wpa_supplicant源码制作第三方库调用

wpa_supplicant是一款配置无线网络的开源工具，功能很强大，编译出来只有2个工具，一个wpa_supplicant和wpa_cli。
wpa_supplicant用来做后台守护进程，wpa_cli做实际配置用。关于配置网络的常用命令这里我就不多讲了，很多地方都能找到
，这里我们要讲的是另外一种情况：能不能把wpa_cli的功能部分做成库文件，通过一个接口来实现wpa_cli命令的功能，执行后
的状态信息返回到这个接口的buffer中，在代码中分析buffer中的内容做相应的处理？
网上也有类似的处理，如 浓咖啡jy https://blog.csdn.net/jy1075518049/article/details/51304346,这里我详细介绍下具体实现过程。

1.在wpa_supplicant源码目录下，复制一份wpa_cli3.c
2.修改wpa_cli3.c中的代码，我们注意到，所有的命令最终实现都是在_wpa_ctrl_command函数中，因此，需要对其进行改造，加入char *buf，接收返回的状态信息。如下：

//static int _wpa_ctrl_command(struct wpa_ctrl *ctrl, char *cmd, int print)
static int _wpa_ctrl_command(struct wpa_ctrl *ctrl, char *buf ,char *cmd, int print)
{
	char buf_ret[2048];
	size_t len;
	int ret;

	if (ctrl_conn == NULL) {
		printf("Not connected to wpa_supplicant - command dropped.\n");
		return -1;
	}
	len = sizeof(buf_ret) - 1;
	ret = wpa_ctrl_request(ctrl, cmd, os_strlen(cmd), buf_ret, &len,
			       wpa_cli_msg_cb);
	if (ret == -2) {
		printf("'%s' command timed out.\n", cmd);
		return -2;
	} else if (ret < 0) {
		printf("'%s' command failed.\n", cmd);
		return -1;
	}
	
	if(buf){ //复制状态信息
		buf_ret[len] = '\0';
		memcpy(buf,buf_ret,2048);
	}

	if (print) {
		buf_ret[len] = '\0';
		printf("%s", buf_ret);
		if (interactive && len > 0 && buf_ret[len - 1] != '\n')
			printf("\n");
	}
	return 0;
}

3.代码中其余部分有调用_wpa_ctrl_command函数的都需要添加char* buf参数进行相应的修改。如下

static int wpa_cli_cmd_scan(struct wpa_ctrl *ctrl, int argc, char *buf, char *argv[])
{
	return wpa_ctrl_command(ctrl, buf, "SCAN");
}

4.上述修改完成后。在wpa_cli3.c目录下，新建一个wpa_cli3.h，内容如下：

#ifndef __WPA_CLI3_H
#define __WPA_CLI3_H

//外部调用的接口函数
//pcm：字符串   buf:返回的信息缓冲   argu:附加命令
int wpa_cli_cmd_function(char *pcm, char *buf, char* argu);

#endif

5.wpa_cli3.c中新建 int wpa_cli_cmd_function(char *pcm, char *buf, char* argu);接口函数，下面是实现

//初始化部分
static int wpa_cli_start(void)
{
	//1.变量初始化
	int conectNum = 0;
	ctrl_ifname = NULL;
	ctrl_conn = NULL;
	mon_conn = NULL;

	if (os_program_init())
		return -1;
	if (eloop_init())
		return -1;

	eloop_register_signal_terminate(wpa_cli_terminate, NULL);
	
	//2.与wpa_supplicant建立连接
	while(1)
	{
		if(ctrl_ifname==NULL)
		{
			ctrl_ifname = wpa_cli_get_default_ifname();
			if(ctrl_ifname == NULL){
				printf("failed to wpa_cli_get_default_ifname");
				return -1;
			}
		}

		wpa_cli_open_connection(ctrl_ifname,0);
				
		if (ctrl_conn || mon_conn){ 
			printf("wpa_supplicant connection established");
			break;
		}else{
			if(conectNum++ >=3){ 
				printf("wpa_supplicant connection established err");
				return -1;
			}
			printf("wpa_supplicant connection established err, we will try agin");
			usleep(20000);
			continue;
		}
	}
	return 0;

}

int wpa_cli_cmd_function(char *pcm, char *buf, char *argu)
{
	int ret = 0;
	char augubuf[64];
	ret = wpa_cli_start();
	if(ret<0)
	{
		perror("wpa_cli_start fail!\n");
	}

	if(argu == NULL)
	{
		if(     strcmp(pcm,"status")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "STATUS");  
		}
		else if(strcmp(pcm,"list_networks")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "LIST_NETWORKS");
		}
		else if(strcmp(pcm,"ping")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "PING");
		}
		else if(strcmp(pcm,"disconnect")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "DISCONNECT");
		}
		else if(strcmp(pcm,"reconnect")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "RECONNECT");
		}
		else if(strcmp(pcm,"save_config")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "SAVE_CONFIG");
		}
		else if(strcmp(pcm,"scan")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "SCAN");
		}
		else if(strcmp(pcm,"scan_results")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "SCAN_RESULTS");
		}
		else if(strcmp(pcm,"logon")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "LOGON");
		}
		else if(strcmp(pcm,"logoff")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "LOGOFF"); 
		}
		else if(strcmp(pcm,"add_network")==0)
		{
			ret = wpa_ctrl_command(ctrl_conn, buf, "ADD_NETWORK"); 
		}
	}
	else if(argu)
	{
		if(     strcmp(pcm,"set_network")==0)
		{
			sprintf(augubuf,"SET_NETWORK %s",argu);
			ret = wpa_ctrl_command(ctrl_conn, buf, augubuf); 
		}
		else if(strcmp(pcm,"enable_network")==0)
		{
			sprintf(augubuf,"ENABLE_NETWORK %s",argu);
			ret = wpa_ctrl_command(ctrl_conn, buf, augubuf); 
		}
		else if(strcmp(pcm,"disable_network")==0)
		{
			sprintf(augubuf,"DISABLE_NETWORK %s",argu);
			ret = wpa_ctrl_command(ctrl_conn, buf, augubuf); 
		}

	}
	
	os_free(ctrl_ifname);
	eloop_destroy();
	wpa_cli_cleanup();

	return ret;
}

6.修改wpa_cli3.c目录下的Makefile,使其编译生成库文件，这里我们就定义名称为wpa_cli3.a。

7.make，在当前目录生成libwpa_cli3.a，就是我们需要的静态库文件，配上wpa_cli3.h就可以在代码中进行接口调用了。

8.写代码测试。这里只实现扫描，和显示扫描结果的功能。

int main(int argc, char *argv[])
{
	int ret;
	char buff[2048];
	ret = wpa_cli_start();
	if(ret<0)
	{
		perror("wpa_cli_start fail!\n");
	}

	wpa_cli_cmd_function("scan",buff,NULL);
	sleep(3);

	wpa_cli_cmd_function("scan_results",buff,NULL);
	buff[2047]='\0';

	printf("buff=%s\n",buff);

	return 0;
}

实际测试效果，可见打印的buff=有信息输出了。