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RSOCKET(7)               Librdmacm Programmer's Manual              RSOCKET(7)

       rsocket - RDMA socket API

       #include <rdma/rsocket.h>

       RDMA socket API and protocol

       Rsockets  is a protocol over RDMA that supports a socket-level API for applications.  Rsocket APIs are intended
       to match the behavior of corresponding socket calls, except where noted.  Rsocket functions match the name  and
       function signature of socket calls, with the exception that all function calls are prefixed with an 'r'.

       The following functions are defined:


       rbind, rlisten, raccept, rconnect

       rshutdown, rclose

       rrecv, rrecvfrom, rrecvmsg, rread, rreadv

       rsend, rsendto, rsendmsg, rwrite, rwritev

       rpoll, rselect

       rgetpeername, rgetsockname

       rsetsockopt, rgetsockopt, rfcntl

       Functions  take  the same parameters as that used for sockets.  The follow capabilities and flags are supported
       at this time:


       SOL_SOCKET -  SO_ERROR,  SO_KEEPALIVE  (flag  supported,  but  ignored),  SO_LINGER,  SO_OOBINLINE,  SO_RCVBUF,




       Rsockets  provides  extensions  beyond  normal  socket routines that allow for direct placement of data into an
       application's buffer.  This is also known as zero-copy support, since  data  is  sent  and  received  directly,
       bypassing  copies  into network controlled buffers.  The following calls and options support direct data place-

       riomap, riounmap, riowrite

       off_t riomap(int socket, void *buf, size_t len, int prot, int flags, off_t offset)

       Riomap registers an application buffer with the RDMA hardware
              associated with an rsocket.  The buffer is registered either for local only access  (PROT_NONE)  or  for
              remote  write  access  (PROT_WRITE).  When registered for remote access, the buffer is mapped to a given
              offset.  The offset is either provided by the user, or if the user selects -1 for the  offset,  rsockets
              selects  one.   The remote peer may access an iomapped buffer directly by specifying the correct offset.
              The mapping is not guaranteed to be available until after the remote peer receives a data transfer  ini-
              tiated after riomap has completed.

       In  order  to enable the use of remote IO mapping calls on an rsocket, an application must set the number of IO
       mappings that are available to the remote peer.  This may be done using the rsetsockopt RDMA_IOMAPSIZE  option.
       By default, an rsocket does not support remote IO mappings.  riounmap

       int riounmap(int socket, void *buf, size_t len)

       Riounmap removes the mapping between a buffer and an rsocket.


       size_t riowrite(int socket, const void *buf, size_t count, off_t offset, int flags)

       Riowrite allows an application to transfer data over an rsocket
              directly  into  a remotely iomapped buffer.  The remote buffer is specified through an offset parameter,
              which corresponds to a remote iomapped buffer.  From the sender's perspective, riowrite behaves  similar
              to  rwrite.   From  a receiver's view, riowrite transfers are silently redirected into a pre- determined
              data buffer.  Data is received automatically, and the receiver is not informed of  the  transfer.   How-
              ever,  iowrite  data is still considered part of the data stream, such that iowrite data will be written
              before a subsequent transfer is received.  A message sent immediately after initiating an iowrite may be
              used to notify the receiver of the iowrite.

       In  addition  to  standard  socket  options,  rsockets supports options specific to RDMA devices and protocols.
       These options are accessible through rsetsockopt using SOL_RDMA option level.

       RDMA_SQSIZE - Integer size of the underlying send queue.

       RDMA_RQSIZE - Integer size of the underlying receive queue.

       RDMA_INLINE - Integer size of inline data.

       RDMA_IOMAPSIZE - Integer number of remote IO mappings supported

       RDMA_ROUTE - struct ibv_path_data of path record for connection.

       Note that rsockets fd's cannot be passed into non-rsocket calls.  For applications which must mix rsocket  fd's
       with standard socket fd's or opened files, rpoll and rselect support polling both rsockets and normal fd's.

       Existing  applications  can make use of rsockets through the use of a preload library.  Because rsockets imple-
       ments an end-to-end protocol, both sides of a connection must use rsockets.  The rdma_cm library provides  such
       a  preload  library,  librspreload.  To reduce the chance of the preload library intercepting calls without the
       user's explicit knowledge, the librspreload library is installed into %libdir%/rsocket subdirectory.

       The preload library can be used by setting LD_PRELOAD when running.  Note that not all applications  will  work
       with  rsockets.  Support is limited based on the socket options used by the application.  Support for fork() is
       limited, but available.  To use rsockets with the preload library for applications that call fork,  users  must
       set  the  environment variable RDMAV_FORK_SAFE=1 on both the client and server side of the connection.  In gen-
       eral, fork is supportable for server applications that accept a connection, then fork off a process  to  handle
       the new connection.

       rsockets  uses  configuration files that give an administrator control over the default settings used by rsock-
       ets.  Use files under %sysconfig%/rdma/rsocket as shown:

       mem_default - default size of receive buffer(s)

       wmem_default - default size of send buffer(s)

       sqsize_default - default size of send queue

       rqsize_default - default size of receive queue

       inline_default - default size of inline data

       iomap_size - default size of remote iomapping table

       polling_time - default number of microseconds to poll for data before waiting

       All configuration files should contain a single integer value.  Values may be set by issuing a command  similar
       to the following example.

       echo 1000000 > /etc/rdma/rsocket/mem_default

       If  configuration  files are not available, rsockets uses internal defaults.  Applications can override default
       values programmatically through the rsetsockopt routine.


librdmacm                         2013-01-21                        RSOCKET(7)