Tribblix: manual page: sdp.4d

SDP(4D) Devices SDP(4D)

NAME

sdp - Sockets Direct Protocol driver

SYNOPSIS

#include <sys/socket.h>

#include <netinet/in.h>

s = socket(AF_INET, SOCK_STREAM, PROTO_SDP);

s = socket(AF_INET6, SOCK_STREAM, PROTO_SDP);

DESCRIPTION

The Sockets Direct Protocol (SDP) is a transport protocol layered
over the Infiniband Transport Framework (IBTF). SDP is a standard
implementation based on Annex 4 of the Infiniband Architecture
Specification Vol 1 and provides reliable byte-stream, flow
controlled two-way data transmission that closely mimics the
Transmission Control Protocol (TCP).

SDP supports a sockets-based SOCK_STREAM interface to application
programs. It also supports graceful close (including half-closed
sockets), IP addressing (IPv4 or IPv6), the connecting/accepting
connect model, out-of-band (OOB) data and common socket options. The
SDP protocol also supports kernel bypass data transfers and data
transfers from send-upper-layer-protocol (ULP) buffers to receive ULP
buffers. A SDP message includes a BSDH header followed by data. (A
BSDH header advertises the amount of available buffers on the local
side).

SDP networking functionality is broken into the sdp driver and a
function call-based sockfs implementation. A new protocol family of
PROTO_SDP is introduced to use the SDP transport provided by the
driver.

Sockets utilizing SDP are either active or passive. Active sockets
initiate connections to passive sockets. Both active and passive
sockets must have their local IP or IPv6 address and SDP port number
bound with the bind(3SOCKET) system call after the socket is created.
By default, SDP sockets are active. A passive socket is created by
calling the listen(3SOCKET) system call after binding the socket with
bind(). This process establishes a queueing parameter for the passive
socket. Connections to the passive socket can be received with the
accept(3SOCKET) system call. Active sockets use the connect(3SOCKET)
call after binding to initiate connections.

In most cases, SDP sends data when it is presented. When outstanding
data is not yet acknowledged, SDP gathers small amounts of output to
be sent in a single packet once an acknowledgement is received. For a
small number of clients this packetization may cause significant
delays. To circumvent this problem, SDP provided by the driver
supplies SDP_NODELAY, a socket-level boolean option. Note that this
behavior is similar to the TCP_NODELAY option.

SDP provides an urgent data mechanism that can be invoked using the
out-of-band provisions of send(3SOCKET). The out-of-band delivery
behavior is identical to TCP. The caller may mark one byte as
"urgent" with the MSG_OOB flag to send(3SOCKET). This sets an "urgent
pointer" pointing to the byte in the SDP stream. The receiver of the
stream is notified of the urgent data by a SIGURG signal. The
SIOCATMARK ioctl(2) request returns a value indicating whether the
stream is at the urgent mark. Because the system never returns data
across the urgent mark in a single read(2) call, it is possible to
advance to the urgent data in a simple loop which reads data, testing
the socket with the SIOCATMARK ioctl() request until it reaches the
mark.

ADDRESS FORMATS

SDP uses IP/IPv6 addresses to refer to local and remote devices and
opens a reliable connected IB connection between two end points. The
sdp driver supports a point-to-point connection, however broadcasting
and multicasting are not supported.

SOCKET OPTIONS

SDP supports setsockopt and getsockopt to set and read socket
options. Very few socket options affect SDP protocol operations.
Other common socket options are processed but do not affect SDP
protocol operation. All socket options are checked for validity. A
getsockopt returns the values set or toggled by setsockopt. Socket
options that affect protocol operations are SO_LINGER, SO_DEBUG,
SO_REUSEADDR and SO_OOBINLINE.

ERRORS

EISCONN
A connect() operation was attempted on a
socket on which a connect() operation had
already been performed.

ECONNRESET
The remote peer forced the connection to
be closed. This usually occurs when the
remote machine loses state information
about the connection due to a crash.

ECONNREFUSED
The remote peer actively refused
connection establishment. This usually
occurs because no process is listening to
the port.

EADDRINUSE
A bind() operation was attempted on a
socket with a network address/port pair
that has already been bound to another
socket.

EADDRNOTAVAIL
A bind() operation was attempted on a
socket with a network address for which
no network interface exists.

EACCES
A bind() operation was attempted with a
reserved port number and the effective
user ID of the process was not the
privileged user.

ENOBUFS
The system ran out of memory for internal
data structures.

FILES

/kernel/drv/amd64/sdp

64-bit ELF kernel module (x86).

/kernel/drv/sparcv9/sdp

64-bit ELF kernel module (SPARC).

/kernel/drv/amd64/sdpib

64-bit ELF kernel module (x86).

/kernel/drv/sparcv9/sdpib

64-bit ELF kernel module (SPARC).

ATTRIBUTES