CVSROOT:        /cvs
Module name:    src
Changes by:    2022/02/15 19:22:39

Modified files:
        sys/net        : if_tun.c 

Log message:
prevent (re)opening of tun/tap interfaces that are being destroyed.

if an open tun (or tap) device is destroyed via the clone destroy
ioctl (eg, like what ifconfig destroy does), there is a window while
the open device is being revoked on the vfs side that a third thread
can come and open it again. this in turn triggers a kassert in the
ifconfig destroy path where it expects the
device to be closed.

fix this by having tun_dev_open check for the TUN_DEAD flag that
the destroy function sets. this still relies on the kernel lock for

ok visa@

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