+++ /dev/null
-==================
- Network Protocol
-==================
-
-This file describes the network protocol used by Ceph. In order to understand
-the way the structures are defined it is recommended to read the introduction
-of :doc:`/dev/network-encoding` first.
-
-Hello
-=====
-
-The protocol starts with a handshake that confirms that both nodes are talking
-ceph and shares some basic information.
-
-Banner
-------
-
-The first action is the server sending banner to the client. The banner is
-defined in ``CEPH_BANNER`` from ``src/include/msgr.h``. This is followed by
-the server's then client's address each encoded as a ``entity_addr_t``.
-
-Once the client verifies that the servers banner matches its own it replies with
-its banner and its address.
-
-Connect
--------
-
-Once the banners have been verified and the addresses exchanged the connection
-negotiation begins. First the client sends a ``ceph_msg_connect`` structure
-with its information.
-
-::
-
- // From src/include/msgr.h
- struct ceph_msg_connect {
- u64le features; // Supported features (CEPH_FEATURE_*)
- u32le host_type; // CEPH_ENTITY_TYPE_*
- u32le global_seq; // Number of connections initiated by this host.
- u32le connect_seq; // Number of connections initiated in this session.
- u32le protocol_version;
- u32le authorizer_protocol;
- u32le authorizer_len;
- u8 flags; // CEPH_MSG_CONNECT_*
- u8 authorizer[authorizer_len];
- }
-
-Connect Reply
--------------
-
-Once the connect has been sent the connection has effectively been opened,
-however the first message the server sends must be a connect reply message.
-
-::
-
- struct ceph_msg_connect_reply {
- u8 tag; // Tag indicating response code.
- u64le features;
- u32le global_seq;
- u32le connect_seq;
- u32le protocol_version;
- u32le authorizer_len;
- u8 flags;
- u8 authorizer[authorizer_len];
- }
-
-MSGR Protocol
-=============
-
-This is a low level protocol over which messages are delivered. The messages
-at this level consist of a tag byte, identifying the type of message, followed
-by the message data.
-
-::
-
- // Virtual structure.
- struct {
- u8 tag; // CEPH_MSGR_TAG_*
- u8 data[]; // Length depends on tag and data.
- }
-
-The length of ``data`` is determined by the tag byte and depending on the
-message type via information in the ``data`` array itself.
-
-.. note::
- There is no way to determine the length of the message if you do not
- understand the type of message.
-
-The message tags are defined in ``src/include/msgr.h`` and the current ones
-are listed below along with the data they include. Note that the defined
-structures don't exist in the source and are merely for representing the
-protocol.
-
-CEPH_MSGR_TAG_CLOSE (0x06)
---------------------------
-
-::
-
- struct ceph_msgr_close {
- u8 tag = 0x06;
- u8 data[0]; // No data.
- }
-
-The close message indicates that the connection is being closed.
-
-CEPH_MSGR_TAG_MSG (0x07)
-------------------------
-
-::
-
- struct ceph_msgr_msg {
- u8 tag = 0x07;
- ceph_msg_header header;
- u8 front [header.front_len ];
- u8 middle[header.middle_len];
- u8 data [header.data_len ];
- ceph_msg_footer footer;
- }
-
- // From src/include/msgr.h
- struct ceph_msg_header {
- u64le seq; // Sequence number.
- u64le tid; // Transaction ID.
- u16le type; // Message type (CEPH_MSG_* or MSG_*).
- u16le priority; // Priority (higher is more important).
- u16le version; // Version of message encoding.
-
- u32le front_len; // The size of the front section.
- u32le middle_len; // The size of the middle section.
- u32le data_len; // The size of the data section.
- u16le data_off; // The way data should be aligned by the reciever.
-
- ceph_entity_name src; // Information about the sender.
-
- u16le compat_version; // Oldest compatible encoding version.
- u16le reserved; // Unused.
- u32le crc; // CRC of header.
- }
-
- // From src/include/msgr.h
- struct ceph_msg_footer {
- u32le front_crc; // Checksums of the various sections.
- u32le middle_crc; //
- u32le data_crc; //
- u64le sig; // Crypographic signature.
- u8 flags;
- }
-
-Messages are the business logic of Ceph. They are what is used to send data and
-requests between nodes. The message header contains the length of the message
-so unknown messages can be handled gracefully.
-
-There are two names for the message type constants ``CEPH_MSG_*`` and ``MSG_*``.
-The only difference between the two is that the first are considered "public"
-while the second is for internal use only. There is no protocol-level
-difference.
-
-CEPH_MSGR_TAG_ACK (0x08)
-------------------------
-
-::
-
- struct ceph_msgr_ack {
- u8 tag = 0x08;
- u64le seq; // The sequence number of the message being acknowledged.
- }
-
-CEPH_MSGR_TAG_KEEPALIVE (0x09)
-------------------------------
-
-::
-
- struct ceph_msgr_keepalive {
- u8 tag = 0x09;
- u8 data[0]; // No data.
- }
-
-CEPH_MSGR_TAG_KEEPALIVE2 (0x0E)
--------------------------------
-
-::
-
- struct ceph_msgr_keepalive2 {
- u8 tag = 0x0E;
- utime_t timestamp;
- }
-
-CEPH_MSGR_TAG_KEEPALIVE2_ACK (0x0F)
------------------------------------
-
-::
-
- struct ceph_msgr_keepalive2_ack {
- u8 tag = 0x0F;
- utime_t timestamp;
- }
-
-.. vi: textwidth=80 noexpandtab
Code Review / stor4nfv.git / blobdiff