ares_send.c

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/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */
 
 
#include <sys/types.h>
 
#ifndef WIN32
#include <netinet/in.h>
#ifndef __CYGWIN__
#  include "ares_nameser.h"
#endif
#endif
 
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "ares.h"
#include "ares_dns.h"
#include "ares_private.h"
 
void ares_send(ares_channel channel, const unsigned char* qbuf, int qlen,
   ares_callback callback, void* arg)
{
   struct query* query;
   int i;
   time_t now;
 
   /* Verify that the query is at least long enough to hold the header. */
   if (qlen < HFIXEDSZ || qlen >= (1 << 16))
   {
      callback(arg, ARES_EBADQUERY, NULL, 0);
      return;
   }
 
   if (channel->nservers < 1)
   {
      callback(arg, ARES_ESERVFAIL, NULL, 0);
      return;
   }
 
   /* Allocate space for query and allocated fields. */
   query = malloc(sizeof(struct query));
   if (!query)
   {
      callback(arg, ARES_ENOMEM, NULL, 0);
      return;
   }
   query->tcpbuf = malloc(qlen + 2);
   if (!query->tcpbuf)
   {
      free(query);
      callback(arg, ARES_ENOMEM, NULL, 0);
      return;
   }
   query->skip_server = malloc(channel->nservers * sizeof(int));
   if (!query->skip_server)
   {
      free(query->tcpbuf);
      free(query);
      callback(arg, ARES_ENOMEM, NULL, 0);
      return;
   }
 
   /* Compute the query ID.  Start with no timeout. */
   query->qid = DNS_HEADER_QID(qbuf);
   query->timeout = 0;
 
   /* Form the TCP query buffer by prepending qlen (as two
    * network-order bytes) to qbuf.
    */
   query->tcpbuf[0] = (qlen >> 8) & 0xff;
   query->tcpbuf[1] = qlen & 0xff;
   memcpy(query->tcpbuf + 2, qbuf, qlen);
   query->tcplen = qlen + 2;
 
   /* Fill in query arguments. */
   query->qbuf = query->tcpbuf + 2;
   query->qlen = qlen;
   query->callback = callback;
   query->arg = arg;
 
   /* Initialize query status. */
   query->itry = 0;
   query->server = 0;
   for (i = 0; i < channel->nservers; i++)
      query->skip_server[i] = 0;
   query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > PACKETSZ;
   query->error_status = ARES_ECONNREFUSED;
 
   /* Chain the query into this channel's query list. */
   query->next = channel->queries;
   channel->queries = query;
 
   /* Perform the first query action. */
   time(&now);
   ares__send_query(channel, query, now);
}