Add the ability to redirect packets to other devices via XDP_REDIRECT
and to receive redirected frames from other devices via ndo_xdp_xmit.

New functionality:
- XDP_REDIRECT case in e1000_run_xdp() using xdp_do_redirect()
- e1000_xdp_xmit() as the ndo_xdp_xmit callback for receiving
  redirected frames from other devices
- xdp_do_flush() in e1000_finalize_xdp() for REDIR completions
- xdp_features_set/clear_redirect_target() in e1000_xdp_setup()
- NETDEV_XDP_ACT_REDIRECT and NETDEV_XDP_ACT_NDO_XMIT advertised

Assisted-by: claude-opus-4-6
Signed-off-by: Matteo Croce <teknoraver@meta.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 85 +++++++++++++++++++++-
 1 file changed, 81 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 821b466b6673..1e28eaed7ae3 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -41,6 +41,7 @@ char e1000e_driver_name[] = "e1000e";
 #define E1000_XDP_PASS		0
 #define E1000_XDP_CONSUMED	BIT(0)
 #define E1000_XDP_TX		BIT(1)
+#define E1000_XDP_REDIR		BIT(2)
 
 static int debug = -1;
 module_param(debug, int, 0);
@@ -804,6 +805,9 @@ static void e1000_finalize_xdp(struct e1000_adapter *adapter,
 {
 	struct e1000_ring *tx_ring = adapter->tx_ring;
 
+	if (xdp_xmit & E1000_XDP_REDIR)
+		xdp_do_flush();
+
 	if (xdp_xmit & E1000_XDP_TX) {
 		/* Force memory writes to complete before letting h/w
 		 * know there are new descriptors to fetch.
@@ -822,13 +826,14 @@ static void e1000_finalize_xdp(struct e1000_adapter *adapter,
  * @adapter: board private structure
  * @xdp: XDP buffer containing packet data
  *
- * Returns E1000_XDP_PASS, E1000_XDP_TX, or E1000_XDP_CONSUMED
+ * Returns E1000_XDP_PASS, E1000_XDP_TX, E1000_XDP_REDIR, or E1000_XDP_CONSUMED
  **/
 static int e1000_run_xdp(struct e1000_adapter *adapter, struct xdp_buff *xdp)
 {
 	struct bpf_prog *xdp_prog = READ_ONCE(adapter->xdp_prog);
 	struct net_device *netdev = adapter->netdev;
 	int result = E1000_XDP_PASS;
+	int err;
 	u32 act;
 
 	if (!xdp_prog)
@@ -845,6 +850,12 @@ static int e1000_run_xdp(struct e1000_adapter *adapter, struct xdp_buff *xdp)
 		if (result == E1000_XDP_CONSUMED)
 			goto out_failure;
 		break;
+	case XDP_REDIRECT:
+		err = xdp_do_redirect(netdev, xdp, xdp_prog);
+		if (err)
+			goto out_failure;
+		result = E1000_XDP_REDIR;
+		break;
 	default:
 		bpf_warn_invalid_xdp_action(netdev, xdp_prog, act);
 		fallthrough;
@@ -1039,11 +1050,11 @@ static bool e1000_clean_rx_irq_xdp(struct e1000_ring *rx_ring, int *work_done,
 
 			/* page consumed by skb */
 			buffer_info->page = NULL;
-		} else if (xdp_res & E1000_XDP_TX) {
+		} else if (xdp_res & (E1000_XDP_TX | E1000_XDP_REDIR)) {
 			xdp_xmit |= xdp_res;
 			total_rx_bytes += length;
 			total_rx_packets++;
-			/* page consumed by XDP TX */
+			/* page consumed by XDP TX/redirect */
 			buffer_info->page = NULL;
 		} else {
 			/* XDP_DROP / XDP_ABORTED - recycle page */
@@ -7815,6 +7826,11 @@ static int e1000_xdp_setup(struct net_device *netdev, struct netdev_bpf *bpf)
 	if (!need_reset)
 		return 0;
 
+	if (prog)
+		xdp_features_set_redirect_target(netdev, true);
+	else
+		xdp_features_clear_redirect_target(netdev);
+
 	if (running)
 		e1000e_open(netdev);
 
@@ -7831,6 +7847,64 @@ static int e1000_xdp(struct net_device *netdev, struct netdev_bpf *xdp)
 	}
 }
 
+/**
+ * e1000_xdp_xmit - transmit XDP frames from another device
+ * @netdev: network interface device structure
+ * @n: number of frames to transmit
+ * @frames: array of XDP frame pointers
+ * @flags: XDP transmit flags
+ *
+ * This is the ndo_xdp_xmit callback, called when other devices redirect
+ * frames to this device.
+ **/
+static int e1000_xdp_xmit(struct net_device *netdev, int n,
+			   struct xdp_frame **frames, u32 flags)
+{
+	struct e1000_adapter *adapter = netdev_priv(netdev);
+	struct e1000_ring *tx_ring = adapter->tx_ring;
+	struct netdev_queue *nq = netdev_get_tx_queue(netdev, 0);
+	int cpu = smp_processor_id();
+	int nxmit = 0;
+	int i;
+
+	if (unlikely(test_bit(__E1000_DOWN, &adapter->state)))
+		return -ENETDOWN;
+
+	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
+		return -EINVAL;
+
+	if (!adapter->xdp_prog)
+		return -ENXIO;
+
+	__netif_tx_lock(nq, cpu);
+	txq_trans_cond_update(nq);
+
+	for (i = 0; i < n; i++) {
+		int err;
+
+		err = e1000_xdp_xmit_ring(adapter, tx_ring, frames[i]);
+		if (err != E1000_XDP_TX)
+			break;
+		nxmit++;
+	}
+
+	if (unlikely(flags & XDP_XMIT_FLUSH)) {
+		/* Force memory writes to complete before letting h/w
+		 * know there are new descriptors to fetch.
+		 */
+		wmb();
+		if (adapter->flags2 & FLAG2_PCIM2PCI_ARBITER_WA)
+			e1000e_update_tdt_wa(tx_ring,
+					     tx_ring->next_to_use);
+		else
+			writel(tx_ring->next_to_use, tx_ring->tail);
+	}
+
+	__netif_tx_unlock(nq);
+
+	return nxmit;
+}
+
 static const struct net_device_ops e1000e_netdev_ops = {
 	.ndo_open		= e1000e_open,
 	.ndo_stop		= e1000e_close,
@@ -7854,6 +7928,7 @@ static const struct net_device_ops e1000e_netdev_ops = {
 	.ndo_hwtstamp_get	= e1000e_hwtstamp_get,
 	.ndo_hwtstamp_set	= e1000e_hwtstamp_set,
 	.ndo_bpf		= e1000_xdp,
+	.ndo_xdp_xmit		= e1000_xdp_xmit,
 };
 
 /**
@@ -8064,7 +8139,9 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	netdev->max_mtu = adapter->max_hw_frame_size -
 			  (VLAN_ETH_HLEN + ETH_FCS_LEN);
 
-	netdev->xdp_features = NETDEV_XDP_ACT_BASIC;
+	netdev->xdp_features = NETDEV_XDP_ACT_BASIC |
+			       NETDEV_XDP_ACT_REDIRECT |
+			       NETDEV_XDP_ACT_NDO_XMIT;
 
 	if (e1000e_enable_mng_pass_thru(&adapter->hw))
 		adapter->flags |= FLAG_MNG_PT_ENABLED;
-- 
2.53.0