From 4ebb582a060f2418da6f045b832f8f746426edb8 Mon Sep 17 00:00:00 2001
From: Mylloon <kennel.anri@tutanota.com>
Date: Tue, 4 Jul 2023 13:12:59 +0200
Subject: [PATCH] resolver

---
 lib/network.ml | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/lib/network.ml b/lib/network.ml
index db83c46..c2fec9a 100644
--- a/lib/network.ml
+++ b/lib/network.ml
@@ -1,5 +1,6 @@
 open Unix
 open Query
+open Types
 
 let send_request dns url record_type =
   let query = build url record_type in
@@ -24,3 +25,35 @@ let send ip_address domain_name record_type =
   let query = send_request ip_address domain_name record_type in
   Response.parse_dns_packet query
 ;;
+
+let rec resolve domain_name record_type = resolve_aux "198.41.0.4" domain_name record_type
+
+and resolve_aux nameserver domain_name record_type =
+  Printf.printf "Querying %s for %s\n" nameserver domain_name;
+  let response = send nameserver domain_name record_type in
+  match get_answer response with
+  | Some ip -> String.of_bytes ip
+  | None ->
+    (match get_nameserver_ip response with
+     | Some ns_ip -> resolve_aux ns_ip domain_name record_type
+     | None ->
+       (match get_nameserver response with
+        | Some ns_domain ->
+          resolve_aux (resolve ns_domain DNSType.a) domain_name record_type
+        | None -> raise (Failure "Something went wrong")))
+
+and get_answer packet =
+  match List.find_opt (fun el -> el.type_ = DNSType.a) packet.answers with
+  | Some record -> Some record.data
+  | None -> None
+
+and get_nameserver_ip packet =
+  match List.find_opt (fun el -> el.type_ = DNSType.a) packet.additionals with
+  | Some record -> Some (String.of_bytes record.data)
+  | None -> None
+
+and get_nameserver packet =
+  match List.find_opt (fun el -> el.type_ = DNSType.ns) packet.authorities with
+  | Some record -> Some (String.of_bytes record.data)
+  | None -> None
+;;