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>

1 files changed, 57 insertions, 8 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 2c35c02a931e..d3acc4dff4ae 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -267,13 +267,12 @@ static __always_inline void __flow_hash_secret_init(void)
 	net_get_random_once(&hashrnd, sizeof(hashrnd));
 }
 
-static __always_inline u32 __flow_hash_3words(u32 a, u32 b, u32 c)
+static __always_inline u32 __flow_hash_3words(u32 a, u32 b, u32 c, u32 keyval)
 {
-	__flow_hash_secret_init();
-	return jhash_3words(a, b, c, hashrnd);
+	return jhash_3words(a, b, c, keyval);
 }
 
-static inline u32 __flow_hash_from_keys(struct flow_keys *keys)
+static inline u32 __flow_hash_from_keys(struct flow_keys *keys, u32 keyval)
 {
 	u32 hash;
 
@@ -287,7 +286,8 @@ static inline u32 __flow_hash_from_keys(struct flow_keys *keys)
 
 	hash = __flow_hash_3words((__force u32)keys->dst,
 				  (__force u32)keys->src,
-				  (__force u32)keys->ports);
+				  (__force u32)keys->ports,
+				  keyval);
 	if (!hash)
 		hash = 1;
 
@@ -296,10 +296,47 @@ static inline u32 __flow_hash_from_keys(struct flow_keys *keys)
 
 u32 flow_hash_from_keys(struct flow_keys *keys)
 {
-	return __flow_hash_from_keys(keys);
+	__flow_hash_secret_init();
+	return __flow_hash_from_keys(keys, hashrnd);
 }
 EXPORT_SYMBOL(flow_hash_from_keys);
 
+static inline u32 ___skb_get_hash(const struct sk_buff *skb,
+				  struct flow_keys *keys, u32 keyval)
+{
+	if (!skb_flow_dissect(skb, keys))
+		return 0;
+
+	return __flow_hash_from_keys(keys, keyval);
+}
+
+struct _flow_keys_digest_data {
+	__be16	n_proto;
+	u8	ip_proto;
+	u8	padding;
+	__be32	ports;
+	__be32	src;
+	__be32	dst;
+};
+
+void make_flow_keys_digest(struct flow_keys_digest *digest,
+			   const struct flow_keys *flow)
+{
+	struct _flow_keys_digest_data *data =
+	    (struct _flow_keys_digest_data *)digest;
+
+	BUILD_BUG_ON(sizeof(*data) > sizeof(*digest));
+
+	memset(digest, 0, sizeof(*digest));
+
+	data->n_proto = flow->n_proto;
+	data->ip_proto = flow->ip_proto;
+	data->ports = flow->ports;
+	data->src = flow->src;
+	data->dst = flow->dst;
+}
+EXPORT_SYMBOL(make_flow_keys_digest);
+
 /*
  * __skb_get_hash: calculate a flow hash based on src/dst addresses
  * and src/dst port numbers.  Sets hash in skb to non-zero hash value
@@ -309,8 +346,12 @@ EXPORT_SYMBOL(flow_hash_from_keys);
 void __skb_get_hash(struct sk_buff *skb)
 {
 	struct flow_keys keys;
+	u32 hash;
 
-	if (!skb_flow_dissect(skb, &keys))
+	__flow_hash_secret_init();
+
+	hash = ___skb_get_hash(skb, &keys, hashrnd);
+	if (!hash)
 		return;
 
 	if (keys.ports)
@@ -318,10 +359,18 @@ void __skb_get_hash(struct sk_buff *skb)
 
 	skb->sw_hash = 1;
 
-	skb->hash = __flow_hash_from_keys(&keys);
+	skb->hash = hash;
 }
 EXPORT_SYMBOL(__skb_get_hash);
 
+__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb)
+{
+	struct flow_keys keys;
+
+	return ___skb_get_hash(skb, &keys, perturb);
+}
+EXPORT_SYMBOL(skb_get_hash_perturb);
+
 /*
  * Returns a Tx hash based on the given packet descriptor a Tx queues' number
  * to be used as a distribution range.