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      1 
      2 /* Copyright 1998 by the Massachusetts Institute of Technology.
      3  *
      4  * Permission to use, copy, modify, and distribute this
      5  * software and its documentation for any purpose and without
      6  * fee is hereby granted, provided that the above copyright
      7  * notice appear in all copies and that both that copyright
      8  * notice and this permission notice appear in supporting
      9  * documentation, and that the name of M.I.T. not be used in
     10  * advertising or publicity pertaining to distribution of the
     11  * software without specific, written prior permission.
     12  * M.I.T. makes no representations about the suitability of
     13  * this software for any purpose.  It is provided "as is"
     14  * without express or implied warranty.
     15  */
     16 
     17 #include "ares_setup.h"
     18 
     19 #ifdef HAVE_SYS_SOCKET_H
     20 #  include <sys/socket.h>
     21 #endif
     22 #ifdef HAVE_NETINET_IN_H
     23 #  include <netinet/in.h>
     24 #endif
     25 #ifdef HAVE_ARPA_NAMESER_H
     26 #  include <arpa/nameser.h>
     27 #else
     28 #  include "nameser.h"
     29 #endif
     30 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
     31 #  include <arpa/nameser_compat.h>
     32 #endif
     33 
     34 #include <stdlib.h>
     35 #include <string.h>
     36 #include <time.h>
     37 #include "ares.h"
     38 #include "ares_dns.h"
     39 #include "ares_private.h"
     40 
     41 void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen,
     42                ares_callback callback, void *arg)
     43 {
     44   struct query *query;
     45   int i;
     46   struct timeval now;
     47 
     48   /* Verify that the query is at least long enough to hold the header. */
     49   if (qlen < HFIXEDSZ || qlen >= (1 << 16))
     50     {
     51       callback(arg, ARES_EBADQUERY, 0, NULL, 0);
     52       return;
     53     }
     54 
     55   /* Allocate space for query and allocated fields. */
     56   query = malloc(sizeof(struct query));
     57   if (!query)
     58     {
     59       callback(arg, ARES_ENOMEM, 0, NULL, 0);
     60       return;
     61     }
     62   query->tcpbuf = malloc(qlen + 2);
     63   if (!query->tcpbuf)
     64     {
     65       free(query);
     66       callback(arg, ARES_ENOMEM, 0, NULL, 0);
     67       return;
     68     }
     69   query->server_info = malloc(channel->nservers *
     70                               sizeof(query->server_info[0]));
     71   if (!query->server_info)
     72     {
     73       free(query->tcpbuf);
     74       free(query);
     75       callback(arg, ARES_ENOMEM, 0, NULL, 0);
     76       return;
     77     }
     78 
     79   /* Compute the query ID.  Start with no timeout. */
     80   query->qid = (unsigned short)DNS_HEADER_QID(qbuf);
     81   query->timeout.tv_sec = 0;
     82   query->timeout.tv_usec = 0;
     83 
     84   /* Form the TCP query buffer by prepending qlen (as two
     85    * network-order bytes) to qbuf.
     86    */
     87   query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
     88   query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
     89   memcpy(query->tcpbuf + 2, qbuf, qlen);
     90   query->tcplen = qlen + 2;
     91 
     92   /* Fill in query arguments. */
     93   query->qbuf = query->tcpbuf + 2;
     94   query->qlen = qlen;
     95   query->callback = callback;
     96   query->arg = arg;
     97 
     98   /* Initialize query status. */
     99   query->try_count = 0;
    100 
    101   /* Choose the server to send the query to. If rotation is enabled, keep track
    102    * of the next server we want to use. */
    103   query->server = channel->last_server;
    104   if (channel->rotate == 1)
    105     channel->last_server = (channel->last_server + 1) % channel->nservers;
    106 
    107   for (i = 0; i < channel->nservers; i++)
    108     {
    109       query->server_info[i].skip_server = 0;
    110       query->server_info[i].tcp_connection_generation = 0;
    111     }
    112   query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > PACKETSZ;
    113   query->error_status = ARES_ECONNREFUSED;
    114   query->timeouts = 0;
    115 
    116   /* Initialize our list nodes. */
    117   ares__init_list_node(&(query->queries_by_qid),     query);
    118   ares__init_list_node(&(query->queries_by_timeout), query);
    119   ares__init_list_node(&(query->queries_to_server),  query);
    120   ares__init_list_node(&(query->all_queries),        query);
    121 
    122   /* Chain the query into the list of all queries. */
    123   ares__insert_in_list(&(query->all_queries), &(channel->all_queries));
    124   /* Keep track of queries bucketed by qid, so we can process DNS
    125    * responses quickly.
    126    */
    127   ares__insert_in_list(
    128     &(query->queries_by_qid),
    129     &(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE]));
    130 
    131   /* Perform the first query action. */
    132   now = ares__tvnow();
    133   ares__send_query(channel, query, &now);
    134 }
    135