Motivation:
DnsCache (an interface) is coupled to DnsCacheEntry (a final class). This means that DnsCache implementations can't implement their own DnsCacheEntry objects if the default behavior isn't appropriate.
Modifications:
- DnsCacheEntry should be moved to DefaultDnsCache as it is an implementation detail
- DnsCache#cache(..) should return a new DnsCacheEntry
- The methods which from DnsCacheEntry that were used outside the scope of DefaultDnsCache should be moved into an interface
Result:
DnsCache is more extensible and not tightly coupled to a default implementation of DnsCacheEntry.
Motivation:
To be able to build with latest java9 release we need to adjust commons-lang version and maven-enforcer-plugin.
Modifications:
- Use commons-lang 2.6.0
- Use maven-enforcer-plugin 3.0.0.M1 when building with java9
Result:
Netty builds again with latest java9 release
Motivation:
We should not use ipv4 google dns servers if the app is configured to run ipv6.
Modifications:
Use either ipv4 or ipv6 dns servers depending on the system config.
Result:
More correct behaviour
Motivation:
When the hostname portion can not be extracted we should just skip the server as otherwise we will produce and exception when trying to create the InetSocketAddress.
This was happing when trying to run the test-suite on a system and using java7:
java.lang.IllegalArgumentException: hostname can't be null
at java.net.InetSocketAddress.checkHost(InetSocketAddress.java:149)
at java.net.InetSocketAddress.<init>(InetSocketAddress.java:216)
at io.netty.util.internal.SocketUtils$10.run(SocketUtils.java:171)
at io.netty.util.internal.SocketUtils$10.run(SocketUtils.java:168)
at java.security.AccessController.doPrivileged(Native Method)
at io.netty.util.internal.SocketUtils.socketAddress(SocketUtils.java:168)
at io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider.<clinit>(DefaultDnsServerAddressStreamProvider.java:74)
at io.netty.resolver.dns.DnsServerAddressesTest.testDefaultAddresses(DnsServerAddressesTest.java:39)
Modifications:
Skip if hostname can not be extracted.
Result:
No more java.lang.ExceptionInInitializerError.
Motivation:
JNDI allows to specify an port so we should respect it.
Modifications:
Use the specified port and if none is specifed use 53.
Result:
Correct handling of JNDI configured DNS.
Motivation:
DnsNameResolverTest has been observed to timeout on the CI servers. We should increase the timeout from 5 seconds to 30 seconds.
Modifications:
- Increase timeout from 5 to 30 seconds.
Result:
Less false failures due to slower CI machines.
Motivation:
The DNS resolver may use default configuration inherited from the environment. This means the ndots value may change and result in test failure if the tests don't explicitly set the assumed value.
Modifications:
- Explicitly set ndots in resolver-dns unit tests so we don't fail if the environment overrides the search domain and ndots
Result:
Unit tests are less dependent upon the enviroment they run in.
Fixes https://github.com/netty/netty/issues/6966.
Motivation:
UnixResolverDnsServerAddressStreamProvider currently throws an exception if /etc/resolver exists but it empty. This shouldn't be an exception and can be tolerated as if there is no contribution from /etc/resolver.
Modifications:
- Treat /etc/resolver as present and empty the same as not being present
Result:
UnixResolverDnsServerAddressStreamProvider initialization can tolerate empty /etc/resolver directory.
Motivation:
InetSocketAddress#getHostName() may attempt a reverse lookup which may lead to test failures because the expected address will not match.
Modifications:
- Use InetSocketAddress#getHostString() which will not attempt any lookups and instead return the original String
Result:
UnixResolverDnsServerAddressStreamProviderTest is more reliable.
Motivation:
If there are multiple DNS servers to query Java's DNS resolver will attempt to resolve A and AAAA records in sequential order and will terminate with a failure once all DNS servers have been exhausted. Netty's DNS server will share the same DnsServerAddressStream for the different record types which may send the A question to the first host and the AAAA question to the second host. Netty's DNS resolution also may not progress to the next DNS server in all situations and doesn't have a means to know when resolution has completed.
Modifications:
- DnsServerAddressStream should support new methods to allow the same stream to be used to issue multiple queries (e.g. A and AAAA) against the same host.
- DnsServerAddressStream should support a method to determine when the stream will start to repeat, and therefore a failure can be returned.
- Introduce SequentialDnsServerAddressStreamProvider for sequential use cases
Result:
Fixes https://github.com/netty/netty/issues/6926.
Motivation:
ba80fbbe05 modified the UnknownHostException to not include the search domain if the DNS query failed, but this masks what DNS query actually failed. Have the full hostname (including the search domain) provides more visibility and may help diagnose a configuration error if queries are unexpectedly failing.
Modifications:
- Remove DnsNameResolverContext#pristineHostname
Result:
UnknownHostException is more accurate and reflect what hostname actually resulted in failure.
Motivation:
DnsQueryLifecycleObserver is designed to capture the life cycle of every query. DnsNameResolverContext has a custom trace mechanism which consists of a StringBuilder and manual calls throughout the class. We can remove some special case code in DnsNameResolverContext and instead use a special implementation of DnsQueryLifecycleObserver when trace is enabled.
Modifications:
- Remove all references to the boolean trace variables in DnsNameResolverContext and DnsNameResolver
- Introduce TraceDnsQueryLifecycleObserver which will be used when trace is enabled and will log similar data as what trace currently provides
Result:
Less special case code in DnsNameResolverContext and instead delegate to TraceDnsQueryLifecycleObserver to capture trace information.
Motivation:
The DNS resolver supports search domains. However the ndots are not correctly enforced. The search domain should only be appended under the following scenario [1]:
> Resolver queries having fewer than ndots dots (default is 1) in them will be attempted using each component of the search path in turn until a match is found.
The DNS resolver current appends the search domains if ndots is 0 which should never happen (because no domain can have less than 0 dots).
[1] https://linux.die.net/man/5/resolv.conf
Modifications:
- Parse /etc/resolv.conf to get the default value for ndots on Unix platforms
- The search domain shouldn't be used if ndots is 0
- Avoid failing a promise to trigger the search domain queries in DnsNameResolverContext#resolve
Result:
More correct usage of search domains in the DNS resolver.
Fixes https://github.com/netty/netty/issues/6844.
Motivation:
It’s currently complicated to extend `DnsNameResolver` as the default
value for `searchDomain` is package private.
Modifications:
* let `DnsNameResolver` accept a null `searchDomains` and then default
to `DEFAULT_SEARCH_DOMAINS`, just like it’s being done with
`resolvedAddressTypes`.
* set default `DnsNameResolverBuilder#searchDomains` value to null to
avoid cloning internal `DnsNameResolver.DEFAULT_SEARCH_DOMAINS` in
`DnsNameResolver` constructor.
Result:
More versatile `DnsNameResolver` constructor.
No array copy when using default search domains.
Motivation:
UnixResolverDnsServerAddressStreamProvider allows the default name server address stream to be null, but there should always be a default stream to fall back to ([1] Search Strategy).
UnixResolverDnsServerAddressStreamProvider currently shuffles the names servers are multiple are present, but the defined behavior is to try them sequentially [2].
[1] Search Strategy Section - https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html
[2] DESCRIPTION/nameserver Section - https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html
Modifications:
- UnixResolverDnsServerAddressStreamProvider should always use the first file provided to derive the default domain server address stream. Currently if there are multiple domain names in the file identified by the first argument of the constructor then one will be selected at random.
- UnixResolverDnsServerAddressStreamProvider should return name servers sequentially.
- Reduce access level on some methods which don't have known use-cases externally.
Result:
Fixes https://github.com/netty/netty/issues/6736
Motivation:
IDN.toUnicode(...) removes trailing dots when used in Java7 while it not does on java8.
Modifications:
Check if we should test with the trailing dot removed or not.
Result:
Test pass on Java7 as well.
Motivation:
A single DNS query may follow many different paths through resolver-dns. The query may fail for various reasons related to the DNS protocol, general IO errors, it may be cancelled due to the query count being exceeded, or other reasons. A query may also result in other queries as we follow the DNS protocol (e.g. redirects, CNAME, etc...). It is currently impossible to collect information about the life cycle of an individual query though resolver-dns. This information may be valuable when considering which DNS servers are preferred over others.
Modifications:
- Introduce an interface which can provide visibility into all the potential outcomes of an individual DNS query
Result:
resolver-dns provides visibility into individual DNS queries which can be used to avoid poorly performing DNS servers.
Motivation:
1. The use of InternetProtocolFamily is not consistent:
the DnsNameResolverContext and DnsNameResolver contains switches
instead of appropriate methods usage.
2. The InternetProtocolFamily class contains redundant switches in the
constructor.
Modifications:
1. Replacing switches to the use of an appropriate methods.
2. Simplifying the InternetProtocolFamily constructor.
Result:
Code is cleaner and simpler.
Motivation:
Using reflection to obtain the default name servers may fail in Java9 and also in previous Java versions if a SecurityManager is present.
Modifications:
Try using jndi-dns to obtain default name servers and only try using reflection if this fails.
Result:
Be able to detect default name servers in all cases. Fixes [#6347].
Motivation:
DnsServerAddresses loads the default DNS servers used for DNS resolution in a static initialization block. This is subject to blocking and may cause unexpected delays. We can move this initialization to DefaultDnsServerAddressStreamProvider where it is more expected to load the JDK's default configuration.
Modifications:
- Move all the static initialization from DnsServerAddresses to DefaultDnsServerAddressStreamProvider
- Deprecate static methods in DnsServerAddresses which have moved to DefaultDnsServerAddressStreamProvider
- Remove usage of deprecated methods in DnsServerAddresses
Result:
Usage of JDK's blocking DNS resolver is not required to use resolver-dns.
Motivation:
DnsNameResolverContext completes its DNS query promise automatically
when no queries are in progress, which means there's no need to fail the
promise explicitly.
Modifications:
- Do not fail a DNS query promise explicitly but add an informational
trace
Result:
- Fixes#6600
- Unexpected exception on one question type does not fail the promise
too soon. If the other question succeeds, the query will succeed,
making the resolver more robust.
Motivation:
Recently DnsServerAddressStreamProvider was introduced to allow control for each query as to which DNS server should be used for resolution to respect the local host's default DNS server configuration. However resolver-dns also accepts a stream of DNS servers to use by default, but this stream is not host name aware. This creates an ambiguity as to which method is used to determine the DNS server to user during resolution, and in which order. We can remove this ambiguity and provide a more general API by just supporting DnsServerAddressStreamProvider.
Modifications:
- Remove the fixed DnsServerAddresses and instead only accept a DnsServerAddressStreamProvider.
- Add utility methods to help use DnsServerAddressStreamProvider for a single entry, a list of entries, and get the default for the current machine.
Result:
Fixes https://github.com/netty/netty/issues/6573.
Motivation:
We have our own ThreadLocalRandom implementation to support older JDKs . That said we should prefer the JDK provided when running on JDK >= 7
Modification:
Using ThreadLocalRandom implementation of the JDK when possible.
Result:
Make use of JDK implementations when possible.
Motivation:
54c9ecf682 introduced a unit tests which attempted to exclude addresses which resolved to loop back addresses from an assert statement. This was done with a static check for localhost but depending on machine configuration it is possible for other interfaces to be resolved.
Modifications:
- Use InetAddress#isLoopbackAddress() instead of string match on localhost
Result:
DnsNameResolverTest#testNameServerCache is more reliable.
Motivation:
The JDK uses gethostbyname for blocking hostname resoltuion. gethostbyname can be configured on Unix systems according to [1][2]. This may impact the name server that is used to resolve particular domains or just override the default fall-back resolver. DnsNameResolver currently ignores these configuration files which means the default resolution behavior is different than the JDK. This may lead to unexpected resolution failures which succeed when using the JDK's resolver.
Modifications:
- Add an interface which can override what DnsServerAddressStream to use for a given hostname
- Provide a Unix specific implementation of this interface and implement [1][2]. Some elements may be ignored sortlist, timeout, etc...
Result:
DnsNameResolver behaves more like the JDK resolver by default.
[1] https://linux.die.net/man/5/resolver
[2] https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html
Motivation:
HostsFileParser only retains the first address for each given hostname.
This is wrong, and it’s allowed to have both an IPv4 and an IPv6.
Modifications:
* Have `HostsFileParser` now return a `HostsFileEntries` that contains IPv4 entries and IPv6 entries
* Introduce `ResolvedAddressTypes` to describe resolved address types preferences
* Add a new `ResolvedAddressTypes` parameter to `HostsFileEntriesResolver::address` to account for address types preferences
* Change `DnsNameResolver` constructor to take a `ResolvedAddressTypes`, allowing for a null value that would use default
* Change `DnsNameResolverBuilder::resolvedAddressTypes` to take a `ResolvedAddressTypes`
* Make `DnsNameResolver::resolvedAddressTypes` return a `ResolvedAddressTypes`
* Add a static `DnsNameResolverBuilder::computeResolvedAddressTypes` to ease converting from `InternetProtocolFamily`
Result:
We now support hosts files that contains IPv4 and IPv6 pairs for a same
hostname.
Motivation:
a416b79 introduced a check for null or empty host name to be compatible with the JDK resolution. However the doResolve(String, Promise) method, and if the doResolve(String, DnsRecord[], Promise, DnsCache) method was overridden the empty/null hostname would not be correctly resolved.
Modifications:
- Move the empty/null host name check into the lowest level doResolve method in DnsNameResolver
- Remove the duplicate logic in InetNameResolver.java which can be bypassed anyways
Result:
By default (unless behavior is overridden) DnsNameResolver resolves null/empty host names to local host just like the JDK.
Motivation:
We need to ensure we release the AddressedEnvelope if we fail to notify the future (as it may be notified before because of an timeout). Otherwise we may leak.
Modifications:
Call release() if we fail to notify the future.
Result:
No more memory leak on notify failure.
Motivation:
DnsNameResolver does not handle recursive DNS and so fails if you query a DNS server (for example a ROOT dns server) which provides the correct redirect for a domain.
Modification:
Add support for redirects (a.k.a. handling of AUTHORITY section').
Result:
Its now possible to use a DNS server that redirects.
Motivation:
DnsNameResolver will return the domain / host name as ascii code using punycode (https://tools.ietf.org/html/rfc3492). This is different to what the JDK does which always convert it to unicode. We should do the same by default but allow to also not do it.
Modifications:
- Add new builder method on DnsNameResolverBuilder which allow to disable / enable converting. Default is to convert just like the JDK does.
- Add unit tests for it.
Result:
DnsNameResolver and JDK impl behave the same way.
Motivation:
When an empty hostname is used in DnsNameResolver.resolve*(...) it will never notify the future / promise. The root cause is that we not correctly guard against errors of IDN.toASCII(...) which will throw an IllegalArgumentException when it can not parse its input. That said we should also handle an empty hostname the same way as the JDK does and just use "localhost" when this happens.
Modifications:
- If the try to resolve an empty hostname we use localhost
- Correctly guard against errors raised by IDN.toASCII(...) so we will always noify the future / promise
- Add unit test.
Result:
DnsNameResolver.resolve*(...) will always notify the future.
