关于PPPd拨号程序的虚拟网络接口PPP0数据交换问题

[愿达前程]

PPP0 设备与linux内核交互接口IOCTL()进行数据交换，为什么需要创建SOCKET()来初始化IOCTL()操作，且开启的是个基于

SOCK_DGRAM 类型UDP socket。下面是创建与初始化函数：

int ppp_available(void)｛
////////......

fd = open("/dev/ppp", O_RDWR);

#if 0
if (fd < 0 && errno == ENOENT) {
/* try making it and see if that helps. */
if (mknod("/dev/ppp", S_IFCHR | S_IRUSR | S_IWUSR,
makedev(108, 0)) >= 0) {
fd = open("/dev/ppp", O_RDWR);
if (fd >= 0)
info("Created /dev/ppp device node");
else
unlink("/dev/ppp"); /* didn't work, undo the mknod */
} else if (errno == EEXIST) {
fd = open("/dev/ppp", O_RDWR);
}
}
#endif /* 0 */


///////......

/*
* Open a socket for doing the ioctl operations.
*/
s = socket(AF_INET, SOCK_DGRAM, 0);
if (s < 0)
return 0;

strlcpy (ifr.ifr_name, "ppp0", sizeof (ifr.ifr_name));
ok = ioctl(s, SIOCGIFFLAGS, (caddr_t) &ifr) >= 0;

//////........


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[熙风]

http://topic.csdn.net/u/20120601/16/54a32f01-fe32-429d-98ab-712f436eaa18.html