use of a reader so we always store the full data content when parsing response, using a pointer logic

This commit is contained in:
Mylloon 2023-06-14 18:41:43 +02:00
parent 7a5fd1e472
commit 4951920f67
Signed by: Anri
GPG key ID: A82D63DFF8D1317F
3 changed files with 21 additions and 13 deletions

View file

@ -3,9 +3,9 @@ open Dnstoy
let () = let () =
let response = Network.send_request "8.8.8.8" "www.example.com" in let response = Network.send_request "8.8.8.8" "www.example.com" in
print_endline (Utils.get_bytecode response); print_endline (Utils.get_bytecode response);
let response', dns_header = Response.parse_header response in let reader, dns_header = Response.parse_header { data = response; pointer = 0 } in
let response'', dns_question = Response.parse_question response' in let reader', dns_question = Response.parse_question reader in
let dns_record = Response.parse_record response'' in let dns_record = Response.parse_record reader' in
Debug.print_dns_header dns_header; Debug.print_dns_header dns_header;
Debug.print_dns_question dns_question; Debug.print_dns_question dns_question;
Debug.print_dns_record dns_record Debug.print_dns_record dns_record

View file

@ -3,36 +3,39 @@ open Utils
let parse_header reader = let parse_header reader =
let max_size = 6 in let max_size = 6 in
match List.init max_size (fun offset -> unpack_short_be reader (offset * 2)) with 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 ] -> | [ id; flags; num_questions; num_answers; num_authorities; num_additionals ] ->
( bytes_forward reader (max_size * 2) ( { reader with pointer = reader.pointer + (max_size * 2) }
, { id; flags; num_questions; num_answers; num_authorities; num_additionals } ) , { id; flags; num_questions; num_answers; num_authorities; num_additionals } )
| _ -> failwith "Invalid number of fields" | _ -> failwith "Invalid number of fields"
;; ;;
let rec parse_question reader = let rec parse_question reader =
let reader', name_b = decode_name_simple reader in let name, offset_name = decode_name_simple reader in
let name = String.to_bytes name_b in let data = bytes_forward reader.data (reader.pointer + offset_name) in
let max_size = 2 in let max_size = 2 in
match List.init max_size (fun offset -> unpack_short_be reader' (offset * 2)) with match List.init max_size (fun offset -> unpack_short_be data (offset * 2)) with
| [ type_; class_ ] -> bytes_forward reader' (max_size * 2), { name; type_; class_ } | [ type_; class_ ] ->
( { reader with pointer = reader.pointer + offset_name + (max_size * 2) }
, { name; type_; class_ } )
| _ -> failwith "Invalid number of fields" | _ -> failwith "Invalid number of fields"
and decode_name_simple reader = and decode_name_simple reader =
let rec read_parts parts pos = let rec read_parts parts pos =
let length = int_of_char (Bytes.get reader pos) in let length = int_of_char (Bytes.get reader.data (reader.pointer + pos)) in
if length = 0 if length = 0
then 1, parts then 1, parts
else ( else (
let part = Bytes.sub_string reader (pos + 1) length in 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 let last_length, parts' = read_parts (parts @ [ part ]) (pos + 1 + length) in
last_length + length + 1, parts') last_length + length + 1, parts')
in in
let offset, parts = read_parts [] 0 in let offset, parts = read_parts [] 0 in
bytes_forward reader offset, String.concat "." parts String.to_bytes (String.concat "." parts), offset
;; ;;
let parse_record _reader = let parse_record _reader =
let name, type_, class_, ttl, data = Bytes.empty, 0, 0, 0, Bytes.empty in let name, _offset_name = Bytes.empty, 0 (* decode_name_simple reader *) in
let type_, class_, ttl, data = 0, 0, 0, Bytes.empty in
{ name; type_; class_; ttl; data } { name; type_; class_; ttl; data }
;; ;;

View file

@ -20,3 +20,8 @@ type dns_record =
; ttl : int ; ttl : int
; data : bytes ; data : bytes
} }
type reader =
{ data : bytes
; pointer : int
}