qede: Support XDP adjustment of headers

In case an XDP program is attached, reserve XDP_PACKET_HEADROOM
bytes at the beginning of the packet for the program to play
with.

Modify the XDP logic in the driver to fill-in the missing bits
and re-calculate offsets and length after the program has finished
running to properly reflect the current status of the packet.

We can then go and remove the limitation of not supporting XDP programs
where xdp_adjust_head is set.

Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qede/qede_filter.c

@@ -520,11 +520,6 @@ static int qede_xdp_set(struct qede_dev *edev, struct bpf_prog *prog)
 {
 	struct qede_reload_args args;
 
-	if (prog && prog->xdp_adjust_head) {
-		DP_ERR(edev, "Does not support bpf_xdp_adjust_head()\n");
-		return -EOPNOTSUPP;
-	}
-
 	/* If we're called, there was already a bpf reference increment */
 	args.func = &qede_xdp_reload_func;
 	args.u.new_prog = prog;

drivers/net/ethernet/qlogic/qede/qede_fp.c

@@ -994,14 +994,14 @@ static bool qede_rx_xdp(struct qede_dev *edev,
 			struct bpf_prog *prog,
 			struct sw_rx_data *bd,
 			struct eth_fast_path_rx_reg_cqe *cqe,
-			u16 data_offset)
+			u16 *data_offset, u16 *len)
 {
-	u16 len = le16_to_cpu(cqe->len_on_first_bd);
 	struct xdp_buff xdp;
 	enum xdp_action act;
 
-	xdp.data = page_address(bd->data) + data_offset;
-	xdp.data_end = xdp.data + len;
+	xdp.data_hard_start = page_address(bd->data);
+	xdp.data = xdp.data_hard_start + *data_offset;
+	xdp.data_end = xdp.data + *len;
 
 	/* Queues always have a full reset currently, so for the time
 	 * being until there's atomic program replace just mark read
@@ -1011,6 +1011,10 @@ static bool qede_rx_xdp(struct qede_dev *edev,
 	act = bpf_prog_run_xdp(prog, &xdp);
 	rcu_read_unlock();
 
+	/* Recalculate, as XDP might have changed the headers */
+	*data_offset = xdp.data - xdp.data_hard_start;
+	*len = xdp.data_end - xdp.data;
+
 	if (act == XDP_PASS)
 		return true;
 
@@ -1029,7 +1033,7 @@ static bool qede_rx_xdp(struct qede_dev *edev,
 		/* Now if there's a transmission problem, we'd still have to
 		 * throw current buffer, as replacement was already allocated.
 		 */
-		if (qede_xdp_xmit(edev, fp, bd, data_offset, len)) {
+		if (qede_xdp_xmit(edev, fp, bd, *data_offset, *len)) {
 			dma_unmap_page(rxq->dev, bd->mapping,
 				       PAGE_SIZE, DMA_BIDIRECTIONAL);
 			__free_page(bd->data);
@@ -1231,7 +1235,8 @@ static int qede_rx_process_cqe(struct qede_dev *edev,
 
 	/* Run eBPF program if one is attached */
 	if (xdp_prog)
-		if (!qede_rx_xdp(edev, fp, rxq, xdp_prog, bd, fp_cqe, pad))
+		if (!qede_rx_xdp(edev, fp, rxq, xdp_prog, bd, fp_cqe,
+				 &pad, &len))
 			return 0;
 
 	/* If this is an error packet then drop it */

drivers/net/ethernet/qlogic/qede/qede_main.c

@@ -1187,6 +1187,7 @@ static int qede_alloc_mem_rxq(struct qede_dev *edev, struct qede_rx_queue *rxq)
 	rxq->num_rx_buffers = edev->q_num_rx_buffers;
 
 	rxq->rx_buf_size = NET_IP_ALIGN + ETH_OVERHEAD + edev->ndev->mtu;
+	rxq->rx_headroom = edev->xdp_prog ? XDP_PACKET_HEADROOM : 0;
 
 	/* Make sure that the headroom and  payload fit in a single page */
 	if (rxq->rx_buf_size + rxq->rx_headroom > PAGE_SIZE)