net: core: rework basic flow dissection helper

When the core networking needs to detect the transport offset in a given
packet and parse it explicitly, a full-blown flow_keys struct is used for
storage.
This patch introduces a smaller keys store, rework the basic flow dissect
helper to use it, and apply this new helper where possible - namely in
skb_probe_transport_header(). The used flow dissector data structures
are renamed to match more closely the new role.

The above gives ~50% performance improvement in micro benchmarking around
skb_probe_transport_header() and ~30% around eth_get_headlen(), mostly due
to the smaller memset. Small, but measurable improvement is measured also
in macro benchmarking.

v1 -> v2: use the new helper in eth_get_headlen() and skb_get_poff(),
  as per DaveM suggestion

Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 8 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 908d66e55b14..693564a9a979 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1171,7 +1171,7 @@ void __skb_get_hash(struct sk_buff *skb);
 u32 __skb_get_hash_symmetric(const struct sk_buff *skb);
 u32 skb_get_poff(const struct sk_buff *skb);
 u32 __skb_get_poff(const struct sk_buff *skb, void *data,
-		   const struct flow_keys *keys, int hlen);
+		   const struct flow_keys_basic *keys, int hlen);
 __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
 			    void *data, int hlen_proto);
 
@@ -1208,13 +1208,14 @@ static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
 				  NULL, 0, 0, 0, flags);
 }
 
-static inline bool skb_flow_dissect_flow_keys_buf(struct flow_keys *flow,
-						  void *data, __be16 proto,
-						  int nhoff, int hlen,
-						  unsigned int flags)
+static inline bool
+skb_flow_dissect_flow_keys_basic(const struct sk_buff *skb,
+				 struct flow_keys_basic *flow, void *data,
+				 __be16 proto, int nhoff, int hlen,
+				 unsigned int flags)
 {
 	memset(flow, 0, sizeof(*flow));
-	return __skb_flow_dissect(NULL, &flow_keys_buf_dissector, flow,
+	return __skb_flow_dissect(skb, &flow_keys_basic_dissector, flow,
 				  data, proto, nhoff, hlen, flags);
 }
 
@@ -2350,11 +2351,12 @@ static inline void skb_pop_mac_header(struct sk_buff *skb)
 static inline void skb_probe_transport_header(struct sk_buff *skb,
 					      const int offset_hint)
 {
-	struct flow_keys keys;
+	struct flow_keys_basic keys;
 
 	if (skb_transport_header_was_set(skb))
 		return;
-	else if (skb_flow_dissect_flow_keys(skb, &keys, 0))
+
+	if (skb_flow_dissect_flow_keys_basic(skb, &keys, 0, 0, 0, 0, 0))
 		skb_set_transport_header(skb, keys.control.thoff);
 	else
 		skb_set_transport_header(skb, offset_hint);