/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.resolver.dns;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.socket.DatagramChannel;
import io.netty.handler.codec.dns.DnsQuery;
import io.netty.handler.codec.dns.DnsQuestion;
import io.netty.handler.codec.dns.DnsResource;
import io.netty.handler.codec.dns.DnsResponse;
import io.netty.handler.codec.dns.DnsType;
import io.netty.resolver.dns.DnsNameResolver.DnsCacheEntry;
import io.netty.util.concurrent.Promise;
import io.netty.util.concurrent.ScheduledFuture;
import io.netty.util.internal.OneTimeTask;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.ThreadLocalRandom;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.Iterator;
import java.util.concurrent.TimeUnit;
final class DnsQueryContext {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(DnsQueryContext.class);
private final DnsNameResolver parent;
private final Promise<DnsResponse> promise;
private final int id;
private final DnsQuestion question;
private final DnsResource optResource;
private final Iterator<InetSocketAddress> nameServerAddresses;
private final boolean recursionDesired;
private final int maxTries;
private int remainingTries;
private volatile ScheduledFuture<?> timeoutFuture;
private StringBuilder trace;
DnsQueryContext(DnsNameResolver parent,
Iterable<InetSocketAddress> nameServerAddresses,
DnsQuestion question, Promise<DnsResponse> promise) {
this.parent = parent;
this.promise = promise;
this.question = question;
id = allocateId();
recursionDesired = parent.isRecursionDesired();
maxTries = parent.maxTriesPerQuery();
remainingTries = maxTries;
optResource = new DnsResource("", DnsType.OPT, parent.maxPayloadSizeClass(), 0, Unpooled.EMPTY_BUFFER);
this.nameServerAddresses = nameServerAddresses.iterator();
}
private int allocateId() {
int id = ThreadLocalRandom.current().nextInt(parent.promises.length());
final int maxTries = parent.promises.length() << 1;
int tries = 0;
for (;;) {
if (parent.promises.compareAndSet(id, null, this)) {
return id;
}
id = id + 1 & 0xFFFF;
if (++ tries >= maxTries) {
throw new IllegalStateException("query ID space exhausted: " + question);
}
}
}
Promise<DnsResponse> promise() {
return promise;
}
DnsQuestion question() {
return question;
}
ScheduledFuture<?> timeoutFuture() {
return timeoutFuture;
}
void query() {
final DnsQuestion question = this.question;
if (remainingTries <= 0 || !nameServerAddresses.hasNext()) {
parent.promises.set(id, null);
int tries = maxTries - remainingTries;
UnknownHostException cause;
if (tries > 1) {
cause = new UnknownHostException(
"failed to resolve " + question + " after " + tries + " attempts:" +
trace);
} else {
cause = new UnknownHostException("failed to resolve " + question + ':' + trace);
}
cache(question, cause);
promise.tryFailure(cause);
return;
}
remainingTries --;
final InetSocketAddress nameServerAddr = nameServerAddresses.next();
final DnsQuery query = new DnsQuery(id, nameServerAddr);
query.addQuestion(question);
query.header().setRecursionDesired(recursionDesired);
query.addAdditionalResource(optResource);
final DatagramChannel ch = parent.ch;
if (logger.isDebugEnabled()) {
logger.debug("{} WRITE: [{}: {}], {}", ch, id, nameServerAddr, question);
}
final ChannelFuture writeFuture = ch.writeAndFlush(query);
if (writeFuture.isDone()) {
onQueryWriteCompletion(writeFuture, nameServerAddr);
} else {
writeFuture.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
onQueryWriteCompletion(writeFuture, nameServerAddr);
}
});
}
}
private void onQueryWriteCompletion(ChannelFuture writeFuture, final InetSocketAddress nameServerAddr) {
if (!writeFuture.isSuccess()) {
retry(nameServerAddr, "failed to send a query: " + writeFuture.cause());
return;
}
// Schedule a query timeout task if necessary.
final long queryTimeoutMillis = parent.queryTimeoutMillis();
if (queryTimeoutMillis > 0) {
timeoutFuture = parent.ch.eventLoop().schedule(new OneTimeTask() {
@Override
public void run() {
if (promise.isDone()) {
// Received a response before the query times out.
return;
}
retry(nameServerAddr, "query timed out after " + queryTimeoutMillis + " milliseconds");
}
}, queryTimeoutMillis, TimeUnit.MILLISECONDS);
}
}
void retry(InetSocketAddress nameServerAddr, String message) {
if (promise.isCancelled()) {
return;
}
if (trace == null) {
trace = new StringBuilder(128);
}
trace.append(StringUtil.NEWLINE);
trace.append("\tfrom ");
trace.append(nameServerAddr);
trace.append(": ");
trace.append(message);
query();
}
private void cache(final DnsQuestion question, Throwable cause) {
final int negativeTtl = parent.negativeTtl();
if (negativeTtl == 0) {
return;
}
parent.cache(question, new DnsCacheEntry(cause), negativeTtl);
}
}