resolver.c

非常好的dns解析软件

		isc_buffer_putuint16(&tcpbuffer, (isc_uint16_t)r.length);
		isc_buffer_add(&tcpbuffer, r.length);
	}

	/*
	 * We're now done with the query message.
	 */
	dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

	socket = dns_dispatch_getsocket(query->dispatch);
	/*
	 * Send the query!
	 */
	if ((query->options & DNS_FETCHOPT_TCP) == 0)
		address = &query->addrinfo->sockaddr;
	isc_buffer_usedregion(buffer, &r);

	/*
	 * XXXRTH  Make sure we don't send to ourselves!  We should probably
	 *	   prune out these addresses when we get them from the ADB.
	 */
	result = isc_socket_sendto(socket, &r, task, resquery_senddone,
				   query, address, NULL);
	if (result != ISC_R_SUCCESS)
		goto cleanup_message;
	query->sends++;
	QTRACE("sent");

	return (ISC_R_SUCCESS);

 cleanup_message:
	if (cleanup_cctx)
		dns_compress_invalidate(&cctx);

	dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

	/*
	 * Stop the dispatcher from listening.
	 */
	dns_dispatch_removeresponse(&query->dispentry, NULL);

 cleanup_temps:
	if (qname != NULL)
		dns_message_puttempname(fctx->qmessage, &qname);
	if (qrdataset != NULL)
		dns_message_puttemprdataset(fctx->qmessage, &qrdataset);

	return (result);
}

static void
resquery_connected(isc_task_t *task, isc_event_t *event) {
	isc_socketevent_t *sevent = (isc_socketevent_t *)event;
	resquery_t *query = event->ev_arg;
	isc_boolean_t retry = ISC_FALSE;
	isc_result_t result;
	unsigned int attrs;
	fetchctx_t *fctx;

	REQUIRE(event->ev_type == ISC_SOCKEVENT_CONNECT);
	REQUIRE(VALID_QUERY(query));

	QTRACE("connected");

	UNUSED(task);

	/*
	 * XXXRTH
	 *
	 * Currently we don't wait for the connect event before retrying
	 * a query.  This means that if we get really behind, we may end
	 * up doing extra work!
	 */

	query->connects--;
	fctx = query->fctx;

	if (RESQUERY_CANCELED(query)) {
		/*
		 * This query was canceled while the connect() was in
		 * progress.
		 */
		isc_socket_detach(&query->tcpsocket);
		resquery_destroy(&query);
	} else {
		switch (sevent->result) {
		case ISC_R_SUCCESS:
			/*
			 * We are connected.  Create a dispatcher and
			 * send the query.
			 */
			attrs = 0;
			attrs |= DNS_DISPATCHATTR_TCP;
			attrs |= DNS_DISPATCHATTR_PRIVATE;
			attrs |= DNS_DISPATCHATTR_CONNECTED;
			if (isc_sockaddr_pf(&query->addrinfo->sockaddr) ==
			    AF_INET)
				attrs |= DNS_DISPATCHATTR_IPV4;
			else
				attrs |= DNS_DISPATCHATTR_IPV6;
			attrs |= DNS_DISPATCHATTR_MAKEQUERY;

			result = dns_dispatch_createtcp(query->dispatchmgr,
						     query->tcpsocket,
						     query->fctx->res->taskmgr,
						     4096, 2, 1, 1, 3, attrs,
						     &query->dispatch);

			/*
			 * Regardless of whether dns_dispatch_create()
			 * succeeded or not, we don't need our reference
			 * to the socket anymore.
			 */
			isc_socket_detach(&query->tcpsocket);

			if (result == ISC_R_SUCCESS)
				result = resquery_send(query);

			if (result != ISC_R_SUCCESS) {
				fctx_cancelquery(&query, NULL, NULL,
						 ISC_FALSE);
				fctx_done(fctx, result);
			}
			break;

		case ISC_R_NETUNREACH:
		case ISC_R_HOSTUNREACH:
		case ISC_R_CONNREFUSED:
		case ISC_R_NOPERM:
		case ISC_R_ADDRNOTAVAIL:
		case ISC_R_CONNECTIONRESET:
			/*
			 * No route to remote.
			 */
			isc_socket_detach(&query->tcpsocket);
			fctx_cancelquery(&query, NULL, NULL, ISC_TRUE);
			retry = ISC_TRUE;
			break;

		default:
			isc_socket_detach(&query->tcpsocket);
			fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
			break;
		}
	}

	isc_event_free(&event);
	
	if (retry) {
		/*
		 * Behave as if the idle timer has expired.  For TCP
		 * connections this may not actually reflect the latest timer.
		 */
		fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
		result = fctx_stopidletimer(fctx);
		if (result != ISC_R_SUCCESS)
			fctx_done(fctx, result);
		else
			fctx_try(fctx);
	}
}

static void
fctx_finddone(isc_task_t *task, isc_event_t *event) {
	fetchctx_t *fctx;
	dns_adbfind_t *find;
	dns_resolver_t *res;
	isc_boolean_t want_try = ISC_FALSE;
	isc_boolean_t want_done = ISC_FALSE;
	isc_boolean_t bucket_empty = ISC_FALSE;
	unsigned int bucketnum;

	find = event->ev_sender;
	fctx = event->ev_arg;
	REQUIRE(VALID_FCTX(fctx));
	res = fctx->res;

	UNUSED(task);

	FCTXTRACE("finddone");

	INSIST(fctx->pending > 0);
	fctx->pending--;

	if (ADDRWAIT(fctx)) {
		/*
		 * The fetch is waiting for a name to be found.
		 */
		INSIST(!SHUTTINGDOWN(fctx));
		fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
		if (event->ev_type == DNS_EVENT_ADBMOREADDRESSES)
			want_try = ISC_TRUE;
		else if (fctx->pending == 0) {
			/*
			 * We've got nothing else to wait for and don't
			 * know the answer.  There's nothing to do but
			 * fail the fctx.
			 */
			want_done = ISC_TRUE;
		}
	} else if (SHUTTINGDOWN(fctx) && fctx->pending == 0 &&
		   fctx->nqueries == 0 && ISC_LIST_EMPTY(fctx->validators)) {
		bucketnum = fctx->bucketnum;
		LOCK(&res->buckets[bucketnum].lock);
		/*
		 * Note that we had to wait until we had the lock before
		 * looking at fctx->references.
		 */
		if (fctx->references == 0)
			bucket_empty = fctx_destroy(fctx);
		UNLOCK(&res->buckets[bucketnum].lock);
	}

	isc_event_free(&event);
	dns_adb_destroyfind(&find);

	if (want_try)
		fctx_try(fctx);
	else if (want_done)
		fctx_done(fctx, ISC_R_FAILURE);
	else if (bucket_empty)
		empty_bucket(res);
}


static inline isc_boolean_t
bad_server(fetchctx_t *fctx, isc_sockaddr_t *address) {
	isc_sockaddr_t *sa;

	for (sa = ISC_LIST_HEAD(fctx->bad);
	     sa != NULL;
	     sa = ISC_LIST_NEXT(sa, link)) {
		if (isc_sockaddr_equal(sa, address))
			return (ISC_TRUE);
	}

	return (ISC_FALSE);
}

static inline isc_boolean_t
mark_bad(fetchctx_t *fctx) {
	dns_adbfind_t *curr;
	dns_adbaddrinfo_t *addrinfo;
	isc_boolean_t all_bad = ISC_TRUE;

	/*
	 * Mark all known bad servers, so we don't try to talk to them
	 * again.
	 */

	/*
	 * Mark any bad nameservers.
	 */
	for (curr = ISC_LIST_HEAD(fctx->finds);
	     curr != NULL;
	     curr = ISC_LIST_NEXT(curr, publink)) {
		for (addrinfo = ISC_LIST_HEAD(curr->list);
		     addrinfo != NULL;
		     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
			if (bad_server(fctx, &addrinfo->sockaddr))
				addrinfo->flags |= FCTX_ADDRINFO_MARK;
			else
				all_bad = ISC_FALSE;
		}
	}

	/*
	 * Mark any bad forwarders.
	 */
	for (addrinfo = ISC_LIST_HEAD(fctx->forwaddrs);
	     addrinfo != NULL;
	     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
		if (bad_server(fctx, &addrinfo->sockaddr))
			addrinfo->flags |= FCTX_ADDRINFO_MARK;
		else
			all_bad = ISC_FALSE;
	}

	/*
	 * Mark any bad alternates.
	 */
	for (curr = ISC_LIST_HEAD(fctx->altfinds);
	     curr != NULL;
	     curr = ISC_LIST_NEXT(curr, publink)) {
		for (addrinfo = ISC_LIST_HEAD(curr->list);
		     addrinfo != NULL;
		     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
			if (bad_server(fctx, &addrinfo->sockaddr))
				addrinfo->flags |= FCTX_ADDRINFO_MARK;
			else
				all_bad = ISC_FALSE;
		}
	}

	for (addrinfo = ISC_LIST_HEAD(fctx->altaddrs);
	     addrinfo != NULL;
	     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
		if (bad_server(fctx, &addrinfo->sockaddr))
			addrinfo->flags |= FCTX_ADDRINFO_MARK;
		else
			all_bad = ISC_FALSE;
	}

	return (all_bad);
}

static void
add_bad(fetchctx_t *fctx, isc_sockaddr_t *address, isc_result_t reason) {
	char namebuf[DNS_NAME_FORMATSIZE];
	char addrbuf[ISC_SOCKADDR_FORMATSIZE];
	char classbuf[64];
	char typebuf[64];
	char code[64];
	isc_buffer_t b;
	isc_sockaddr_t *sa;
	const char *sep1, *sep2;

	if (bad_server(fctx, address)) {
		/*
		 * We already know this server is bad.
		 */
		return;
	}

	FCTXTRACE("add_bad");

	sa = isc_mem_get(fctx->res->buckets[fctx->bucketnum].mctx,
			 sizeof(*sa));
	if (sa == NULL)
		return;
	*sa = *address;
	ISC_LIST_INITANDAPPEND(fctx->bad, sa, link);

	if (reason == DNS_R_LAME)	/* already logged */
		return;

	if (reason == DNS_R_UNEXPECTEDRCODE) {
		isc_buffer_init(&b, code, sizeof(code) - 1);
		dns_rcode_totext(fctx->rmessage->rcode, &b);
		code[isc_buffer_usedlength(&b)] = '\0';
		sep1 = "(";
		sep2 = ") ";
	} else if (reason == DNS_R_UNEXPECTEDOPCODE) {
		isc_buffer_init(&b, code, sizeof(code) - 1);
		dns_opcode_totext((dns_opcode_t)fctx->rmessage->opcode, &b);
		code[isc_buffer_usedlength(&b)] = '\0';
		sep1 = "(";
		sep2 = ") ";
	} else {
		code[0] = '\0';
		sep1 = "";
		sep2 = "";
	}
	dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
	dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));
	dns_rdataclass_format(fctx->res->rdclass, classbuf, sizeof(classbuf));
	isc_sockaddr_format(address, addrbuf, sizeof(addrbuf));
	isc_log_write(dns_lctx, DNS_LOGCATEGORY_LAME_SERVERS,
		      DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
		      "%s %s%s%sresolving '%s/%s/%s': %s",
		      dns_result_totext(reason), sep1, code, sep2,
		      namebuf, typebuf, classbuf, addrbuf);
}

static void
sort_adbfind(dns_adbfind_t *find) {
	dns_adbaddrinfo_t *best, *curr;
	dns_adbaddrinfolist_t sorted;

	/*
	 * Lame N^2 bubble sort.
	 */

	ISC_LIST_INIT(sorted);
	while (!ISC_LIST_EMPTY(find->list)) {
		best = ISC_LIST_HEAD(find->list);
		curr = ISC_LIST_NEXT(best, publink);
		while (curr != NULL) {
			if (curr->srtt < best->srtt)
				best = curr;
			curr = ISC_LIST_NEXT(curr, publink);
		}
		ISC_LIST_UNLINK(find->list, best, publink);
		ISC_LIST_APPEND(sorted, best, publink);
	}
	find->list = sorted;
}

static void
sort_finds(fetchctx_t *fctx) {
	dns_adbfind_t *best, *curr;
	dns_adbfindlist_t sorted;
	dns_adbaddrinfo_t *addrinfo, *bestaddrinfo;

	/*
	 * Lame N^2 bubble sort.
	 */

	ISC_LIST_INIT(sorted);
	while (!ISC_LIST_EMPTY(fctx->finds)) {
		best = ISC_LIST_HEAD(fctx->finds);
		bestaddrinfo = ISC_LIST_HEAD(best->list);
		INSIST(bestaddrinfo != NULL);
		curr = ISC_LIST_NEXT(best, publink);
		while (curr != NULL) {
			addrinfo = ISC_LIST_HEAD(curr->list);
			INSIST(addrinfo != NULL);
			if (addrinfo->srtt < bestaddrinfo->srtt) {
				best = curr;
				bestaddrinfo = addrinfo;
			}
			curr = ISC_LIST_NEXT(curr, publink);
		}
		ISC_LIST_UNLINK(fctx->finds, best, publink);
		ISC_LIST_APPEND(sorted, best, publink);
	}
	fctx->finds = sorted;

	ISC_LIST_INIT(sorted);
	while (!ISC_LIST_EMPTY(fctx->altfinds)) {
		best = ISC_LIST_HEAD(fctx->altfinds);
		bestaddrinfo = ISC_LIST_HEAD(best->list);
		INSIST(bestaddrinfo != NULL);
		curr = ISC_LIST_NEXT(best, publink);
		while (curr != NULL) {
			addrinfo = ISC_LIST_HEAD(curr->list);
			INSIST(addrinfo != NULL);
			if (addrinfo->srtt < bestaddrinfo->srtt) {
				best = curr;
				bestaddrinfo = addrinfo;
			}
			curr = ISC_LIST_NEXT(curr, publink);
		}
		ISC_LIST_UNLINK(fctx->altfinds, best, publink);
		ISC_LIST_APPEND(sorted, best, publink);
	}
	fctx->altfinds = sorted;
}

static void
findname(fetchctx_t *fctx, dns_name_t *name, in_port_t port,
	 unsigned int options, unsigned int flags, isc_stdtime_t now,
	 isc_boolean_t *need_alternate)
{
	dns_adbaddrinfo_t *ai;
	dns_adbfind_t *find;
	dns_resolver_t *res;
	isc_boolean_t unshared;
	isc_result_t result;

	res = fctx->res;
	unshared = ISC_TF((fctx->options | DNS_FETCHOPT_UNSHARED) != 0);
	/*
	 * If this name is a subdomain of the query domain, tell
	 * the ADB to start looking using zone/hint data. This keeps us
	 * from getting stuck if the nameserver is beneath the zone cut
	 * and we don't know its address (e.g. because the A record has
	 * expired).
	 */
	if (dns_name_issubdomain(name, &fctx->domain))
		options |= DNS_ADBFIND_STARTATZONE;
	options |= DNS_ADBFIND_GLUEOK;
	options |= DNS_ADBFIND_HINTOK;

	/*
	 * See what we know about this address.
	 */
	find = NULL;
	result = dns_adb_createfind(fctx->adb,
				    res->buckets[fctx->bucketnum].task,
				    fctx_finddone, fctx, name,
				    &fctx->name, fctx->type,
				    options, now, NULL,
				    res->view->dstport, &find);
	if (result != ISC_R_SUCCESS) {
		if (result == DNS_R_ALIAS) {
			/*
			 * XXXRTH  Follow the CNAME/DNAME chain?
			 */
			dns_adb_destroyfind(&find);
		}
	} else if (!ISC_LIST_EMPTY(find->list)) {
		/*
		 * We have at least some of the addresses for the
		 * name.
		 */
		INSIST((find->options & DNS_ADBFIND_WANTEVENT) == 0);
		sort_adbfind(find);
		if (flags != 0 || port != 0) {
			for (ai = ISC_LIST_HEAD(find->list);
			     ai != NULL;
			     ai = ISC_LIST_NEXT(ai, publink)) {
				ai->flags |= flags;
				if (port != 0)
					isc_sockaddr_setport(&ai->sockaddr,
							     port);
			}
		}
		if ((flags & FCTX_ADDRINFO_FORWARDER) != 0)
			ISC_LIST_APPEND(fctx->altfinds, find, publink);
		else
			ISC_LIST_APPEND(fctx->finds, find, publink);
	} else {
		/*
		 * We don't know any of the addresses for this
		 * name.
		 */
		if ((find->options & DNS_ADBFIND_WANTEVENT) != 0) {
			/*
			 * We're looking for them and will get an
			 * event about it later.
			 */