[dnsdist] What is so magical on \044

[Marco Davids (SIDN)]

Hi there,

I spent too much time on this, but at least I was able to crunch it down 
to something easily reproducible.

Here's the situation:

function bugornot(dq)
   dq.dh:setAA(true)
   return DNSAction.SpoofRaw, 
"\0441234567890abcdefghijklmnopqrstuvwxyzABCDEFGH"
end

addAction(AndRule({QNameRule('bugornot.singlens.forfun.net.'), 
QClassRule(DNSClass.IN), QTypeRule(DNSQType.TXT)}), LuaAction(bugornot))

The length of the string in the TXT record is 44 bytes. The result is a 
malformed packet (the length-byte is not included).

When it is 43 bytes, or 45 bytes, this setup works. But when it is 44 
buts (',' in ASCII, perhaps that matters?), it fails.

A demonstrator can be found here (at least at the time of writing):

dig -p 530 TXT bugornot.singlens.forfun.net @li1.forfun.net

It runs on DNSdist 1.7.2.

Is this a bug perhaps?

-- 
Marco

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