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