Subject: [PATCH bpf-next v2 2/4] net: core: Add support for XDP redirection to slave device

From: [email-masked]
Date: Thu, 24 Jun 2021 09:18:41 +0000

From: Jussi Maki <[email-masked]>

This adds the ndo_xdp_get_xmit_slave hook for transforming XDP_TX
into XDP_REDIRECT after BPF program run when the ingress device
is a bond slave.

Signed-off-by: Jussi Maki <[email-masked]>
---
 include/linux/filter.h    | 13 ++++++++++++-
 include/linux/netdevice.h |  5 +++++
 net/core/filter.c         | 25 +++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c5ad7df029ed..752ba6a474a4 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -760,6 +760,10 @@ static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
 
 DECLARE_BPF_DISPATCHER(xdp)
 
+DECLARE_STATIC_KEY_FALSE(bpf_master_redirect_enabled_key);
+
+u32 xdp_master_redirect(struct xdp_buff *xdp);
+
 static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
 					    struct xdp_buff *xdp)
 {
@@ -769,7 +773,14 @@ static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
 	 * already takes rcu_read_lock() when fetching the program, so
 	 * it's not necessary here anymore.
 	 */
-	return __BPF_PROG_RUN(prog, xdp, BPF_DISPATCHER_FUNC(xdp));
+	u32 act = __BPF_PROG_RUN(prog, xdp, BPF_DISPATCHER_FUNC(xdp));
+
+	if (static_branch_unlikely(&bpf_master_redirect_enabled_key)) {
+		if (act == XDP_TX && netif_is_bond_slave(xdp->rxq->dev))
+			act = xdp_master_redirect(xdp);
+	}
+
+	return act;
 }
 
 void bpf_prog_change_xdp(struct bpf_prog *prev_prog, struct bpf_prog *prog);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5cbc950b34df..1a6cc6356498 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1321,6 +1321,9 @@ struct netdev_net_notifier {
  *	that got dropped are freed/returned via xdp_return_frame().
  *	Returns negative number, means general error invoking ndo, meaning
  *	no frames were xmit'ed and core-caller will free all frames.
+ * struct net_device *(*ndo_xdp_get_xmit_slave)(struct net_device *dev,
+ *					        struct xdp_buff *xdp);
+ *      Get the xmit slave of master device based on the xdp_buff.
  * int (*ndo_xsk_wakeup)(struct net_device *dev, u32 queue_id, u32 flags);
  *      This function is used to wake up the softirq, ksoftirqd or kthread
  *	responsible for sending and/or receiving packets on a specific
@@ -1539,6 +1542,8 @@ struct net_device_ops {
 	int			(*ndo_xdp_xmit)(struct net_device *dev, int n,
 						struct xdp_frame **xdp,
 						u32 flags);
+	struct net_device *	(*ndo_xdp_get_xmit_slave)(struct net_device *dev,
+							  struct xdp_buff *xdp);
 	int			(*ndo_xsk_wakeup)(struct net_device *dev,
 						  u32 queue_id, u32 flags);
 	struct devlink_port *	(*ndo_get_devlink_port)(struct net_device *dev);
diff --git a/net/core/filter.c b/net/core/filter.c
index caa88955562e..3c20edb0a0ff 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3947,6 +3947,31 @@ void bpf_clear_redirect_map(struct bpf_map *map)
 	}
 }
 
+DEFINE_STATIC_KEY_FALSE(bpf_master_redirect_enabled_key);
+EXPORT_SYMBOL_GPL(bpf_master_redirect_enabled_key);
+
+u32 xdp_master_redirect(struct xdp_buff *xdp)
+{
+	struct net_device *master, *slave;
+	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+
+	master = netdev_master_upper_dev_get_rcu(xdp->rxq->dev);
+	slave = master->netdev_ops->ndo_xdp_get_xmit_slave(master, xdp);
+	if (slave && slave != xdp->rxq->dev) {
+		/* The target device is different from the receiving device, so
+		 * redirect it to the new device.
+		 * Using XDP_REDIRECT gets the correct behaviour from XDP enabled
+		 * drivers to unmap the packet from their rx ring.
+		 */
+		ri->tgt_index = slave->ifindex;
+		ri->map_id = INT_MAX;
+		ri->map_type = BPF_MAP_TYPE_UNSPEC;
+		return XDP_REDIRECT;
+	}
+	return XDP_TX;
+}
+EXPORT_SYMBOL_GPL(xdp_master_redirect);
+
 int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 		    struct bpf_prog *xdp_prog)
 {
-- 
2.27.0