mlx4: xdp: Reserve headroom for receiving packet when XDP prog is active

Reserve XDP_PACKET_HEADROOM for packet and enable bpf_xdp_adjust_head()
support.  This patch only affects the code path when XDP is active.

After testing, the tx_dropped counter is incremented if the xdp_prog sends
more than wire MTU.

Signed-off-by: Martin KaFai Lau <[email protected]>
Acked-by: Saeed Mahameed <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
4 files changed