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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>
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@ -42,4 +42,20 @@ static inline __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8
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u32 flow_hash_from_keys(struct flow_keys *keys);
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unsigned int flow_get_hlen(const unsigned char *data, unsigned int max_len,
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__be16 protocol);
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/* struct flow_keys_digest:
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*
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* This structure is used to hold a digest of the full flow keys. This is a
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* larger "hash" of a flow to allow definitively matching specific flows where
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* the 32 bit skb->hash is not large enough. The size is limited to 16 bytes so
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* that it can by used in CB of skb (see sch_choke for an example).
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*/
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#define FLOW_KEYS_DIGEST_LEN 16
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struct flow_keys_digest {
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u8 data[FLOW_KEYS_DIGEST_LEN];
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};
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void make_flow_keys_digest(struct flow_keys_digest *digest,
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const struct flow_keys *flow);
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#endif
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@ -310,6 +310,33 @@ static inline u32 ___skb_get_hash(const struct sk_buff *skb,
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return __flow_hash_from_keys(keys, keyval);
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}
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struct _flow_keys_digest_data {
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__be16 n_proto;
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u8 ip_proto;
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u8 padding;
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__be32 ports;
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__be32 src;
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__be32 dst;
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};
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void make_flow_keys_digest(struct flow_keys_digest *digest,
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const struct flow_keys *flow)
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{
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struct _flow_keys_digest_data *data =
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(struct _flow_keys_digest_data *)digest;
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BUILD_BUG_ON(sizeof(*data) > sizeof(*digest));
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memset(digest, 0, sizeof(*digest));
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data->n_proto = flow->n_proto;
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data->ip_proto = flow->ip_proto;
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data->ports = flow->ports;
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data->src = flow->src;
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data->dst = flow->dst;
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}
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EXPORT_SYMBOL(make_flow_keys_digest);
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/*
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* __skb_get_hash: calculate a flow hash based on src/dst addresses
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* and src/dst port numbers. Sets hash in skb to non-zero hash value
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