ceph主要数据结构解析1

1.Msgr.h文件：定义消息传输层的数据类型，以供ceph使用

（1）默认的监控端口：

#define CEPH_MON_PORT    6789

（2）客户端处理端口范围定义：

#define CEPH_PORT_FIRST  6789//监控
#define CEPH_PORT_START  6800  //开始
#define CEPH_PORT_LAST   6900//结束

（3）tcp协议标识和版本信息：

#define CEPH_BANNER "ceph v027"
#define CEPH_BANNER_MAX_LEN 30//最大长度

（4）ceph中的实体名称：在网络传输中使用，例如mds0表示元数据服务器0

struct ceph_entity_name {
__u8 type;      /* CEPH_ENTITY_TYPE_* */
__le64 num;
} __attribute__ ((packed));//按照紧凑模式分配内存，而不是内存对齐

#define CEPH_ENTITY_TYPE_MON    0x01//监控服务器实体
#define CEPH_ENTITY_TYPE_MDS    0x02//元数据服务器实体
#define CEPH_ENTITY_TYPE_OSD    0x04//对象存储设备实体
#define CEPH_ENTITY_TYPE_CLIENT 0x08//客户端实体
#define CEPH_ENTITY_TYPE_AUTH   0x20//权限实体
#define CEPH_ENTITY_TYPE_ANY    0xFF//任何

同时提供一个函数用于将类型转换为名字字符串的函数如下：

const char *ceph_entity_type_name(int type)
{
switch (type) {
case CEPH_ENTITY_TYPE_MDS: return "mds";
case CEPH_ENTITY_TYPE_OSD: return "osd";
case CEPH_ENTITY_TYPE_MON: return "mon";
case CEPH_ENTITY_TYPE_CLIENT: return "client";
case CEPH_ENTITY_TYPE_AUTH: return "auth";
default: return "unknown";
}
}

（5）实体网络地址以及与名字实体的对应关系结构体

struct ceph_entity_addr {
__le32 type;
__le32 nonce;  /* unique id for process (e.g. pid) */
struct sockaddr_storage in_addr;
} __attribute__ ((packed));

struct ceph_entity_inst {
struct ceph_entity_name name;
struct ceph_entity_addr addr;
} __attribute__ ((packed));

（6）消息交换协议定义：

#define CEPH_MSGR_TAG_READY         1  /* server->client: ready for messages */
#define CEPH_MSGR_TAG_RESETSESSION  2  /* server->client: reset, try again */
#define CEPH_MSGR_TAG_WAIT          3  /* server->client: wait for racing
  incoming connection */
#define CEPH_MSGR_TAG_RETRY_SESSION 4  /* server->client + cseq: try again
  with higher cseq */
#define CEPH_MSGR_TAG_RETRY_GLOBAL  5  /* server->client + gseq: try again
  with higher gseq */
#define CEPH_MSGR_TAG_CLOSE         6  /* closing pipe */
#define CEPH_MSGR_TAG_MSG           7  /* message */
#define CEPH_MSGR_TAG_ACK           8  /* message ack */
#define CEPH_MSGR_TAG_KEEPALIVE     9  /* just a keepalive byte! */
#define CEPH_MSGR_TAG_BADPROTOVER  10  /* bad protocol version */
#define CEPH_MSGR_TAG_BADAUTHORIZER 11 /* bad authorizer */
#define CEPH_MSGR_TAG_FEATURES      12 /* insufficient features */
#define CEPH_MSGR_TAG_SEQ           13 /* 64-bit int follows with seen seq number */

（7）连接协商

struct ceph_msg_connect {//连接消息结构体
__le64 features;     /* supported feature bits */支持的特征位
__le32 host_type;    /* CEPH_ENTITY_TYPE_* */上面提到的实体类型
__le32 global_seq;   /* count connections initiated by this host */主机初始化的连接数量
__le32 connect_seq;  /* count connections initiated in this session */在这个对话中的连接数量
__le32 protocol_version;//协议版本
__le32 authorizer_protocol;//权限协议
__le32 authorizer_len;//权限长度
__u8  flags;         /* CEPH_MSG_CONNECT_* */
} __attribute__ ((packed));

struct ceph_msg_connect_reply {//连接回复消息结构体
__u8 tag;//上面定义传递消息的类型
__le64 features;     /* feature bits for this session */这个对话的特征位
__le32 global_seq;
__le32 connect_seq;
__le32 protocol_version;
__le32 authorizer_len;
__u8 flags;
} __attribute__ ((packed));

#define CEPH_MSG_CONNECT_LOSSY  1  /* messages i send may be safely dropped */

（8）消息头部结构：有老的

struct ceph_msg_header_old {
__le64 seq;       /* message seq# for this session */消息序列号
__le64 tid;       /* transaction id */传输id
__le16 type;      /* message type */消息类型
__le16 priority;  /* priority.  higher value == higher priority */优先级，值高优先级就高
__le16 version;   /* version of message encoding */消息编码版本

__le32 front_len; /* bytes in main payload */开头主要的有效数据的长度
__le32 middle_len;/* bytes in middle payload */
__le32 data_len;  /* bytes of data payload */数据
__le16 data_off;  /* sender: include full offset;
     receiver: mask against ~PAGE_MASK */

struct ceph_entity_inst src, orig_src;
__le32 reserved;
__le32 crc;       /* header crc32c */
} __attribute__ ((packed));

struct ceph_msg_header {
__le64 seq;       /* message seq# for this session */
__le64 tid;       /* transaction id */
__le16 type;      /* message type */
__le16 priority;  /* priority.  higher value == higher priority */
__le16 version;   /* version of message encoding */

__le32 front_len; /* bytes in main payload */
__le32 middle_len;/* bytes in middle payload */
__le32 data_len;  /* bytes of data payload */
__le16 data_off;  /* sender: include full offset;
     receiver: mask against ~PAGE_MASK */

struct ceph_entity_name src;

/* oldest code we think can decode this.  unknown if zero. */
__le16 compat_version;
__le16 reserved;
__le32 crc;       /* header crc32c */
} __attribute__ ((packed));

#define CEPH_MSG_PRIO_LOW     64
#define CEPH_MSG_PRIO_DEFAULT 127
#define CEPH_MSG_PRIO_HIGH    196
#define CEPH_MSG_PRIO_HIGHEST 255

（9）数据有效载荷结构

struct ceph_msg_footer {
__le32 front_crc, middle_crc, data_crc;
__u8 flags;
} __attribute__ ((packed));

#define CEPH_MSG_FOOTER_COMPLETE  (1<<0)   /* msg wasn't aborted */
#define CEPH_MSG_FOOTER_NOCRC     (1<<1)   /* no data crc */