response.c

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#include "dns.h"
#include "byte.h"
#include "uint_t.h"
#include "response.h"
 
char response[65535];
unsigned int response_len = 0; /* <= 65535 */
unsigned int max_response_len;
unsigned int do_dnssec = 0;
static unsigned int tctarget;
 
#define NAMES 100
static char name[NAMES][128];
static unsigned int name_ptr[NAMES]; /* each < 16384 */
static unsigned int name_num;
 
int response_addbytes(const char *buf,unsigned int len)
{
  if (len > 65535 - response_len) return 0;
  byte_copy(response + response_len,len,buf);
  response_len += len;
  return 1;
}
 
int response_addname(const char *d)
{
  unsigned int dlen;
  unsigned int i;
  char buf[2];
 
  dlen = dns_domain_length(d);
 
  while (*d) {
    for (i = 0; i < name_num; ++i)
      if (dns_domain_equal(d,name[i])) {
        uint16_pack_big(buf,49152 + name_ptr[i]);
        return response_addbytes(buf,2);
      }
    if ((dlen <= 128) && (response_len < 16384))
      if (name_num < NAMES) {
        byte_copy(name[name_num],dlen,d);
        name_ptr[name_num] = response_len;
        ++name_num;
      }
    i = (unsigned char) *d;
    ++i;
    if (!response_addbytes(d,i)) return 0;
    d += i;
    dlen -= i;
  }
  return response_addbytes(d,1);
}
 
int response_query(const char *q,const char qtype[2],const char qclass[2])
{
  response_len = 0;
  name_num = 0;
  if (!response_addbytes("\0\0\201\200\0\1\0\0\0\0\0\0",12)) return 0;
  if (!response_addname(q)) return 0;
  if (!response_addbytes(qtype,2)) return 0;
  if (!response_addbytes(qclass,2)) return 0;
  tctarget = response_len;
  return 1;
}
 
static unsigned int dpos;
 
static int flaghidettl = 0;
 
void response_hidettl(void)
{
  flaghidettl = 1;
}
 
int response_rstart(const char *d,const char type[2],uint32 ttl)
{
  char ttlstr[4];
  if (!response_addname(d)) return 0;
  if (!response_addbytes(type,2)) return 0;
  if (!response_addbytes(DNS_C_IN,2)) return 0;
  if (flaghidettl) ttl = 0;
  uint32_pack_big(ttlstr,ttl);
  if (!response_addbytes(ttlstr,4)) return 0;
  if (!response_addbytes("\0\0",2)) return 0;
  dpos = response_len;
  return 1;
}
 
void response_rfinish(int x)
{
  uint16_pack_big(response + dpos - 2,response_len - dpos);
  if (!++response[x + 1]) ++response[x];
}
 
int response_cname(const char *c,const char *d,uint32 ttl)
{
  if (!response_rstart(c,DNS_T_CNAME,ttl)) return 0;
  if (!response_addname(d)) return 0;
  response_rfinish(RESPONSE_ANSWER);
  return 1;
}
 
void response_nxdomain(void)
{
  response[3] |= 3;
  response[2] |= 4;
}
 
void response_servfail(void)
{
  response[3] |= 2;
}
 
void response_id(const char id[2])
{
  byte_copy(response,2,id);
}
 
void response_tc(void)
{
  response[2] |= 2;
  response_len = tctarget;
}