struct rte_ring_headtail {
   volatile uint32_t head;  /**< Prod/consumer head. */
   volatile uint32_t tail;  /**< Prod/consumer tail. */
   uint32_t single;         /**< True if single prod/cons */
};

struct rte_ring {
   char name[RTE_MEMZONE_NAMESIZE] __rte_cache_aligned; /**< Name of the ring. */
   int flags;               /**< Flags supplied at creation. */
   const struct rte_memzone *memzone;
         /**< Memzone, if any, containing the rte_ring */
   uint32_t size;           /**< Size of ring. */
   uint32_t mask;           /**< Mask (size-1) of ring. */
   uint32_t capacity;       /**< Usable size of ring */
 
   /** Ring producer status. */
   struct rte_ring_headtail prod __rte_aligned(PROD_ALIGN);
 
   /** Ring consumer status. */
   struct rte_ring_headtail cons __rte_aligned(CONS_ALIGN);
};

struct ether_addr {
   uint8_t addr_bytes[ETHER_ADDR_LEN]; /**< Addr bytes in tx order */ // 包含6個uint8_t的數組表示MAC地址
} __attribute__((__packed__));
 
struct ether_hdr {
   struct ether_addr d_addr; /**< Destination address. */ // 目的MAC地址
   struct ether_addr s_addr; /**< Source address. */      // 源MAC地址
   uint16_t ether_type;      /**< Frame type. */          // 不帶VLAN時：類型（IP為0x0800、ARP為0x0806）
                                                          // 帶VLAN時：TPID（0x8100）
} __attribute__((__packed__));
 
struct vlan_hdr {
   uint16_t vlan_tci; /**< Priority (3) + CFI (1) + Identifier Code (12) */ // 3位PCP + 1位DEI + 12位VID
   uint16_t eth_proto;/**< Ethernet type of encapsulated frame. */          // 類型（IP為0x0800、ARP為0x0806）
} __attribute__((__packed__));

struct arp_ipv4 {
	struct ether_addr arp_sha;  /**< sender hardware address */ // 發送端以太網地址
	uint32_t          arp_sip;  /**< sender IP address */       // 發送端IP地址
	struct ether_addr arp_tha;  /**< target hardware address */ // 目的以太網地址
	uint32_t          arp_tip;  /**< target IP address */       // 目的IP地址
} __attribute__((__packed__));

struct arp_hdr {
	uint16_t arp_hrd;    /* format of hardware address */           // 硬件類型
#define ARP_HRD_ETHER     1  /* ARP Ethernet address format */

	uint16_t arp_pro;    /* format of protocol address */           // 協議類型
	uint8_t  arp_hln;    /* length of hardware address */           // 硬件地址長度
	uint8_t  arp_pln;    /* length of protocol address */           // 協議地址長度
	uint16_t arp_op;     /* ARP opcode (command) */
#define	ARP_OP_REQUEST    1 /* request to resolve address */
#define	ARP_OP_REPLY      2 /* response to previous request */
#define	ARP_OP_REVREQUEST 3 /* request proto addr given hardware */ 
#define	ARP_OP_REVREPLY   4 /* response giving protocol address */
#define	ARP_OP_INVREQUEST 8 /* request to identify peer */
#define	ARP_OP_INVREPLY   9 /* response identifying peer */

	struct arp_ipv4 arp_data;
} __attribute__((__packed__));
 
struct ipv4_hdr {
   uint8_t  version_ihl;     /**< version and header length */ // 4位版本 + 4位首部長度（word數）
   uint8_t  type_of_service;  /**< type of service */
   uint16_t total_length;    /**< length of packet */          // 總長度
   uint16_t packet_id;       /**< packet ID */
   uint16_t fragment_offset;  /**< fragmentation offset */
   uint8_t  time_to_live;    /**< time to live */
   uint8_t  next_proto_id;       /**< protocol ID */           // 協議（ICMP為1、TCP為6、UDP為17、GRE為47）
   uint16_t hdr_checksum;    /**< header checksum */
   uint32_t src_addr;    /**< source address */                // 源IP地址
   uint32_t dst_addr;    /**< destination address */           // 目的IP地址
} __attribute__((__packed__));

struct icmp_hdr {
   uint8_t  icmp_type;   /* ICMP packet type. */            // 類型
   uint8_t  icmp_code;   /* ICMP packet code. */            // 代碼
   uint16_t icmp_cksum;  /* ICMP packet checksum. */        // 檢驗和
   uint16_t icmp_ident;  /* ICMP packet identifier. */      // 標識符
   uint16_t icmp_seq_nb; /* ICMP packet sequence number. */ // 序列號
} __attribute__((__packed__));

struct tcp_hdr {
   uint16_t src_port;  /**< TCP source port. */                         // 源端口號
   uint16_t dst_port;  /**< TCP destination port. */                    // 目的端口號
   uint32_t sent_seq;  /**< TX data sequence number. */                 // 序列號  
   uint32_t recv_ack;  /**< RX data acknowledgement sequence number. */ // 確認號
   uint8_t  data_off;  /**< Data offset. */                             // 4位首部長度（word數） + 4位保留
   uint8_t  tcp_flags; /**< TCP flags */                                // 2位保留 + FIN/SYN/RST/PSH/ACK/URG
   uint16_t rx_win;    /**< RX flow control window. */
   uint16_t cksum;     /**< TCP checksum. */
   uint16_t tcp_urp;   /**< TCP urgent pointer, if any. */
} __attribute__((__packed__));
 
struct udp_hdr {
   uint16_t src_port;    /**< UDP source port. */      // 源端口號
   uint16_t dst_port;    /**< UDP destination port. */ // 目的端口號
   uint16_t dgram_len;   /**< UDP datagram length */   // 總長度
   uint16_t dgram_cksum; /**< UDP datagram checksum */
} __attribute__((__packed__));

struct vxlan_hdr {
   uint32_t vx_flags; /**< flag (8) + Reserved (24). */ // 8位Flags（0x08） + 24位保留
   uint32_t vx_vni;   /**< VNI (24) + Reserved (8). */  // 24位VNI + 8位保留
} __attribute__((__packed__));