rdma_connect(3) — Linux manual page

NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | RETURN VALUE | NOTES | CONNECTION PROPERTIES | INFINIBAND SPECIFIC | IWARP SPECIFIC | SEE ALSO | COLOPHON

RDMA_CONNECT(3)       Librdmacm Programmer's Manual      RDMA_CONNECT(3)

NAME         top

       rdma_connect - Initiate an active connection request.

SYNOPSIS         top

       #include <rdma/rdma_cma.h>

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

ARGUMENTS         top

       id          RDMA identifier.

       conn_param  connection parameters.  See CONNECTION PROPERTIES
                   below for details.

DESCRIPTION         top

       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         top

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

NOTES         top

       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         top

       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         top

       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         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the rdma-core (RDMA Core Userspace Libraries
       and Daemons) project.  Information about the project can be found
       at ⟨https://github.com/linux-rdma/rdma-core⟩.  If you have a bug
       report for this manual page, send it to
       linux-rdma@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2021-08-27.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-08-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

librdmacm                      2010-07-19                RDMA_CONNECT(3)

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