flow_dissector: Abstract out hash computation

Move the hash computation located in __skb_get_hash to be a separate
function which takes flow_keys as input. This will allow flow hash
computation in other contexts where we only have addresses and ports.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 29 insertions, 16 deletions

diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
index fbefdca5e283..6667a054763a 100644
--- a/include/net/flow_keys.h
+++ b/include/net/flow_keys.h
@@ -29,4 +29,5 @@ struct flow_keys {
 
 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow);
 __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto);
+u32 flow_hash_from_keys(struct flow_keys *keys);
 #endif
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index c2b53c1b21d2..2ff8cd4dfc5f 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -202,6 +202,33 @@ static __always_inline u32 __flow_hash_1word(u32 a)
         return jhash_1word(a, hashrnd);
 }
 
+static inline u32 __flow_hash_from_keys(struct flow_keys *keys)
+{
+        u32 hash;
+
+        /* get a consistent hash (same value on both flow directions) */
+        if (((__force u32)keys->dst < (__force u32)keys->src) ||
+            (((__force u32)keys->dst == (__force u32)keys->src) &&
+             ((__force u16)keys->port16[1] < (__force u16)keys->port16[0]))) {
+                swap(keys->dst, keys->src);
+                swap(keys->port16[0], keys->port16[1]);
+        }
+
+        hash = __flow_hash_3words((__force u32)keys->dst,
+                                  (__force u32)keys->src,
+                                  (__force u32)keys->ports);
+        if (!hash)
+                hash = 1;
+
+        return hash;
+}
+
+u32 flow_hash_from_keys(struct flow_keys *keys)
+{
+        return __flow_hash_from_keys(keys);
+}
+EXPORT_SYMBOL(flow_hash_from_keys);
+
 /*
  * __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
@@ -211,7 +238,6 @@ static __always_inline u32 __flow_hash_1word(u32 a)
 void __skb_get_hash(struct sk_buff *skb)
 {
         struct flow_keys keys;
-        u32 hash;
 
         if (!skb_flow_dissect(skb, &keys))
                 return;
@@ -219,21 +245,7 @@ void __skb_get_hash(struct sk_buff *skb)
         if (keys.ports)
                 skb->l4_hash = 1;
 
-        /* get a consistent hash (same value on both flow directions) */
-        if (((__force u32)keys.dst < (__force u32)keys.src) ||
-            (((__force u32)keys.dst == (__force u32)keys.src) &&
-             ((__force u16)keys.port16[1] < (__force u16)keys.port16[0]))) {
-                swap(keys.dst, keys.src);
-                swap(keys.port16[0], keys.port16[1]);
-        }
-
-        hash = __flow_hash_3words((__force u32)keys.dst,
-                                  (__force u32)keys.src,
-                                  (__force u32)keys.ports);
-        if (!hash)
-                hash = 1;
-
-        skb->hash = hash;
+        skb->hash = __flow_hash_from_keys(&keys);
 }
 EXPORT_SYMBOL(__skb_get_hash);