Package org.xbill.DNS

Class DohResolver

java.lang.Object

org.xbill.DNS.DohResolverCommon

org.xbill.DNS.DohResolver

All Implemented Interfaces:

Resolver

public final class DohResolver
extends DohResolverCommon

Proof-of-concept DNS over HTTP (DoH) resolver. This class is not suitable for high load scenarios because of the shortcomings of Java's built-in HTTP clients. For more control, implement your own Resolver using e.g. OkHttp.

On Java 8, it uses HTTP/1.1, which is against the recommendation of RFC 8484 to use HTTP/2 and thus slower. On Java 11 or newer, HTTP/2 is always used, but the built-in HttpClient has its own issues with connection handling.

As of 2020-09-13, the following limits of public resolvers for HTTP/2 were observed:

https://cloudflare-dns.com/dns-query: max streams=250, idle timeout=400s

https://dns.google/dns-query: max streams=100, idle timeout=240s

Since:

3.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	DohResolver.SendAndGetMessageBytesResponse

Field Summary

Fields

Modifier and Type	Field	Description
private final SSLSocketFactory	sslSocketFactory

Fields inherited from class org.xbill.DNS.DohResolverCommon

APPLICATION_DNS_MESSAGE, defaultExecutor, lastRequest, maxConcurrentRequests, queryOPT, timeout, tsig, uriTemplate, usePost

Constructor Summary

Constructors

Constructor	Description
DohResolver(String uriTemplate)	Creates a new DoH resolver that performs lookups with HTTP GET and the default timeout (5s).
DohResolver(String uriTemplate, int maxConcurrentRequests, Duration idleConnectionTimeout)	Creates a new DoH resolver that performs lookups with HTTP GET and the default timeout (5s).

Method Summary

Modifier and Type	Method	Description
private void	discardStream(InputStream es)
protected <T> CompletableFuture<T>	failedFuture(Throwable e)
private DohResolver.SendAndGetMessageBytesResponse	sendAndGetMessageBytes(String url, byte[] queryBytes, long startTime)
CompletionStage<Message>	sendAsync(Message query)	Asynchronously sends a message using the default ForkJoinPool.commonPool().
CompletionStage<Message>	sendAsync(Message query, Executor executor)	Asynchronously sends a message.
void	setEDNS(int version, int payloadSize, int flags, List<EDNSOption> options)	Sets the EDNS information on outgoing messages.

Methods inherited from class org.xbill.DNS.DohResolverCommon

getExecutor, getNanoTime, getTimeout, getUriTemplate, getUrl, isUsePost, prepareQuery, setExecutor, setIgnoreTruncation, setPort, setTCP, setTimeout, setTSIGKey, setUriTemplate, setUsePost, timeoutFailedFuture, timeoutFailedFuture, toString, verifyTSIG

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.xbill.DNS.Resolver

send, sendAsync, setEDNS, setEDNS, setTimeout, setTimeout

Field Details

sslSocketFactory

private final SSLSocketFactory sslSocketFactory

Constructor Details

DohResolver

public DohResolver(String uriTemplate)

Creates a new DoH resolver that performs lookups with HTTP GET and the default timeout (5s).

Parameters:

uriTemplate - the URI to use for resolving, e.g. https://dns.google/dns-query

DohResolver

public DohResolver(String uriTemplate,
 int maxConcurrentRequests,
 Duration idleConnectionTimeout)

Creates a new DoH resolver that performs lookups with HTTP GET and the default timeout (5s).

Parameters:

uriTemplate - the URI to use for resolving, e.g. https://dns.google/dns-query

maxConcurrentRequests - Maximum concurrent HTTP/2 streams for Java 11+ or HTTP/1.1 connections for Java 8. On Java 8 this cannot exceed the system property http.maxConnections.

idleConnectionTimeout - Max. idle time for HTTP/2 connections until a request is serialized. Applies to Java 11+ only.

Since:

3.3

Method Details

setEDNS

public void setEDNS(int version,
 int payloadSize,
 int flags,
 List<EDNSOption> options)

Sets the EDNS information on outgoing messages.

Specified by:

setEDNS in interface Resolver

Overrides:

setEDNS in class DohResolverCommon

Parameters:

version - The EDNS version to use. 0 indicates EDNS0 and -1 indicates no EDNS.

payloadSize - ignored

flags - EDNS extended flags to be set in the OPT record.

options - EDNS options to be set in the OPT record

See Also:

• OPTRecord

sendAsync

public CompletionStage<Message> sendAsync(Message query)

Description copied from interface: Resolver

Asynchronously sends a message using the default ForkJoinPool.commonPool().

The default implementation calls the deprecated Resolver.sendAsync(Message, ResolverListener). Implementors must override at least one of the sendAsync methods or a stack overflow will occur.

Parameters:

query - The query to send.

Returns:

A future that completes when the query is finished.

sendAsync

public CompletionStage<Message> sendAsync(Message query,
 Executor executor)

Description copied from interface: Resolver

Asynchronously sends a message.

The default implementation calls the deprecated Resolver.sendAsync(Message, ResolverListener). Implementors must override at least one of the sendAsync methods or a stack overflow will occur.

Parameters:

query - The query to send.

executor - The service to use for async operations.

Returns:

A future that completes when the query is finished.

sendAndGetMessageBytes

private DohResolver.SendAndGetMessageBytesResponse sendAndGetMessageBytes(String url,
 byte[] queryBytes,
 long startTime)
                                                                   throws IOException,
URISyntaxException

Throws:

IOException

URISyntaxException

discardStream

private void discardStream(InputStream es)
                    throws IOException

Throws:

IOException

failedFuture

protected <T> CompletableFuture<T> failedFuture(Throwable e)

Specified by:

failedFuture in class DohResolverCommon