Zebra: Data structures for RMAC processing in FPM

Zebra: Data structures for RMAC processing in FPM

- FPM MAC structure: This data structure will contain all the information
required for FPM message generation for an RMAC.

struct fpm_mac_info_t {
	struct ethaddr macaddr;
	uint32_t zebra_flags; /* Could be used to build FPM messages */
	vni_t vni;
	ifindex_t vxlan_if;
	ifindex_t svi_if; /* L2 or L3 Bridge interface */
	struct in_addr r_vtep_ip; /* Remote VTEP IP */
	/* Linkage to put MAC on the FPM processing queue. */
	TAILQ_ENTRY(fpm_mac_info_t) fpm_mac_q_entries;
	uint8_t fpm_flags;
};

- Queue structure for FPM processing:
    For FPM processing, we build a queue of "fpm_mac_info_t". When RMAC is
    added or deleted from zebra, fpm_mac_info_t node is enqueued in this queue
    for the corresponding operation. FPM thread will dequeue these nodes one by
    one to generate a netlink message.

    TAILQ_HEAD(zfpm_mac_q, fpm_mac_info_t) mac_q;

- Hash table for "fpm_mac_info_t"
    When zebra tries to enqueue fpm_mac_info_t for a new RMAC add/delete
    operation, it is possible that this RMAC is already present in the queue. So,
    to avoid multiple messages for duplicate RMAC nodes, insert fpm_mac_info_t
    into a hash table.

    struct hash *fpm_mac_info_table;

    - Before enqueueing any MAC, try to fetch the fpm_mac_info_t from the hash
      table first.
    - Entry is deleted from the hash table when the node is dequeued.
    - For hash table key generation, parameters used are "mac adress" and "vni"
      This will provide a fairly unique key for a MAC(fpm_mac_info_hash_keymake).
    - Compare function uses "mac address", "RVTEP address" and "VNI" as the key
      which is sufficient to distinguish any two RMACs. This compare function is
      used for fpm_mac_info_t lookup (zfpm_mac_info_cmp).

Signed-off-by: Ameya Dharkar <adharkar@vmware.com>