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NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | RETURN VALUE | NOTES | EVENT DATA | UD EVENT DATA | CONN EVENT DATA | EVENT TYPES | SEE ALSO | COLOPHON |
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RDMA_GET_CM_EVENT(3) Librdmacm Programmer's Manual RDMA_GET_CM_EVENT(3)
rdma_get_cm_event - Retrieves the next pending communication
event.
#include <rdma/rdma_cma.h>
int rdma_get_cm_event (struct rdma_event_channel *channel, struct
rdma_cm_event **event);
channel Event channel to check for events.
event Allocated information about the next communication
event.
Retrieves a communication event. If no events are pending, by
default, the call will block until an event is received.
Returns 0 on success, or -1 on error. If an error occurs, errno
will be set to indicate the failure reason.
The default synchronous behavior of this routine can be changed by
modifying the file descriptor associated with the given channel.
All events that are reported must be acknowledged by calling
rdma_ack_cm_event. Destruction of an rdma_cm_id will block until
related events have been acknowledged.
Communication event details are returned in the rdma_cm_event
structure. This structure is allocated by the rdma_cm and
released by the rdma_ack_cm_event routine. Details of the
rdma_cm_event structure are given below.
id The rdma_cm identifier associated with the event. If
the event type is RDMA_CM_EVENT_CONNECT_REQUEST, then
this references a new id for that communication.
listen_id For RDMA_CM_EVENT_CONNECT_REQUEST event types, this
references the corresponding listening request
identifier.
event Specifies the type of communication event which
occurred. See EVENT TYPES below.
status Returns any asynchronous error information associated
with an event. The status is zero if the operation
was successful, otherwise the status value is non-zero
and is either set to a negative errno or a transport
specific value. For details on transport specific
status values, see the event type information below.
param Provides additional details based on the type of
event. Users should select the conn or ud subfields
based on the rdma_port_space of the rdma_cm_id
associated with the event. See UD EVENT DATA and CONN
EVENT DATA below.
Event parameters related to unreliable datagram (UD) services:
RDMA_PS_UDP and RDMA_PS_IPOIB. The UD event data is valid for
RDMA_CM_EVENT_ESTABLISHED and RDMA_CM_EVENT_MULTICAST_JOIN events,
unless stated otherwise.
private_data
References any user-specified data associated with
RDMA_CM_EVENT_CONNECT_REQUEST or
RDMA_CM_EVENT_ESTABLISHED events. The data referenced
by this field matches that specified by the remote
side when calling rdma_connect or rdma_accept. This
field is NULL if the event does not include private
data. The buffer referenced by this pointer is
deallocated when calling rdma_ack_cm_event.
private_data_len
The size of the private data buffer. Users should
note that the size of the private data buffer may be
larger than the amount of private data sent by the
remote side. Any additional space in the buffer will
be zeroed out.
ah_attr Address information needed to send data to the remote
endpoint(s). Users should use this structure when
allocating their address handle.
qp_num QP number of the remote endpoint or multicast group.
qkey QKey needed to send data to the remote endpoint(s).
Event parameters related to connected QP services: RDMA_PS_TCP.
The connection related event data is valid for
RDMA_CM_EVENT_CONNECT_REQUEST and RDMA_CM_EVENT_ESTABLISHED
events, unless stated otherwise.
private_data
References any user-specified data associated with the
event. The data referenced by this field matches that
specified by the remote side when calling rdma_connect
or rdma_accept. This field is NULL if the event does
not include private data. The buffer referenced by
this pointer is deallocated when calling
rdma_ack_cm_event.
private_data_len
The size of the private data buffer. Users should
note that the size of the private data buffer may be
larger than the amount of private data sent by the
remote side. Any additional space in the buffer will
be zeroed out.
responder_resources
The number of responder resources requested of the
recipient. This field matches the initiator depth
specified by the remote node when calling rdma_connect
and rdma_accept.
initiator_depth
The maximum number of outstanding RDMA read/atomic
operations that the recipient may have outstanding.
This field matches the responder resources specified
by the remote node when calling rdma_connect and
rdma_accept.
flow_control
Indicates if hardware level flow control is provided
by the sender.
retry_count For RDMA_CM_EVENT_CONNECT_REQUEST events only,
indicates the number of times that the recipient
should retry send operations.
rnr_retry_count
The number of times that the recipient should retry
receiver not ready (RNR) NACK errors.
srq Specifies if the sender is using a shared-receive
queue.
qp_num Indicates the remote QP number for the connection.
The following types of communication events may be reported.
RDMA_CM_EVENT_ADDR_RESOLVED
Address resolution (rdma_resolve_addr) completed
successfully.
RDMA_CM_EVENT_ADDR_ERROR
Address resolution (rdma_resolve_addr) failed.
RDMA_CM_EVENT_ROUTE_RESOLVED
Route resolution (rdma_resolve_route) completed
successfully.
RDMA_CM_EVENT_ROUTE_ERROR
Route resolution (rdma_resolve_route) failed.
RDMA_CM_EVENT_CONNECT_REQUEST
Generated on the passive side to notify the user of a new
connection request.
RDMA_CM_EVENT_CONNECT_RESPONSE
Generated on the active side to notify the user of a
successful response to a connection request. It is only
generated on rdma_cm_id's that do not have a QP associated
with them.
RDMA_CM_EVENT_CONNECT_ERROR
Indicates that an error has occurred trying to establish or
a connection. May be generated on the active or passive
side of a connection.
RDMA_CM_EVENT_UNREACHABLE
Generated on the active side to notify the user that the
remote server is not reachable or unable to respond to a
connection request. If this event is generated in response
to a UD QP resolution request over InfiniBand, the event
status field will contain an errno, if negative, or the
status result carried in the IB CM SIDR REP message.
RDMA_CM_EVENT_REJECTED
Indicates that a connection request or response was
rejected by the remote end point. The event status field
will contain the transport specific reject reason if
available. Under InfiniBand, this is the reject reason
carried in the IB CM REJ message.
RDMA_CM_EVENT_ESTABLISHED
Indicates that a connection has been established with the
remote end point.
RDMA_CM_EVENT_DISCONNECTED
The connection has been disconnected.
RDMA_CM_EVENT_DEVICE_REMOVAL
The local RDMA device associated with the rdma_cm_id has
been removed. Upon receiving this event, the user must
destroy the related rdma_cm_id.
RDMA_CM_EVENT_MULTICAST_JOIN
The multicast join operation (rdma_join_multicast)
completed successfully.
RDMA_CM_EVENT_MULTICAST_ERROR
An error either occurred joining a multicast group, or, if
the group had already been joined, on an existing group.
The specified multicast group is no longer accessible and
should be rejoined, if desired.
RDMA_CM_EVENT_ADDR_CHANGE
The network device associated with this ID through address
resolution changed its HW address, eg following of bonding
failover. This event can serve as a hint for applications
who want the links used for their RDMA sessions to align
with the network stack.
RDMA_CM_EVENT_TIMEWAIT_EXIT
The QP associated with a connection has exited its timewait
state and is now ready to be re-used. After a QP has been
disconnected, it is maintained in a timewait state to allow
any in flight packets to exit the network. After the
timewait state has completed, the rdma_cm will report this
event.
rdma_ack_cm_event(3), rdma_create_event_channel(3),
rdma_resolve_addr(3), rdma_resolve_route(3), rdma_connect(3),
rdma_listen(3), rdma_join_multicast(3), rdma_destroy_id(3),
rdma_event_str(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 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-04.) 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 2007-10-31 RDMA_GET_CM_EVENT(3)
Pages that refer to this page: rdma_accept(3), rdma_ack_cm_event(3), rdma_connect(3), rdma_create_event_channel(3), rdma_destroy_event_channel(3), rdma_disconnect(3), rdma_establish(3), rdma_event_str(3), rdma_get_dst_port(3), rdma_get_request(3), rdma_join_multicast(3), rdma_join_multicast_ex(3), rdma_listen(3), rdma_migrate_id(3), rdma_reject(3), rdma_resolve_addr(3), rdma_resolve_route(3), rdma_cm(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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