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UnixResolverDnsServerAddressStreamProvider default name server selection and ordering bug

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Motivation:
UnixResolverDnsServerAddressStreamProvider allows the default name server address stream to be null, but there should always be a default stream to fall back to ([1] Search Strategy).
UnixResolverDnsServerAddressStreamProvider currently shuffles the names servers are multiple are present, but the defined behavior is to try them sequentially [2].

[1] Search Strategy Section - https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html
[2] DESCRIPTION/nameserver Section - https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html

Modifications:
- UnixResolverDnsServerAddressStreamProvider should always use the first file provided to derive the default domain server address stream. Currently if there are multiple domain names in the file identified by the first argument of the constructor then one will be selected at random.
- UnixResolverDnsServerAddressStreamProvider should return name servers sequentially.
- Reduce access level on some methods which don't have known use-cases externally.

Result:
Fixes https://github.com/netty/netty/issues/6736
This commit is contained in:
Scott Mitchell 2017-05-17 16:36:33 -07:00
parent 4c6d946fba
commit 0f1a2ca5ae
2 changed files with 121 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
resolver-dns/src/main/java/io/netty/resolver/dns/UnixResolverDnsServerAddressStreamProvider.java
View File

@ -27,11 +27,13 @@ import java.io.FileReader;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import static io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider.DNS_PORT;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.StringUtil.indexOfNonWhiteSpace;
/**
@ -54,7 +56,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
* Attempt to parse {@code /etc/resolv.conf} and files in the {@code /etc/resolver} directory by default.
* A failure to parse will return {@link DefaultDnsServerAddressStreamProvider}.
*/
public static DnsServerAddressStreamProvider parseSilently() {
static DnsServerAddressStreamProvider parseSilently() {
try {
UnixResolverDnsServerAddressStreamProvider nameServerCache =
new UnixResolverDnsServerAddressStreamProvider("/etc/resolv.conf", "/etc/resolver");
@ -80,21 +82,25 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
* @throws IOException If an error occurs while parsing the input files.
*/
public UnixResolverDnsServerAddressStreamProvider(File etcResolvConf, File... etcResolverFiles) throws IOException {
if (etcResolvConf == null && (etcResolverFiles == null || etcResolverFiles.length == 0)) {
throw new IllegalArgumentException("no files to parse");
if (etcResolverFiles != null && etcResolverFiles.length == 0) {
throw new IllegalArgumentException("etcResolverFiles must either be null or non-empty");
}
if (etcResolverFiles != null) {
domainToNameServerStreamMap = parse(etcResolverFiles);
if (etcResolvConf != null) {
Map<String, DnsServerAddresses> etcResolvConfMap = parse(etcResolvConf);
defaultNameServerAddresses = etcResolvConfMap.remove(etcResolvConf.getName());
domainToNameServerStreamMap.putAll(etcResolvConfMap);
} else {
defaultNameServerAddresses = null;
Map<String, DnsServerAddresses> etcResolvConfMap = parse(checkNotNull(etcResolvConf, "etcResolvConf"));
domainToNameServerStreamMap = etcResolverFiles != null ? parse(etcResolverFiles) : etcResolvConfMap;
DnsServerAddresses defaultNameServerAddresses = etcResolvConfMap.get(etcResolvConf.getName());
if (defaultNameServerAddresses == null) {
Collection<DnsServerAddresses> values = etcResolvConfMap.values();
if (values.isEmpty()) {
throw new IllegalArgumentException(etcResolvConf + " didn't provide any name servers");
}
this.defaultNameServerAddresses = values.iterator().next();
} else {
domainToNameServerStreamMap = parse(etcResolvConf);
defaultNameServerAddresses = domainToNameServerStreamMap.remove(etcResolvConf.getName());
this.defaultNameServerAddresses = defaultNameServerAddresses;
}
if (etcResolverFiles != null) {
domainToNameServerStreamMap.putAll(etcResolvConfMap);
}
}
@ -113,7 +119,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
*/
public UnixResolverDnsServerAddressStreamProvider(String etcResolvConf, String etcResolverDir) throws IOException {
this(etcResolvConf == null ? null : new File(etcResolvConf),
etcResolverDir == null ? null :new File(etcResolverDir).listFiles());
etcResolverDir == null ? null : new File(etcResolverDir).listFiles());
}
@Override
@ -121,7 +127,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
for (;;) {
int i = hostname.indexOf('.', 1);
if (i < 0 || i == hostname.length() - 1) {
return defaultNameServerAddresses != null ? defaultNameServerAddresses.stream() : null;
return defaultNameServerAddresses.stream();
}
DnsServerAddresses addresses = domainToNameServerStreamMap.get(hostname);
@ -133,9 +139,8 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
}
}
boolean mayOverrideNameServers() {
return !domainToNameServerStreamMap.isEmpty() ||
defaultNameServerAddresses != null && defaultNameServerAddresses.stream().next() != null;
private boolean mayOverrideNameServers() {
return !domainToNameServerStreamMap.isEmpty() || defaultNameServerAddresses.stream().next() != null;
}
private static Map<String, DnsServerAddresses> parse(File... etcResolverFiles) throws IOException {
@ -176,7 +181,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
port = Integer.parseInt(maybeIP.substring(i + 1));
maybeIP = maybeIP.substring(0, i);
}
addresses.add(new InetSocketAddress(SocketUtils.addressByName(maybeIP), port));
addresses.add(SocketUtils.socketAddress(maybeIP, port));
} else if (line.startsWith(DOMAIN_ROW_LABEL)) {
int i = indexOfNonWhiteSpace(line, DOMAIN_ROW_LABEL.length());
if (i < 0) {
@ -184,7 +189,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
" in file " + etcResolverFile + " value: " + line);
}
domainName = line.substring(i);
if (addresses != null && !addresses.isEmpty()) {
if (!addresses.isEmpty()) {
putIfAbsent(domainToNameServerStreamMap, domainName, addresses);
}
addresses = new ArrayList<InetSocketAddress>(2);
@ -199,7 +204,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
logger.info("row type {} not supported. ignoring line: {}", SORTLIST_ROW_LABEL, line);
}
}
if (addresses != null && !addresses.isEmpty()) {
if (!addresses.isEmpty()) {
putIfAbsent(domainToNameServerStreamMap, domainName, addresses);
}
} finally {
@ -217,7 +222,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
String domainName,
List<InetSocketAddress> addresses) {
// TODO(scott): sortlist is being ignored.
putIfAbsent(domainToNameServerStreamMap, domainName, DnsServerAddresses.shuffled(addresses));
putIfAbsent(domainToNameServerStreamMap, domainName, DnsServerAddresses.sequential(addresses));
}
private static void putIfAbsent(Map<String, DnsServerAddresses> domainToNameServerStreamMap,

94
resolver-dns/src/test/java/io/netty/resolver/dns/UnixResolverDnsServerAddressStreamProviderTest.java Normal file
View File

@ -0,0 +1,94 @@
/*
* Copyright 2017 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.util.CharsetUtil;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.TemporaryFolder;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import static org.junit.Assert.assertEquals;
public class UnixResolverDnsServerAddressStreamProviderTest {
@Rule
public final TemporaryFolder folder = new TemporaryFolder();
@Test
public void defaultLookupShouldReturnResultsIfOnlySingleFileSpecified() throws Exception {
File f = buildFile("domain linecorp.local\n" +
"nameserver 127.0.0.2\n" +
"nameserver 127.0.0.3\n");
UnixResolverDnsServerAddressStreamProvider p =
new UnixResolverDnsServerAddressStreamProvider(f, null);
DnsServerAddressStream stream = p.nameServerAddressStream("somehost");
assertHostNameEquals("127.0.0.2", stream.next());
assertHostNameEquals("127.0.0.3", stream.next());
}
@Test
public void defaultReturnedWhenNoBetterMatch() throws Exception {
File f = buildFile("domain linecorp.local\n" +
"nameserver 127.0.0.2\n" +
"nameserver 127.0.0.3\n");
File f2 = buildFile("domain squarecorp.local\n" +
"nameserver 127.0.0.4\n" +
"nameserver 127.0.0.5\n");
UnixResolverDnsServerAddressStreamProvider p =
new UnixResolverDnsServerAddressStreamProvider(f, f2);
DnsServerAddressStream stream = p.nameServerAddressStream("somehost");
assertHostNameEquals("127.0.0.2", stream.next());
assertHostNameEquals("127.0.0.3", stream.next());
}
@Test
public void moreRefinedSelectionReturnedWhenMatch() throws Exception {
File f = buildFile("domain linecorp.local\n" +
"nameserver 127.0.0.2\n" +
"nameserver 127.0.0.3\n");
File f2 = buildFile("domain dc1.linecorp.local\n" +
"nameserver 127.0.0.4\n" +
"nameserver 127.0.0.5\n");
UnixResolverDnsServerAddressStreamProvider p =
new UnixResolverDnsServerAddressStreamProvider(f, f2);
DnsServerAddressStream stream = p.nameServerAddressStream("myhost.dc1.linecorp.local");
assertHostNameEquals("127.0.0.4", stream.next());
assertHostNameEquals("127.0.0.5", stream.next());
}
private File buildFile(String contents) throws IOException {
File f = folder.newFile();
OutputStream out = new FileOutputStream(f);
try {
out.write(contents.getBytes(CharsetUtil.UTF_8));
} finally {
out.close();
}
return f;
}
private static void assertHostNameEquals(String expectedHostname, InetSocketAddress next) {
assertEquals("unexpected hostname: " + next, expectedHostname, next.getHostName());
}
}