【iwinfo命令解析】

一、首先认识一个iwinfo_ops结构体（include/iwinfo.h），初始化的时候该结构体指针就会指向对应网卡驱动的结构

struct iwinfo_ops {
	const char *name;
    int (*mode)(const char *, int *);
    int (*channel)(const char *, int *);
    int (*frequency)(const char *, int *);
    int (*frequency_offset)(const char *, int *);
    int (*txpower)(const char *, int *);
    int (*txpower_offset)(const char *, int *);
    int (*bitrate)(const char *, int *);
    int (*signal)(const char *, int *);
    int (*noise)(const char *, int *);
    int (*quality)(const char *, int *);
    int (*quality_max)(const char *, int *);
    int (*mbssid_support)(const char *, int *);
    int (*hwmodelist)(const char *, int *);
    int (*ssid)(const char *, char *);
    int (*bssid)(const char *, char *);
    int (*country)(const char *, char *);
    int (*hardware_id)(const char *, char *);
    int (*hardware_name)(const char *, char *);
    int (*encryption)(const char *, char *);
    int (*assoclist)(const char *, char *, int *);
    int (*txpwrlist)(const char *, char *, int *);
    int (*scanlist)(const char *, char *, int *);
    int (*freqlist)(const char *, char *, int *);
    int (*countrylist)(const char *, char *, int *);
    int (*beacon_int)(const char *, int *);
    void (*close)(void);
};

二、iwinfo源码：

1）、入口文件iwinfo_cli.c

int main(int argc, char **argv)
{
int i;
char *p;
//定义一个iwinfo_ops结构指针iw
const struct iwinfo_ops *iw;
glob_t globbuf;

//命令行参数为2个时候提示命令输入格式
if (argc > 1 && argc < 3)
{
	fprintf(stderr,
		"Usage:\n"
		"	iwinfo  info\n"
		"	iwinfo  scan\n"
		"	iwinfo  txpowerlist\n"
		"	iwinfo  freqlist\n"
		"	iwinfo  assoclist\n"
		"	iwinfo  countrylist\n"
	);

	return 1;
}
//命令行只有iwinfo时候执行glob函数,遍历/sys/class/net/下的device并将所有可用的device信息打印
if (argc == 1)
{
	glob("/sys/class/net/*", 0, NULL, &globbuf);

	for (i = 0; i < globbuf.gl_pathc; i++)
	{
		p = strrchr(globbuf.gl_pathv[i], '/');

		if (!p)
			continue;

		iw = iwinfo_backend(++p);

		if (!iw)
			continue;

		print_info(iw, p);
		printf("\n");
	}

	globfree(&globbuf);
	return 0;
}
//参数在三个以上
//iwinfo_backend初始化并获取对应device驱动的iwinfo_ops结构指针iw
iw = iwinfo_backend(argv[1]);

if (!iw)
{
	fprintf(stderr, "No such wireless device: %s\n", argv[1]);
	return 1;
}

for (i = 2; i < argc; i++)
{
	switch(argv[i][0]) //只匹配第一个字母 所以用iwinfo wlan0 s 也就等于 iwinfo wlan0 scan
	{
	case 'i':
		print_info(iw, argv[1]); //iwinfo  info
		break;

	case 's':
		print_scanlist(iw, argv[1]); //iwinfo  scan
		break;

	case 't':
		print_txpwrlist(iw, argv[1]); //iwinfo  txpowerlist
		break;

	case 'f':
		print_freqlist(iw, argv[1]); //iwinfo  freqlist
		break;

	case 'a':
		print_assoclist(iw, argv[1]); //iwinfo  assoclist
		break;

	case 'c':
		print_countrylist(iw, argv[1]); //iwinfo  countrylist
		break;

	default:
		fprintf(stderr, "Unknown command: %s\n", argv[i]);
		return 1;
	}
}
//关闭socket
iwinfo_finish();

return 0;

}

2）、关于入口函数iwinfo_backend(argv[1])说明：

iwinfo_backend()函数来初始化并获取对应驱动的iwinfo_ops结构指针，文件 iwinfo_lib.c

const struct iwinfo_ops * iwinfo_backend(const char *ifname)
{
int i;

for (i = 0; i < ARRAY_SIZE(backends); i++)
    if (backends[i]->probe(ifname))
        return backends[i];   //返回ifname的ops

return NULL;

}

封装了nl80211、madwifi、qcawifi、wl_ops等驱动接口，然后将这些接口封装成统一的API接口
static const struct iwinfo_ops *backends[] = {
#ifdef USE_NL80211
&nl80211_ops,
#endif
#ifdef USE_MADWIFI
&madwifi_ops,
#endif
#ifdef USE_WL
&wl_ops,
#endif
&wext_ops,
};

3）、iwinfo mesh0 XXX（cmd) 命令执行函数

以iwinfo mesh0 assoclist 命令为例
/********************************************

• iwinfo mesh0 assoclist 命令执行函数

• 参数

•  iw: 获取对应驱动的iwinfo_ops结构指针
  

•  ifname: device
  

• ******************************************/
  static void print_assoclist(const struct iwinfo_ops *iw, const char *ifname)
  {
  int i, len;
  char buf[IWINFO_BUFSIZE];
  struct iwinfo_assoclist_entry *e;

  if (iw->assoclist(ifname, buf, &len))
  {
  printf(“No information available\n”);
  return;
  }
  else if (len <= 0)
  {
  printf(“No station connected\n”);
  return;
  }

  for (i = 0; i < len; i += sizeof(struct iwinfo_assoclist_entry))
  {
  e = (struct iwinfo_assoclist_entry *) &buf[i];

   printf("%s  %s / %s (SNR %d)  %d ms ago\n",
       format_bssid(e->mac),
       format_signal(e->signal),
       format_noise(e->noise),
       (e->signal - e->noise),
       e->inactive);
  
   printf("    RX: %-38s  %8d Pkts.\n",
       format_assocrate(&e->rx_rate),
       e->rx_packets
   );
  
   printf("    TX: %-38s  %8d Pkts.\n",
       format_assocrate(&e->tx_rate),
       e->tx_packets
   	);
  
   printf("    TX: %-38s  %8d Pkts.\n",
       format_assocrate(&e->tx_rate),
       e->tx_packets
   );
  
   printf("    expected throughput: %s\n\n",
       format_rate(e->thr));
  

  }
  }

三、具体执行结果