Commit Graph

152 Commits

Author SHA1 Message Date
jimin
9621a5b981 remove unused imports (#9287)
Motivation:

Some imports are not used

Modification:

remove unused imports

Result:

Code cleanup
2019-06-26 21:08:31 +02:00
Norman Maurer
9dd1aab482
Fix flaky DnsNameResolverTest.testTruncatedWithTcpFallback (#9262)
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.
2019-06-21 09:28:51 +02:00
Norman Maurer
9c6365ee95
Only try to use reflection to access default nameservers when using Java8 and lower (#9157)
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.
2019-05-18 08:21:33 +02:00
Norman Maurer
f17bfd0f64
Only use static Exception instances when we can ensure addSuppressed … (#9152)
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.
2019-05-17 22:23:02 +02:00
Norman Maurer
1672b6d12c
Add support for TCP fallback when we receive a truncated DnsResponse (#9139)
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.
2019-05-17 14:37:11 +02:00
Norman Maurer
6ee8b651e6
DnsNameResolver.resolveAll(DnsQuestion) should not try to filter duplicates (#9141)
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
2019-05-13 06:59:06 +02:00
Norman Maurer
df20a125aa
Allow to have DnsNameResolver.resolveAll(...) notify as soon as the preferred records were resolved (#9136)
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.
2019-05-09 08:06:52 +02:00
Norman Maurer
075cf8c02e
DnsNameResolver.resolve(...) should notify future as soon as one preferred record was resolved (#9050)
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.
2019-04-15 21:42:04 +02:00
Norman Maurer
4b36a5b08b
Correctly calculate ttl for AuthoritativeNameServer when update existing records (#9051)
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.
2019-04-15 21:41:04 +02:00
Norman Maurer
dde3f561bc
Use ResolvedAddressTypes.IPV4_ONLY in DnsNameResolver by default if n… (#9048)
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.
2019-04-15 13:07:05 +02:00
Norman Maurer
26cd59c328
DnsNameResolver.resolveAll(...) should also contain non preferred addresses (#9044)
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(...)
2019-04-15 10:19:54 +02:00
Norman Maurer
c0d3444f6d
DnsNameResolver should log in trace level if notification of the promise fails (#9022)
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.
2019-04-10 07:13:53 +02:00
Norman Maurer
e63c596f24
DnsNameResolver.resolveAll(...) should not include duplicates (#9021)
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
2019-04-09 09:44:23 +02:00
Norman Maurer
0ee067082b
Add unit test for query TXT records. (#8923)
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.
2019-03-09 21:41:28 +01:00
Norman Maurer
df5eb060f7
Only handle NXDOMAIN as failure when nameserver is authoritive or no other nameservers are left. (#8731)
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
2019-01-18 21:06:44 +01:00
Norman Maurer
82ec6ba815
Correctly detect and handle CNAME loops. (#8691)
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.
2019-01-14 08:17:44 +01:00
kashike
6fdd7fcddb Fix minor spelling issues in javadocs (#8701)
Motivation:

Javadocs contained some spelling errors, we should fix these.

Modification:

Fix spelling

Result:

Javadoc cleanup.
2019-01-14 07:24:34 +01:00
Norman Maurer
a3844da10b
NoClassDefFoundError on Android platform when try to use DefaultDnsServerAddressStreamProvider. (#8656)
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.
2018-12-14 21:31:21 +01:00
Norman Maurer
d728a72e74
Combine flushes in DnsNameResolver to allow usage of sendmmsg to reduce syscall costs (#8470)
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.
2018-11-21 06:42:40 +01:00
Norman Maurer
cb0d23923f
Refresh DNS configuration each 5 minutes. (#8468)
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.
2018-11-16 10:37:29 +01:00
Stephane Landelle
f4cf674f01 Fix NPE when trying to build a DnsNameResolver with a null resolvedAddressTypes (#8445)
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
2018-10-30 13:15:16 +01:00
Norman Maurer
2a4bb346cf
Correctly parse /etc/resolv.conf when contain multiple entries for searchdomain. (#8351)
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.
2018-10-12 05:00:32 +02:00
Norman Maurer
b81c8ed55c
Use AuthoritativeDnsServerCache for creating the new redirect stream. (#8316)
* 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.
2018-09-27 19:45:58 +02:00
Norman Maurer
5650db5826
Add cache for CNAME mappings resolved during lookup of DNS entries. (#8314)
* 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.
2018-09-27 17:05:35 +02:00
Matt Ayres
ba594bcf4a Fixed illegal reflective access by not relying on a sun.net.dns class. (#8318) (#8319)
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).
2018-09-26 20:55:46 +02:00
Norman Maurer
9eb124bb62
Don't cause ClassCastException if registration fails during constructing DnsNameResolver. (#8280)
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.
2018-09-11 20:34:37 +02:00
Norman Maurer
bbb6e126b1
Correctly handle DNS redirects for NS servers that have no ADDITIONAL record (#8177)
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.
2018-08-22 17:49:22 +02:00
Norman Maurer
2fa7a0aa57
Keep the amount of scheduled tasks for DefaultDnsCache at a minimum (#8187)
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
2018-08-15 09:07:13 +02:00
Norman Maurer
f22781f176
Correctly handle hostnames with and without trailing dot in the DefaultDnsCache and use it for searchdomains. (#8181)
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
2018-08-10 08:53:59 +02:00
Norman Maurer
56eb1e92cc
Add tests to verify caches are cleared when the resolver is closed. (#8186)
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.
2018-08-10 08:46:15 +02:00
Scott Mitchell
b3b04d0de2 DnsNameResolver hangs if search domain results in invalid hostname (#8180)
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.
2018-08-08 08:14:18 +02:00
Norman Maurer
55fec94592
Also clear the authoritativeDnsServerCache when closing the Channel. (#8174)
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.
2018-08-06 08:31:17 +02:00
Norman Maurer
83710cb2e1
Replace toArray(new T[size]) with toArray(new T[0]) to eliminate zero-out and allow the VM to optimize. (#8075)
Motivation:

Using toArray(new T[0]) is usually the faster aproach these days. We should use it.

See also https://shipilev.net/blog/2016/arrays-wisdom-ancients/#_conclusion.

Modifications:

Replace toArray(new T[size]) with toArray(new T[0]).

Result:

Faster code.
2018-06-29 07:56:04 +02:00
Norman Maurer
a214f2eb96 Remove id from DnsQueryContextManager whenever the promise is fullfilled.
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.
2018-06-27 10:20:59 +02:00
Norman Maurer
5e42e758be Also remove the id from the DnsQueryContextManager if query fails due parent Channel activation error.
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.
2018-06-26 07:22:41 +02:00
Norman Maurer
369d64c3e6
Always follow cnames even if a matching A or AAAA record was found. (#7919)
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.
2018-05-09 13:48:20 +02:00
Norman Maurer
f01a590154
Enfore upper limit for minTtl when using DefaultCacheEntry. (#7920)
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.
2018-05-09 08:57:20 +02:00
Norman Maurer
18b170bd7a
Cleanup resolver-dns test code. (#7916)
Motivation:

We had some stuff that could be cleaned up in the resolver-dns test classes.

Modifications:

Cleanup code.

Result:

Cleaner code.
2018-05-08 08:55:17 +02:00
Norman Maurer
d03bd44e9d
Add test for caching failed queries in DefaultDnsCache. (#7909)
Motivation:

We had no test that validated the handling of caching failures for DefaultDnsCache.

Modifications:

Add testcase.

Result:

More tests FTW.
2018-05-04 20:09:38 +02:00
Norman Maurer
b83328606f
DefaultDnsCache should store more then one Entry per hostname. (#7906)
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 .
2018-05-04 14:19:26 +02:00
Norman Maurer
a598c3b69b
Enforce sane upper limit for TTL in DefaultDnsCache. (#7907)
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.
2018-05-04 13:38:08 +02:00
Alexey Kachayev
c0ae5e697c DnsAddressResolverGroup to use pluggable DnsNameResolverBuilder (#7793)
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
2018-04-26 08:04:01 +02:00
Anuraag Agrawal
4cd39cc4b3 Filter DNS results so they only contain the expected type when multiple types are present. (#7875)
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.
2018-04-19 10:52:22 +02:00
Trustin Lee
cd4594d292 Add DnsNameResolver.resolveAll(DnsQuestion) (#7803)
* 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.
2018-03-29 22:01:25 +02:00
Norman Maurer
c6c0984b8e Ensure we always release the AddressEnvelope when doing DNS queries.
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]
2018-02-20 12:06:21 +01:00
Shohei Kamimori
73f23c5faa Fix typos in docs.
Motivation:

There are same typos in the docs.

Modifications:

Fix typos. Docs only changing.

Result:

More correct docs.
2018-02-14 08:44:07 +01:00
Scott Mitchell
46e66b45bd DnsNameResovlerContext#followCname sending extra queries
Motivation:
When following a CNAME response DnsNameResovlerContext may issue a A and AAAA query. However the DnsNameResolverContext would have already issued a A and AAAA query to get the CNAME response, and this may result in 2 additional A/AAAA queries per CNAME response.

Modifications:
- DnsNameResovlerContext#followCname shouldn't issue 2 queries, but instead just a single query with the same record type as the original query

Result:
No more duplicate queries as a result of CNAME responses.
2018-02-02 07:46:10 +01:00
Scott Mitchell
5257ec49ec DnsNameResolverContext reuse of DnsServerAddressStream without duplicate
Motivation:
DnsServerAddressStream provides an iterator like interface but maybe expected to start at a specific point upon each new usage. If a DnsServerAddressStream is re-used in multiple independent iterations the order of iteration maybe incorrect. DnsNameResolverContext has a fallback DnsServerAddressStream reference if the cache doesn't contain a hit, but it is shared across multiple independent iterations. This may lead to undesirable DNS query order.

Modifications:
- DnsNameResolverContext#getNameServers should duplicate the default DnsServerAddressStream

Result:
Consistent iteration over the default DnsServerAddressStream in DnsNameResolverContext.
2018-02-02 07:24:11 +01:00
Scott Mitchell
fe5c69bdd9 DnsNameResolverContext#followCname only uses first name server
Motivation:
When following a CNAME it is possible there are multiple name servers to query against. However DnsNameResolverContext#followCname explicitly only uses the first name server address when attempting the query. This may lead to resolution failures because we didn't try all the available name servers.

Modifications:
DnsNameResolverContext#followCname should not just try the first name server, but it should try all name servers

Result:
More complete CNAME resolution.
2018-02-01 09:31:07 +01:00
Norman Maurer
b874edbf65 DefaultDnsCache should expire all records per hostname when one TTL is reached.
Motivation:

At the moment DefaultDnsCache will expire each record dependong on its own TTL. This may result in unexpected results for the end-user especially if the user for example uses IPV4_PREFERED but the cached AAAA records has a higher TTL then the A records and so the A record was removed. In this case we would only return the AAAA record and not even try to refresh.

Modifications:

Always expire all records for a hostname when one TTL is reached.

Result:

Fixes [#7329]
2018-01-31 14:39:31 +01:00