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: John Fastabend <john.fastab...@gmail.com>
Tested-by: Andy Gospodarek <a...@greyhouse.net>
Acked-by: Daniel Borkmann <dan...@iogearbox.net>
---
net/core/dev.c | 208 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 113 insertions(+), 95 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index a91572a..28b9939 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3865,6 +3865,107 @@ static int enqueue_to_backlog(struct sk_buff *skb, int
cpu,
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;
@@ -4468,17 +4492,11 @@ 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) {
- rcu_read_unlock();
- if (act == XDP_TX)
- generic_xdp_tx(skb, xdp_prog);
- return NET_RX_DROP;
- }
+ if (ret != XDP_PASS) {
+ rcu_read_unlock();
+ return NET_RX_DROP;
}
}
