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