rdma_accept(3)

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

6       rdma_accept - Called to accept a connection request.
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SYNOPSIS

9       #include <rdma/rdma_cma.h>
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11       int   rdma_accept   (struct   rdma_cm_id  *id,  struct  rdma_conn_param
12       *conn_param);
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ARGUMENTS

15       id          Connection identifier associated with the request.
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17       conn_param  Information needed to establish the connection.   See  CON‐
18                   NECTION PROPERTIES below for details.
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DESCRIPTION

21       Called  from the listening side to accept a connection or datagram ser‐
22       vice lookup request.
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RETURN VALUE

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

29       Unlike  the  socket accept routine, rdma_accept is not called on a lis‐
30       tening rdma_cm_id.  Instead, after calling rdma_listen, the user  waits
31       for   an  RDMA_CM_EVENT_CONNECT_REQUEST  event  to  occur.   Connection
32       request events give the user a newly created rdma_cm_id, similar  to  a
33       new  socket,  but  the  rdma_cm_id  is bound to a specific RDMA device.
34       rdma_accept is called on the new rdma_cm_id.
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CONNECTION PROPERTIES

37       The following properties are used to configure  the  communication  and
38       specified  by  the  conn_param parameter when accepting a connection or
39       datagram communication request.  Users should use  the  rdma_conn_param
40       values  reported in the connection request event to determine appropri‐
41       ate values for these fields when accepting.  Users  may  reference  the
42       rdma_conn_param structure in the connection event directly, or can ref‐
43       erence their own structure.  If the rdma_conn_param structure  from  an
44       event  is referenced, the event must not be acked until after this call
45       returns.
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47       If the conn_param parameter is NULL, the values reported in the connec‐
48       tion  request  event  are  used,  adjusted down based on local hardware
49       restrictions.
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51       private_data
52              References a user-controlled data buffer.  The contents  of  the
53              buffer are copied and transparently passed to the remote side as
54              part of the communication request.  May be NULL if  private_data
55              is not required.
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57       private_data_len
58              Specifies  the  size  of  the user-controlled data buffer.  Note
59              that the actual amount of data transferred to the remote side is
60              transport dependent and may be larger than that requested.
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62       responder_resources
63              The  maximum  number  of outstanding RDMA read and atomic opera‐
64              tions that the local side will  accept  from  the  remote  side.
65              Applies  only  to  RDMA_PS_TCP.  This value must be less than or
66              equal to the local RDMA  device  attribute  max_qp_rd_atom,  but
67              preferably  greater  than  or  equal  to the responder_resources
68              value reported in the connect request event.
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70       initiator_depth
71              The maximum number of outstanding RDMA read  and  atomic  opera‐
72              tions that the local side will have to the remote side.  Applies
73              only to RDMA_PS_TCP.  This value must be less than or  equal  to
74              the local RDMA device attribute max_qp_init_rd_atom and the ini‐
75              tiator_depth value reported in the connect request event.
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77       flow_control
78              Specifies if hardware flow control is available.  This value  is
79              exchanged  with the remote peer and is not used to configure the
80              QP.  Applies only to RDMA_PS_TCP.
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82       retry_count
83              This value is ignored.
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85       rnr_retry_count
86              The maximum number of times  that  a  send  operation  from  the
87              remote  peer should be retried on a connection after receiving a
88              receiver not ready (RNR) error.  RNR errors are generated when a
89              send  request arrives before a buffer has been posted to receive
90              the incoming data.  Applies only to RDMA_PS_TCP.
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92       srq    Specifies if the QP associated with the connection  is  using  a
93              shared receive queue.  This field is ignored by the library if a
94              QP  has  been  created  on  the  rdma_cm_id.   Applies  only  to
95              RDMA_PS_TCP.
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97       qp_num Specifies  the  QP  number associated with the connection.  This
98              field is ignored by the library if a QP has been created on  the
99              rdma_cm_id.
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INFINIBAND SPECIFIC

102       In  addition to the connection properties defined above, InfiniBand QPs
103       are configured with minimum RNR NAK timer and local ACK timeout values.
104       The  minimum  RNR  NAK  timer value is set to 0, for a delay of 655 ms.
105       The local ACK timeout is calculated based on the  packet  lifetime  and
106       local  HCA ACK delay.  The packet lifetime is determined by the Infini‐
107       Band Subnet Administrator and is part of the route (path record) infor‐
108       mation  obtained  by  the  active  side of the connection.  The HCA ACK
109       delay is a property of the locally used HCA.
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111       The RNR retry count is a 3-bit value.
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113       The length of the private data provided by the user is limited  to  196
114       bytes for RDMA_PS_TCP, or 136 bytes for RDMA_PS_UDP.
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