c - IFF_UP 和 IFF_RUNNING 有什么区别？

Question

这两个标志经常一起设置。它们有什么区别？

Answer 1

来自 Linux Device Drivers 3 :

IFF_UP This flag is read-only for the driver. The kernel turns it on when the interface is active and ready to transfer packets.

...

IFF_RUNNING

This flag indicates that the interface is up and running. It is mostly present for BSD compatibility; the kernel makes little use of it. Most network drivers need not worry about IFF_RUNNING.

再深入一点，似乎有一个显着差异:

IFF_RUNNING 应该反射(reflect)网络接口(interface)上的操作状态，而不是其管理状态。举个例子，一个以太网接口(interface)可能被管理员UP(例如ifconfig eth0 up)，但它不会被认为是可操作的(即RUNNING 根据 RFC2863)如果电缆未插入。