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: John Fastabend <john.fastabend@gmail.com>
Tested-by: Andy Gospodarek <andy@greyhouse.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 0244051..a1ed7b4 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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;
@@ -4468,17 +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;
                }
        }