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On Fri, 9 Jul 1999, Jan Kasprzak wrote:

> Hello,
> what is the difference between the IFF_UP and IFF_RUNNING?
> I have looked into the ifconfig's source, and the "ifconfig up" command
> sets both the IFF_UP and IFF_RUNNING flags, while the "ifconfig down"
> clears the IFF_UP only. This can mean that the IFF_UP is for
> "administrative status" of an interface (i.e. system administrator
> want the interface to be active), and the IFF_RUNNING is the
> "operative status" (in Cis*o terminology) - the line protocol
> (keepalive/linefill, linkbeat) on the interface is running.
> Am I right with this guess? If so, then I think the
> drivers/net/syncppp.c uses these two flags in the opposite sense:
> The code around line 530 is the following:
> if (! (dev->flags & IFF_UP) &&
> (dev->flags & IFF_RUNNING)) {
> /* Coming out of loopback mode. */
> dev->flags |= IFF_UP;
> printk (KERN_INFO "%s: up\n", dev->name);
> I think device driver should never set the administrative
> status (IFF_UP) itself, but can set the operative status (IFF_RUNNING),
> if the line become OK (e.g. it gets correct LCP or keepalive packet).

I have already fixed the syncppp driver (and dev.c to keep IFF_RUNNING
consistent) when integrating the comx drivers. You can download the full
patch from


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