Consider a trailing dot when resolve DNS with search domains #5963
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Motivation:
There was a report from LY internally where DNS resolver warns for `NXDomain`.
```
java.util.concurrent.CompletionException: java.lang.IllegalArgumentException: Empty label is not a legal name
at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315)
...
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver.resolve0(SearchDomainDnsResolver.java:99)
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver.resolve(SearchDomainDnsResolver.java:88)
at com.linecorp.armeria.internal.client.dns.HostsFileDnsResolver.resolve(HostsFileDnsResolver.java:130)
at com.linecorp.armeria.internal.client.dns.DefaultDnsResolver.resolveOne(DefaultDnsResolver.java:89)
at com.linecorp.armeria.internal.client.dns.DefaultDnsResolver.resolve(DefaultDnsResolver.java:81)
at com.linecorp.armeria.client.endpoint.dns.DnsEndpointGroup.sendQueries(DnsEndpointGroup.java:155)
at com.linecorp.armeria.client.endpoint.dns.DnsEndpointGroup.lambda$sendQueries$3(DnsEndpointGroup.java:173)
...
Caused by: java.lang.IllegalArgumentException: Empty label is not a legal name
at java.base/java.net.IDN.toASCIIInternal(IDN.java:284)
at java.base/java.net.IDN.toASCII(IDN.java:123)
at java.base/java.net.IDN.toASCII(IDN.java:152)
at com.linecorp.armeria.internal.client.dns.DnsQuestionWithoutTrailingDot.<init>(DnsQuestionWithoutTrailingDot.java:53)
at com.linecorp.armeria.internal.client.dns.DnsQuestionWithoutTrailingDot.of(DnsQuestionWithoutTrailingDot.java:48)
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver$SearchDomainQuestionContext.newQuestion(SearchDomainDnsResolver.java:190)
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver$SearchDomainQuestionContext.nextQuestion0(SearchDomainDnsResolver.java:177)
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver$SearchDomainQuestionContext.nextQuestion(SearchDomainDnsResolver.java:150)
at com.linecorp.armeria.internal.client.dns.SearchDomainDnsResolver.lambda$resolve0$1(SearchDomainDnsResolver.java:103)
... 19 common frames omitted
```
The NX domain has with a trailing dot and search domains starts with
`.`. As a result, `example.com..search.domain` was made and rejected by `java.net.IDN`
Modifications:
- Remove a leading dot from the normalized search domains.
- Infix a dot when a hostname does not have a trailing dot.
Result:
DNS resolver now correctly adds search domains for hostnames with trailing dots.
… into trailing-dot-searchdomain
- Stop to send queries with search domains when it was resovled. - Fix a bug where the original hostname was sent as the last query when the number of dots in a hostname >= `ndots`. - Explicitly set `ResolvedAddressTypes.IPV4_ONLY` to avoid flakyness.
minwoox
approved these changes
Nov 7, 2024
core/src/main/java/com/linecorp/armeria/internal/client/dns/DefaultDnsResolver.java
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Motivation:
There was a report from LY internally where DNS resolver warned for
NXDomainunexpectedly.The NX domain has a trailing dot and search domains start with a dot (
.).As a result,
example.com..search.domainwas made and rejected byjava.net.IDNModifications:
Result:
DNS resolver now correctly adds search domains for hostnames with trailing dots.