long ttl;
  72         unsigned int rdlength;
  73 };
  74
  75 #define DNS_POINTER_VALUE 0xc000
  76
  77 static s_connection *connection_head = NULL; /* linked list of open DNS queries; populated by dns_add_query(), decimated by dns_getresult_s() */
  78
  79 struct s_header { /* DNS query header */
  80         unsigned char id[2];
  81         unsigned int flags1;
  82 #define FLAGS1_MASK_QR 0x80
  83 #define FLAGS1_MASK_OPCODE 0x78 /* bitshift right 3 */
  84 #define FLAGS1_MASK_AA 0x04
  85 #define FLAGS1_MASK_TC 0x02
  86 #define FLAGS1_MASK_RD 0x01
  87         unsigned int flags2;
  88 #define FLAGS2_MASK_RA 0x80
  89 #define FLAGS2_MASK_Z  0x70
  90 #define FLAGS2_MASK_RCODE 0x0f
  91         unsigned int qdcount;
  92         unsigned int ancount;
  93         unsigned int nscount;
  94         unsigned int arcount;
  95         unsigned char payload[512]; /* DNS question, populated by dns_build_query_payload() */
  96 };
  97
  98 extern time_t TIME;
  99
 100 void *dns_align(void *inp) {
 101         char *p = (char*)inp;
 102         int offby = ((char *)p - (char *)0) % DNS_ALIGN;
 103         if (offby != 0)
 104                 return p + (DNS_ALIGN - offby);
 105         else
 106                 return p;
 107 }
 108
 109 /*
 110  * These little hacks are here to avoid alignment and type sizing issues completely by doing manual copies
 111  */
 112 void dns_fill_rr(s_rr_middle* rr, const unsigned char *input) {
 113         rr->type = input[0] * 256 + input[1];
 114         rr->_class = input[2] * 256 + input[3];
 115         rr->ttl = input[4] * 16777216 + input[5] * 65536 + input[6] * 256 + input[7];
 116         rr->rdlength = input[8] * 256 + input[9];
 117 }
 118
 119 void dns_fill_header(s_header *header, const unsigned char *input, const int l) {
 120         header->id[0] = input[0];
 121         header->id[1] = input[1];
 122         header->flags1 = input[2];
 123         header->flags2 = input[3];
 124         header->qdcount = input[4] * 256 + input[5];
 125         header->ancount = input[6] * 256 + input[7];
 126         header->nscount = input[8] * 256 + input[9];
 127         header->arcount = input[10] * 256 + input[11];
 128         memcpy(header->payload,&input[12],l);
 129 }
 130
 131 void dns_empty_header(unsigned char *output, const s_header *header, const int l) {
 132         output[0] = header->id[0];
 133         output[1] = header->id[1];
 134         output[2] = header->flags1;
 135         output[3] = header->flags2;
 136         output[4] = header->qdcount / 256;
 137         output[5] = header->qdcount % 256;
 138         output[6] = header->ancount / 256;
 139         output[7] = header->ancount % 256;
 140         output[8] = header->nscount / 256;
 141         output[9] = header->nscount % 256;
 142         output[10] = header->arcount / 256;
 143         output[11] = header->arcount % 256;
 144         memcpy(&output[12],header->payload,l);
 145 }
 146
 147 void dns_close(int fd) { /* close query */
 148         if (fd == lastcreate) {
 149                 wantclose = 1;
 150                 return;
 151         }
 152         close(fd);
 153         return;
 154 }
 155
 156 void DNS::dns_init() { /* on first call only: populates servers4 struct with up to DNS_MAX nameserver IP addresses from /etc/resolv.conf */
 157         FILE *f;
 158         int i;
 159         in_addr addr4;
 160         char buf[1024];
 161         if (initdone == 1)
 162                 return;
 163         i4 = 0;
 164
 165         initdone = 1;
 166         srand((unsigned int) TIME);
 167         memset(servers4,'\0',sizeof(in_addr) * DNS_MAX);
 168         f = fopen(DNS_CONFIG_FBCK,"r");
 169         if (f == NULL)
 170                 return;
 171         while (fgets(buf,1024,f) != NULL) {
 172                 if (strncmp(buf,"nameserver",10) == 0) {
 173                         i = 10;
 174                         while (buf[i] == ' ' || buf[i] == '\t')
 175                                 i++;
 176                         if (i4 < DNS_MAX) {
 177                                 if (dns_aton4_s(&buf[i],&addr4) != NULL)
 178                                         memcpy(&servers4[i4++],&addr4,sizeof(in_addr));
 179                         }
 180                 }
 181         }
 182         fclose(f);
 183 }
 184
 185 void DNS::dns_init_2(const char* dnsserver) { /* populates servers4 struct with address from the given parameter */
 186         FILE *f;
 187         int i;
 188         in_addr addr4;
 189         char buf[1024];
 190         i4 = 0;
 191         srand((unsigned int) TIME);
 192         memset(servers4,'\0',sizeof(in_addr) * DNS_MAX);
 193         if (dns_aton4_s(dnsserver,&addr4) != NULL)
 194             memcpy(&servers4[i4++],&addr4,sizeof(in_addr));
 195 }
 196
 197
 198 static int dns_send_requests(const s_header *h, const s_connection *s, const int l) { /* send DNS query */
 199         int i;
 200         sockaddr_in addr4;
 201         unsigned char payload[sizeof(s_header)];
 202
 203         dns_empty_header(payload,h,l);
 204
 205
 206         for (i = 0; i < i4; i++) {
 207                 /* otherwise send via standard ipv4 boringness */
 208                 memset(&addr4,0,sizeof(addr4));
 209                 memcpy(&addr4.sin_addr,&servers4[i],sizeof(addr4.sin_addr));
 210                 addr4.sin_family = AF_INET;
 211                 addr4.sin_port = htons(DNS_PORT);
 212                 if (sendto(s->fd, payload, l + 12, 0, (sockaddr *) &addr4, sizeof(addr4)) == -1)
 213                 {
 214                         return -1;
 215                 }
 216         }
 217
 218         return 0;
 219 }
 220
 221 static s_connection *dns_add_query(s_header *h) { /* build DNS query, add to list */
 222         s_connection * s;
 223
 224         s = new s_connection;
 225
 226         /* set header flags */
 227         h->id[0] = s->id[0] = rand() % 255; /* verified by dns_getresult_s() */
 228         h->id[1] = s->id[1] = rand() % 255;
 229         h->flags1 = 0 | FLAGS1_MASK_RD;
 230         h->flags2 = 0;
 231         h->qdcount = 1;
 232         h->ancount = 0;
 233         h->nscount = 0;
 234         h->arcount = 0;
 235
 236         /* turn off want_list by default */
 237         s->want_list = 0;
 238
 239         /* try to create ipv6 or ipv4 socket */
 240                 s->fd = socket(PF_INET, SOCK_DGRAM, 0);
 241                 if (s->fd != -1) {
 242                         if (fcntl(s->fd, F_SETFL, O_NONBLOCK) != 0) {
 243                                 close(s->fd);
 244                                 s->fd = -1;
 245                         }
 246                 }
 247                 if (s->fd != -1) {
 248                         sockaddr_in addr;
 249                         memset(&addr,0,sizeof(addr));
 250                         addr.sin_family = AF_INET;
 251                         addr.sin_port = 0;
 252                         addr.sin_addr.s_addr = INADDR_ANY;
 253                         if (bind(s->fd,(sockaddr *)&addr,sizeof(addr)) != 0) {
 254                                 close(s->fd);
 255                                 s->fd = -1;
 256                         }
 257                 }
 258                 if (s->fd == -1) {
 259                         delete s;
 260                         return NULL;
 261                 }
 262         /* create new connection object, add to linked list */
 263         s->next = connection_head;
 264         connection_head = s;
 265
 266         if (wantclose == 1) {
 267                 close(lastcreate);
 268                 wantclose = 0;
 269         }
 270         lastcreate = s->fd;
 271         return s;
 272 }
 273
 274 static int dns_build_query_payload(const char * const name, const unsigned short rr, const unsigned short _class, unsigned char * const payload) {
 275         short payloadpos;
 276         const char * tempchr, * tempchr2;
 277         unsigned short l;
 278
 279         payloadpos = 0;
 280         tempchr2 = name;
 281
 282         /* split name up into labels, create query */
 283         while ((tempchr = strchr(tempchr2,'.')) != NULL) {
 284                 l = tempchr - tempchr2;
 285                 if (payloadpos + l + 1 > 507)
 286                         return -1;
 287                 payload[payloadpos++] = l;
 288                 memcpy(&payload[payloadpos],tempchr2,l);
 289                 payloadpos += l;
 290                 tempchr2 = &tempchr[1];
 291         }
 292         l = strlen(tempchr2);
 293         if (l) {
 294                 if (payloadpos + l + 2 > 507)
 295                         return -1;
 296                 payload[payloadpos++] = l;
 297                 memcpy(&payload[payloadpos],tempchr2,l);
 298                 payloadpos += l;
 299                 payload[payloadpos++] = '\0';
 300         }
 301         if (payloadpos > 508)
 302                 return -1;
 303         l = htons(rr);
 304         memcpy(&payload[payloadpos],&l,2);
 305         l = htons(_class);
 306         memcpy(&payload[payloadpos + 2],&l,2);
 307         return payloadpos + 4;
 308 }
 309
 310 in_addr* DNS::dns_aton4(const char * const ipstring) { /* ascii to numeric: convert string to static 4part IP addr struct */
 311         in_addr ip;
 312         return dns_aton4_s(ipstring,&ip);
 313 }
 314
 315 in_addr* DNS::dns_aton4_r(const char *ipstring) { /* ascii to numeric (reentrant): convert string to new 4part IP addr struct */
 316         in_addr* ip;
 317         ip = new in_addr;
 318         if(dns_aton4_s(ipstring,ip) == NULL) {
 319                 delete ip;
 320                 return NULL;
 321         }
 322         return ip;
 323 }
 324
 325 in_addr* DNS::dns_aton4_s(const char *ipstring, in_addr *ip) { /* ascii to numeric (buffered): convert string to given 4part IP addr struct */
 326         unsigned char *myip;
 327         int i,part = 0;
 328         myip = (unsigned char *)ip;
 329
 330         memset(myip,'\0',4);
 331         for (i = 0; i < 16; i++) {
 332                 switch (ipstring[i]) {
 333                         case '\0':
 334                                 if (part != 3)
 335                                         return NULL;
 336                                 return ip;
 337                                 break;
 338                         case '0':
 339                         case '1':
 340                         case '2':
 341                         case '3':
 342                         case '4':
 343                         case '5':
 344                         case '6':
 345                         case '7':
 346                         case '8':
 347                         case '9':
 348                                 if (myip[part] > 25)
 349                                         return NULL;
 350                                 myip[part] *= 10;
 351                                 if (myip[part] == 250 && ipstring[i] - '0' > 6)
 352                                         return NULL;
 353                                 myip[part] += ipstring[i] - '0';
 354                                 break;
 355                         case '.':
 356                                 if (part == 3)
 357                                         return ip;
 358                                 else
 359                                         part++;
 360                                 break;
 361                         default:
 362                                 if (part == 3)
 363                                         return ip;
 364                                 else
 365                                         return NULL;
 366                                 break;
 367                 }
 368         }
 369         if (part == 3)
 370                 return ip;
 371         else
 372                 return NULL;
 373 }
 374
 375 int DNS::dns_getip4(const char *name) { /* build, add and send A query; retrieve result with dns_getresult() */
 376         s_header h;
 377         s_connection *s;
 378         int l;
 379
 380         dns_init();
 381
 382
 383         l = dns_build_query_payload(name,DNS_QRY_A,1,(unsigned char *)&h.payload);
 384         if (l == -1)
 385                 return -1;
 386         s = dns_add_query(&h);
 387         if (s == NULL)
 388                 return -1;
 389         s->_class = 1;
 390         s->type = DNS_QRY_A;
 391         if (dns_send_requests(&h,s,l) == -1)
 392                 return -1;
 393
 394         return s->fd;
 395 }
 396
 397 int DNS::dns_getip4list(const char *name) { /* build, add and send A query; retrieve result with dns_getresult() */
 398         s_header h;
 399         s_connection *s;
 400         int l;
 401
 402         dns_init();
 403
 404
 405         l = dns_build_query_payload(name,DNS_QRY_A,1,(unsigned char *)&h.payload);
 406         if (l == -1)
 407                 return -1;
 408         s = dns_add_query(&h);
 409         if (s == NULL)
 410                 return -1;
 411         s->_class = 1;
 412         s->type = DNS_QRY_A;
 413         s->want_list = 1;
 414         if (dns_send_requests(&h,s,l) == -1)
 415                 return -1;
 416
 417         return s->fd;
 418 }
 419
 420 int DNS::dns_getname4(const in_addr *ip) { /* build, add and send PTR query; retrieve result with dns_getresult() */
 421         char query[512];
 422         s_header h;
 423         s_connection * s;
 424         unsigned char *c;
 425         int l;
 426
 427         dns_init();
 428
 429         c = (unsigned char *)&ip->s_addr;
 430
 431         sprintf(query,"%d.%d.%d.%d.in-addr.arpa",c[3],c[2],c[1],c[0]);
 432
 433         l = dns_build_query_payload(query,DNS_QRY_PTR,1,(unsigned char *)&h.payload);
 434         if (l == -1)
 435                 return -1;
 436         s = dns_add_query(&h);
 437         if (s == NULL)
 438                 return -1;
 439         s->_class = 1;
 440         s->type = DNS_QRY_PTR;
 441         if (dns_send_requests(&h,s,l) == -1)
 442                 return -1;
 443
 444         return s->fd;
 445 }
 446
 447 char* DNS::dns_ntoa4(const in_addr * const ip) { /* numeric to ascii: convert 4part IP addr struct to static string */
 448         static char result[256];
 449         return dns_ntoa4_s(ip,result);
 450 }
 451
 452 char* DNS::dns_ntoa4_r(const in_addr *ip) { /* numeric to ascii (reentrant): convert 4part IP addr struct to new string */
 453         char *result;
 454         result = new char[256];
 455         return dns_ntoa4_s(ip,result);
 456 }
 457
 458 char* DNS::dns_ntoa4_s(const in_addr *ip, char *result) { /* numeric to ascii (buffered): convert 4part IP addr struct to given string */
 459         unsigned char *m;
 460         m = (unsigned char *)&ip->s_addr;
 461         sprintf(result,"%d.%d.%d.%d",m[0],m[1],m[2],m[3]);
 462         return result;
 463 }
 464
 465 char* DNS::dns_getresult(const int fd) { /* retrieve result of DNS query */
 466         static char result[RESULTSIZE];
 467         return dns_getresult_s(fd,result);
 468 }
 469
 470 char* DNS::dns_getresult_r(const int fd) { /* retrieve result of DNS query (reentrant) */
 471         char *result;
 472         result = new char[RESULTSIZE];
 473         if(dns_getresult_s(fd,result) == NULL) {
 474                 delete result;
 475                 return NULL;
 476         }
 477         return result;
 478 }
 479
 480 char* DNS::dns_getresult_s(const int fd, char *result) { /* retrieve result of DNS query (buffered) */
 481         s_header h;
 482         s_connection *c, *prev;
 483         int l,i,q,curanswer,o;
 484         s_rr_middle rr;
 485         unsigned char buffer[sizeof(s_header)];
 486         unsigned short p;
 487
 488         if (result)
 489         {
 490                 result[0] = 0;
 491         }
 492
 493         prev = NULL;
 494         c = connection_head;
 495         while (c != NULL) { /* find query in list of open queries */
 496                 if (c->fd == fd)
 497                         break;
 498                 prev = c;
 499                 c = c->next;
 500         }
 501         if (c == NULL) {
 502                 return NULL; /* query not found */
 503         }
 504         /* query found-- pull from list: */
 505         if (prev != NULL)
 506                 prev->next = c->next;
 507         else
 508                 connection_head = c->next;
 509
 510         l = recv(c->fd,buffer,sizeof(s_header),0);
 511         dns_close(c->fd);
 512         if (l < 12) {
 513                 delete c;
 514                 return NULL;
 515         }
 516         dns_fill_header(&h,buffer,l - 12);
 517         if (c->id[0] != h.id[0] || c->id[1] != h.id[1]) {
 518                 delete c;
 519                 return NULL; /* ID mismatch */
 520         }
 521         if ((h.flags1 & FLAGS1_MASK_QR) == 0) {
 522                 delete c;
 523                 return NULL;
 524         }
 525         if ((h.flags1 & FLAGS1_MASK_OPCODE) != 0) {
 526                 delete c;
 527                 return NULL;
 528         }
 529         if ((h.flags2 & FLAGS2_MASK_RCODE) != 0) {
 530                 delete c;
 531                 return NULL;
 532         }
 533         if (h.ancount < 1)  { /* no sense going on if we don't have any answers */
 534                 delete c;
 535                 return NULL;
 536         }
 537         /* skip queries */
 538         i = 0;
 539         q = 0;
 540         l -= 12;
 541         while (q < h.qdcount && i < l) {
 542                 if (h.payload[i] > 63) { /* pointer */
 543                         i += 6; /* skip pointer, _class and type */
 544                         q++;
 545                 } else { /* label */
 546                         if (h.payload[i] == 0) {
 547                                 q++;
 548                                 i += 5; /* skip nil, _class and type */
 549                         } else
 550                                 i += h.payload[i] + 1; /* skip length and label */
 551                 }
 552         }
 553         /* &h.payload[i] should now be the start of the first response */
 554         curanswer = 0;
 555         while (curanswer < h.ancount) {
 556                 q = 0;
 557                 while (q == 0 && i < l) {
 558                         if (h.payload[i] > 63) { /* pointer */
 559                                 i += 2; /* skip pointer */
 560                                 q = 1;
 561                         } else { /* label */
 562                                 if (h.payload[i] == 0) {
 563                                         i++;
 564                                         q = 1;
 565                                 } else
 566                                         i += h.payload[i] + 1; /* skip length and label */
 567                         }
 568                 }
 569                 if (l - i < 10) {
 570                         delete c;
 571                         return NULL;
 572                 }
 573                 dns_fill_rr(&rr,&h.payload[i]);
 574                 i += 10;
 575                 if (rr.type != c->type) {
 576                         curanswer++;
 577                         i += rr.rdlength;
 578                         continue;
 579                 }
 580                 if (rr._class != c->_class) {
 581                         curanswer++;
 582                         i += rr.rdlength;
 583                         continue;
 584                 }
 585                 break;
 586         }
 587         if (curanswer == h.ancount)
 588                 return NULL;
 589         if (i + rr.rdlength > l)
 590                 return NULL;
 591         if (rr.rdlength > 1023)
 592                 return NULL;
 593
 594         switch (rr.type) {
 595                 case DNS_QRY_PTR:
 596                         o = 0;
 597                         q = 0;
 598                         while (q == 0 && i < l && o + 256 < 1023) {
 599                                 if (h.payload[i] > 63) { /* pointer */
 600                                         memcpy(&p,&h.payload[i],2);
 601                                         i = ntohs(p) - DNS_POINTER_VALUE - 12;
 602                                 } else { /* label */
 603                                         if (h.payload[i] == 0)
 604                                                 q = 1;
 605                                         else {
 606                                                 result[o] = '\0';
 607                                                 if (o != 0)
 608                                                         result[o++] = '.';
 609                                                 memcpy(&result[o],&h.payload[i + 1],h.payload[i]);
 610                                                 o += h.payload[i];
 611                                                 i += h.payload[i] + 1;
 612                                         }
 613                                 }
 614                         }
 615                         result[o] = '\0';
 616                         break;
 617                 case DNS_QRY_A:
 618                         if (c->want_list) {
 619                                 dns_ip4list *alist = (dns_ip4list *) result; /* we have to trust that this is aligned */
 620                                 while ((char *)alist - (char *)result < 700) {
 621                                         if (rr.type != DNS_QRY_A)
 622                                                 break;
 623                                         if (rr._class != 1)
 624                                                 break;
 625                                         if (rr.rdlength != 4) {
 626                                                 delete c;
 627                                                 return NULL;
 628                                         }
 629                                         memcpy(&alist->ip,&h.payload[i],4);
 630                                         if (++curanswer >= h.ancount)
 631                                                 break;
 632                                         i += rr.rdlength;
 633                                         {
 634                                                 /* skip next name */
 635                                                 q = 0;
 636                                                 while (q == 0 && i < l) {
 637                                                         if (h.payload[i] > 63) { /* pointer */
 638                                                                 i += 2; /* skip pointer */
 639                                                                 q = 1;
 640                                                         } else { /* label */
 641                                                                 if (h.payload[i] == 0) {
 642                                                                         i++;
 643                                                                         q = 1;
 644                                                                 } else
 645                                                                         i += h.payload[i] + 1; /* skip length and label */
 646                                                         }
 647                                                 }
 648                                         }
 649                                         if (l - i < 10) {
 650                                                 delete c;
 651                                                 return NULL;
 652                                         }
 653                                         dns_fill_rr(&rr,&h.payload[i]);
 654                                         i += 10;
 655                                         alist->next = (dns_ip4list *) dns_align(((char *) alist) + sizeof(dns_ip4list));
 656                                         alist = alist->next;
 657                                         alist->next = NULL;
 658                                 }
 659                                 alist->next = NULL;
 660                                 break;
 661                         }
 662                         goto defaultcase;
 663                         break;
 664                 default:
 665                 defaultcase:
 666                         memcpy(result,&h.payload[i],rr.rdlength);
 667                         result[rr.rdlength] = '\0';
 668                         break;
 669         }
 670         delete c;
 671         return result;
 672 }
 673
 674 DNS::DNS()
 675 {
 676         dns_init();
 677 }
 678
 679 DNS::DNS(std::string dnsserver)
 680 {
 681         dns_init_2(dnsserver.c_str());
 682 }
 683
 684 void DNS::SetNS(std::string dnsserver)
 685 {
 686         dns_init_2(dnsserver.c_str());
 687 }
 688
 689 DNS::~DNS()
 690 {
 691 }
 692
 693 bool DNS::ReverseLookup(std::string ip)
 694 {
 695         binip = dns_aton4(ip.c_str());
 696         if (binip == NULL) {
 697                 return false;
 698         }
 699         this->fd = dns_getname4(binip);
 700         if (this->fd == -1)
 701                 return false;
 702         return true;
 703 }
 704
 705 bool DNS::ForwardLookup(std::string host)
 706 {
 707 }
 708
 709 bool DNS::HasResult()
 710 {
 711         pollfd polls;
 712         polls.fd = this->fd;
 713         polls.events = POLLIN;
 714         int ret = poll(&polls,1,1);
 715         return (ret > 0);
 716 }
 717
 718 int DNS::GetFD()
 719 {
 720         return this->fd;
 721 }
 722
 723 std::string DNS::GetResult()
 724 {
 725         result = dns_getresult(this->fd);
 726         if (result) {
 727                 dns_close(this->fd);
 728                 return result;
 729         } else {
 730                 return "";
 731         }
 732 }