Add support for Client Subnet in DNS Queries (RFC7871), close AsyncHttpClient#1337

Motivation:

RFC7871 defines an extension which allows to request responses for a
given subset.

Modifications:

- Add DnsOptPseudoRrRecord which can act as base class for extensions
based on EDNS(0) as defined in RFC6891
- Add DnsOptEcsRecord to support the Client Subnet in DNS Queries
extension
- Add tests

Result:

Client Subnet in DNS Queries extension is now supported.

Author: slandelle

netty-bp/codec-dns/src/main/java/io/netty/channel/socket/InternetProtocolFamily2.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2012 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.channel.socket;
+
+import io.netty.util.NetUtil;
+
+import java.net.Inet4Address;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+
+/**
+ * Internet Protocol (IP) families used byte the {@link DatagramChannel}
+ */
+public enum InternetProtocolFamily2 {
+    IPv4(Inet4Address.class),
+    IPv6(Inet6Address.class);
+
+    private final Class<? extends InetAddress> addressType;
+    private final int addressNumber;
+    private final InetAddress localHost;
+
+    InternetProtocolFamily2(Class<? extends InetAddress> addressType) {
+        this.addressType = addressType;
+        addressNumber = addressNumber(addressType);
+        localHost = localhost(addressType);
+    }
+
+    /**
+     * Returns the address type of this protocol family.
+     */
+    public Class<? extends InetAddress> addressType() {
+        return addressType;
+    }
+
+    /**
+     * Returns the
+     * <a href="http://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml">address number</a>
+     * of the family.
+     */
+    public int addressNumber() {
+        return addressNumber;
+    }
+
+    /**
+     * Returns the {@link InetAddress} that represent the {@code LOCALHOST} for the family.
+     */
+    public InetAddress localhost() {
+        return localHost;
+    }
+
+    private static InetAddress localhost(Class<? extends InetAddress> addressType) {
+        if (addressType.isAssignableFrom(Inet4Address.class)) {
+            return NetUtil.LOCALHOST4;
+        }
+        if (addressType.isAssignableFrom(Inet6Address.class)) {
+            return NetUtil.LOCALHOST6;
+        }
+        throw new Error();
+    }
+
+    private static int addressNumber(Class<? extends InetAddress> addressType) {
+        if (addressType.isAssignableFrom(Inet4Address.class)) {
+            return 1;
+        }
+        if (addressType.isAssignableFrom(Inet6Address.class)) {
+            return 2;
+        }
+        throw new IllegalArgumentException("addressType " + addressType + " not supported");
+    }
+
+    /**
+     * Returns the {@link InternetProtocolFamily} for the given {@link InetAddress}.
+     */
+    public static InternetProtocolFamily2 of(InetAddress address) {
+        if (address instanceof Inet4Address) {
+            return IPv4;
+        }
+        if (address instanceof Inet6Address) {
+            return IPv6;
+        }
+        throw new IllegalArgumentException("address " + address + " not supported");
+    }
+}

netty-bp/codec-dns/src/main/java/io/netty/handler/codec/dns/AbstractDnsOptPseudoRrRecord.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2016 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.handler.codec.dns;
+
+import io.netty.util.internal.StringUtil;
+import io.netty.util.internal.UnstableApi;
+
+/**
+ * An <a href="https://tools.ietf.org/html/rfc6891#section-6.1">OPT RR</a> record.
+ *
+ * This is used for <a href="https://tools.ietf.org/html/rfc6891#section-6.1.3">
+ *     Extension Mechanisms for DNS (EDNS(0))</a>.
+ */
+@UnstableApi
+public abstract class AbstractDnsOptPseudoRrRecord extends AbstractDnsRecord implements DnsOptPseudoRecord {
+
+    protected AbstractDnsOptPseudoRrRecord(int maxPayloadSize, int extendedRcode, int version) {
+        super(StringUtil.EMPTY_STRING, DnsRecordType.OPT, maxPayloadSize, packIntoLong(extendedRcode, version));
+    }
+
+    protected AbstractDnsOptPseudoRrRecord(int maxPayloadSize) {
+        super(StringUtil.EMPTY_STRING, DnsRecordType.OPT, maxPayloadSize, 0);
+    }
+
+    // See https://tools.ietf.org/html/rfc6891#section-6.1.3
+    private static long packIntoLong(int val, int val2) {
+        // We are currently not support DO and Z fields, just use 0.
+        return ((val & 0xff) << 24 | (val2 & 0xff) << 16 | (0 & 0xff) <<  8 | 0 & 0xff) & 0xFFFFFFFFL;
+    }
+
+    @Override
+    public int extendedRcode() {
+        return (short) (((int) timeToLive() >> 24) & 0xff);
+    }
+
+    @Override
+    public int version() {
+        return (short) (((int) timeToLive() >> 16) & 0xff);
+    }
+
+    @Override
+    public int flags() {
+       return (short) ((short) timeToLive() & 0xff);
+    }
+
+    @Override
+    public String toString() {
+        return toStringBuilder().toString();
+    }
+
+    final StringBuilder toStringBuilder() {
+        return new StringBuilder(64)
+                .append(StringUtil.simpleClassName(this))
+                .append('(')
+                .append("OPT flags:")
+                .append(flags())
+                .append(" version:")
+                .append(version())
+                .append(" extendedRecode:")
+                .append(extendedRcode())
+                .append(" udp:")
+                .append(dnsClass())
+                .append(')');
+    }
+}

netty-bp/codec-dns/src/main/java/io/netty/handler/codec/dns/DefaultDnsOptEcsRecord.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2016 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.handler.codec.dns;
+
+import io.netty.channel.socket.InternetProtocolFamily2;
+import io.netty.util.internal.UnstableApi;
+
+import java.net.InetAddress;
+import java.util.Arrays;
+
+/**
+ * Default {@link DnsOptEcsRecord} implementation.
+ */
+@UnstableApi
+public final class DefaultDnsOptEcsRecord extends AbstractDnsOptPseudoRrRecord implements DnsOptEcsRecord {
+    private final int srcPrefixLength;
+    private final byte[] address;
+
+    /**
+     * Creates a new instance.
+     *
+     * @param maxPayloadSize the suggested max payload size in bytes
+     * @param extendedRcode the extended rcode
+     * @param version the version
+     * @param srcPrefixLength the prefix length
+     * @param address the bytes of the {@link InetAddress} to use
+     */
+    public DefaultDnsOptEcsRecord(int maxPayloadSize, int extendedRcode, int version,
+                                  int srcPrefixLength, byte[] address) {
+        super(maxPayloadSize, extendedRcode, version);
+        this.srcPrefixLength = srcPrefixLength;
+        this.address = verifyAddress(address).clone();
+    }
+
+    /**
+     * Creates a new instance.
+     *
+     * @param maxPayloadSize the suggested max payload size in bytes
+     * @param srcPrefixLength the prefix length
+     * @param address the bytes of the {@link InetAddress} to use
+     */
+    public DefaultDnsOptEcsRecord(int maxPayloadSize, int srcPrefixLength, byte[] address) {
+        this(maxPayloadSize, 0, 0, srcPrefixLength, address);
+    }
+
+    /**
+     * Creates a new instance.
+     *
+     * @param maxPayloadSize the suggested max payload size in bytes
+     * @param protocolFamily the {@link InternetProtocolFamily2} to use. This should be the same as the one used to
+     *                       send the query.
+     */
+    public DefaultDnsOptEcsRecord(int maxPayloadSize, InternetProtocolFamily2 protocolFamily) {
+        this(maxPayloadSize, 0, 0, 0, protocolFamily.localhost().getAddress());
+    }
+
+    private static byte[] verifyAddress(byte[] bytes) {
+        if (bytes.length == 4 || bytes.length == 16) {
+            return bytes;
+        }
+        throw new IllegalArgumentException("bytes.length must either 4 or 16");
+    }
+
+    @Override
+    public int sourcePrefixLength() {
+        return srcPrefixLength;
+    }
+
+    @Override
+    public int scopePrefixLength() {
+        return 0;
+    }
+
+    @Override
+    public byte[] address() {
+        return address.clone();
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = toStringBuilder();
+        sb.setLength(sb.length() - 1);
+        return sb.append(" address:")
+          .append(Arrays.toString(address))
+          .append(" sourcePrefixLength:")
+          .append(sourcePrefixLength())
+          .append(" scopePrefixLength:")
+          .append(scopePrefixLength())
+          .append(')').toString();
+    }
+}