Allow blocking calls when parsing etcResolver/hosts files (#11009)

Motivation:

When etcResolver/hosts files are parsed, FileInputStream.read(...) is internally called by

- UnixResolverDnsServerAddressStreamProvider#parseEtcResolverSearchDomains
- UnixResolverDnsServerAddressStreamProvider#parseEtcResolverOptions
- HostsFileParser#parse

This will cause the error below when BlockHound is enabled

reactor.blockhound.BlockingOperationError: Blocking call! java.io.FileInputStream#readBytes
     	at java.io.FileInputStream.readBytes(FileInputStream.java)
     	at java.io.FileInputStream.read(FileInputStream.java:255)

Modifications:

- Add whitelist entries to BlockHound configuration
- Fix typos in UnixResolverDnsServerAddressStreamProvider
- Add tests

Result:

Fixes #11004

common/src/main/java/io/netty/util/internal/Hidden.java

@@ -119,6 +119,18 @@ class Hidden {
                     "io.netty.resolver.dns.UnixResolverDnsServerAddressStreamProvider",
                     "parse");
 
+            builder.allowBlockingCallsInside(
+                    "io.netty.resolver.dns.UnixResolverDnsServerAddressStreamProvider",
+                    "parseEtcResolverSearchDomains");
+
+            builder.allowBlockingCallsInside(
+                    "io.netty.resolver.dns.UnixResolverDnsServerAddressStreamProvider",
+                    "parseEtcResolverOptions");
+
+            builder.allowBlockingCallsInside(
+                    "io.netty.resolver.HostsFileParser",
+                    "parse");
+
             builder.nonBlockingThreadPredicate(new Function<Predicate<Thread>, Predicate<Thread>>() {
                 @Override
                 public Predicate<Thread> apply(final Predicate<Thread> p) {

resolver-dns/src/main/java/io/netty/resolver/dns/UnixResolverDnsServerAddressStreamProvider.java

@@ -86,7 +86,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
      * the default DNS server to use, and also overrides for individual domains. Also parse list of files of the format
      * <a href="
      * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
-     * /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains.
+     * /etc/resolver</a> which may contain multiple files to override the name servers used for multiple domains.
      * @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
      * @param etcResolverFiles List of files of the format defined in
      * <a href="
@@ -121,7 +121,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
      * the default DNS server to use, and also overrides for individual domains. Also parse a directory of the format
      * <a href="
      * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
-     * /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains.
+     * /etc/resolver</a> which may contain multiple files to override the name servers used for multiple domains.
      * @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
      * @param etcResolverDir Directory containing files of the format defined in
      * <a href="
@@ -379,7 +379,7 @@ public final class UnixResolverDnsServerAddressStreamProvider implements DnsServ
                 } else if (line.startsWith(SEARCH_ROW_LABEL)) {
                     int i = indexOfNonWhiteSpace(line, SEARCH_ROW_LABEL.length());
                     if (i >= 0) {
-                        // May contain more then one entry, either seperated by whitespace or tab.
+                        // May contain more then one entry, either separated by whitespace or tab.
                         // See https://linux.die.net/man/5/resolver
                         String[] domains = WHITESPACE_PATTERN.split(line.substring(i));
                         Collections.addAll(searchDomains, domains);

transport-blockhound-tests/src/test/java/io/netty/util/internal/NettyBlockHoundIntegrationTest.java

@@ -26,6 +26,7 @@ import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.nio.NioDatagramChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
 import io.netty.handler.ssl.SslContext;
@@ -35,7 +36,7 @@ import io.netty.handler.ssl.SslHandshakeCompletionEvent;
 import io.netty.handler.ssl.SslProvider;
 import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
 import io.netty.handler.ssl.util.SelfSignedCertificate;
-import io.netty.resolver.dns.DnsServerAddressStreamProvider;
+import io.netty.resolver.dns.DnsNameResolverBuilder;
 import io.netty.resolver.dns.DnsServerAddressStreamProviders;
 import io.netty.util.HashedWheelTimer;
 import io.netty.util.ReferenceCountUtil;
@@ -59,6 +60,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Queue;
 import java.util.ServiceLoader;
+import java.util.concurrent.Callable;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
@@ -320,7 +322,30 @@ public class NettyBlockHoundIntegrationTest {
     }
 
     @Test(timeout = 5000L)
-    public void testParseEtcResolverFilesAllowsBlockingCalls() throws InterruptedException {
+    public void testUnixResolverDnsServerAddressStreamProvider_Parse() throws InterruptedException {
+        doTestParseResolverFilesAllowsBlockingCalls(DnsServerAddressStreamProviders::unixDefault);
+    }
+
+    @Test(timeout = 5000L)
+    public void testHostsFileParser_Parse() throws InterruptedException {
+        doTestParseResolverFilesAllowsBlockingCalls(DnsNameResolverBuilder::new);
+    }
+
+    @Test(timeout = 5000L)
+    public void testUnixResolverDnsServerAddressStreamProvider_ParseEtcResolverSearchDomainsAndOptions()
+            throws InterruptedException {
+        NioEventLoopGroup group = new NioEventLoopGroup();
+        try {
+            DnsNameResolverBuilder builder = new DnsNameResolverBuilder(group.next())
+                    .channelFactory(NioDatagramChannel::new);
+            doTestParseResolverFilesAllowsBlockingCalls(builder::build);
+        } finally {
+            group.shutdownGracefully();
+        }
+    }
+
+    private static void doTestParseResolverFilesAllowsBlockingCalls(Callable<Object> callable)
+            throws InterruptedException {
         SingleThreadEventExecutor executor =
                 new SingleThreadEventExecutor(null, new DefaultThreadFactory("test"), true) {
                     @Override
@@ -335,11 +360,11 @@ public class NettyBlockHoundIntegrationTest {
                 };
         try {
             CountDownLatch latch = new CountDownLatch(1);
-            List<DnsServerAddressStreamProvider> result = new ArrayList<>();
+            List<Object> result = new ArrayList<>();
             List<Throwable> error = new ArrayList<>();
             executor.execute(() -> {
                 try {
-                    result.add(DnsServerAddressStreamProviders.unixDefault());
+                    result.add(callable.call());
                 } catch (Throwable t) {
                     error.add(t);
                 }