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HADOOP-18087. fix bug when getting CNAME chain records and no record from remote dns server #3911

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HADOOP-18087. fix bug when getting CNAME chain records and no record from remote dns server #3911

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21 changes: 16 additions & 5 deletions ...ject/hadoop-registry/src/main/java/org/apache/hadoop/registry/server/dns/RegistryDNS.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1127,18 +1127,28 @@ private byte remoteLookup(Message response, Name name, int type,

// Always add any CNAMEs to the response first
if (type != Type.CNAME) {
Record[] cnameAnswers = getRecords(name, Type.CNAME);
if (cnameAnswers != null) {
Name targetName = name;
// support for CNAME chaining
for (int i = iterations; i < 6; i++) {
Record[] cnameAnswers = getRecords(targetName, Type.CNAME);
if (cnameAnswers == null) {
break;
}
for (Record cnameR : cnameAnswers) {
if (!response.findRecord(cnameR)) {
response.addRecord(cnameR, Section.ANSWER);
targetName = ((CNAMERecord) cnameR).getTarget();
}
}
}
}

// Forward lookup to primary DNS servers
Record[] answers = getRecords(name, type);
// no answer
if (answers == null) {
return Rcode.NOERROR;
}
try {
for (Record r : answers) {
if (!response.findRecord(r)) {
Expand All @@ -1148,10 +1158,11 @@ private byte remoteLookup(Message response, Name name, int type,
response.addRecord(r, Section.ANSWER);
}
}
if (r.getType() == Type.CNAME) {
Name cname = r.getName();
// when desired type is CNAME, don't follow CNAME chain
if (type != Type.CNAME && r.getType() == Type.CNAME) {
if (iterations < 6) {
remoteLookup(response, cname, type, iterations + 1);
Name cname = ((CNAMERecord) r).getTarget();
return remoteLookup(response, cname, type, iterations + 1);
}
}
}
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