Take a look at the dev_ifsioc() function in ioctl32.c-- it does not
copy the data back to userspace except for SIOCSIFMAP, and judging
from the strict definition of TUNSETIFF it should not be required to
do so.

I think if this is functionality that is required (I see no TUNGETIFF,
but I don't play with this stuff enough to know) the directionality of
the ioctl definition should be _IOWR rather than _IOR; in any case,
the "argument" field should  not be "int" but rather "struct ifreq*"
in if_tun.h.  Likely, neither will change for historical reasons....

E


On Mon, 14 Feb 2005 20:41:33 +0100 (CET), Michael Tautschnig
<[EMAIL PROTECTED]> wrote:
> Hello!
> 
> Thanks for the information regarding userland/kernelspace - I think I
> understood ...
> 
> The reason of my question were problems using the tun/tap interface - I've
> got an application (namely l2tpns) demanding the ifreq-structure being
> copied back to userspace - which AFAIK doesn't happen in case of the
> TUNSETIFF-ioctl. Is this a bug or are there any reasons why this shouldn't
> happen in dev_ifsioc ?
> 
> Thanks,
> Michael
> 
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