Re: destroy ppp(4) on closing tty

[Yasuoka Masahiko <yasuoka%iij.ad.jp@localhost>]

On Fri, 04 Apr 2008 09:50:57 -0400
Greg Troxel <gdt%ir.bbn.com@localhost> wrote:
> Yasuoka Masahiko <yasuoka%iij.ad.jp@localhost> writes:
> > I wonder why ppp(4) destroys itself when the attached tty is closed.  
> > tun(4) doesn't destroy itself when the attached device file is closed.
> >
> > Is there somebody knows the reason?
> 
> Does the ppp(4) get created when something on the tty sets line
> discipline to PPP?  If so, it makes sense to destroy on close.

When ppp(4) is running, it has some disciplines by the tty.  But after
the closing proccess on net/{ppp_tty,if_ppp}.c, it seems to release
all restraints by the tty.

> If a tun is created by a call on a descriptor, I'd say it too should be
> destroyed on close.  If it's created by 'ifconfig tun0 create', then it
> shouldn't be destroyed on close.

tun(4) is not destroyed on both cases, but ppp(4) is destroyed on both
cases.

I think if ppp(4) has no special reason to be destroyed, it sould do
same behavior as other pseudo interfaces.

--yasuoka