Date: Fri, 13 Aug 2004 11:59:30 -0700 From: Sam Leffler <sam@errno.com> To: Roman Kurakin <rik@cronyx.ru> Cc: John Polstra <jdp@polstra.com> Subject: Re: cvs commit: src/sys/net if_tap.c Message-ID: <200408131159.30682.sam@errno.com> In-Reply-To: <411D0795.6010406@cronyx.ru> References: <XFMail.20040813103440.jdp@polstra.com> <200408131114.46274.sam@errno.com> <411D0795.6010406@cronyx.ru>
next in thread | previous in thread | raw e-mail | index | archive | help
On Friday 13 August 2004 11:25 am, Roman Kurakin wrote: > Sam Leffler wrote: > >On Friday 13 August 2004 10:34 am, John Polstra wrote: > >>On 13-Aug-2004 Roman Kurakin wrote: > >>>John Polstra wrote: > >>>>On 13-Aug-2004 Roman Kurakin wrote: > >>>>>John Polstra wrote: > >>>>>>That's pretty much correct. IFF_UP is an administrative control > >>>>>>that expresses the desired state of the interface. The driver never > >>>>>>changes IFF_UP. IFF_RUNNING is the driver's idea of the _actual_ > >>>>> > >>>>>PPP state machine can remove IFF_UP. For example if connection is not > >>>>>persistent and link > >>>>>was broken for any reason. > >>>> > >>>>I call that a bug. > >>> > >>>This is not a bug, this is feature of protocol. Some times link should > >>>go down (or other > >>>state from which it could go up only by administrator (or program) > >>>intervention). > >> > >>Sorry, but I disagree. PPP should clear IFF_RUNNING in that case, > >>but should leave IFF_UP untouched. > > > >IFF_RUNNING was intended to mark a device "ready for use" and should be > >managed by the driver. IFF_UP was to be administratively controlled and > > any automated change is contrary to the original intent/design. The only > > case that I'm aware of where IFF_UP is touched as a side-effect of > > another operation is when setting an interface's address and I consider > > that a bug. Unfortunately fixing it has widespread consequences and each > > time I've tried I've given up in disgust. > > Ok. Since IFF_UP is used this way by many implementations we have to > agree that this > is normal behavior that was introduced by evolution and practice like > word spelling could > be changed from its origin. The instances that I am aware of are misdesigns that need correcting. Folks that query IFF_UP to mean something it is not may need an alternative state bit but overloading IFF_UP to mean something it does not is wrong. FWIW netbsd does this correctly. I can't comment on PPP as I haven't looked at the code. Sam
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200408131159.30682.sam>