This patch adds possibility to get tun device's net namespace fd
in the same way we allow to do that for sockets.
Socket ioctl numbers do not intersect with tun-specific, and there
is already SIOCSIFHWADDR used in tun code. So, SIOCGSKNS number
is choosen instead of custom-made for this functionality.
Note, that open_related_ns() uses plain get_net_ns() and it's safe
(net can't be already dead at this moment):
tun socket is allocated via sk_alloc() with zero last arg (kern = 0).
So, each alive socket increments net::count, and the socket is definitely
alive during ioctl syscall.
Also, common variable net is introduced, so small cleanup in TUNSETIFF
is made.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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