i40e: fix xdp handle calculations

Currently, we don't add headroom to the handle in i40e_zca_free,
i40e_alloc_buffer_slow_zc and i40e_alloc_buffer_zc. The addition of the
headroom to the handle was removed in
commit 2f86c80 ("i40e: modify driver for handling offsets"), which
will break things when headroom is non-zero. This patch fixes this and uses
xsk_umem_adjust_offset to add it appropritely based on the mode being run.

Fixes: 2f86c80 ("i40e: modify driver for handling offsets")
Reported-by: Bjorn Topel <bjorn.topel@intel.com>
Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/intel/i40e/i40e_xsk.c

@@ -267,7 +267,7 @@ static bool i40e_alloc_buffer_zc(struct i40e_ring *rx_ring,
 	bi->addr = xdp_umem_get_data(umem, handle);
 	bi->addr += hr;
 
-	bi->handle = handle;
+	bi->handle = xsk_umem_adjust_offset(umem, handle, umem->headroom);
 
 	xsk_umem_discard_addr(umem);
 	return true;
@@ -304,7 +304,7 @@ static bool i40e_alloc_buffer_slow_zc(struct i40e_ring *rx_ring,
 	bi->addr = xdp_umem_get_data(umem, handle);
 	bi->addr += hr;
 
-	bi->handle = handle;
+	bi->handle = xsk_umem_adjust_offset(umem, handle, umem->headroom);
 
 	xsk_umem_discard_addr_rq(umem);
 	return true;
@@ -469,7 +469,8 @@ void i40e_zca_free(struct zero_copy_allocator *alloc, unsigned long handle)
 	bi->addr = xdp_umem_get_data(rx_ring->xsk_umem, handle);
 	bi->addr += hr;
 
-	bi->handle = (u64)handle;
+	bi->handle = xsk_umem_adjust_offset(rx_ring->xsk_umem, (u64)handle,
+					    rx_ring->xsk_umem->headroom);
 }
 
 /**