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/*
* Copyright 2021 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:
*
* https://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 com.datastax.oss.driver.shaded.netty.resolver;
import com.datastax.oss.driver.shaded.netty.util.NetUtil;
import com.datastax.oss.driver.shaded.netty.util.internal.PlatformDependent;
import com.datastax.oss.driver.shaded.netty.util.internal.logging.InternalLogger;
import com.datastax.oss.driver.shaded.netty.util.internal.logging.InternalLoggerFactory;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.regex.Pattern;
import static com.datastax.oss.driver.shaded.netty.util.internal.ObjectUtil.checkNotNull;
/**
* A container of hosts file entries
*/
public final class HostsFileEntriesProvider {
public interface Parser {
/**
* Parses the hosts file at standard OS location using the system default {@link Charset} for decoding.
*
* @return a new {@link HostsFileEntriesProvider}
* @throws IOException file could not be read
*/
HostsFileEntriesProvider parse() throws IOException;
/**
* Parses the hosts file at standard OS location using the given {@link Charset}s one after another until
* parse something or none is left.
*
* @param charsets the {@link Charset}s to try as file encodings when parsing
* @return a new {@link HostsFileEntriesProvider}
* @throws IOException file could not be read
*/
HostsFileEntriesProvider parse(Charset... charsets) throws IOException;
/**
* Parses the provided hosts file using the given {@link Charset}s one after another until
* parse something or none is left. In case {@link Charset}s are not provided,
* the system default {@link Charset} is used for decoding.
*
* @param file the file to be parsed
* @param charsets the {@link Charset}s to try as file encodings when parsing, in case {@link Charset}s
* are not provided, the system default {@link Charset} is used for decoding
* @return a new {@link HostsFileEntriesProvider}
* @throws IOException file could not be read
*/
HostsFileEntriesProvider parse(File file, Charset... charsets) throws IOException;
/**
* Performs the parsing operation using the provided reader of hosts file format.
*
* @param reader the reader of hosts file format
* @return a new {@link HostsFileEntriesProvider}
*/
HostsFileEntriesProvider parse(Reader reader) throws IOException;
/**
* Parses the hosts file at standard OS location using the system default {@link Charset} for decoding.
*
* @return a new {@link HostsFileEntriesProvider}
*/
HostsFileEntriesProvider parseSilently();
/**
* Parses the hosts file at standard OS location using the given {@link Charset}s one after another until
* parse something or none is left.
*
* @param charsets the {@link Charset}s to try as file encodings when parsing
* @return a new {@link HostsFileEntriesProvider}
*/
HostsFileEntriesProvider parseSilently(Charset... charsets);
/**
* Parses the provided hosts file using the given {@link Charset}s one after another until
* parse something or none is left. In case {@link Charset}s are not provided,
* the system default {@link Charset} is used for decoding.
*
* @param file the file to be parsed
* @param charsets the {@link Charset}s to try as file encodings when parsing, in case {@link Charset}s
* are not provided, the system default {@link Charset} is used for decoding
* @return a new {@link HostsFileEntriesProvider}
*/
HostsFileEntriesProvider parseSilently(File file, Charset... charsets);
}
/**
* Creates a parser for {@link HostsFileEntriesProvider}.
*
* @return a new {@link HostsFileEntriesProvider.Parser}
*/
public static Parser parser() {
return ParserImpl.INSTANCE;
}
static final HostsFileEntriesProvider EMPTY =
new HostsFileEntriesProvider(
Collections.>emptyMap(),
Collections.>emptyMap());
private final Map> ipv4Entries;
private final Map> ipv6Entries;
HostsFileEntriesProvider(Map> ipv4Entries, Map> ipv6Entries) {
this.ipv4Entries = Collections.unmodifiableMap(new HashMap>(ipv4Entries));
this.ipv6Entries = Collections.unmodifiableMap(new HashMap>(ipv6Entries));
}
/**
* The IPv4 entries.
*
* @return the IPv4 entries
*/
public Map> ipv4Entries() {
return ipv4Entries;
}
/**
* The IPv6 entries.
*
* @return the IPv6 entries
*/
public Map> ipv6Entries() {
return ipv6Entries;
}
private static final class ParserImpl implements Parser {
private static final String WINDOWS_DEFAULT_SYSTEM_ROOT = "C:\\Windows";
private static final String WINDOWS_HOSTS_FILE_RELATIVE_PATH = "\\system32\\drivers\\etc\\hosts";
private static final String X_PLATFORMS_HOSTS_FILE_PATH = "/etc/hosts";
private static final Pattern WHITESPACES = Pattern.compile("[ \t]+");
private static final InternalLogger logger = InternalLoggerFactory.getInstance(Parser.class);
static final ParserImpl INSTANCE = new ParserImpl();
private ParserImpl() {
// singleton
}
@Override
public HostsFileEntriesProvider parse() throws IOException {
return parse(locateHostsFile(), Charset.defaultCharset());
}
@Override
public HostsFileEntriesProvider parse(Charset... charsets) throws IOException {
return parse(locateHostsFile(), charsets);
}
@Override
public HostsFileEntriesProvider parse(File file, Charset... charsets) throws IOException {
checkNotNull(file, "file");
checkNotNull(charsets, "charsets");
if (charsets.length == 0) {
charsets = new Charset[]{Charset.defaultCharset()};
}
if (file.exists() && file.isFile()) {
for (Charset charset : charsets) {
BufferedReader reader = new BufferedReader(
new InputStreamReader(new FileInputStream(file), charset));
try {
HostsFileEntriesProvider entries = parse(reader);
if (entries != HostsFileEntriesProvider.EMPTY) {
return entries;
}
} finally {
reader.close();
}
}
}
return HostsFileEntriesProvider.EMPTY;
}
@Override
public HostsFileEntriesProvider parse(Reader reader) throws IOException {
checkNotNull(reader, "reader");
BufferedReader buff = new BufferedReader(reader);
try {
Map> ipv4Entries = new HashMap>();
Map> ipv6Entries = new HashMap>();
String line;
while ((line = buff.readLine()) != null) {
// remove comment
int commentPosition = line.indexOf('#');
if (commentPosition != -1) {
line = line.substring(0, commentPosition);
}
// skip empty lines
line = line.trim();
if (line.isEmpty()) {
continue;
}
// split
List lineParts = new ArrayList();
for (String s : WHITESPACES.split(line)) {
if (!s.isEmpty()) {
lineParts.add(s);
}
}
// a valid line should be [IP, hostname, alias*]
if (lineParts.size() < 2) {
// skip invalid line
continue;
}
byte[] ipBytes = NetUtil.createByteArrayFromIpAddressString(lineParts.get(0));
if (ipBytes == null) {
// skip invalid IP
continue;
}
// loop over hostname and aliases
for (int i = 1; i < lineParts.size(); i++) {
String hostname = lineParts.get(i);
String hostnameLower = hostname.toLowerCase(Locale.ENGLISH);
InetAddress address = InetAddress.getByAddress(hostname, ipBytes);
List addresses;
if (address instanceof Inet4Address) {
addresses = ipv4Entries.get(hostnameLower);
if (addresses == null) {
addresses = new ArrayList();
ipv4Entries.put(hostnameLower, addresses);
}
} else {
addresses = ipv6Entries.get(hostnameLower);
if (addresses == null) {
addresses = new ArrayList();
ipv6Entries.put(hostnameLower, addresses);
}
}
addresses.add(address);
}
}
return ipv4Entries.isEmpty() && ipv6Entries.isEmpty() ?
HostsFileEntriesProvider.EMPTY :
new HostsFileEntriesProvider(ipv4Entries, ipv6Entries);
} finally {
try {
buff.close();
} catch (IOException e) {
logger.warn("Failed to close a reader", e);
}
}
}
@Override
public HostsFileEntriesProvider parseSilently() {
return parseSilently(locateHostsFile(), Charset.defaultCharset());
}
@Override
public HostsFileEntriesProvider parseSilently(Charset... charsets) {
return parseSilently(locateHostsFile(), charsets);
}
@Override
public HostsFileEntriesProvider parseSilently(File file, Charset... charsets) {
try {
return parse(file, charsets);
} catch (IOException e) {
if (logger.isWarnEnabled()) {
logger.warn("Failed to load and parse hosts file at " + file.getPath(), e);
}
return HostsFileEntriesProvider.EMPTY;
}
}
private static File locateHostsFile() {
File hostsFile;
if (PlatformDependent.isWindows()) {
hostsFile = new File(System.getenv("SystemRoot") + WINDOWS_HOSTS_FILE_RELATIVE_PATH);
if (!hostsFile.exists()) {
hostsFile = new File(WINDOWS_DEFAULT_SYSTEM_ROOT + WINDOWS_HOSTS_FILE_RELATIVE_PATH);
}
} else {
hostsFile = new File(X_PLATFORMS_HOSTS_FILE_PATH);
}
return hostsFile;
}
}
}
