Provided by: librdmacm-dev_1.0.14.1-2_amd64 bug

NAME

       rdma_cm - RDMA communication manager.

SYNOPSIS

       #include <rdma/rdma_cma.h>

DESCRIPTION

       Used to establish communication over RDMA transports.

NOTES

       The  RDMA  CM  is a communication manager used to setup reliable, connected and unreliable
       datagram data transfers.  It provides an RDMA transport neutral interface for establishing
       connections.  The API concepts are based on sockets, but adapted for queue pair (QP) based
       semantics: communication must be over a specific  RDMA  device,  and  data  transfers  are
       message based.

       The  RDMA  CM  can  control  both  the QP and communication management (connection setup /
       teardown) portions of an RDMA API, or only the communication management piece.   It  works
       in  conjunction  with  the  verbs  API  defined by the libibverbs library.  The libibverbs
       library provides the underlying interfaces needed to send and receive data.

       The RDMA CM can operate  asynchronously  or  synchronously.   The  mode  of  operation  is
       controlled  by the user through the use of the rdma_cm event channel parameter in specific
       calls.  If an event channel is provided, an rdma_cm identifier will report its event  data
       (results of connecting, for example), on that channel.  If a channel is not provided, then
       all rdma_cm operations for the selected rdma_cm identifier will block until they complete.

RDMA VERBS

       The rdma_cm supports the full range of verbs available through the libibverbs library  and
       interfaces.   However,  it  also  provides wrapper functions for some of the more commonly
       used verbs funcationality.  The full set of abstracted verb calls are:

       rdma_reg_msgs  - register an array of buffers for sending and receiving

       rdma_reg_read  - registers a buffer for RDMA read operations

       rdma_reg_write - registers a buffer for RDMA write operations

       rdma_dereg_mr  - deregisters a memory region

       rdma_post_recv  - post a buffer to receive a message

       rdma_post_send  - post a buffer to send a message

       rdma_post_read  - post an RDMA to read data into a buffer

       rdma_post_write - post an RDMA to send data from a buffer

       rdma_post_recvv  - post a vector of buffers to receive a message

       rdma_post_sendv  - post a vector of buffers to send a message

       rdma_post_readv  - post a vector of buffers to receive an RDMA read

       rdma_post_writev - post a vector of buffers to send an RDMA write

       rdma_post_ud_send - post a buffer to send a message on a UD QP

       rdma_get_send_comp - get completion status for a send or RDMA operation

       rdma_get_recv_comp - get information about a completed receive

CLIENT OPERATION

       This section provides a general overview of the basic operation for the active, or client,
       side  of  communication.   This  flow  assume  asynchronous  operation with low level call
       details  shown.   For   synchronous   operation,   calls   to   rdma_create_event_channel,
       rdma_get_cm_event,  rdma_ack_cm_event, and rdma_destroy_event_channel would be eliminated.
       Abstracted calls, such as rdma_create_ep encapsulate  serveral  of  these  calls  under  a
       single API.  Users may also refer to the example applications for code samples.  A general
       connection flow would be:

       rdma_getaddrinfo
              retrieve address information of the destination

       rdma_create_event_channel
              create channel to receive events

       rdma_create_id
              allocate an rdma_cm_id, this is conceptually similar to a socket

       rdma_resolve_addr
              obtain a local RDMA device to reach the remote address

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_ADDR_RESOLVED event

       rdma_ack_cm_event
              ack event

       rdma_create_qp
              allocate a QP for the communication

       rdma_resolve_route
              determine the route to the remote address

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_ROUTE_RESOLVED event

       rdma_ack_cm_event
              ack event

       rdma_connect
              connect to the remote server

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_ESTABLISHED event

       rdma_ack_cm_event
              ack event

       Perform data transfers over connection

       rdma_disconnect
              tear-down connection

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_DISCONNECTED event

       rdma_ack_cm_event
              ack event

       rdma_destroy_qp
              destroy the QP

       rdma_destroy_id
              release the rdma_cm_id

       rdma_destroy_event_channel
              release the event channel

       An almost identical process is  used  to  setup  unreliable  datagram  (UD)  communication
       between  nodes.   No  actual connection is formed between QPs however, so disconnection is
       not needed.

       Although this example shows the  client  initiating  the  disconnect,  either  side  of  a
       connection may initiate the disconnect.

SERVER OPERATION

       This  section  provides  a  general  overview  of  the basic operation for the passive, or
       server, side of communication.  A general connection flow would be:

       rdma_create_event_channel
              create channel to receive events

       rdma_create_id
              allocate an rdma_cm_id, this is conceptually similar to a socket

       rdma_bind_addr
              set the local port number to listen on

       rdma_listen
              begin listening for connection requests

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_CONNECT_REQUEST event with a new rdma_cm_id

       rdma_create_qp
              allocate a QP for the communication on the new rdma_cm_id

       rdma_accept
              accept the connection request

       rdma_ack_cm_event
              ack event

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_ESTABLISHED event

       rdma_ack_cm_event
              ack event

       Perform data transfers over connection

       rdma_get_cm_event
              wait for RDMA_CM_EVENT_DISCONNECTED event

       rdma_ack_cm_event
              ack event

       rdma_disconnect
              tear-down connection

       rdma_destroy_qp
              destroy the QP

       rdma_destroy_id
              release the connected rdma_cm_id

       rdma_destroy_id
              release the listening rdma_cm_id

       rdma_destroy_event_channel
              release the event channel

RETURN CODES

       =  0   success

       = -1   error - see errno for more details

       Most librdmacm functions return 0 to indicate success, and a -1 return value  to  indicate
       failure.   If  a  function  operates  asynchronously,  a  return value of 0 means that the
       operation was successfully started.  The operation could still complete  in  error;  users
       should  check the status of the related event.  If the return value is -1, then errno will
       contain additional information regarding the reason for the failure.

       Prior versions of the library would return -errno and not set errno for some cases related
       to  ENOMEM,  ENODEV,  ENODATA,  EINVAL, and EADDRNOTAVAIL codes. Applications that want to
       check these codes and have compatability with prior library  versions  must  manually  set
       errno to the negative of the return code if it is < -1.

SEE ALSO

       rdma_accept(3),       rdma_ack_cm_event(3),       rdma_bind_addr(3),      rdma_connect(3),
       rdma_create_ep(3),  rdma_create_event_channel(3),  rdma_create_id(3),   rdma_create_qp(3),
       rdma_dereg_mr(3),  rdma_destroy_ep(3),  rdma_destroy_event_channel(3), rdma_destroy_id(3),
       rdma_destroy_qp(3),    rdma_disconnect(3),    rdma_event_str(3),     rdma_free_devices(3),
       rdma_getaddrinfo(3),   rdma_get_cm_event(3),   rdma_get_devices(3),  rdma_get_dst_port(3),
       rdma_get_local_addr(3), rdma_get_peer_addr(3), rdma_get_recv_comp(3), rdma_get_request(3),
       rdma_get_send_comp(3),            rdma_get_src_port(3),            rdma_join_multicast(3),
       rdma_leave_multicast(3),     rdma_listen(3),      rdma_migrate_id(3),      rdma_notify(3),
       rdma_post_read(3)      rdma_post_readv(3),      rdma_post_recv(3),     rdma_post_recvv(3),
       rdma_post_send(3),    rdma_post_sendv(3),    rdma_post_ud_send(3),     rdma_post_write(3),
       rdma_post_writev(3),      rdma_reg_msgs(3),      rdma_reg_read(3),      rdma_reg_write(3),
       rdma_reject(3), rdma_resolve_addr(3), rdma_resolve_route(3), rdma_set_option(3)  mckey(1),
       rdma_client(1), rdma_server(1), rping(1), ucmatose(1), udaddy(1)