From 2f59e1ebaa7f762c8825871b5486b5f5b4fa952f Mon Sep 17 00:00:00 2001 From: Tom Herbert Date: Fri, 1 May 2015 11:30:17 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/net/flow_keys.h | 16 ++++++++++++++++ net/core/flow_dissector.c | 27 +++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) 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 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; +} +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 -- 2.20.1