UodeMCU UDP DNS Query Format

Question

I look at this example from an involuntary portal built on the NodeMCU platform, and I'm trying to understand how DNS queries work. (Corresponding file dns-liar.lua). I have more or less decoded what an answer is, but I don’t know what each part of it does, and I can’t find any online resources that show a similar package structure.

NodeMCU Node IP:

a.b.c.d

Request:

|A|B| ... |(13th byte) \0 terminated string (str)| ...

Answer: (bytes separated by "|")

| A | B | x80 | x00 | x00 | x01 | x00 | x01 | x00 | x00 | x00 | x00 | str | x00 | x01 | x00 | x01 | xC0 | x0C | x00 | x01 | x00 | x01 | x00 | x00 | x03 | x00 | x00 | x04 | a | b | c | d |

I understand that str, most likely, the domain to search for abcdis just NodeMCU responding to each request with its own IP address, but I'm not sure what any of the other bytes do.

Answer 1

Phew! It is always difficult when people decide to pre-prepare almost the whole package, especially when it covers several subsections of the RFC.

, CaptiveIntraweb DNS. PR , , , . ( DNS-), , :

• - ,
• 10 , .. (..._ str1).
• X ,
• 4 - (/), 14 - NAME, //ttl/ (..._ str2).
• , IP- node.