Tor由於經過了長年的開發，版本到現在已經有很多。筆者選用的是tor-0.2.3.25版本。關於版本變遷和更新說明，請大家自行查看：
https://gitweb.torproject.org/tor.git (需翻牆)
1. 源碼目錄關係圖
Tor的源碼目錄中包括doc, contrib, src等一些列很莫名的文件。其實，在這些所有的文件中，除了src文件夾，其他都可以在初期暫時不去理會。所以，這裏我們就談src文件夾下的目錄結構，也是Tor源碼核心的目錄結構。
上面兩圖已經基本給出了各個子目錄之間的關係和引用次數。總的來說，src目錄下包括下列這樣的目錄：
1）win32：用於Windows的目錄，內部只含有一個orconfig.h文件。主要用於Tor源碼的跨平臺編譯。
2）common：Tor源碼中基本通用函數的封裝目錄。包括：OpenSSL,Libevent的封裝，TLS的封裝，鏈表和哈希表的實現等。
3）tools：Tor使用工具目錄。包括：密鑰驗證，證書生成，域名解析和防火牆輔助的實現。
4）or：Tor核心程序邏輯目錄。（Tor系統所有核心協議的實現目錄）包括：客戶端身份核心代碼，路由身份核心代碼，目錄服務器身份核心代碼等。
5）test：Tor源碼各功能模塊的測試代碼目錄。
6）config：配置文件模板目錄
2. or目錄下的各文件
or目錄是Tor源代碼的核心，有必要簡要介紹下該目錄下的文件的主要作用：（細節部分後期會逐個文件分別進行分析）
以下部分同時用於OP與OR：(Onion Proxy, Onion Router)
1）Buffers：緩衝區相關結構體及處理函數；
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：鏈路建立相關函數；
The actual details of building circuits.
3）Circuitlist：鏈路列表及鏈路控制相關函數；
Manage the global circuit list.
4）Circuituse：鏈路獲取或使用相關函數；
Launch the right sort of circuits and attach streams to them.
5）Command：Tor Cell數據包的所有命令處理函數；
Functions for processing incoming cells.
6）Config：Tor系統配置選項處理函數；
Code to parse and interpret configuration files.
7）Connection：通用連接相關函數；
General high-level functions to handle reading and writing on connections.
8）Connection_edge：邊緣連接相關函數；（邊緣連接包括應用代理連接AP和出口連接EXIT）
Handle edge streams.
9）Connection_or：OR連接相關函數；
Functions to handle OR connections, TLS handshaking, and cells on the network.
10）Control：Tor系統控制相關函數；
Implementation for Tor's control-socket interface. See doc/spec/control-spec.txt for full details on protocol.
11）Cpuworker：多線程（加解密）處理函數；
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：目錄服務器連接相關操作函數；
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功能相關函數；（一般用於Bridge用戶來自的國家統計）
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：休眠相關處理函數；
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：微描述符處理相關函數；
17）Networkstatus：網絡狀態文檔處理函數；
Functions and structures for handling network status documents as a client or cache.
18）Nodelist：路由節點列表相關處理函數；
19）Ntmain：nt服務相關函數；
20）Onion：Cell封裝處理相關函數；
Functions to queue create cells, and handle onionskin parsing and creation.
21）Policies：出入口策略相關函數；
Code to parse and use address policies and exit policies.
22）Reason：差錯原因相關函數；
Convert circuit, stream, and orconn error reasons to and/or from strings and errno values.
23）Relay：Relay Cell相關處理函數；
Handle relay cell encryption/decryption, plus packaging and receiving from circuits, plus queuing on circuits.
24）Rendcommon：Hidden Service通用代碼；
Rendezvous implementation: shared code between introducers, services, clients, and rendezvous points.
25）Routerlist：路由信息列表相關處理函數；
Code to maintain and access the global list of routerinfos for known servers.
26）Routerparse：路由描述符與目錄的解析與驗證相關函數；
Code to parse and validate router descriptors and directories.
27）Status：狀態保存與秒記錄函數；
Keep status information and log the heartbeat messages.
28）Tormain：主函數接口；
Stub module containing a main() function. Allows unit test binary to link againstmain.c.
29）Transports：Pluggable Transports related code.
30）Rephist：歷史信息與數據統計相關函數；
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.
以下部分用於OR：(Onion Router)
1）Dirsev：目錄服務器核心實現，生成及管理目錄內容；
Directory server core implementation. Manages directory contents and generates directories.
2）Dirvote：目錄服務器投票與共識相關操作函數；
Functions to compute directory consensus, and schedule voting.
3）Dns：服務器域名解析服務相關函數；
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中間服務點實現代碼；
Implement introductions points and rendezvous points.
5）Rendservice：Hidden Service服務功能代碼；
The hidden-service side of rendezvous functionality.
6）Router：Onion Router核心實現；
OR functionality, including key maintenance, generating and uploading server descriptors, retrying OR connections.
以下部分用於OP：(Onion Proxy)
1）Dnsserv：客戶端域名解析代理服務器相關函數；
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：暫略
3）Rendclient：Hidden Service客戶端代碼；
Client code to access location-hidden services.
筆者暫時沒有全部查閱上述代碼，如果有差錯的地方，請大家指點。