use of a reader so we always store the full data content when parsing response, using a pointer logic
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3 changed files with 21 additions and 13 deletions
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@ -3,9 +3,9 @@ open Dnstoy
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let () =
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let response = Network.send_request "8.8.8.8" "www.example.com" in
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print_endline (Utils.get_bytecode response);
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let response', dns_header = Response.parse_header response in
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let response'', dns_question = Response.parse_question response' in
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let dns_record = Response.parse_record response'' in
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let reader, dns_header = Response.parse_header { data = response; pointer = 0 } in
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let reader', dns_question = Response.parse_question reader in
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let dns_record = Response.parse_record reader' in
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Debug.print_dns_header dns_header;
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Debug.print_dns_question dns_question;
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Debug.print_dns_record dns_record
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@ -3,36 +3,39 @@ open Utils
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let parse_header reader =
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let max_size = 6 in
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match List.init max_size (fun offset -> unpack_short_be reader (offset * 2)) with
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match List.init max_size (fun offset -> unpack_short_be reader.data (offset * 2)) with
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| [ id; flags; num_questions; num_answers; num_authorities; num_additionals ] ->
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( bytes_forward reader (max_size * 2)
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( { reader with pointer = reader.pointer + (max_size * 2) }
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, { id; flags; num_questions; num_answers; num_authorities; num_additionals } )
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| _ -> failwith "Invalid number of fields"
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;;
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let rec parse_question reader =
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let reader', name_b = decode_name_simple reader in
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let name = String.to_bytes name_b in
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let name, offset_name = decode_name_simple reader in
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let data = bytes_forward reader.data (reader.pointer + offset_name) in
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let max_size = 2 in
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match List.init max_size (fun offset -> unpack_short_be reader' (offset * 2)) with
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| [ type_; class_ ] -> bytes_forward reader' (max_size * 2), { name; type_; class_ }
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match List.init max_size (fun offset -> unpack_short_be data (offset * 2)) with
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| [ type_; class_ ] ->
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( { reader with pointer = reader.pointer + offset_name + (max_size * 2) }
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, { name; type_; class_ } )
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| _ -> failwith "Invalid number of fields"
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and decode_name_simple reader =
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let rec read_parts parts pos =
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let length = int_of_char (Bytes.get reader pos) in
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let length = int_of_char (Bytes.get reader.data (reader.pointer + pos)) in
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if length = 0
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then 1, parts
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else (
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let part = Bytes.sub_string reader (pos + 1) length in
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let part = Bytes.sub_string reader.data (reader.pointer + pos + 1) length in
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let last_length, parts' = read_parts (parts @ [ part ]) (pos + 1 + length) in
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last_length + length + 1, parts')
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in
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let offset, parts = read_parts [] 0 in
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bytes_forward reader offset, String.concat "." parts
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String.to_bytes (String.concat "." parts), offset
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;;
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let parse_record _reader =
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let name, type_, class_, ttl, data = Bytes.empty, 0, 0, 0, Bytes.empty in
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let name, _offset_name = Bytes.empty, 0 (* decode_name_simple reader *) in
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let type_, class_, ttl, data = 0, 0, 0, Bytes.empty in
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{ name; type_; class_; ttl; data }
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;;
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@ -20,3 +20,8 @@ type dns_record =
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; ttl : int
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; data : bytes
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}
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type reader =
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{ data : bytes
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; pointer : int
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}
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