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 can just use Objects.requireNonNull(...) as a replacement for ObjectUtil.checkNotNull(....)
Modifications:
- Use Objects.requireNonNull(...)
Result:
Less code to maintain.
Motivation:
We can use lambdas now as we use Java8.
Modification:
use lambda function for all package, #8751 only migrate transport package.
Result:
Code cleanup.
Motivation:
As netty 4.x supported Java 6 we had various if statements to check for java versions < 8. We can remove these now.
Modification:
Remove unnecessary if statements that check for java versions < 8.
Result:
Cleanup code.
Motivation:
We can use the diamond operator these days.
Modification:
Use diamond operator whenever possible.
Result:
More modern code and less boiler-plate.
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:
ByteBuf supports “marker indexes”. The intended use case for these is if a speculative operation (e.g. decode) is in process the user can “mark” and interface and refer to it later if the operation isn’t successful (e.g. not enough data). However this is rarely used in practice,
requires extra memory to maintain, and introduces complexity in the state management for derived/pooled buffer initialization, resizing, and other operations which may modify reader/writer indexes.
Modifications:
Remove support for marking and adjust testcases / code.
Result:
Fixes https://github.com/netty/netty/issues/8535.
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.
* 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.
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 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:
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 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:
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.
