Tor系统是用于匿名通信的一个系统，源代码的维护到今天已经快10年。笔者从今年3月份开始陆陆续续研究Tor系统的源码，由于源码量大，也有很多需要总结的地方，所以特地在这里开辟个Tor源码分析的系列文章，供自己总结，也供大家共同探讨。
1. 源码查看工具 -- SourceInsight
本来Tor源码在Linux下分析和调试都可以比在Windows下更专业些，但是因为笔者本身大部分时间需要在Windows下工作，所以选择了Windows下的源码分析软件。SourceInsight是个非常好的源码分析软件，用于查看各种开源代码工程都非常方便。这里选用SourceInsight作为Tor源码的基本浏览和修改工具。
2. 文档生成工具 -- Doxygen
关于Doxygen的基本介绍大家可以在网上找到很多。简单的说，Doxygen就是将源码内的信息进行总结，生成包括函数调用关系，函数介绍等信息。这对于宏观查看代码非常重要。Tor源码内很多函数都连续嵌套非常多层，靠人为记住是非常困难的。利用Doxygen的函数调用图，能帮助我们更好的查看函数之间的调用关系。这里不介绍Doxygen如何使用，百度上有许多。注：使用Doxygen时定要打开函数调用图的生成功能。
3. 编译工具 -- MinGW MSYS msyDTK
为了在Windows上完成对Tor的编译，需要使用到下面一些列套件。好在这些部分在Tor的FAQ中已经很详细地说明如何使用，这里就仅仅将Tor中关于如何在WIndows下编译Tor源码的部分复制于此，请大家自行查看。
##
## Instructions for building Tor with MinGW (http://www.mingw.org/)
##
Stage One: Download and Install MinGW.
---------------------------------------
Download mingw:
http://prdownloads.sf.net/mingw/MinGW-5.1.6.exe?download
Download msys:
http://prdownloads.sf.net/ming/MSYS-1.0.11.exe?download
Download msysDTK:
http://sourceforge.net/projects/mingw/files/MSYS%20Supplementary%20Tools/msysDTK-1.0.1/msysDTK-1.0.1.exe/download
Install MinGW, msysDTK, and MSYS in that order.
Make sure your PATH includes C:\MinGW\bin. You can verify this by right
clicking on "My Computer", choose "Properties", choose "Advanced",
choose "Environment Variables", select PATH.
Start MSYS(rxvt).
Create a directory called "tor-mingw".
Stage Two: Download, extract, compile openssl
----------------------------------------------
Download openssl:
http://www.openssl.org/source/openssl-0.9.8l.tar.gz
Extract openssl:
Copy the openssl tarball into the "tor-mingw" directory.
Type "cd tor-mingw/"
Type "tar zxf openssl-0.9.8l.tar.gz"
(Note: There are many symlink errors because Windows doesn't support
symlinks. You can ignore these errors.)
Make openssl libraries:
Type "cd tor-mingw/openssl-0.9.8l/"
Type "./Configure -no-idea -no-rc5 -no-mdc2 mingw"
Edit Makefile and remove the "test:" and "tests:" sections.
Type "rm -rf ./test"
Type "cd crypto/"
Type "find ./ -name "*.h" -exec cp {} ../include/openssl/ \;"
Type "cd ../ssl/"
Type "find ./ -name "*.h" -exec cp {} ../include/openssl/ \;"
Type "cd .."
Type "cp *.h include/openssl/"
Type "find ./fips -type f -name "*.h" -exec cp {} include/openssl/ \;"
# The next steps can take up to 30 minutes to complete.
Type "make"
Type "make install"
Stage Three: Download, extract, compile zlib
---------------------------------------------
Download zlib source:
http://www.zlib.net/zlib-1.2.3.tar.gz
Extract zlib:
Copy the zlib tarball into the "tor-mingw" directory
Type "cd tor-mingw/"
Type "tar zxf zlib-1.2.3.tar.gz"
CHOICE:
Make zlib.a:
Type "cd tor-mingw/zlib-1.2.3/"
Type "./configure"
Type "make"
Type "make install"
Done.
Stage Four: Download, extract, and compile libevent
------------------------------------------------------
Download the latest libevent release:
http://www.monkey.org/~provos/libevent/
Copy the libevent tarball into the "tor-mingw" directory.
Type "cd tor-mingw"
Extract libevent.
Type "./configure --enable-static --disable-shared"
Type "make"
Type "make install"
Stage Five: Build Tor
----------------------
Download the current Tor alpha release source code from https://torproject.org/download.html.
Copy the Tor tarball into the "tor-mingw" directory.
Extract Tor:
Type "tar zxf latest-tor-alpha.tar.gz"
cd tor-<version>
Type "./configure"
Type "make"
You now have a tor.exe in src/or/. This is Tor.
You now have a tor-resolve.exe in src/tools/.
Stage Six: Build the installer
-------------------------------
Install the latest NSIS:
http://nsis.sourceforge.net/Download
Run the package script in contrib:
From the Tor build directory above, run:
"./contrib/package_nsis-mingw.sh"
The resulting Tor installer executable is in ./win_tmp/.
上述所有的工具及源码都下载，安装完毕之后，就可以进入Tor源码的细节分析阶段。不过，在此之前，如果可能，还需要通读Tor源码的设计文档：
https://www.torproject.org/docs/documentation.html.en
上述网址需要翻墙才可以阅读，所以，或许还需要使用VPN或者GoAgent的方式事先翻墙。
重点必读的设计文档包括：<Tor: the second-generation onion router>, <Tor main specification>