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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)
rdma_connect - Initiate an active connection request.
#include <rdma/rdma_cma.h>
int rdma_connect (struct rdma_cm_id *id, struct rdma_conn_param
*conn_param);
id RDMA identifier.
conn_param connection parameters. See CONNECTION PROPERTIES below
for details.
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.
Returns 0 on success, or -1 on error. If an error occurs, errno will
be set to indicate the failure reason.
Users must have resolved a route to the destination address by having
called rdma_resolve_route or rdma_create_ep before calling this
routine.
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.
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.
Connections established over iWarp RDMA devices currently require
that the active side of the connection send the first message.
rdma_cm(7), rdma_create_id(3), rdma_resolve_route(3),
rdma_disconnect(3), rdma_listen(3), rdma_get_cm_event(3)
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 2020-08-13. (At
that time, the date of the most recent commit that was found in the
repository was 2020-08-05.) 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)
Pages that refer to this page: rdma_create_ep(3) , rdma_create_id(3) , rdma_disconnect(3) , rdma_getaddrinfo(3) , rdma_get_cm_event(3) , rdma_get_dst_port(3) , rdma_get_request(3) , rdma_listen(3) , rdma_notify(3) , rdma_post_read(3) , rdma_post_readv(3) , rdma_post_send(3) , rdma_post_sendv(3) , rdma_post_ud_send(3) , rdma_post_write(3) , rdma_post_writev(3) , rdma_resolve_addr(3) , rdma_resolve_route(3) , rdma_cm(7)