141 lines
5.2 KiB
Erlang
141 lines
5.2 KiB
Erlang
%%%-------------------------------------------------------------------
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%%% @author anlicheng
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%%% @copyright (C) 2025, <COMPANY>
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%%% @doc
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%%%
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%%% @end
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%%% Created : 03. 12月 2025 18:26
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%%%-------------------------------------------------------------------
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-module(dns_resolver).
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-author("anlicheng").
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-include_lib("dns_erlang/include/dns.hrl").
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-behaviour(gen_server).
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%% API
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-export([start_link/1]).
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%% gen_server callbacks
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-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
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-export([forward/5]).
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-define(SERVER, ?MODULE).
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-record(state, {
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socket,
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idx :: integer(),
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dns_servers = []
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}).
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%%%===================================================================
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%%% API
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%%%===================================================================
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forward(Pid, ReceiverPid, Ref, Request, QueryMsg) ->
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gen_server:cast(Pid, {forward, ReceiverPid, Ref, Request, QueryMsg}).
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%% @doc Spawns the server and registers the local name (unique)
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-spec(start_link(Args :: list()) ->
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{ok, Pid :: pid()} | ignore | {error, Reason :: term()}).
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start_link(Args) when is_list(Args) ->
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gen_server:start_link(?MODULE, [], []).
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%%%===================================================================
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%%% gen_server callbacks
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%%%===================================================================
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%% @private
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%% @doc Initializes the server
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-spec(init(Args :: term()) ->
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{ok, State :: #state{}} | {ok, State :: #state{}, timeout() | hibernate} |
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{stop, Reason :: term()} | ignore).
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init([]) ->
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{ok, DnsServers} = application:get_env(sdlan, public_dns_servers),
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{ok, Sock} = gen_udp:open(0, [binary, {active, true}]),
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Idx = erlang:unique_integer([monotonic, positive]),
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{ok, #state{socket = Sock, idx = Idx, dns_servers = DnsServers}}.
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%% @private
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%% @doc Handling call messages
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-spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
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State :: #state{}) ->
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{reply, Reply :: term(), NewState :: #state{}} |
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{reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
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{noreply, NewState :: #state{}} |
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{noreply, NewState :: #state{}, timeout() | hibernate} |
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{stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
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{stop, Reason :: term(), NewState :: #state{}}).
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handle_call(_Request, _From, State = #state{}) ->
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{reply, ok, State}.
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%% @private
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%% @doc Handling cast messages
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-spec(handle_cast(Request :: term(), State :: #state{}) ->
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{noreply, NewState :: #state{}} |
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{noreply, NewState :: #state{}, timeout() | hibernate} |
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{stop, Reason :: term(), NewState :: #state{}}).
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handle_cast({forward, ReceiverPid, Ref, Request, #dns_message{id = TxId, questions = [#dns_query{name = QName, type = QType, class = QClass}|_]}},
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State = #state{socket = Socket, idx = Idx, dns_servers = DnsServers}) ->
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lists:foreach(fun({DnsIp, DnsPort}) ->
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ok = gen_udp:send(Socket, DnsIp, DnsPort, Request),
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Key = {Idx, TxId, DnsIp, DnsPort, QName, QType, QClass},
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logger:debug("[dns_resolver] key: ~p, send to: ~p, packet: ~p", [Key, {DnsIp, DnsPort}, Request]),
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dns_pending_wheel:insert(Key, {Ref, ReceiverPid})
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end, DnsServers),
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{noreply, State}.
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%% @private
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%% @doc Handling all non call/cast messages
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-spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
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{noreply, NewState :: #state{}} |
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{noreply, NewState :: #state{}, timeout() | hibernate} |
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{stop, Reason :: term(), NewState :: #state{}}).
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handle_info({udp, Socket, TargetIp, TargetPort, Resp}, State = #state{socket = Socket, idx = Idx}) ->
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try dns:decode_message(Resp) of
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#dns_message{id = TxId, questions = [#dns_query{name = QName, type = QType, class = QClass}|_]} ->
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Key = {Idx, TxId, TargetIp, TargetPort, QName, QType, QClass},
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Records = dns_pending_wheel:lookup(Key),
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dns_pending_wheel:delete(Key),
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resolver_reply(Records, Resp);
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_ ->
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ok
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catch error:_ ->
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ok
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end,
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{noreply, State}.
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%% @private
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%% @doc This function is called by a gen_server when it is about to
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%% terminate. It should be the opposite of Module:init/1 and do any
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%% necessary cleaning up. When it returns, the gen_server terminates
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%% with Reason. The return value is ignored.
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-spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | term()),
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State :: #state{}) -> term()).
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terminate(_Reason, _State = #state{}) ->
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ok.
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%% @private
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%% @doc Convert process state when code is changed
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-spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
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Extra :: term()) ->
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{ok, NewState :: #state{}} | {error, Reason :: term()}).
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code_change(_OldVsn, State = #state{}, _Extra) ->
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{ok, State}.
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%%%===================================================================
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%%% Internal functions
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%%%===================================================================
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-spec resolver_reply(list(), Resp :: binary()) -> no_return().
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resolver_reply(Records, Resp) when is_binary(Resp) ->
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lists:foreach(fun({_, {Ref, ReceiverPid}}) ->
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case is_process_alive(ReceiverPid) of
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true ->
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ReceiverPid ! {dns_resolver_reply, Ref, Resp};
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false ->
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ok
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end
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end, Records). |