75 lines
2.5 KiB
OCaml
75 lines
2.5 KiB
OCaml
open Types
|
|
open Utils
|
|
|
|
let parse_header reader =
|
|
let max_size = 6 in
|
|
match List.init max_size (fun offset -> unpack_short_be reader.data (offset * 2)) with
|
|
| [ id; flags; num_questions; num_answers; num_authorities; num_additionals ] ->
|
|
( { reader with pointer = reader.pointer + (max_size * 2) }
|
|
, { id; flags; num_questions; num_answers; num_authorities; num_additionals } )
|
|
| _ -> failwith "Invalid number of fields"
|
|
;;
|
|
|
|
let rec parse_question reader =
|
|
let name, offset_name = decode_name_simple reader in
|
|
let data = bytes_forward reader.data (reader.pointer + offset_name) in
|
|
let max_size = 2 in
|
|
match List.init max_size (fun offset -> unpack_short_be data (offset * 2)) with
|
|
| [ type_; class_ ] ->
|
|
( { reader with pointer = reader.pointer + offset_name + (max_size * 2) }
|
|
, { name; type_; class_ } )
|
|
| _ -> failwith "Invalid number of fields"
|
|
|
|
and decode_name_simple reader =
|
|
let rec read_parts parts pos =
|
|
let length = int_of_char (Bytes.get reader.data (reader.pointer + pos)) in
|
|
if length = 0
|
|
then 1, parts
|
|
else if length land 0b1100_0000 <> 0
|
|
then (
|
|
let decoded_name = decode_compressed_name reader length in
|
|
length + 1, decoded_name :: parts)
|
|
else (
|
|
let part = Bytes.sub_string reader.data (reader.pointer + pos + 1) length in
|
|
let last_length, parts' = read_parts (parts @ [ part ]) (pos + 1 + length) in
|
|
last_length + length + 1, parts')
|
|
in
|
|
let offset, parts = read_parts [] 0 in
|
|
String.to_bytes (String.concat "." parts), offset
|
|
|
|
(*
|
|
---
|
|
def decode_compressed_name(length, reader):
|
|
pointer_bytes = bytes([length & 0b0011_1111]) + reader.read(1)
|
|
pointer = struct.unpack("!H", pointer_bytes)[0]
|
|
current_pos = reader.tell()
|
|
reader.seek(pointer)
|
|
result = decode_name(reader)
|
|
reader.seek(current_pos)
|
|
return result
|
|
---
|
|
*)
|
|
and decode_compressed_name _reader _length =
|
|
(* TODO *)
|
|
String.empty
|
|
;;
|
|
|
|
(*
|
|
---
|
|
def parse_record(reader):
|
|
name = decode_name_simple(reader)
|
|
# the the type, class, TTL, and data length together are 10 bytes (2 + 2 + 4 + 2 = 10)
|
|
# so we read 10 bytes
|
|
data = reader.read(10)
|
|
# HHIH means 2-byte int, 2-byte-int, 4-byte int, 2-byte int
|
|
type_, class_, ttl, data_len = struct.unpack("!HHIH", data)
|
|
data = reader.read(data_len)
|
|
return DNSRecord(name, type_, class_, ttl, data)
|
|
---
|
|
*)
|
|
let parse_record reader =
|
|
let name, _offset_name = decode_name_simple reader in
|
|
(* TODO *)
|
|
let type_, class_, ttl, data = 0, 0, 0, Bytes.empty in
|
|
{ name; type_; class_; ttl; data }
|
|
;;
|