Commit d4455169 authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

net: xdp: support xdp generic on virtual devices 



XDP generic allows users to test XDP programs and/or run them with
degraded performance on devices that do not yet support XDP. For
testing I typically test eBPF programs using a set of veth devices.
This allows testing topologies that would otherwise be difficult to
setup especially in the early stages of development.

This patch adds a xdp generic hook to the netif_rx_internal()
function which is called from dev_forward_skb(). With this addition
attaching XDP programs to veth devices works as expected! Also I
noticed multiple drivers using netif_rx(). These devices will also
benefit and generic XDP will work for them as well.

Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Tested-by: default avatarAndy Gospodarek <andy@greyhouse.net>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 90382dca

net/core/dev.c

+113 −95
Original line number Diff line number Diff line
@@ -3865,6 +3865,107 @@ drop: 
	return NET_RX_DROP;

}



static u32 netif_receive_generic_xdp(struct sk_buff *skb,

				     struct bpf_prog *xdp_prog)

{

	struct xdp_buff xdp;

	u32 act = XDP_DROP;

	void *orig_data;

	int hlen, off;

	u32 mac_len;



	/* Reinjected packets coming from act_mirred or similar should

	 * not get XDP generic processing.

	 */

	if (skb_cloned(skb))

		return XDP_PASS;



	if (skb_linearize(skb))

		goto do_drop;



	/* The XDP program wants to see the packet starting at the MAC

	 * header.

	 */

	mac_len = skb->data - skb_mac_header(skb);

	hlen = skb_headlen(skb) + mac_len;

	xdp.data = skb->data - mac_len;

	xdp.data_end = xdp.data + hlen;

	xdp.data_hard_start = skb->data - skb_headroom(skb);

	orig_data = xdp.data;



	act = bpf_prog_run_xdp(xdp_prog, &xdp);



	off = xdp.data - orig_data;

	if (off > 0)

		__skb_pull(skb, off);

	else if (off < 0)

		__skb_push(skb, -off);



	switch (act) {

	case XDP_TX:

		__skb_push(skb, mac_len);

		/* fall through */

	case XDP_PASS:

		break;



	default:

		bpf_warn_invalid_xdp_action(act);

		/* fall through */

	case XDP_ABORTED:

		trace_xdp_exception(skb->dev, xdp_prog, act);

		/* fall through */

	case XDP_DROP:

	do_drop:

		kfree_skb(skb);

		break;

	}



	return act;

}



/* When doing generic XDP we have to bypass the qdisc layer and the

 * network taps in order to match in-driver-XDP behavior.

 */

static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)

{

	struct net_device *dev = skb->dev;

	struct netdev_queue *txq;

	bool free_skb = true;

	int cpu, rc;



	txq = netdev_pick_tx(dev, skb, NULL);

	cpu = smp_processor_id();

	HARD_TX_LOCK(dev, txq, cpu);

	if (!netif_xmit_stopped(txq)) {

		rc = netdev_start_xmit(skb, dev, txq, 0);

		if (dev_xmit_complete(rc))

			free_skb = false;

	}

	HARD_TX_UNLOCK(dev, txq);

	if (free_skb) {

		trace_xdp_exception(dev, xdp_prog, XDP_TX);

		kfree_skb(skb);

	}

}



static struct static_key generic_xdp_needed __read_mostly;



static int do_xdp_generic(struct sk_buff *skb)

{

	struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog);



	if (xdp_prog) {

		u32 act = netif_receive_generic_xdp(skb, xdp_prog);



		if (act != XDP_PASS) {

			if (act == XDP_TX)

				generic_xdp_tx(skb, xdp_prog);

			return XDP_DROP;

		}

	}

	return XDP_PASS;

}



static int netif_rx_internal(struct sk_buff *skb)

{

	int ret;
@@ -3872,6 +3973,14 @@ static int netif_rx_internal(struct sk_buff *skb) 
	net_timestamp_check(netdev_tstamp_prequeue, skb);



	trace_netif_rx(skb);



	if (static_key_false(&generic_xdp_needed)) {

		int ret = do_xdp_generic(skb);



		if (ret != XDP_PASS)

			return NET_RX_DROP;

	}



#ifdef CONFIG_RPS

	if (static_key_false(&rps_needed)) {

		struct rps_dev_flow voidflow, *rflow = &voidflow;
@@ -4338,8 +4447,6 @@ static int __netif_receive_skb(struct sk_buff *skb) 
	return ret;

}



static struct static_key generic_xdp_needed __read_mostly;



static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)

{

	struct bpf_prog *old = rtnl_dereference(dev->xdp_prog);
@@ -4373,89 +4480,6 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp) 
	return ret;

}



static u32 netif_receive_generic_xdp(struct sk_buff *skb,

				     struct bpf_prog *xdp_prog)

{

	struct xdp_buff xdp;

	u32 act = XDP_DROP;

	void *orig_data;

	int hlen, off;

	u32 mac_len;



	/* Reinjected packets coming from act_mirred or similar should

	 * not get XDP generic processing.

	 */

	if (skb_cloned(skb))

		return XDP_PASS;



	if (skb_linearize(skb))

		goto do_drop;



	/* The XDP program wants to see the packet starting at the MAC

	 * header.

	 */

	mac_len = skb->data - skb_mac_header(skb);

	hlen = skb_headlen(skb) + mac_len;

	xdp.data = skb->data - mac_len;

	xdp.data_end = xdp.data + hlen;

	xdp.data_hard_start = skb->data - skb_headroom(skb);

	orig_data = xdp.data;



	act = bpf_prog_run_xdp(xdp_prog, &xdp);



	off = xdp.data - orig_data;

	if (off > 0)

		__skb_pull(skb, off);

	else if (off < 0)

		__skb_push(skb, -off);



	switch (act) {

	case XDP_TX:

		__skb_push(skb, mac_len);

		/* fall through */

	case XDP_PASS:

		break;



	default:

		bpf_warn_invalid_xdp_action(act);

		/* fall through */

	case XDP_ABORTED:

		trace_xdp_exception(skb->dev, xdp_prog, act);

		/* fall through */

	case XDP_DROP:

	do_drop:

		kfree_skb(skb);

		break;

	}



	return act;

}



/* When doing generic XDP we have to bypass the qdisc layer and the

 * network taps in order to match in-driver-XDP behavior.

 */

static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)

{

	struct net_device *dev = skb->dev;

	struct netdev_queue *txq;

	bool free_skb = true;

	int cpu, rc;



	txq = netdev_pick_tx(dev, skb, NULL);

	cpu = smp_processor_id();

	HARD_TX_LOCK(dev, txq, cpu);

	if (!netif_xmit_stopped(txq)) {

		rc = netdev_start_xmit(skb, dev, txq, 0);

		if (dev_xmit_complete(rc))

			free_skb = false;

	}

	HARD_TX_UNLOCK(dev, txq);

	if (free_skb) {

		trace_xdp_exception(dev, xdp_prog, XDP_TX);

		kfree_skb(skb);

	}

}



static int netif_receive_skb_internal(struct sk_buff *skb)

{

	int ret;
@@ -4468,19 +4492,13 @@ static int netif_receive_skb_internal(struct sk_buff *skb) 
	rcu_read_lock();



	if (static_key_false(&generic_xdp_needed)) {

		struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog);



		if (xdp_prog) {

			u32 act = netif_receive_generic_xdp(skb, xdp_prog);

		int ret = do_xdp_generic(skb);



			if (act != XDP_PASS) {

		if (ret != XDP_PASS) {

			rcu_read_unlock();

				if (act == XDP_TX)

					generic_xdp_tx(skb, xdp_prog);

			return NET_RX_DROP;

		}

	}

	}



#ifdef CONFIG_RPS

	if (static_key_false(&rps_needed)) {

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