tap(4) should go UP if opened

[Frank Behrens]

I want to diskuss the tap(4) behaviour before I create a PR:

The tap(4) interface does not go automatically in UP state (IFF_UP) when opened by a 
process. Therefore an additional command "ifconfig tapx up" is necessary, which can 
execute root only. On the other site the interface goes down automatically when closed.

I propose that tap(4) is set to UP when opened by an user process. This can be achieved 
with the following patch (on FreeBSD 6.2-STABLE-200703081613):
--- sys/net/if_tap.c.orig       Thu Mar  8 19:10:59 2007
+++ sys/net/if_tap.c    Fri Mar  9 10:05:57 2007
@@ -501,6 +501,7 @@
        s = splimp();
        ifp->if_drv_flags |= IFF_DRV_RUNNING;
        ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;
+       ifp->if_flags |= IFF_UP;
        splx(s);

        TAPDEBUG("%s is open. minor = %#x\n", ifp->if_xname, minor(dev));

How does tun(4) handle this? tun(4) is also set to down, when closed. It is not set to up, when 
ist is opened, but when an address is assigned by the user process. This is fine, because it 
needs always an ip address. tap(4) as layer 2 tunnel device does not need an ip address, so 
setting it up on open is IMHO the best solution.

Sound this reasonable or how should I handle the tap(4) open by an user process, when this 
process does not run as root?

Regards,
   Frank
-- 
Frank Behrens, Osterwieck, Germany
PGP-key 0x5B7C47ED on public servers available.