xdp: make generic xdp redirect use tracepoint trace_xdp_redirect

If the xdp_do_generic_redirect() call fails, it trigger the
trace_xdp_exception tracepoint.  It seems better to use the same
tracepoint trace_xdp_redirect, as the native xdp_do_redirect{,_map} does.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/filter.h

@@ -718,7 +718,8 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
  * because we only track one map and force a flush when the map changes.
  * This does not appear to be a real limitation for existing software.
  */
-int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb);
+int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,
+			    struct bpf_prog *prog);
 int xdp_do_redirect(struct net_device *dev,
 		    struct xdp_buff *xdp,
 		    struct bpf_prog *prog);

net/core/dev.c

@@ -3953,7 +3953,8 @@ int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff *skb)
 		if (act != XDP_PASS) {
 			switch (act) {
 			case XDP_REDIRECT:
-				err = xdp_do_generic_redirect(skb->dev, skb);
+				err = xdp_do_generic_redirect(skb->dev, skb,
+							      xdp_prog);
 				if (err)
 					goto out_redir;
 			/* fallthru to submit skb */
@@ -3966,7 +3967,6 @@ int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff *skb)
 	}
 	return XDP_PASS;
 out_redir:
-	trace_xdp_exception(skb->dev, xdp_prog, XDP_REDIRECT);
 	kfree_skb(skb);
 	return XDP_DROP;
 }

net/core/filter.c

@@ -2553,26 +2553,37 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
 
-int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb)
+int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,
+			    struct bpf_prog *xdp_prog)
 {
 	struct redirect_info *ri = this_cpu_ptr(&redirect_info);
-	unsigned int len;
 	u32 index = ri->ifindex;
+	struct net_device *fwd;
+	unsigned int len;
+	int err = 0;
 
-	dev = dev_get_by_index_rcu(dev_net(dev), index);
+	fwd = dev_get_by_index_rcu(dev_net(dev), index);
 	ri->ifindex = 0;
-	if (unlikely(!dev)) {
-		return -EINVAL;
+	if (unlikely(!fwd)) {
+		err = -EINVAL;
+		goto out;
 	}
 
-	if (unlikely(!(dev->flags & IFF_UP)))
-		return -ENETDOWN;
-	len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
-	if (skb->len > len)
-		return -E2BIG;
+	if (unlikely(!(fwd->flags & IFF_UP))) {
+		err = -ENETDOWN;
+		goto out;
+	}
 
-	skb->dev = dev;
-	return 0;
+	len = fwd->mtu + fwd->hard_header_len + VLAN_HLEN;
+	if (skb->len > len) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	skb->dev = fwd;
+out:
+	trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT, err);
+	return err;
 }
 EXPORT_SYMBOL_GPL(xdp_do_generic_redirect);