What is the difference between the iff_up and iff_running of the NIC?

Because I did not find the most original location, I can only give an indirect address: http://blog.csdn.net/zqt520/article/details/17567053

Excerpts are as follows:

For how to get the status of the network interface under Linux, in the past, "Get the Network Device (Netdevice) system Message" mentioned, basically the whole operation is very simple and clear, should not have too much problem.

Someone has written to ask me, iff_up and iff_running the difference between. As far as the actual function is concerned, both represent the normal operation of the network device, but more careful observation can be found that the removal of the network line will cause iff_running changes, as for the iff_up will not be caused by the insertion and extraction of network lines and any changes.

In fact, for Linux, IFF_UP is the core of the main operation of the flag, and iff_running purely for the BSD compatible with the existence, if you want to write a Linux network device driver, it is more necessary to iff_up more ink 。