Merge branch 'flow_keys_digest'

Tom Herbert says:

====================
net: Eliminate calls to flow_dissector and introduce flow_keys_digest

In this patch set we add skb_get_hash_perturb which gets the skbuff
hash for a packet and perturbs it using a provided key and jhash1.
This function is used in serveral qdiscs and eliminates many calls
to flow_dissector and jhash3 to get a perturbed hash for a packet.

To handle the sch_choke issue (passes flow_keys in skbuff cb) we
add flow_keys_digest which is a digest of a flow constructed
from a flow_keys structure.

This is the second version of these patches I posted a while ago,
and is prerequisite work to increasing the size of the flow_keys
structure and hashing over it (full IPv6 address, flow label, VLAN ID,
etc.).

Version 2:

- Add keyval parameter to __flow_hash_from_keys which allows caller to
  set the initval for jhash
- Perturb always does flow dissection and creates hash based on
  input perturb value which acts as the keyval to __flow_hash_from_keys
- Added a _flow_keys_digest_data which is used in make_flow_keys_digest.
  This fills out the digest by populating individual fields instead
  of copying the whole structure.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 66e374d62f64..acb83e249e3f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -927,6 +927,8 @@ static inline __u32 skb_get_hash(struct sk_buff *skb)
 	return skb->hash;
 }
 
+__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb);
+
 static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
 {
 	return skb->hash;
diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
index dc8fd81412bf..6d6ef626811a 100644
--- a/include/net/flow_keys.h
+++ b/include/net/flow_keys.h
@@ -42,4 +42,20 @@ static inline __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8
 u32 flow_hash_from_keys(struct flow_keys *keys);
 unsigned int flow_get_hlen(const unsigned char *data, unsigned int max_len,
 			   __be16 protocol);
+
+/* struct flow_keys_digest:
+ *
+ * This structure is used to hold a digest of the full flow keys. This is a
+ * larger "hash" of a flow to allow definitively matching specific flows where
+ * the 32 bit skb->hash is not large enough. The size is limited to 16 bytes so
+ * that it can by used in CB of skb (see sch_choke for an example).
+ */
+#define FLOW_KEYS_DIGEST_LEN	16
+struct flow_keys_digest {
+	u8	data[FLOW_KEYS_DIGEST_LEN];
+};
+
+void make_flow_keys_digest(struct flow_keys_digest *digest,
+			   const struct flow_keys *flow);
+
 #endif