linux下的DNS服务器

idn wrapper - Client Side IDN Conversion Software for Windows Copyright (c) 2000,2001,2002 Japan Network Information Center. All rights reserved. *** NOTICE ****************************************************** If you have installed mDN Wrapper (former version of idn wrapper) on your system, you should unwrap all the programs before installing idn wrapper. ***************************************************************** 1. Introduction For supporting internationalized domain names, each client application should convert domain names (their encodings) to that DNS server accepts. This requires applications to handle internationalized domain names in its core, and it is the vendor's responsibility to make their programs IDN-compatible. Although there are ongoing efforts in IETF to standardize IDN framework (architecture, encoding etc.) and several RFCs are expected to be published soon as the result, not many applications support IDN to this date. So, there are needs for some helper application which makes legacy applications IDN-aware. `runidn' in idnkit is one of such solutions for Unix-like operating systems, and this software, `idn wrapper' is the one for Windows. On windows, name resolving request is passed to WINSOCK DLL. idn wrapper replaces WINSOCK DLL with the one that can handle IDN, which makes legacy windows applications compatible with IDN. 2. Architecture 2.1. Wrapper DLL Wrapper DLL resides between application and original DLL. It intercept application's calls to original DLL, and preforms some additional processing on those calls. +------------+ Call +------------+ Call +------------+ | |------->| |------->| | |Application | |Wrapper DLL | |Original DLL| | |<-------| |<-------| | +------------+ Return +------------+ Return +------------+ additional processing here DLL call from apllication is passed to wrapper DLL. Wrapper DLL then performs some additional processing on that call, and then calls original DLL. Also, result from original DLL will once passed to wrapper DLL and wrapper does additional process on that result, and finally result will passed to the application. idn wrapper provides wrapper DLLs for WINSOCK, WSOCK32.DLL WINSOCK V1.1 WS2_32.DLL WINSOCK V2.0 to resolve multi-lingual domain names. 2.2. Wrapping APIs idn wrapper performs additional processing on name resolving APIs in WINSOCK, listed below. both WINSOCK 1.1, WINSOCK 2.0 gethostbyaddr gethostbyname WSAAsyncGetHostByAddr WSAAsyncGetHostByName only in WINSOCK 2.0 getaddrinfo freeaddrinfo getnameinfo WSALookupServiceBeginA WSALookupServiceNextA WSALookupServiceEnd Some applications do not use these APIs to resolve domain names. `nslookup' is one of those programs. `nslookup' builds and parse DNS messages internally and does not use WINSOCK's name resolver APIs. idn wrapper cannot make those programs IDN-aware. NOTE: WINSOCK 2.0 also contains WIDE-CHARACTER based name resolution APIs, WSALookupServiceBeginW WSALookupServiceNextW idn wrapper does not wrap these APIs. These APIs are used in Microsoft's own internationalization framework. It is dangerous to convert to another internationalization framework. 2.3. Other APIs in WINSOCK For other APIs in WINSOCK, idn wrapper does nothing, only calls original DLL's entries. idn wrapper copies original WINSOCK DLLs with renaming as below, and forward requests to them. wsock32.dll -> wsock32o.dll ws2_32.dll -> ws2_32o.dll Wrappper DLL will be installed with original DLL names. So after installation of idn wrapper, WINSOCK DLLs should be wsock32.dll idn wrapper for WINSOCK V1.1 ws2_32.dll idn wrapper for WINSOCK V2.0 wsock32o.dll Original WINSOCK V1.1 DLL ws2_32o.dll Original WINSOCK V2.0 DLL 2.4. Asynchronous API Domain name conversion take place on request to DNS convert from local encoding to DNS compatible encoding response from DNS convert from DNS encoding to local encoding For synchronous APIs, local to DNS conversion is done before calling original API, and after return from original API, name should be converted from DNS encoding to local encoding. But WINSOCK having some asynchronous APIs, such as WSAAsyncGetHostByAddr WSAAsyncGetHostByName In these APIs, completion is notified with windows message. To perform DNS to local conversion, wrapper should hook target window procedure to capture those completion messages. So, if asynchronous API was called, idn wrapper set hook to target window procedure (passed with API parameter). If hook found notify message (also given with API parameter), then convert resulting name (in DNS encoding) to local encoding. 2.5. Installing Wrapper DLLs WINSOCK DLLs are placed at Windows's system directory. To wrap WINSOCK DLLs, one could do following sequence at system directory. + Rename Original WINSOCK DLLs ren wsock32.dll wsock32o.dll ren ws2_32.dll ws2_32o.dll + Install (copy in) Wrapper DLLs copy somewhere\wsock32.dll wsock32.dll copy somewhere\ws2_32.dll ws2_32.dll copy another DLLs also However, replacing DLLs in Window's system directory is very dangerous: a) If you re-install idn wrapper again, original WINSOCK DLLs may be lost. b) Some application or service pack will replace WINSOCK DLLs. It may corrupt WINSOCK environment. If these happen, at least networking does not work, and worse, Windows never startup again. So, idn wrapper usually does not wrap in the system directory, but wrap in each indivisual application's directory. In Windows, DLL will be searched in the following places: Application's Load Directory %SystemRoot%\System32 %SystemRoot% Directories in PATH and loaded & linked first found one. So if installed wrapper DLLs is found on application's load directory, the application's call to WINSOCK will wrapped. But some applications or DLLs are binded to specific DLL, they do not rely on above DLL's search path. For those applcaitons or DLLs, idn wrapper (in standard installation) cannot wrap them. NOTE: Netscape is one of those program. It cannot be wrapped if installed to applications directory. Also WINSOCK DLLs are also binded to related DLLs in system directory. On the other hand, Internet Explore or Window Media Player relys on standard DLL search path, and well wrapped with idn wrapper. 2.6. At which point conversion applied If windows supporting WINSOCK 2.0, there are DLLs one for 1.1 and another for 2.0, and call to WINSOCK 1.1 will redirected to 2.0 DLL. +------------+ Call +------------+ Call +------------+ | |------->| |------->| | |Application | |WINSOCK 1.1 | |WINSOCK 2.0 | | |<-------| |<-------| | +------------+ Return +------------+ Return +------------+ In this case, calls to 1.1 and 2.0 are both passed to 2.0 DLL. So conversion will done in WINSOCK 2.0 DLL side. If windows only supports WINSOCK 1.1, there's 1.1 DLL only. +------------+ Call +------------+ | |------->| | |Application | |WINSOCK 1.1 | | |<-------| | +--------