xdp: Add batching support to redirect map

For performance reasons we want to avoid updating the tail pointer in
the driver tx ring as much as possible. To accomplish this we add
batching support to the redirect path in XDP.

This adds another ndo op "xdp_flush" that is used to inform the driver
that it should bump the tail pointer on the TX ring.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
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>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index ce8211fa91c7..3323ee91c172 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -712,10 +712,17 @@ bool bpf_helper_changes_pkt_data(void *func);
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 				       const struct bpf_insn *patch, u32 len);
 
+/* The pair of xdp_do_redirect and xdp_do_flush_map MUST be called in the
+ * same cpu context. Further for best results no more than a single map
+ * for the do_redirect/do_flush pair should be used. This limitation is
+ * because we only track one map and force a flush when the map changes.
+ * This does not appear to be a real limiation for existing software.
+ */
 int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb);
 int xdp_do_redirect(struct net_device *dev,
 		    struct xdp_buff *xdp,
 		    struct bpf_prog *prog);
+void xdp_do_flush_map(void);
 
 void bpf_warn_invalid_xdp_action(u32 act);
 void bpf_warn_invalid_xdp_redirect(u32 ifindex);