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 <[email protected]>
---
 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 3ee5246f0b84..83f188f9b510 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);
@@ -805,6 +806,9 @@ 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.
@@ -823,13 +827,14 @@ 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)
@@ -846,6 +851,12 @@ 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;
@@ -1040,11 +1051,11 @@ 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 */
@@ -7811,6 +7822,11 @@ 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);
 
@@ -7827,6 +7843,64 @@ 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,
@@ -7850,6 +7924,7 @@ 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,
 };
 
 /**
@@ -8060,7 +8135,9 @@ 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

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