NAME

       rdma_connect - Initiate an active connection request.

SYNOPSIS

       #include <rdma/rdma_cma.h>

       int rdma_connect (struct rdma_cm_id *id, struct rdma_conn_param *conn_param);

ARGUMENTS

       id          RDMA identifier.

       conn_param  connection parameters.  See CONNECTION PROPERTIES below for details.

DESCRIPTION

       For  an rdma_cm_id of type RDMA_PS_TCP, this call initiates a connection request to a remote destination.
       For an rdma_cm_id of type RDMA_PS_UDP, it initiates a lookup of the  remote  QP  providing  the  datagram
       service.

RETURN VALUE

       Returns  0  on  success,  or  -1 on error.  If an error occurs, errno will be set to indicate the failure
       reason.

NOTES

       Users must have resolved a route to the  destination  address  by  having  called  rdma_resolve_route  or
       rdma_create_ep before calling this routine.

CONNECTION PROPERTIES

       The  following  properties  are  used  to  configure  the  communication  and specified by the conn_param
       parameter when connecting or establishing datagram communication.

       private_data
              References a user-controlled data buffer.  The contents of the buffer are copied and transparently
              passed to the remote side as part of the communication request.  May be NULL  if  private_data  is
              not required.

       private_data_len
              Specifies  the  size  of  the  user-controlled  data  buffer.  Note that the actual amount of data
              transferred to the remote side is transport dependent and may be larger than that requested.

       responder_resources
              The maximum number of outstanding RDMA read and atomic operations that the local side will  accept
              from  the remote side.  Applies only to RDMA_PS_TCP.  This value must be less than or equal to the
              local RDMA device attribute max_qp_rd_atom and remote RDMA device  attribute  max_qp_init_rd_atom.
              The remote endpoint can adjust this value when accepting the connection.

       initiator_depth
              The maximum number of outstanding RDMA read and atomic operations that the local side will have to
              the remote side.  Applies only to RDMA_PS_TCP.  This value must be less than or equal to the local
              RDMA  device  attribute  max_qp_init_rd_atom and remote RDMA device attribute max_qp_rd_atom.  The
              remote endpoint can adjust this value when accepting the connection.

       flow_control
              Specifies if hardware flow control is available.  This value is exchanged with the remote peer and
              is not used to configure the QP.  Applies only to RDMA_PS_TCP.

       retry_count
              The maximum number of times that a data transfer operation should be  retried  on  the  connection
              when  an  error occurs.  This setting controls the number of times to retry send, RDMA, and atomic
              operations when timeouts occur.  Applies only to RDMA_PS_TCP.

       rnr_retry_count
              The maximum number of times that a send operation from the remote peer  should  be  retried  on  a
              connection after receiving a receiver not ready (RNR) error.  RNR errors are generated when a send
              request  arrives  before  a  buffer has been posted to receive the incoming data.  Applies only to
              RDMA_PS_TCP.

       srq    Specifies if the QP associated with the connection is using a shared receive queue.  This field is
              ignored by the library if a QP has been created on the rdma_cm_id.  Applies only to RDMA_PS_TCP.

       qp_num Specifies the QP number associated with the connection.  This field is ignored by the library if a
              QP has been created on the rdma_cm_id.  Applies only to RDMA_PS_TCP.

INFINIBAND SPECIFIC

       In addition to the connection properties defined above, InfiniBand QPs are configured  with  minimum  RNR
       NAK  timer and local ACK timeout values.  The minimum RNR NAK timer value is set to 0, for a delay of 655
       ms.  The local ACK timeout is calculated based on the packet lifetime  and  local  HCA  ACK  delay.   The
       packet  lifetime  is  determined by the InfiniBand Subnet Administrator and is part of the resolved route
       (path record) information.  The HCA ACK delay is a property of the locally used HCA.

       Retry count and RNR retry count values are 3-bit values.

       The length of the private data provided by the user is limited to 56 bytes for RDMA_PS_TCP, or 180  bytes
       for RDMA_PS_UDP.

IWARP SPECIFIC

       Connections  established over iWarp RDMA devices currently require that the active side of the connection
       send the first message.

SEE ALSO

       rdma_cm(7),     rdma_create_id(3),     rdma_resolve_route(3),     rdma_disconnect(3),     rdma_listen(3),
       rdma_get_cm_event(3)

librdmacm                                          2010-07-19                                    RDMA_CONNECT(3)