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From "Enrique Rodriguez (JIRA)" <>
Subject [jira] Commented: (DIRSERVER-831) Proposed protocol-dns changes
Date Mon, 29 Jan 2007 20:04:49 GMT


Enrique Rodriguez commented on DIRSERVER-831:

Binary test PDU's for MX-QUERY and MX-RESPONSE were applied and the unit tests were enabled.

Patch applied:

Binary PDU's added and tests enabled:

> Proposed protocol-dns changes
> -----------------------------
>                 Key: DIRSERVER-831
>                 URL:
>             Project: Directory ApacheDS
>          Issue Type: Improvement
>          Components: dns
>            Reporter: Richard Wallace
>         Assigned To: Enrique Rodriguez
>         Attachments: MX-QUERY.pdu, MX-RESPONSE.pdu, MX-TRAFFIC.libpcap, patch.diff
> Hello,
> Here are the first set of changes I'd like to contribute to the
> protocol-dns subproject.  Here's a list of things I've done.
> 1) Converted the enumeration types ServiceType, ProtocolType,
> RecordClass, OpCode, RecordType, MessageType and ResponseCode into
> actual Java 5 enums.  Because we need to encode and decode the actual
> values we can't rely on the ordinals the compiler will assign to them,
> so I've used a technique I found on the Java Specialists site
> (, to
> efficiently do a conversion between enums and values with minimal code
> duplication.
> 2) Removed QuestionRecords and ResourceRecords classes since they were
> really just type-safe wrappers around Lists and replaced their usage
> with generic Lists.
> 3) Moved any encoding and decoding code that was in the MINA
> ProtocolEncoder and ProtocolDecoder to classes in the
> and io.decoder packages called DnsMessageEncoder
> and DnsMessageDecoder, respectively.
> 4) Removed the dependency by the encoders and decoders in the
> packages on MINA.  The only thing they really used were
> the ByteBuffers from MINA and it was a pretty simple task to just switch
> to java.nio.ByteBuffers instead.  The only hurdle I had to overcome was
> in the allocation of temporary buffers for things like enecoding domain
> names, which leads me to...
> 5) Instead of creating (or having to pull them from the MINA ByteBuffer
> pool) several ByteBuffers during encoding, I simply wrote directly to
> the buffer that was passed in.  From what I could tell, the main reason
> for allocating the temporary buffers was to do the actual encoding of
> the domain name, get the byte array that was written to the buffer,
> write the length of the data to the actual ByteBuffer, then write the
> byte array from the temporary ByteBuffer.  Instead, what I did was to
> record the position of the ByteBuffer, increment it by one, write the
> data (the domain name for instance), find the difference between the
> starting position + 1 and the current position, then go back to the
> starting position and write the length of the data and finally jump back
> to the end of the data and go onto the next bit of encoding.  This
> should be more efficient because we're not constantly having to get
> ByteBuffers from a pool or have new ones allocated, and we also don't
> have to then create byte arrays and have the data from those temporary
> ByteBuffers read into the byte arrays.
> 6) Moved all the (get|put)Unsigned(Byte|Short|Int) methods into a
> utility class called ByteBufferUtil.
> 7) Changed the DnsMessage.transactionId property to be an int because it
> actually needs to be an unsigned short.
> 8) Fixed a bug with decoding domain names when they are compressed.  The
> new position to jump to wasn't being calculated right all the time. 
> There also seemed to be an assumption that the first thing to do after
> jumping was to read a label, but it could be the case that the new
> position is another jump so we need to call recurseDomainName() right
> after doing the jump in position.
> 9) Updated existing tests to actually check that what is encoded and
> decoded are correct.  For this I also had to add equals() and hashCode()
> methods to classes that didn't already have them, like DnsMessage,
> ResourceRecordImpl, and others.  I simply used the commons-lang equals
> and hashCode builders for this because I've found them to be
> tremendously useful for this in the past.
> 10) Added additional test for MX query and response parsing.  I used the
> MX records from
> 11) Added decoders to make the tests added in (10) pass.  these are the
> IPv6RecordDecoder, MailExchangeRecordDecoder, AddressRecordDecoder, and
> NameServerRecordDecoder.
> That should cover it all.  I'd like to add a few more decoders for
> things like TXT and SOA records.  That should cover about 90% of the
> records in use on most DNS servers.
> Then I'd like to get things separated a little bit more and create
> subprojects within protocol-dns.  I'm thinking something like
> protocol-dns/
>   core/
>   mina-shared/
>   server/
>     shared/
>     mina/
>     store/
>   client/
> core would contain all the DNS message and record types as well as the
> decoders and encoders in right now.  mina-shared would contain
> the ProtocolCodec stuff in dns.protocol.
> server/shared would contain the DnsConfiguration and other stuff that
> would be shard among server implementations, whether they use MINA or
> some other IO framework and whether they use ApacheDS for the store or
> some other backend like Bind zone files.
> server/mina would contain the DnsProtocolHandler from dns.protocol as
> well as the DnsServer class itself. 
> server/store would contain the the backend store type stuff.  It would
> probably wind up being separate subprojects itself, one for LDAP, JDBC,
> or Bind zone files.
> client would obviously contain any code for developers to generate and
> send queries to dns servers, and maybe an implementation of the dig
> command line tool.
> I wouldn't mind actually seeing this becoming a separate project of it's
> own, like  That would be really cool.
> What do you think of these changes?

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