rdma_connect(3)

1RDMA_CONNECT(3)          Librdmacm Programmer's Manual         RDMA_CONNECT(3)
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NAME

6       rdma_connect - Initiate an active connection request.
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SYNOPSIS

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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ARGUMENTS

15       id          RDMA identifier.
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17       conn_param  connection parameters.  See CONNECTION PROPERTIES below for
18                   details.
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DESCRIPTION

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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RETURN VALUE

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

31       Users  must  have resolved a route to the destination address by having
32       called rdma_resolve_route or rdma_create_ep before  calling  this  rou‐
33       tine.
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CONNECTION PROPERTIES

36       The  following  properties  are used to configure the communication and
37       specified by the conn_param parameter when connecting  or  establishing
38       datagram communication.
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40       private_data
41              References  a  user-controlled data buffer.  The contents of the
42              buffer are copied and transparently passed to the remote side as
43              part  of the communication request.  May be NULL if private_data
44              is not required.
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46       private_data_len
47              Specifies the size of the  user-controlled  data  buffer.   Note
48              that the actual amount of data transferred to the remote side is
49              transport dependent and may be larger than that requested.
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51       responder_resources
52              The maximum number of outstanding RDMA read  and  atomic  opera‐
53              tions  that  the  local  side  will accept from the remote side.
54              Applies only to RDMA_PS_TCP.  This value must be  less  than  or
55              equal  to  the  local  RDMA  device attribute max_qp_rd_atom and
56              remote RDMA device attribute  max_qp_init_rd_atom.   The  remote
57              endpoint can adjust this value when accepting the connection.
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59       initiator_depth
60              The  maximum  number  of outstanding RDMA read and atomic opera‐
61              tions that the local side will have to the remote side.  Applies
62              only  to  RDMA_PS_TCP.  This value must be less than or equal to
63              the local RDMA device attribute max_qp_init_rd_atom  and  remote
64              RDMA  device  attribute max_qp_rd_atom.  The remote endpoint can
65              adjust this value when accepting the connection.
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67       flow_control
68              Specifies if hardware flow control is available.  This value  is
69              exchanged  with the remote peer and is not used to configure the
70              QP.  Applies only to RDMA_PS_TCP.
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72       retry_count
73              The maximum number of  times  that  a  data  transfer  operation
74              should  be retried on the connection when an error occurs.  This
75              setting controls the number of times to retry  send,  RDMA,  and
76              atomic   operations   when  timeouts  occur.   Applies  only  to
77              RDMA_PS_TCP.
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79       rnr_retry_count
80              The maximum number of times  that  a  send  operation  from  the
81              remote  peer should be retried on a connection after receiving a
82              receiver not ready (RNR) error.  RNR errors are generated when a
83              send  request arrives before a buffer has been posted to receive
84              the incoming data.  Applies only to RDMA_PS_TCP.
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86       srq    Specifies if the QP associated with the connection  is  using  a
87              shared receive queue.  This field is ignored by the library if a
88              QP  has  been  created  on  the  rdma_cm_id.   Applies  only  to
89              RDMA_PS_TCP.
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91       qp_num Specifies  the  QP  number associated with the connection.  This
92              field is ignored by the library if a QP has been created on  the
93              rdma_cm_id.  Applies only to RDMA_PS_TCP.
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INFINIBAND SPECIFIC

96       In  addition to the connection properties defined above, InfiniBand QPs
97       are configured with minimum RNR NAK timer and local ACK timeout values.
98       The  minimum  RNR  NAK  timer value is set to 0, for a delay of 655 ms.
99       The local ACK timeout is calculated based on the  packet  lifetime  and
100       local  HCA ACK delay.  The packet lifetime is determined by the Infini‐
101       Band Subnet Administrator and is  part  of  the  resolved  route  (path
102       record)  information.   The  HCA ACK delay is a property of the locally
103       used HCA.
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105       Retry count and RNR retry count values are 3-bit values.
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107       The length of the private data provided by the user is  limited  to  56
108       bytes for RDMA_PS_TCP, or 180 bytes for RDMA_PS_UDP.
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IWARP SPECIFIC

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