The tx data offset of packet mmap tx ring used to be :
(TPACKET2_HDRLEN - sizeof(struct sockaddr_ll))

The problem is that, with SOCK_RAW socket, the payload (14 bytes after
the beginning of the user data) is misaligned.

This patch allows to let the user gives an offset for it's tx data if
he desires.

Set sock option PACKET_TX_HAS_OFF to 1, then specify in each frame of
your tx ring tp_net for SOCK_DGRAM, or tp_mac for SOCK_RAW.
Signed-off-by: NPaul Chavent <paul.chavent@onera.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Reported value is the same reported by the FANOUT getsockoption, but
unlike it, the absent fanout setup results in absent nlattr, rather
than in nlattr with zero value. This is done so, since zero fanout
report may mean both -- no fanout, and fanout with both id and type zero.
Signed-off-by: NPavel Emelyanov <xemul@parallels.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The diag module will need to access some private packet_sock data, so
move it to a header in advance. This file will be shared between the
af_packet.c and the diag.c
Signed-off-by: NPavel Emelyanov <xemul@parallels.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>