response.c

   1 #include "dns.h"
   2 #include "byte.h"
   3 #include "uint16.h"
   4 #include "response.h"
   5
   6 char response[65535];
   7 unsigned int response_len = 0; /* <= 65535 */
   8 static unsigned int tctarget;
   9
  10 #define NAMES 100
  11 static char name[NAMES][128];
  12 static unsigned int name_ptr[NAMES]; /* each < 16384 */
  13 static unsigned int name_num;
  14
  15 int response_addbytes(const char *buf,unsigned int len)
  16 {
  17   if (len > 65535 - response_len) return 0;
  18   byte_copy(response + response_len,len,buf);
  19   response_len += len;
  20   return 1;
  21 }
  22
  23 int response_addname(const char *d)
  24 {
  25   unsigned int dlen;
  26   unsigned int i;
  27   char buf[2];
  28
  29   dlen = dns_domain_length(d);
  30
  31   while (*d) {
  32     for (i = 0;i < name_num;++i)
  33       if (dns_domain_equal(d,name[i])) {
  34         uint16_pack_big(buf,49152 + name_ptr[i]);
  35         return response_addbytes(buf,2);
  36       }
  37     if (dlen <= 128)
  38       if (name_num < NAMES) {
  39         byte_copy(name[name_num],dlen,d);
  40         name_ptr[name_num] = response_len;
  41         ++name_num;
  42       }
  43     i = (unsigned char) *d;
  44     ++i;
  45     if (!response_addbytes(d,i)) return 0;
  46     d += i;
  47     dlen -= i;
  48   }
  49   return response_addbytes(d,1);
  50 }
  51
  52 int response_query(const char *q,const char qtype[2],const char qclass[2])
  53 {
  54   response_len = 0;
  55   name_num = 0;
  56   if (!response_addbytes("\0\0\201\200\0\1\0\0\0\0\0\0",12)) return 0;
  57   if (!response_addname(q)) return 0;
  58   if (!response_addbytes(qtype,2)) return 0;
  59   if (!response_addbytes(qclass,2)) return 0;
  60   tctarget = response_len;
  61   return 1;
  62 }
  63
  64 static unsigned int dpos;
  65
  66 static int flaghidettl = 0;
  67
  68 void response_hidettl(void)
  69 {
  70   flaghidettl = 1;
  71 }
  72
  73 int response_rstart(const char *d,const char type[2],uint32 ttl)
  74 {
  75   char ttlstr[4];
  76   if (!response_addname(d)) return 0;
  77   if (!response_addbytes(type,2)) return 0;
  78   if (!response_addbytes(DNS_C_IN,2)) return 0;
  79   if (flaghidettl) ttl = 0;
  80   uint32_pack_big(ttlstr,ttl);
  81   if (!response_addbytes(ttlstr,4)) return 0;
  82   if (!response_addbytes("\0\0",2)) return 0;
  83   dpos = response_len;
  84   return 1;
  85 }
  86
  87 void response_rfinish(int x)
  88 {
  89   uint16_pack_big(response + dpos - 2,response_len - dpos);
  90   if (!++response[x + 1]) ++response[x];
  91 }
  92
  93 int response_cname(const char *c,const char *d,uint32 ttl)
  94 {
  95   if (!response_rstart(c,DNS_T_CNAME,ttl)) return 0;
  96   if (!response_addname(d)) return 0;
  97   response_rfinish(RESPONSE_ANSWER);
  98   return 1;
  99 }
 100
 101 void response_nxdomain(void)
 102 {
 103   response[3] |= 3;
 104   response[2] |= 4;
 105 }
 106
 107 void response_servfail(void)
 108 {
 109   response[3] |= 2;
 110 }
 111
 112 void response_id(const char id[2])
 113 {
 114   byte_copy(response,2,id);
 115 }
 116
 117 void response_tc(void)
 118 {
 119   response[2] |= 2;
 120   response_len = tctarget;
 121 }