diff --git a/apps/dns_proxy/include/dns_proxy.hrl b/apps/dns_proxy/include/dns_proxy.hrl new file mode 100644 index 0000000..a9282cc --- /dev/null +++ b/apps/dns_proxy/include/dns_proxy.hrl @@ -0,0 +1,21 @@ +%%%------------------------------------------------------------------- +%%% @author anlicheng +%%% @copyright (C) 2025, +%%% @doc +%%% +%%% @end +%%% Created : 04. 12月 2025 11:41 +%%%------------------------------------------------------------------- +-author("anlicheng"). + +-record(dns_cache, { + %% {Qname, QType, QClass} + key, + answers = [], + authority = [], + additional = [], + rcode :: integer(), + flags = #{}, + % unix time + expire_at :: integer() +}). \ No newline at end of file diff --git a/apps/dns_proxy/src/dns_cache.erl b/apps/dns_proxy/src/dns_cache.erl index 23627cb..86d20d4 100644 --- a/apps/dns_proxy/src/dns_cache.erl +++ b/apps/dns_proxy/src/dns_cache.erl @@ -1,17 +1,48 @@ -module(dns_cache). +-include_lib("dns_proxy.hrl"). +-include_lib("dns_erlang/include/dns.hrl"). +-include_lib("dns_erlang/include/dns_records.hrl"). +-include_lib("dns_erlang/include/dns_terms.hrl"). + -export([init/0, lookup/1, insert/2]). -define(TABLE, dns_cache). init() -> - ets:new(?TABLE, [named_table, set, public, {read_concurrency, true}]). + ets:new(?TABLE, [named_table, set, public, {keypos, 2}, {read_concurrency, true}]). -lookup(Key) -> +lookup(#dns_query{name = Qname, type = QType, class = QClass}) -> + Key = {Qname, QType, QClass}, case ets:lookup(?TABLE, Key) of - [{_Key, Value}] -> {hit, Value}; - [] -> miss + [Cache = #dns_cache{expire_at = ExpireAt}] -> + Now = os:system_time(second), + case ExpireAt > Now of + true -> + {hit, Cache}; + false -> + true = ets:delete(?TABLE, Key), + miss + end; + [] -> + miss end. -insert(Key, DNSMsg) -> - ets:insert(?TABLE, {Key, DNSMsg}), - ok. +insert(#dns_query{name = Qname, type = QType, class = QClass}, + #dns_message{answers = Answers, authority = Authority, additional = Additional, aa = AA}) -> + + TTLs = [RR#dns_rr.ttl || RR <- Answers] ++ [RR#dns_rr.ttl || RR <- Authority] ++ [RR#dns_rr.ttl || RR <- Additional], + TTL = lists:min(TTLs), + ExpireAt = os:system_time(second) + TTL, + + Key = {Qname, QType, QClass}, + Cache = #dns_cache{ + key = Key, + answers = Answers, + authority = Authority, + additional = Additional, + rcode = 0, + flags = #{aa => AA}, + % unix time + expire_at = ExpireAt + }, + true = ets:insert(?TABLE, Cache). diff --git a/apps/dns_proxy/src/dns_handler.erl b/apps/dns_proxy/src/dns_handler.erl index 3c08a35..fd63def 100644 --- a/apps/dns_proxy/src/dns_handler.erl +++ b/apps/dns_proxy/src/dns_handler.erl @@ -14,6 +14,7 @@ -include_lib("dns_erlang/include/dns.hrl"). -include_lib("dns_erlang/include/dns_records.hrl"). -include_lib("dns_erlang/include/dns_terms.hrl"). +-include("dns_proxy.hrl"). %% API -export([start_link/4]). @@ -32,7 +33,7 @@ src_ip, src_port, packet, - qname, + question, dns_servers = [] }). @@ -85,10 +86,10 @@ handle_cast(handle, State = #state{socket = Sock, src_ip = SrcIp, src_port = Src Msg = #dns_message{qc = 1, questions = [Question|_]} -> Qname = Question#dns_query.name, lager:debug("[dns_handler] qname: ~p", [Qname]), - case dns_cache:lookup(Qname) of - {hit, R} -> - lager:debug("[dns_handler] hit cache rr: ~p", [R]), - Resp = build_response(Msg, R), + case dns_cache:lookup(Question) of + {hit, Cache} -> + lager:debug("[dns_handler] hit cache: ~p", [Cache]), + Resp = build_response(Msg, Cache), gen_udp:send(Sock, SrcIp, SrcPort, dns:encode_message(Resp)), {stop, normal, State}; miss -> @@ -96,7 +97,7 @@ handle_cast(handle, State = #state{socket = Sock, src_ip = SrcIp, src_port = Src forward_to_upstream(DnsIp, DnsPort, Packet, Msg), %% 开启定时器，超时后递归请求后面的服务 erlang:start_timer(?UPSTREAM_TIMEOUT, self(), {trigger_next, Msg}), - {noreply, State#state{dns_servers = RestDnsServers, qname = Qname}} + {noreply, State#state{dns_servers = RestDnsServers, question = Question}} end; Other -> lager:warning("[] decode msg get error: ~p", [Other]), @@ -122,12 +123,12 @@ handle_info({timeout, _, handler_max_ttl}, State) -> {stop, normal, State}; %% 收到请求 -handle_info({dns_resolver_reply, Resp}, State = #state{socket = Sock, src_ip = SrcIp, src_port = SrcPort, qname = Qname}) -> +handle_info({dns_resolver_reply, Resp}, State = #state{socket = Sock, src_ip = SrcIp, src_port = SrcPort, question = Question}) -> %% 尝试解析 case dns:decode_message(Resp) of Msg = #dns_message{answers = Answers} -> lager:debug("[dns_handler] get a resolver reply: ~p, bin: ~p", [Msg, Answers]), - dns_cache:insert(Qname, Answers), + dns_cache:insert(Question, Msg), gen_udp:send(Sock, SrcIp, SrcPort, Resp); Other -> lager:debug("[dns_handler] parse reply get error: ~p", [Other]) @@ -162,6 +163,39 @@ forward_to_upstream(TargetIp, TargetPort, Request, Msg) -> dns_resolver:forward(Pid, ReceiverPid, TargetIp, TargetPort, Request, Msg) end). -build_response(Req, RR) -> - Msg = Req, - Msg#dns_message{answers = RR, qr = true, aa = true}. \ No newline at end of file +build_response(Query, #dns_cache{expire_at = ExpireAt, answers = Answers, authority = Authority, additional = Additional}) -> + Now = os:system_time(second), + RemainingTTL = ExpireAt - Now, + + Adjust = fun(RR) -> RR#dns_rr{ttl = max(0, RemainingTTL)} end, + Answers2 = [Adjust(RR) || RR <- Answers], + Authority2 = [Adjust(RR) || RR <- Authority], + + Additional0 = [Adjust(RR) || RR <- Additional], + Additional2 = add_opt_if_needed(Query, Additional0), + + Query#dns_message{ + qr = true, + ra = true, + answers = Answers2, + authority = Authority2, + additional = Additional2 + }. + +add_opt_if_needed(Query, Additional) -> + case dns_opt:find(Query#dns_message.additional) of + false -> + %% 客户端未使用 EDNS → 不在响应中加 OPT + Additional; + {ok, OptReq} -> + %% 客户端使用 EDNS → 构造自身的 OPT RR + UdpSize = dns_opt:udp_payload(OptReq), + DoBit = dns_opt:do_bit(OptReq), + + OptResp = dns_opt:make(UdpSize, DoBit), + + %% 去除上游响应里的旧 OPT（如果有） + Additional2 = [RR || RR <- Additional, RR#dns_rr.type =/= opt], + %% 新的 OPT 一定放在 Additional 最后 + Additional2 ++ [OptResp] + end. \ No newline at end of file diff --git a/apps/dns_proxy/src/dns_opt.erl b/apps/dns_proxy/src/dns_opt.erl new file mode 100644 index 0000000..725fb8a --- /dev/null +++ b/apps/dns_proxy/src/dns_opt.erl @@ -0,0 +1,46 @@ +%%-------------------------------------------------------------------- +%% EDNS (OPT RR) Utility for dns_erlang +%%-------------------------------------------------------------------- +-module(dns_opt). + +-export([find/1, make/2, udp_payload/1, do_bit/1]). + +-include_lib("dns_erlang/include/dns.hrl"). + +%%-------------------------------------------------------------------- +%% 查找 OPT RR（RR type = opt） +%%-------------------------------------------------------------------- +find(RRs) -> + case lists:dropwhile(fun(RR) -> RR#dns_rr.type =/= opt end, RRs) of + [] -> + false; + [RR|_] -> + {ok, RR} + end. + +%%-------------------------------------------------------------------- +%% 获取 DO bit（TTL 的最高 bit） +%%-------------------------------------------------------------------- +do_bit(RR) -> + (RR#dns_rr.ttl band 16#8000) =/= 0. + +%%-------------------------------------------------------------------- +%% 获取 UDP payload size（来自 class 字段） +%%-------------------------------------------------------------------- +udp_payload(RR) -> + RR#dns_rr.class. + +%%-------------------------------------------------------------------- +%% 构造新的 OPT RR（符合 RFC6891） +%% make(UdpPayloadSize, DoBit) +%%-------------------------------------------------------------------- +make(UdpPayloadSize, DoBit) -> + TTL = if DoBit -> 16#8000; true -> 0 end, + #dns_rr{ + name = <<>>, % Root label + type = opt, + class = UdpPayloadSize, + ttl = TTL, + % No EDNS options by default + data = [] + }.