pickdns.c

   1 #include <unistd.h>
   2 #include "byte.h"
   3 #include "case.h"
   4 #include "dns.h"
   5 #include "open.h"
   6 #include "cdb.h"
   7 #include "response.h"
   8
   9 const char *fatal = "pickdns: fatal: ";
  10 const char *starting = "starting pickdns\n";
  11
  12 static char seed[128];
  13
  14 void initialize(void)
  15 {
  16   dns_random_init(seed);
  17 }
  18
  19 static struct cdb c;
  20 static char key[258];
  21 static char data[512];
  22
  23 static int doit(char *q,char qtype[2],char ip[4])
  24 {
  25   int r;
  26   uint32 dlen;
  27   unsigned int qlen;
  28   int flaga;
  29   int flagmx;
  30
  31   qlen = dns_domain_length(q);
  32   if (qlen > 255) return 0; /* impossible */
  33
  34   flaga = byte_equal(qtype,2,DNS_T_A);
  35   flagmx = byte_equal(qtype,2,DNS_T_MX);
  36   if (byte_equal(qtype,2,DNS_T_ANY)) flaga = flagmx = 1;
  37   if (!flaga && !flagmx) goto REFUSE;
  38
  39   key[0] = '%';
  40   byte_copy(key + 1,4,ip);
  41
  42   r = cdb_find(&c,key,5);
  43   if (!r) r = cdb_find(&c,key,4);
  44   if (!r) r = cdb_find(&c,key,3);
  45   if (!r) r = cdb_find(&c,key,2);
  46   if (r == -1) return 0;
  47
  48   key[0] = '+';
  49   byte_zero(key + 1,2);
  50   if (r && (cdb_datalen(&c) == 2))
  51     if (cdb_read(&c,key + 1,2,cdb_datapos(&c)) == -1) return 0;
  52
  53   byte_copy(key + 3,qlen,q);
  54   case_lowerb(key + 3,qlen + 3);
  55
  56   r = cdb_find(&c,key,qlen + 3);
  57   if (!r) {
  58     byte_zero(key + 1,2);
  59     r = cdb_find(&c,key,qlen + 3);
  60   }
  61   if (!r) goto REFUSE;
  62   if (r == -1) return 0;
  63   dlen = cdb_datalen(&c);
  64
  65   if (dlen > 512) dlen = 512;
  66   if (cdb_read(&c,data,dlen,cdb_datapos(&c)) == -1) return 0;
  67
  68   if (flaga) {
  69     dns_sortip(data,dlen);
  70     if (dlen > 12) dlen = 12;
  71     while (dlen >= 4) {
  72       dlen -= 4;
  73       if (!response_rstart(q,DNS_T_A,5)) return 0;
  74       if (!response_addbytes(data + dlen,4)) return 0;
  75       response_rfinish(RESPONSE_ANSWER);
  76     }
  77   }
  78
  79   return 1;
  80
  81
  82   REFUSE:
  83   response[2] &= ~4;
  84   response[3] &= ~15;
  85   response[3] |= 5;
  86   return 1;
  87 }
  88
  89 int respond(char *q,char qtype[2],char ip[4])
  90 {
  91   int fd;
  92   int result;
  93
  94   fd = open_read("data.cdb");
  95   if (fd == -1) return 0;
  96   cdb_init(&c,fd);
  97   result = doit(q,qtype,ip);
  98   cdb_free(&c);
  99   close(fd);
 100   return result;
 101 }