diff options
authorTom Herbert <tom@herbertland.com>2015-05-01 11:30:17 -0700
committerDavid S. Miller <davem@davemloft.net>2015-05-04 00:09:09 -0400
commit2f59e1ebaa7f762c8825871b5486b5f5b4fa952f (patch)
parentada1dba04c273dbabefff6a9a9f8c2bdcb61a858 (diff)
net: Add flow_keys digest
Some users of flow keys (well just sch_choke now) need to pass flow_keys in skbuff cb, and use them for exact comparisons of flows so that skb->hash is not sufficient. In order to increase size of the flow_keys structure, we introduce another structure for the purpose of passing flow keys in skbuff cb. We limit this structure to sixteen bytes, and we will technically treat this as a digest of flow_keys struct hence its name flow_keys_digest. In the first incaranation we just copy the flow_keys structure up to 16 bytes-- this is the same information previously passed in the cb. In the future, we'll adapt this for larger flow_keys and could use something like SHA-1 over the whole flow_keys to improve the quality of the digest. Signed-off-by: Tom Herbert <tom@herbertland.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2 files changed, 43 insertions, 0 deletions
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).
+ */
+struct flow_keys_digest {
+void make_flow_keys_digest(struct flow_keys_digest *digest,
+ const struct flow_keys *flow);
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index b1df995ef06c..d3acc4dff4ae 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -310,6 +310,33 @@ static inline u32 ___skb_get_hash(const struct sk_buff *skb,
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;
* __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

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