Netd学习笔记

1. service netd /system/bin/netd
2.     class main
3.     socket netd stream 0660 root system
4.     socket dnsproxyd stream 0660 root inet

启动/system/bin/netd应用程序为服务，入口函数为main，创建2个名字分别为netd和dnsproxyd的本地socket连接。分别对应：

1. root@android:/ # ll /dev/socket/
2. srwxrwxrwx root inet 1970-01-01 00:00 dnsproxyd
3. srwxrwxrwx root system 1970-01-01 00:00 netd

备注：socket关键字用法，

1. 代码阅读（注：由于说第一次分析netd的代码，我完全跟踪此代码的流程来看，先说init.rc，然后是main，之后依次展开）：
2. //main.cpp:main
3. int main() {
4. //........
5.     if (!(nm = NetlinkManager::Instance())) { //NetlinkManager需要分析，一眼看出它为单根模式。看看他到底做来什么？
6.         LOGE("Unable to create NetlinkManager");
7.         exit(1);
8.     };
9.    
10.    
11.     cl = new CommandListener();//CommandListener需要分析
12.     nm->setBroadcaster((SocketListener *) cl);
13.    
14.     if (nm->start()) { //直接看start函数。
15.         LOGE("Unable to start NetlinkManager (%s)", strerror(errno));
16.         exit(1);
17.     }
18.    
19.     /*
20.      * Now that we're up, we can respond to commands
21.      */
22.     if (cl->startListener()) {
23.         LOGE("Unable to start CommandListener (%s)", strerror(errno));
24.         exit(1);
25.     }
26.    
27.     // Eventually we'll become the monitoring thread
28.     while(1) {
29.         sleep(1000);
30.     }
31.    
32.     LOGI("Netd exiting");
33.     exit(0);
34. }

    直接跟进看NetlinkManager::start()

35. int NetlinkManager::start() {
36.     struct sockaddr_nl nladdr;
37.     int sz = 64 * 1024;
38.    
39.     memset(&nladdr, 0, sizeof(nladdr));
40.     nladdr.nl_family = AF_NETLINK;
41.     nladdr.nl_pid = getpid();
42.     nladdr.nl_groups = 0xffffffff;
43.    
44.     if ((mSock = socket(PF_NETLINK,
45.                         SOCK_DGRAM,NETLINK_KOBJECT_UEVENT)) < 0) {
46.         LOGE("Unable to create uevent socket: %s", strerror(errno));
47.         return -1;
48.     }
49.    
50.     if (setsockopt(mSock, SOL_SOCKET, SO_RCVBUFFORCE, &sz, sizeof(sz)) < 0) {
51.         LOGE("Unable to set uevent socket options: %s", strerror(errno));
52.         return -1;
53.     }
54.     if (bind(mSock, (struct sockaddr *) &nladdr, sizeof(nladdr)) < 0) {
55.         LOGE("Unable to bind uevent socket: %s", strerror(errno));
56.         return -1;
57.     }
58.    
59.     mHandler = new NetlinkHandler(this, mSock);
60.     if (mHandler->start()) {
61.         LOGE("Unable to start NetlinkHandler: %s", strerror(errno));
62.         return -1;
63.     }
64.     return 0;
65. }

    看NetlinkHandler类：

66. #ifndef _NETLINKHANDLER_H
67. #define _NETLINKHANDLER_H
68.    
69. #include <sysutils/NetlinkListener.h>
70. #include "NetlinkManager.h"
71.    
72. class NetlinkHandler: public NetlinkListener { // NetlinkListener类之前有分析，这个是网络监听的框架实现类。
73.     NetlinkManager *mNm;
74.    
75. public:
76.     NetlinkHandler(NetlinkManager *nm, int listenerSocket);
77.     virtual ~NetlinkHandler();
78.    
79.     int start(void);
80.     int stop(void);
81.    
82. protected:
83.     virtual void onEvent(NetlinkEvent *evt);
84.    
85.     void notifyInterfaceAdded(const char *name);
86.     void notifyInterfaceRemoved(const char *name);
87.     void notifyInterfaceChanged(const char *name, bool isUp);
88. };
89. #endif

    晕死，怎么排版乱完了，而且还丢失了部分数据。