The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Monday, July 05, 2021

It's still a sane library for decoding DNS packets, but now it's a sane library for encoding as well

It's software update day here at Chez Boca. In addition to an updated mod_blog, there's also an updated SPCDNS—version 2.0.0!

It only took about ten years (and about four years after it was first requested) but the library now supports full encoding of 30 DNS records. The reason I didn't include such support intially is that the encoding of DNS domain names in the records is not straightforward. It uses a scheme to compress the data such that it's easy to parse, but not so easy to encode without allocating memory which is something I wanted to avoid. A result is that there is a hardcoded limit to the number of domain names that can be encoded, but just how many domain names is … hard to say due to the compression scheme. And because of this, the encoding routine does use a bit more memory than it previously did.

That, and an API change with the Lua wrapper (returning an integer error number instead of a string error message) is why I decided to make this a 2.0.0 release. Users at the C level shouldn't see any change though.

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