xenial (3) rdma_connect.3.gz

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)