1RDMA_CONNECT(3) Librdmacm Programmer's Manual RDMA_CONNECT(3)
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6 rdma_connect - Initiate an active connection request.
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9 #include <rdma/rdma_cma.h>
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11 int rdma_connect (struct rdma_cm_id *id, struct rdma_conn_param
12 *conn_param);
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15 id RDMA identifier.
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17 conn_param connection parameters. See CONNECTION PROPERTIES below for
18 details.
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21 For an rdma_cm_id of type RDMA_PS_TCP, this call initiates a connection
22 request to a remote destination. For an rdma_cm_id of type
23 RDMA_PS_UDP, it initiates a lookup of the remote QP providing the data‐
24 gram service.
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27 Users must have resolved a route to the destination address by having
28 called rdma_resolve_route before calling this routine.
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31 The following properties are used to configure the communication and
32 specified by the conn_param parameter when connecting or establishing
33 datagram communication.
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35 private_data
36 References a user-controlled data buffer. The contents of the
37 buffer are copied and transparently passed to the remote side as
38 part of the communication request. May be NULL if private_data
39 is not required.
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41 private_data_len
42 Specifies the size of the user-controlled data buffer. Note
43 that the actual amount of data transferred to the remote side is
44 transport dependent and may be larger than that requested.
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46 responder_resources
47 The maximum number of outstanding RDMA read and atomic opera‐
48 tions that the local side will accept from the remote side.
49 Applies only to RDMA_PS_TCP. This value must be less than or
50 equal to the local RDMA device attribute max_qp_rd_atom and
51 remote RDMA device attribute max_qp_init_rd_atom. The remote
52 endpoint can adjust this value when accepting the connection.
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54 initiator_depth
55 The maximum number of outstanding RDMA read and atomic opera‐
56 tions that the local side will have to the remote side. Applies
57 only to RDMA_PS_TCP. This value must be less than or equal to
58 the local RDMA device attribute max_qp_init_rd_atom and remote
59 RDMA device attribute max_qp_rd_atom. The remote endpoint can
60 adjust this value when accepting the connection.
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62 flow_control
63 Specifies if hardware flow control is available. This value is
64 exchanged with the remote peer and is not used to configure the
65 QP. Applies only to RDMA_PS_TCP.
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67 retry_count
68 The maximum number of times that a data transfer operation
69 should be retried on the connection when an error occurs. This
70 setting controls the number of times to retry send, RDMA, and
71 atomic operations when timeouts occur. Applies only to
72 RDMA_PS_TCP.
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74 rnr_retry_count
75 The maximum number of times that a send operation from the
76 remote peer should be retried on a connection after receiving a
77 receiver not ready (RNR) error. RNR errors are generated when a
78 send request arrives before a buffer has been posted to receive
79 the incoming data. Applies only to RDMA_PS_TCP.
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81 srq Specifies if the QP associated with the connection is using a
82 shared receive queue. This field is ignored by the library if a
83 QP has been created on the rdma_cm_id. Applies only to
84 RDMA_PS_TCP.
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86 qp_num Specifies the QP number associated with the connection. This
87 field is ignored by the library if a QP has been created on the
88 rdma_cm_id. Applies only to RDMA_PS_TCP.
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91 In addition to the connection properties defined above, InfiniBand QPs
92 are configured with minimum RNR NAK timer and local ACK timeout values.
93 The minimum RNR NAK timer value is set to 0, for a delay of 655 ms.
94 The local ACK timeout is calculated based on the packet lifetime and
95 local HCA ACK delay. The packet lifetime is determined by the Infini‐
96 Band Subnet Administrator and is part of the resolved route (path
97 record) information. The HCA ACK delay is a property of the locally
98 used HCA.
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100 Retry count and RNR retry count values are 3-bit values.
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103 Connections established over iWarp RDMA devices currently require that
104 the active side of the connection send the first message.
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107 rdma_cm(7), rdma_create_id(3), rdma_resolve_route(3), rdma_discon‐
108 nect(3), rdma_listen(3), rdma_get_cm_event(3)
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112librdmacm 2007-10-31 RDMA_CONNECT(3)