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https://github.com/moparisthebest/curl
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3e3d10824f
in man resolv.conf: causes round robin selection of nameservers from among those listed. This has the effect of spreading the query load among all listed servers, rather than having all clients try the first listed server first every time. You can enable it with ARES_OPT_ROTATE
133 lines
3.9 KiB
C
133 lines
3.9 KiB
C
/* $Id$ */
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/* Copyright 1998 by the Massachusetts Institute of Technology.
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*
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* Permission to use, copy, modify, and distribute this
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* software and its documentation for any purpose and without
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* fee is hereby granted, provided that the above copyright
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* notice appear in all copies and that both that copyright
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* notice and this permission notice appear in supporting
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* documentation, and that the name of M.I.T. not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* M.I.T. makes no representations about the suitability of
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* this software for any purpose. It is provided "as is"
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* without express or implied warranty.
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*/
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#include "setup.h"
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#ifdef HAVE_NETINET_IN_H
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# include <netinet/in.h>
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#endif
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#ifdef HAVE_ARPA_NAMESER_H
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# include <arpa/nameser.h>
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#else
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# include "nameser.h"
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#endif
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#ifdef HAVE_ARPA_NAMESER_COMPAT_H
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# include <arpa/nameser_compat.h>
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#endif
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include "ares.h"
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#include "ares_dns.h"
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#include "ares_private.h"
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void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen,
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ares_callback callback, void *arg)
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{
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struct query *query;
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int i;
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struct timeval now;
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/* Verify that the query is at least long enough to hold the header. */
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if (qlen < HFIXEDSZ || qlen >= (1 << 16))
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{
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callback(arg, ARES_EBADQUERY, 0, NULL, 0);
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return;
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}
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/* Allocate space for query and allocated fields. */
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query = malloc(sizeof(struct query));
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if (!query)
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{
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callback(arg, ARES_ENOMEM, 0, NULL, 0);
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return;
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}
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query->tcpbuf = malloc(qlen + 2);
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if (!query->tcpbuf)
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{
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free(query);
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callback(arg, ARES_ENOMEM, 0, NULL, 0);
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return;
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}
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query->server_info = malloc(channel->nservers *
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sizeof(query->server_info[0]));
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if (!query->server_info)
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{
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free(query->tcpbuf);
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free(query);
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callback(arg, ARES_ENOMEM, 0, NULL, 0);
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return;
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}
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/* Compute the query ID. Start with no timeout. */
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query->qid = (unsigned short)DNS_HEADER_QID(qbuf);
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query->timeout.tv_sec = 0;
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query->timeout.tv_usec = 0;
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/* Form the TCP query buffer by prepending qlen (as two
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* network-order bytes) to qbuf.
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*/
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query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
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query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
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memcpy(query->tcpbuf + 2, qbuf, qlen);
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query->tcplen = qlen + 2;
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/* Fill in query arguments. */
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query->qbuf = query->tcpbuf + 2;
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query->qlen = qlen;
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query->callback = callback;
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query->arg = arg;
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/* Initialize query status. */
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query->try = 0;
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/* Choose the server to send the query to. If rotation is enabled, keep track
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* of the next server we want to use. */
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query->server = channel->last_server;
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if (channel->rotate == 1)
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channel->last_server = (channel->last_server + 1) % channel->nservers;
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for (i = 0; i < channel->nservers; i++)
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{
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query->server_info[i].skip_server = 0;
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query->server_info[i].tcp_connection_generation = 0;
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}
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query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > PACKETSZ;
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query->error_status = ARES_ECONNREFUSED;
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query->timeouts = 0;
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/* Initialize our list nodes. */
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ares__init_list_node(&(query->queries_by_qid), query);
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ares__init_list_node(&(query->queries_by_timeout), query);
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ares__init_list_node(&(query->queries_to_server), query);
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ares__init_list_node(&(query->all_queries), query);
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/* Chain the query into the list of all queries. */
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ares__insert_in_list(&(query->all_queries), &(channel->all_queries));
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/* Keep track of queries bucketed by qid, so we can process DNS
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* responses quickly.
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*/
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ares__insert_in_list(
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&(query->queries_by_qid),
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&(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE]));
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/* Perform the first query action. */
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now = ares__tvnow();
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ares__send_query(channel, query, &now);
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}
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