Motivation:
We should just ignore (and so skip) invalid entries in /etc/resolver.conf.
Modifications:
- Skip invalid entries
- Add unit test
Result:
Fix https://github.com/netty/netty/issues/9684
Motivation
A memory leak related to DNS resolution was reported in #9634,
specifically linked to the TCP retry fallback functionality that was
introduced relatively recently. Upon inspection it's apparent that there
are some error paths where the original UDP response might not be fully
released, and more significantly the TCP response actually leaks every
time on the fallback success path.
It turns out that a bug in the unit test meant that the intended TCP
fallback path was not actually exercised, so it did not expose the main
leak in question.
Modifications
- Fix DnsNameResolverTest#testTruncated0 dummy server fallback logic to
first read transaction id of retried query and use it in replayed
response
- Adjust semantic of internal DnsQueryContext#finish method to always
take refcount ownership of passed in envelope
- Reorder some logic in DnsResponseHandler fallback handling to verify
the context of the response is expected, and ensure that the query
response are either released or propagated in all cases. This also
reduces a number of redundant retain/release pairings
Result
Fixes#9634
Motivation:
Classes `AbstractHttp2StreamChannel.Http2StreamChannelConfig`
and `DnsNameResolver.AddressedEnvelopeAdapter` may be static:
it doesn't reference its enclosing instance.
Modification:
Add `static` modifier.
Result:
Prevents a possible memory leak and uses less memory per class instance.
Motivation:
We currently try to access the the domain search list via reflection on windows which will print a illegal access warning when using Java9 and later.
Modifications:
Add a guard against the used java version.
Result:
Fixes https://github.com/netty/netty/issues/9500.
Motivation:
It is possible that the user uses a too big EDNS0 setting for the MTU and so we may receive a truncated datagram packet. In this case we should try to detect this and retry via TCP if possible
Modifications:
- Fix detecting of incomplete records
- Mark response as truncated if we did not consume the whole packet
- Add unit test
Result:
Fixes https://github.com/netty/netty/issues/9365
Motivation:
We should only ever close the underlying tcp socket once we received the envelope to ensure we never race in the test.
Modifications:
- Only close socket once we received the envelope
- Set REUSE_ADDR
Result:
More robust test
Motivation:
testTruncatedWithTcpFallback was flacky as we may end up closing the socket before we could read all data. We should only close the socket after we succesfully read all data.
Modifications:
Move socket.close() to finally block
Result:
Fix flaky test and so make the CI more stable again.
Motivation:
We should only try to use reflection to access default nameservers when using Java8 and lower as otherwise we will produce an Illegal reflective access warning like:
WARNING: Illegal reflective access by io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider
Modifications:
Add Java version check before try to use reflective access.
Result:
No more warning when Java9+ is used.
Motivation:
OOME is occurred by increasing suppressedExceptions because other libraries call Throwable#addSuppressed. As we have no control over what other libraries do we need to ensure this can not lead to OOME.
Modifications:
Only use static instances of the Exceptions if we can either dissable addSuppressed or we run on java6.
Result:
Not possible to OOME because of addSuppressed. Fixes https://github.com/netty/netty/issues/9151.
Motivation:
Sometimes DNS responses can be very large which mean they will not fit in a UDP packet. When this is happening the DNS server will set the TC flag (truncated flag) to tell the resolver that the response was truncated. When a truncated response was received we should allow to retry via TCP and use the received response (if possible) as a replacement for the truncated one.
See https://tools.ietf.org/html/rfc7766.
Modifications:
- Add support for TCP fallback by allow to specify a socketChannelFactory / socketChannelType on the DnsNameResolverBuilder. If this is set to something different then null we will try to fallback to TCP.
- Add decoder / encoder for TCP
- Add unit tests
Result:
Support for TCP fallback as defined by https://tools.ietf.org/html/rfc7766 when using DnsNameResolver.
Motivation:
https://github.com/netty/netty/pull/9021 did apply some changes to filter out duplicates InetAddress when calling resolveAll(...) to mimic JDK behaviour. Unfortunally this also introduced a regression as we should not filter duplicates when the user explicit calls resolveAll(DnsQuestion).
Modifications:
- Only filter duplicates if resolveAll(String) is used
- Add unit test
Result:
Fixes regressions introduces by https://github.com/netty/netty/pull/9021
Motivation:
075cf8c02e introduced a change to allow resolve(...) to notify as soon as the preferred record was resolved. This works great but we should also allow the user to configure that we want to do the same for resolveAll(...), which means we should be able to notify as soon as all records for a preferred record were resolved.
Modifications:
- Add a new DnsNameResolverBuilder method to allow configure this (use false as default to not change default behaviour)
- Add unit test
Result:
Be able to speed up resolving.
Motivation:
At the moment resolve(...) does just delegate to resolveAll(...) and so will only notify the future once all records were resolved. This is wasteful as we are only interested in the first record anyway. We should notify the promise as soon as one record that matches the preferred record type is resolved.
Modifications:
- Introduce DnsResolveContext.isCompleteEarly(...) to be able to detect once we should early notify the promise.
- Make use of this early detecting if resolve(...) is called
- Remove FutureListener which could lead to IllegalReferenceCountException due double releases
- add unit test
Result:
Be able to notify about resolved host more quickly.
Motivation:
We did not correctly calculate the new ttl as we did forget to add `this.`
Modifications:
Add .this and so correctly calculate the TTL
Result:
Use correct TTL for authoritative nameservers when updating these.
Motivation:
To closely mimic what the JDK does we should not try to resolve AAAA records if the system itself does not support IPv6 at all as it is impossible to connect to this addresses later on. In this case we need to use ResolvedAddressTypes.IPV4_ONLY.
Modifications:
Add static method to detect if IPv6 is supported and if not use ResolvedAddressTypes.IPV4_ONLY.
Result:
More consistent behaviour between JDK and our resolver implementation.
Motivation:
At the moment we basically drop all non prefered addresses when calling DnsNameResolver.resolveAll(...). This is just incorrect and was introduced by 4cd39cc4b3. More correct is to still retain these but sort the returned List to have the prefered addresses on the beginning of the List. This also ensures resolve(...) will return the correct return type.
Modifications:
- Introduce PreferredAddressTypeComperator which we use to sort the List so it will contain the preferred address type first.
- Add unit test to verify behaviour
Result:
Include not only preferred addresses in the List that is returned by resolveAll(...)
Motivation:
During investigating some other bug I noticed that we log with warn level if we fail to notify the promise due the fact that it is already full-filled. This is not correct and missleading as there is nothing wrong with it in general. A promise may already been fullfilled because we did multiple queries and one of these was successful.
Modifications:
- Change log level to trace
- Add unit test which before did log with warn level but now does with trace level.
Result:
Less missleading noise in the log.
Motivation:
DnsNameResolver#resolveAll(String) may return duplicate results in the event that the original hostname DNS response includes an IP address X and a CNAME that ends up resolving the same IP address X. This behavior is inconsistent with the JDK’s resolver and is unexpected to retrun a List with duplicate entries from a resolveAll(..) call.
Modifications:
- Filter out duplicates
- Add unit test
Result:
More consistent and less suprising behavior
Motivation:
We did not have any unit tests that queries for TXT records.
Modifications:
Add unit test to query TXT records.
Result:
More test-coverage.
Motivation:
When using multiple nameservers and a nameserver respond with NXDOMAIN we should only fail the query if the nameserver in question is authoritive or no nameservers are left to try.
Modifications:
- Try next nameserver if NXDOMAIN was returned but the nameserver is not authoritive
- Adjust testcase to respect correct behaviour.
Result:
Fixes https://github.com/netty/netty/issues/8261
Motivation:
We do not correctly detect loops when follow CNAMEs and so may try to follow it without any success.
Modifications:
- Correctly detect CNAME loops
- Do not cache CNAME entries which point to itself
- Add unit test.
Result:
Fixes https://github.com/netty/netty/issues/8687.
Motivation:
Andoid does not contain javax.naming.* so we should not try to use it to prevent a NoClassDefFoundError on init.
Modifications:
Only try to use javax.naming.* to retrieve nameservers when not using Android.
Result:
Fixes https://github.com/netty/netty/issues/8654.
Motivation:
Most of the maven modules do not explicitly declare their
dependencies and rely on transitivity, which is not always correct.
Modifications:
For all maven modules, add all of their dependencies to pom.xml
Result:
All of the (essentially non-transitive) depepdencies of the modules are explicitly declared in pom.xml
Motivation:
Some of transports support gathering writes when using datagrams. For example this is the case for EpollDatagramChannel. We should minimize the calls to flush() to allow making efficient usage of sendmmsg in this case.
Modifications:
- minimize flush() operations when we query for multiple address types.
- reduce GC by always directly schedule doResolveAll0(...) on the EventLoop.
Result:
Be able to use sendmmsg internally in the DnsNameResolver.
Motivation:
We should refresh the DNS configuration each 5 minutes to be able to detect changes done by the user. This is inline with what OpenJDK is doing
Modifications:
Refresh config every 5 minutes.
Result:
Be able to consume changes made by the user.
Motivation:
It should be possible to build a DnsNameResolver with a null resolvedAddressTypes, defaulting then to DEFAULT_RESOLVE_ADDRESS_TYPES (see line 309).
Sadly, `preferredAddressType` is then called on line 377 with the original parameter instead of the instance attribute, causing an NPE when it's null.
Modification:
Call preferredAddressType with instance attribuet instead of constructor parameter.
Result:
No more NPE
Motivation:
ba594bcf4a added a utility to parse searchdomains defined in /etc/resolv.conf but did not correctly handle the case when multiple are defined that are seperated by either whitespace or tab.
Modifications:
- Correctly parse multiple entries
- Add unit test.
Result:
Correctly parse multiple searchdomain entries.
* Use AuthoritativeDnsServerCache for creating the new redirect stream.
Motivation:
At the moment if a user wants to provide custom sorting of the nameservers used for redirects it needs to be implemented in two places. This is more complicated as it needs to be.
Modifications:
- Just delegate to the AuthoritativeDnsServerCache always as we fill it before we call newRedirectDnsServerStream anyway.
Result:
Easier way for the user to implement custom sorting.
* Add cache for CNAME mappings resolved during lookup of DNS entries.
Motivation:
If the CNAMEd hostname is backed by load balancing component, typically the final A or AAAA DNS records have small TTL. However, the CNAME record itself is setup with longer TTL.
For example:
* x.netty.io could be CNAMEd to y.netty.io with TTL of 5 min
* A / AAAA records for y.netty.io has a TTL of 0.5 min
In current Netty implementation, original hostname is saved in resolved cached with the TTL of final A / AAAA records. When that cache entry expires, Netty recursive resolver sends at least two queries — 1st one to be resolved as CNAME record and the 2nd one to resolve the hostname in CNAME record.
If CNAME record was cached, only the 2nd query would be needed most of the time. 1st query would be needed less frequently.
Modifications:
Add a new CnameCache that will be used to cache CNAMEs and so may reduce queries.
Result:
Less queries needed when CNAME is used.
Motivation
Applications should not depend on internal packages with Java 9 and later. This cause a warning now, but will break in future versions of Java.
Modification
This change adds methods to UnixResolverDnsServerAddressStreamProvider (following after #6844) that parse /etc/resolv.conf for domain and search entries. Then DnsNameResolver does not need to rely on sun.net.dns.ResolverConfiguration to do this.
Result
Fixes#8318. Furthermore, at least in my testing with Java 11, this also makes multiple search entries work properly (previously I was only getting the first entry).
Motivation:
We should not try to cast the Channel to a DatagramChannel as this will cause a ClassCastException.
Modifications:
- Do not cast
- rethrow from constructor if we detect the registration failed.
- Add unit test.
Result:
Propagate correct exception.
Motiviation:
We incorrectly did ignore NS servers during redirect which had no ADDITIONAL record. This could at worse have the affect that we failed the query completely as none of the NS servers had a ADDITIONAL record. Beside this using a DnsCache to cache authoritative nameservers does not work in practise as we we need different features and semantics when cache these servers (for example we also want to cache unresolved nameservers and resolve these on the fly when needed).
Modifications:
- Correctly take NS records into account that have no matching ADDITIONAL record
- Correctly handle multiple ADDITIONAL records for the same NS record
- Introduce AuthoritativeDnsServerCache as a replacement of the DnsCache when caching authoritative nameservers + adding default implementation
- Add an adapter layer to reduce API breakage as much as possible
- Replace DnsNameResolver.uncachedRedirectDnsServerStream(...) with newRedirectDnsServerStream(...)
- Add unit tests
Result:
Our DnsResolver now correctly handle redirects in all cases.
Motivation:
We are currently always remove all entries from the cache for a hostname if the lowest TTL was reached but schedule one for each of the cached entries. This is wasteful.
Modifications:
- Reimplement logic to schedule TTL to only schedule a new removal task if the requested TTL was actual lower then the one for the already scheduled task.
- Ensure we only remove from the internal map if we did not replace the Entries in the meantime.
Result:
Less overhead in terms of scheduled tasks for the DefaultDnsCache
Motivation:
We should ensure we return the same cached entries for the hostname and hostname ending with dot. Beside this we also should use it for the searchdomains as well.
Modifications:
- Internally always use hostname with a dot as a key and so ensure we correctly handle it in the cache.
- Also query the cache for each searchdomain
- Add unit tests
Result:
Use the same cached entries for hostname with and without trailing dot. Query the cache for each searchdomain query as well
Motivation:
55fec94592 fixed a bug where we did not correctly clear all caches when the resolver was closed but did not add a testcase.
Modifications:
Add testcase.
Result:
More tests.
Motivation:
DnsNameResolver manages search domains and will retry the request with the different search domains provided to it. However if the query results in an invalid hostname, the Future corresponding to the resolve request will never be completed.
Modifications:
- If a resolve attempt results in an invalid hostname and the query isn't issued we should fail the associated promise
Result:
No more hang from DnsNameResolver if search domain results in invalid hostname.
Motivation:
At the moment we only clear the resolveCache when the Channel is closed. We should also do the same for the authoritativeDnsServerCache.
Modifications:
Add authoritativeDnsServerCache.clear() to the Channel closeFuture.
Result:
Correctly clear all caches.
Motivation:
We did not handle the case when the query was cancelled which could lead to an exhausted id space. Beside this we did not not cancel the timeout on failed promises.
Modifications:
- Do the removal of the id from the manager in a FutureListener so its handled in all cases.
- Cancel the timeout whenever the original promise was full-filled.
Result:
Fixes https://github.com/netty/netty/issues/8013.
Motivation:
Whenever we fail the query we should also remove the id from the DnsQueryContextManager.
Modifications:
Remove the id from the DnsQueryContextManager if we fail the query because the channel failed to become active.
Result:
More correct code.
Motivation:
At the moment if you do a resolveAll and at least one A / AAAA record is present we will not follow any CNAMEs that are also present. This is different to how the JDK behaves.
Modifications:
- Allows follow CNAMEs.
- Add unit test.
Result:
Fixes https://github.com/netty/netty/issues/7915.
Motivation:
a598c3b69b added a upper limit for ttl but missed to also do the same for minTtl.
Modifications:
- Add upper limit for minTtl
- Add testcase.
Result:
No more IllegalArgumentException possible.
Motivation:
Due a bug we did never store more then one address per hostname in DefaultDnsCache.
Modifications:
- Correctly store multiple entries per hostname
- Add tests
Result:
DefaultDnsCache correctly stores more then one entry. Also fixes https://github.com/netty/netty/issues/7882 .
Motivation:
In b47fb81799 we limited the max supported delay to match what our internal implementat can support. Because of this it was possible that DefaultDnsCache produced an IllegalArgumentException when it tried to schedule a expiration > 3 years.
Modifications:
Limit the max supported TTL to 2 years which is safe for all our EventLoop implementations.
Result:
No more exceptions when adding records to the cache with a huge TTL.
Motivation:
Right now to customize DNS name resolver when using DnsAddressResolverGroup
one should subclass implementation and override newNameResolver method when
in fact it's possible to collect all settings in a DnsNameResolverBuilder
instance. Described in #7749.
Modifications:
- Added new constructor for DnsNameResolverBuilder in order to delay
EventLoop specification
- Added copy() method to DnsNameResolverBuilder to provide an immutable
copy of the builder
- Added new single-argument constructor for DnsAddressResolverGroup and
RoundRobinDnsAddressResolverGroup accepting DnsNameResolverBuilder
instance
- DnsAddressResolverGroup to build a new resolver using DnsNameResolverBuilder
given instead of creating a new one
- Test cases to check that changing channelFactory after the builder was passed
to create a DnsNameResolverGroup would not propagate to the name resolver
Result:
Much easier to customize DNS settings w/o subclassing DnsAddressResolverGroup
Motivation:
Currently, if a DNS server returns a non-preferred address type before the preferred one, then both will be returned as the result, and when only taking a single one, this usually ends up being the non-preferred type. However, the JDK requires lookups to only return the preferred type when possible to allow for backwards compatibility.
To allow a client to be able to resolve the appropriate address when running on a machine that does not support IPv6 but the DNS server returns IPv6 addresses before IPv4 addresses when querying.
Modification:
Filter the returned records to the expected type when both types are present.
Result:
Allows a client to run on a machine with IPv6 disabled even when a server returns both IPv4 and IPv6 results. Netty-based code can be a drop-in replacement for JDK-based code in such circumstances.
This PR filters results before returning them to respect JDK expectations.
* Add DnsNameResolver.resolveAll(DnsQuestion)
Motivation:
A user is currently expected to use DnsNameResolver.query() when he or
she wants to look up the full DNS records rather than just InetAddres.
However, query() only performs a single query. It does not handle
/etc/hosts file, redirection, CNAMEs or multiple name servers.
As a result, such a user has to duplicate all the logic in
DnsNameResolverContext.
Modifications:
- Refactor DnsNameResolverContext so that it can send queries for
arbitrary record types.
- Rename DnsNameResolverContext to DnsResolveContext
- Add DnsAddressResolveContext which extends DnsResolveContext for
A/AAAA lookup
- Add DnsRecordResolveContext which extends DnsResolveContext for
arbitrary lookup
- Add DnsNameResolverContext.resolveAll(DnsQuestion) and its variants
- Change DnsNameResolverContext.resolve() delegates the resolve request
to resolveAll() for simplicity
- Move the code that decodes A/AAAA record content to DnsAddressDecoder
Result:
- Fixes#7795
- A user does not have to duplicate DnsNameResolverContext in his or her
own code to implement the usual DNS resolver behavior.
Motivation:
When we do DNS queries we need to ensure we always release the AddressEnvelope.
Modifications:
Also release the AddressEnvelope if the original resolution was done in the meantime and we did not cancel the extra query yet.
Result:
Should fix [#7713]
