Tor由于经过了长年的开发，版本到现在已经有很多。笔者选用的是tor-0.2.3.25版本。关于版本变迁和更新说明，请大家自行查看：
https://gitweb.torproject.org/tor.git (需翻墙)
1. 源码目录关系图
Tor的源码目录中包括doc, contrib, src等一些列很莫名的文件。其实，在这些所有的文件中，除了src文件夹，其他都可以在初期暂时不去理会。所以，这里我们就谈src文件夹下的目录结构，也是Tor源码核心的目录结构。
上面两图已经基本给出了各个子目录之间的关系和引用次数。总的来说，src目录下包括下列这样的目录：
1）win32：用于Windows的目录，内部只含有一个orconfig.h文件。主要用于Tor源码的跨平台编译。
2）common：Tor源码中基本通用函数的封装目录。包括：OpenSSL,Libevent的封装，TLS的封装，链表和哈希表的实现等。
3）tools：Tor使用工具目录。包括：密钥验证，证书生成，域名解析和防火墙辅助的实现。
4）or：Tor核心程序逻辑目录。（Tor系统所有核心协议的实现目录）包括：客户端身份核心代码，路由身份核心代码，目录服务器身份核心代码等。
5）test：Tor源码各功能模块的测试代码目录。
6）config：配置文件模板目录
2. or目录下的各文件
or目录是Tor源代码的核心，有必要简要介绍下该目录下的文件的主要作用：（细节部分后期会逐个文件分别进行分析）
以下部分同时用于OP与OR：(Onion Proxy, Onion Router)
1）Buffers：缓冲区相关结构体及处理函数；
a generic interface buffer. Buffers are fairly opaque string holders that can read to or flush from: memory, file descriptors, or TLS connections.
2）Circuitbuild：链路建立相关函数；
The actual details of building circuits.
3）Circuitlist：链路列表及链路控制相关函数；
Manage the global circuit list.
4）Circuituse：链路获取或使用相关函数；
Launch the right sort of circuits and attach streams to them.
5）Command：Tor Cell数据包的所有命令处理函数；
Functions for processing incoming cells.
6）Config：Tor系统配置选项处理函数；
Code to parse and interpret configuration files.
7）Connection：通用连接相关函数；
General high-level functions to handle reading and writing on connections.
8）Connection_edge：边缘连接相关函数；（边缘连接包括应用代理连接AP和出口连接EXIT）
Handle edge streams.
9）Connection_or：OR连接相关函数；
Functions to handle OR connections, TLS handshaking, and cells on the network.
10）Control：Tor系统控制相关函数；
Implementation for Tor’s control-socket interface. See doc/spec/control-spec.txt for full details on protocol.
11）Cpuworker：多线程（加解密）处理函数；
Implements a farm of ‘CPU worker’ processes to perform CPU-intensive tasks in another thread or process, to not interrupt the main thread.
12）Directory：目录服务器连接相关操作函数；
Code to send and fetch directories and router descriptors via HTTP. Directories usedirserv.c to generate the results; clients use routers.c to parse them.
13）Geoip：Geoip功能相关函数；（一般用于Bridge用户来自的国家统计）
Functions related to maintaining an IP-to-country database; to summarizing client connections by country to entry guards, bridges, and directory servers; and for statistics on answering network status requests.
14）Hibernate：休眠相关处理函数；
Functions to close listeners, stop allowing new circuits, etc in preparation for closing down or going dormant; and to track bandwidth and time intervals to know when to hibernate and when to stop hibernating.
15）Main：主程序
Toplevel module. Handles signals, multiplexes between connections, implements main loop, and drives scheduled events.
16）Microdesc：微描述符处理相关函数；
17）Networkstatus：网络状态文档处理函数；
Functions and structures for handling network status documents as a client or cache.
18）Nodelist：路由节点列表相关处理函数；
19）Ntmain：nt服务相关函数；
20）Onion：Cell封装处理相关函数；
Functions to queue create cells, and handle onionskin parsing and creation.
21）Policies：出入口策略相关函数；
Code to parse and use address policies and exit policies.
22）Reason：差错原因相关函数；
Convert circuit, stream, and orconn error reasons to and/or from strings and errno values.
23）Relay：Relay Cell相关处理函数；
Handle relay cell encryption/decryption, plus packaging and receiving from circuits, plus queuing on circuits.
24）Rendcommon：Hidden Service通用代码；
Rendezvous implementation: shared code between introducers, services, clients, and rendezvous points.
25）Routerlist：路由信息列表相关处理函数；
Code to maintain and access the global list of routerinfos for known servers.
26）Routerparse：路由描述符与目录的解析与验证相关函数；
Code to parse and validate router descriptors and directories.
27）Status：状态保存与秒记录函数；
Keep status information and log the heartbeat messages.
28）Tormain：主函数接口；
Stub module containing a main() function. Allows unit test binary to link againstmain.c.
29）Transports：Pluggable Transports related code.
30）Rephist：历史信息与数据统计相关函数；
Basic history and “reputation” functionality to remember which servers have worked in the past, how much bandwidth we’ve been using, which ports we tend to want, and so on; further, exit port statistics, cell statistics, and connection statistics.
以下部分用于OR：(Onion Router)
1）Dirsev：目录服务器核心实现，生成及管理目录内容；
Directory server core implementation. Manages directory contents and generates directories.
2）Dirvote：目录服务器投票与共识相关操作函数；
Functions to compute directory consensus, and schedule voting.
3）Dns：服务器域名解析服务相关函数；
Implements a local cache for DNS results for Tor servers. This is implemented as a wrapper around Adam Langley’seventdns.c code. (We can’t just use gethostbyname() and friends because we really need to be nonblocking.)
4）Rendmid：Hidden Service中间服务点实现代码；
Implement introductions points and rendezvous points.
5）Rendservice：Hidden Service服务功能代码；
The hidden-service side of rendezvous functionality.
6）Router：Onion Router核心实现；
OR functionality, including key maintenance, generating and uploading server descriptors, retrying OR connections.
以下部分用于OP：(Onion Proxy)
1）Dnsserv：客户端域名解析代理服务器相关函数；
Implements client-side DNS proxy server code. Note: this is the DNS Server code, not the Server DNS code. Confused? This code runs on client-side, and acts as a DNS server. The code indns.c, on the other hand, runs on Tor servers, and acts as a DNS client.
2）Eventdns：暂略
3）Rendclient：Hidden Service客户端代码；
Client code to access location-hidden services.
笔者暂时没有全部查阅上述代码，如果有差错的地方，请大家指点。