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{ Copyright (C) 2005 Bas Steendijk and Peter Green
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For conditions of distribution and use, see copyright notice in zlib_license.txt
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which is included in the package
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----------------------------------------------------------------------------- }
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//FIXME: this code only ever seems to use one dns server for a request and does
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//not seem to have any form of retry code.
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unit dnsasync;
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{$ifdef fpc}
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{$mode delphi}
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{$endif}
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interface
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uses
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{$ifdef winasyncdns}
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dnswin,
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{$endif}
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lsocket,lcore,
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classes,binipstuff,dnscore,btime,lcorernd;
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{$include lcoreconfig.inc}
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const
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numsock=1{$ifdef ipv6}+1{$endif};
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type
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//after completion or cancelation a dnswinasync may be reused
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tdnsasync=class(tcomponent)
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private
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//made a load of stuff private that does not appear to be part of the main
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//public interface. If you make any of it public again please consider the
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//consequences when using windows dns. --plugwash.
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sockets: array[0..numsock-1] of tlsocket;
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states: array[0..numsock-1] of tdnsstate;
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destinations: array[0..numsock-1] of tbinip;
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dnsserverids : array[0..numsock-1] of integer;
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startts:double;
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{$ifdef winasyncdns}
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dwas : tdnswinasync;
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{$endif}
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numsockused : integer;
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fresultlist : tbiniplist;
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requestaf : integer;
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procedure asyncprocess(socketno:integer);
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procedure receivehandler(sender:tobject;error:word);
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function sendquery(socketno:integer;const packet:tdnspacket;len:integer):boolean;
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{$ifdef winasyncdns}
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procedure winrequestdone(sender:tobject;error:word);
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{$endif}
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public
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onrequestdone:tsocketevent;
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//addr and port allow the application to specify a dns server specifically
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//for this dnsasync object. This is not a recommended mode of operation
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//because it limits the app to one dns server but is kept for compatibility
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//and special uses.
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addr,port:ansistring;
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overrideaf : integer;
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procedure cancel;//cancel an outstanding dns request
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function dnsresult:ansistring; //get result of dnslookup as a string
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procedure dnsresultbin(var binip:tbinip); //get result of dnslookup as a tbinip
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property dnsresultlist : tbiniplist read fresultlist;
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procedure forwardlookup(const name:ansistring); //start forward lookup,
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//preferring ipv4
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procedure reverselookup(const binip:tbinip); //start reverse lookup
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procedure customlookup(const name:ansistring;querytype:integer); //start custom type lookup
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constructor create(aowner:tcomponent); override;
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destructor destroy; override;
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end;
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implementation
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uses sysutils;
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constructor tdnsasync.create;
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begin
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inherited create(aowner);
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dnsserverids[0] := -1;
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sockets[0] := twsocket.create(self);
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sockets[0].tag := 0;
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{$ifdef ipv6}
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dnsserverids[1] := -1;
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sockets[1] := twsocket.Create(self);
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sockets[1].tag := 1;
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{$endif}
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end;
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destructor tdnsasync.destroy;
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var
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socketno : integer;
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begin
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for socketno := 0 to numsock -1 do begin
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if assigned(sockets[socketno]) then begin
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if dnsserverids[socketno] >= 0 then begin
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reportlag(dnsserverids[socketno],-1);
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dnsserverids[socketno] := -1;
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end;
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sockets[socketno].release;
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setstate_request_init('',states[socketno]);
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end;
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end;
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{$ifdef winasyncdns}
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if assigned(dwas) then begin
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dwas.release;
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dwas := nil;
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end;
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{$endif}
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inherited destroy;
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end;
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procedure tdnsasync.receivehandler(sender:tobject;error:word);
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var
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socketno : integer;
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Src : TInetSockAddrV;
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SrcLen : Integer;
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fromip:tbinip;
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fromport:ansistring;
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begin
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socketno := tlsocket(sender).tag;
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//writeln('got a reply on socket number ',socketno);
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fillchar(states[socketno].recvpacket,sizeof(states[socketno].recvpacket),0);
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SrcLen := SizeOf(Src);
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states[socketno].recvpacketlen := twsocket(sender).ReceiveFrom(@(states[socketno].recvpacket), SizeOf(states[socketno].recvpacket), Src, SrcLen);
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fromip := inaddrvtobinip(Src);
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fromport := inttostr(htons(src.InAddr.port));
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if ((not comparebinip(fromip,destinations[socketno])) or (fromport <> port)) then begin
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// writeln('dnsasync received from wrong IP:port ',ipbintostr(fromip),'#',fromport,', expected ',ipbintostr(destinations[socketno]),'#',port);
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exit;
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end;
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states[socketno].parsepacket := true;
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if states[socketno].resultaction <> action_done then begin
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//we ignore packets that come after we are done
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if dnsserverids[socketno] >= 0 then begin
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reportlag(dnsserverids[socketno],trunc((unixtimefloat-startts)*1000000));
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dnsserverids[socketno] := -1;
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end;
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{ writeln('received reply');}
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asyncprocess(socketno);
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//writeln('processed it');
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end else begin
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//writeln('ignored it because request is done');
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end;
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end;
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function tdnsasync.sendquery(socketno:integer;const packet:tdnspacket;len:integer):boolean;
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var
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destination : tbinip;
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inaddr : tinetsockaddrv;
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trytolisten:integer;
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begin
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{ writeln('sendquery ',decodename(state.packet,state.packetlen,12,0,a),' ',state.requesttype);}
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//writeln('trying to send query on socket number ',socketno);
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result := false;
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if len = 0 then exit; {no packet}
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if sockets[socketno].state <> wsconnected then begin
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startts := unixtimefloat;
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if port = '' then port := '53';
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sockets[socketno].Proto := 'udp';
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sockets[socketno].ondataavailable := receivehandler;
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{we are going to bind on a random local port for the DNS request, against the kaminsky attack
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there is a small chance that we're trying to bind on an already used port, so retry a few times}
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for trytolisten := 3 downto 0 do begin
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try
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sockets[socketno].port := inttostr(1024 + randominteger(65536 - 1024));
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sockets[socketno].listen;
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except
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{writeln('failed to listen ',sockets[socketno].localport,' ',trytolisten);}
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if (trytolisten = 0) then begin
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result := false;
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exit;
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end;
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end;
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end;
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end;
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if addr <> '' then begin
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dnsserverids[socketno] := -1;
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destination := ipstrtobinf(addr);
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end else begin
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destination := getcurrentsystemnameserverbin(dnsserverids[socketno]);
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end;
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destinations[socketno] := destination;
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{$ifdef ipv6}{$ifdef mswindows}
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if destinations[socketno].family = AF_INET6 then if (requestaf = useaf_default) then requestaf := useaf_preferv6;
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{$endif}{$endif}
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makeinaddrv(destinations[socketno],port,inaddr);
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sockets[socketno].sendto(inaddr,sizeof(inaddr), @packet,len);
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result := true;
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end;
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procedure tdnsasync.asyncprocess(socketno:integer);
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begin
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state_process(states[socketno]);
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case states[socketno].resultaction of
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action_ignore: begin {do nothing} end;
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action_done: begin
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{$ifdef ipv6}
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if (numsockused = 1) or (states[socketno xor 1].resultaction=action_done) then
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//if using two sockets we need to wait until both sockets are in the done
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//state before firing the event
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{$endif}
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begin
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fresultlist := biniplist_new;
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if (numsockused = 1) then begin
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//writeln('processing for one state');
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biniplist_addlist(fresultlist,states[0].resultlist);
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{$ifdef ipv6}
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end else if (requestaf = useaf_preferv6) then begin
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//writeln('processing for two states, ipv6 preference');
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//writeln('merging lists '+biniplist_tostr(states[1].resultlist)+' and '+biniplist_tostr(states[0].resultlist));
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biniplist_addlist(fresultlist,states[1].resultlist);
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biniplist_addlist(fresultlist,states[0].resultlist);
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end else begin
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//writeln('processing for two states, ipv4 preference');
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biniplist_addlist(fresultlist,states[0].resultlist);
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biniplist_addlist(fresultlist,states[1].resultlist);
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{$endif}
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end;
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//writeln(biniplist_tostr(fresultlist));
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onrequestdone(self,0);
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end;
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end;
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action_sendquery:begin
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sendquery(socketno,states[socketno].sendpacket,states[socketno].sendpacketlen);
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end;
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end;
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end;
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procedure tdnsasync.forwardlookup;
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var
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bip : tbinip;
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i : integer;
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begin
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ipstrtobin(name,bip);
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if bip.family <> 0 then begin
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// it was an IP address
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fresultlist := biniplist_new;
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biniplist_add(fresultlist,bip);
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onrequestdone(self,0);
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exit;
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end;
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if overrideaf = useaf_default then begin
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{$ifdef ipv6}
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{$ifdef mswindows}if not (usewindns and (addr = '')) then{$endif}
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initpreferredmode;
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{$endif}
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requestaf := useaf;
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end else begin
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requestaf := overrideaf;
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end;
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{$ifdef winasyncdns}
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if usewindns and (addr = '') then begin
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dwas := tdnswinasync.create;
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dwas.onrequestdone := winrequestdone;
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dwas.forwardlookup(name);
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exit;
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end;
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{$endif}
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numsockused := 0;
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fresultlist := biniplist_new;
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if (requestaf <> useaf_v6) then begin
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setstate_forward(name,states[numsockused],af_inet);
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inc(numsockused);
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end;
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{$ifdef ipv6}
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if (requestaf <> useaf_v4) then begin
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setstate_forward(name,states[numsockused],af_inet6);
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inc(numsockused);
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end;
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{$endif}
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for i := 0 to numsockused-1 do begin
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asyncprocess(i);
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end;
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end;
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procedure tdnsasync.reverselookup;
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begin
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{$ifdef winasyncdns}
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if usewindns and (addr = '') then begin
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dwas := tdnswinasync.create;
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dwas.onrequestdone := winrequestdone;
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dwas.reverselookup(binip);
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exit;
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end;
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{$endif}
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setstate_reverse(binip,states[0]);
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numsockused := 1;
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asyncprocess(0);
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end;
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procedure tdnsasync.customlookup;
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begin
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setstate_custom(name,querytype,states[0]);
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numsockused := 1;
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asyncprocess(0);
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end;
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function tdnsasync.dnsresult;
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begin
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if states[0].resultstr <> '' then result := states[0].resultstr else begin
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result := ipbintostr(biniplist_get(fresultlist,0));
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end;
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end;
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procedure tdnsasync.dnsresultbin(var binip:tbinip);
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begin
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binip := biniplist_get(fresultlist,0);
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end;
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procedure tdnsasync.cancel;
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var
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socketno : integer;
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begin
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{$ifdef winasyncdns}
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if assigned(dwas) then begin
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dwas.release;
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dwas := nil;
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end else
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{$endif}
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begin
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for socketno := 0 to numsock-1 do begin
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reportlag(dnsserverids[socketno],-1);
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dnsserverids[socketno] := -1;
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sockets[socketno].close;
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end;
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end;
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for socketno := 0 to numsock-1 do begin
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setstate_failure(states[socketno]);
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end;
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fresultlist := biniplist_new;
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onrequestdone(self,0);
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end;
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{$ifdef winasyncdns}
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procedure tdnsasync.winrequestdone(sender:tobject;error:word);
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begin
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if dwas.reverse then begin
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states[0].resultstr := dwas.name;
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end else begin
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{$ifdef ipv6}
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if (requestaf = useaf_preferv4) then begin
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{prefer mode: sort the IP's}
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fresultlist := biniplist_new;
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addipsoffamily(fresultlist,dwas.iplist,af_inet);
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addipsoffamily(fresultlist,dwas.iplist,af_inet6);
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end else if (requestaf = useaf_preferv6) then begin
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{prefer mode: sort the IP's}
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fresultlist := biniplist_new;
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addipsoffamily(fresultlist,dwas.iplist,af_inet6);
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addipsoffamily(fresultlist,dwas.iplist,af_inet);
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end else
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{$endif}
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begin
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fresultlist := dwas.iplist;
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end;
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end;
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dwas.release;
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onrequestdone(self,error);
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end;
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{$endif}
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end.
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