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https://github.com/moparisthebest/curl
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23f5d145ec
outstanding queries, and processing a DNS response packet was O(n) in the number of outstanding queries. To speed things up in Google, we added a few circular, doubly-linked lists of queries that are hash-bucketed based on the attributes we care about, so most important operations are now O(1). It might be that the number of buckets are higher than most people would need, but on a quick calculation it should only be 100kB or so even on a 64-bit system, so I've let it stay as-is.
180 lines
4.6 KiB
C
180 lines
4.6 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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#if defined(WIN32) && !defined(WATT32)
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#include "nameser.h"
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#else
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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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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#endif
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#include <stdlib.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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struct qquery {
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ares_callback callback;
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void *arg;
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};
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static void qcallback(void *arg, int status, int timeouts, unsigned char *abuf, int alen);
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void ares__rc4(rc4_key* key, unsigned char *buffer_ptr, int buffer_len)
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{
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unsigned char x;
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unsigned char y;
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unsigned char* state;
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unsigned char xorIndex;
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short counter;
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x = key->x;
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y = key->y;
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state = &key->state[0];
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for(counter = 0; counter < buffer_len; counter ++)
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{
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x = (x + 1) % 256;
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y = (state[x] + y) % 256;
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ARES_SWAP_BYTE(&state[x], &state[y]);
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xorIndex = (state[x] + state[y]) % 256;
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buffer_ptr[counter] ^= state[xorIndex];
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}
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key->x = x;
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key->y = y;
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}
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static struct query* find_query_by_id(ares_channel channel, int id)
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{
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unsigned short qid;
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struct list_node* list_head;
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struct list_node* list_node;
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DNS_HEADER_SET_QID(((unsigned char*)&qid), id);
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/* Find the query corresponding to this packet. */
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list_head = &(channel->queries_by_qid[qid % ARES_QID_TABLE_SIZE]);
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for (list_node = list_head->next; list_node != list_head;
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list_node = list_node->next)
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{
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struct query *q = list_node->data;
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if (q->qid == qid)
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return q;
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}
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return NULL;
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}
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/* a unique query id is generated using an rc4 key. Since the id may already
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be used by a running query (as infrequent as it may be), a lookup is
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performed per id generation. In practice this search should happen only
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once per newly generated id
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*/
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static int generate_unique_id(ares_channel channel)
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{
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int id;
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do {
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id = ares__generate_new_id(&channel->id_key);
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} while (find_query_by_id(channel,id));
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return id;
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}
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void ares_query(ares_channel channel, const char *name, int dnsclass,
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int type, ares_callback callback, void *arg)
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{
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struct qquery *qquery;
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unsigned char *qbuf;
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int qlen, rd, status;
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/* Compose the query. */
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rd = !(channel->flags & ARES_FLAG_NORECURSE);
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status = ares_mkquery(name, dnsclass, type, channel->next_id, rd, &qbuf,
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&qlen);
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if (status != ARES_SUCCESS)
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{
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if (qbuf != NULL) free(qbuf);
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callback(arg, status, 0, NULL, 0);
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return;
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}
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channel->next_id = generate_unique_id(channel);
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/* Allocate and fill in the query structure. */
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qquery = malloc(sizeof(struct qquery));
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if (!qquery)
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{
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ares_free_string(qbuf);
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callback(arg, ARES_ENOMEM, 0, NULL, 0);
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return;
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}
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qquery->callback = callback;
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qquery->arg = arg;
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/* Send it off. qcallback will be called when we get an answer. */
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ares_send(channel, qbuf, qlen, qcallback, qquery);
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ares_free_string(qbuf);
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}
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static void qcallback(void *arg, int status, int timeouts, unsigned char *abuf, int alen)
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{
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struct qquery *qquery = (struct qquery *) arg;
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unsigned int ancount;
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int rcode;
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if (status != ARES_SUCCESS)
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qquery->callback(qquery->arg, status, timeouts, abuf, alen);
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else
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{
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/* Pull the response code and answer count from the packet. */
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rcode = DNS_HEADER_RCODE(abuf);
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ancount = DNS_HEADER_ANCOUNT(abuf);
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/* Convert errors. */
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switch (rcode)
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{
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case NOERROR:
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status = (ancount > 0) ? ARES_SUCCESS : ARES_ENODATA;
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break;
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case FORMERR:
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status = ARES_EFORMERR;
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break;
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case SERVFAIL:
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status = ARES_ESERVFAIL;
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break;
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case NXDOMAIN:
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status = ARES_ENOTFOUND;
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break;
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case NOTIMP:
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status = ARES_ENOTIMP;
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break;
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case REFUSED:
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status = ARES_EREFUSED;
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break;
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}
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qquery->callback(qquery->arg, status, timeouts, abuf, alen);
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}
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free(qquery);
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}
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