linux_kernel/include/net/flow_keys.h

#ifndef _NET_FLOW_KEYS_H
#define _NET_FLOW_KEYS_H

/* struct flow_keys:
 *	@src: source ip address in case of IPv4
 *	      For IPv6 it contains 32bit hash of src address
 *	@dst: destination ip address in case of IPv4
 *	      For IPv6 it contains 32bit hash of dst address
 *	@ports: port numbers of Transport header
 *		port16[0]: src port number
 *		port16[1]: dst port number
 *	@thoff: Transport header offset
 *	@n_proto: Network header protocol (eg. IPv4/IPv6)
 *	@ip_proto: Transport header protocol (eg. TCP/UDP)
 * All the members, except thoff, are in network byte order.
 */
struct flow_keys {
	/* (src,dst) must be grouped, in the same way than in IP header */
	__be32 src;
	__be32 dst;
	union {
		__be32 ports;
		__be16 port16[2];
	};
	u16	thoff;
	__be16	n_proto;
	u8	ip_proto;
};

bool __skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow,
			void *data, __be16 proto, int nhoff, int hlen);
static inline bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
{
	return __skb_flow_dissect(skb, flow, NULL, 0, 0, 0);
}
__be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
			    void *data, int hlen_proto);
static inline __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto)
{
	return __skb_flow_get_ports(skb, thoff, ip_proto, NULL, 0);
}
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