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setsockopt(2)
NAME
setsockopt - Sets socket options
SYNOPSIS
#include <sys/socket.h>
int setsockopt (
int socket,
int level,
int option_name,
const void *option_value,
size_t option_len );
[POSIX] The definition of the setsockopt() function in POSIX.1g Draft 6.6
uses a socklen_t data type instead of a size_t data type as specified in
XNS4.0 (the previous definition).
[Tru64 UNIX] The following definition of the setsockopt() function does
not conform to current standards and is supported only for backward
compatibility (see standards(5)):
#include <sys/socket.h>
int setsockopt (
int socket,
int level,
int option_name,
char *option_value,
int option_len );
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
setsockopt(): [XNS4.0]
The setsockopt function also supports POSIX.1g Draft 6.6.
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
socket Specifies the file descriptor for the socket.
level Specifies the protocol level at which the option resides. To set
options at the socket level, specify the level parameter as
SOL_SOCKET. To set options at other levels, supply the
appropriate protocol number for the protocol controlling the
option. For example, to indicate that an option will be
interpreted by the TCP protocol, set level to the protocol number
of TCP, as defined in the netinet/in.h file or as determined by
using the getprotobyname() function.
option_name
Specifies the option to set. The option_name parameter and any
specified options are passed uninterpreted to the appropriate
protocol module for interpretation. The sys/socket.h header file
defines the socket level options. The socket level options can
be enabled or disabled. The options are:
SO_DEBUG
Turns on recording of debugging information. This option
enables or disables debugging in the underlying protocol
modules. This option takes an int value.
SO_BROADCAST
Permits sending of broadcast messages. This option takes an
int value.
SO_CLUA_DEFAULT_SRC
[Tru64 UNIX] In a cluster, specifies that if the local
address has not already been set through a call to bind(),
the socket will use the default cluster alias as its source
address.
SO_CLUA_IN_NOALIAS
[Tru64 UNIX] In a cluster, specifies that the socket can
only receive packets addressed to this cluster member.
Attempts to bind the socket to a cluster alias address will
fail. A bind to an dynamic port (greater than or equal to
IPPORT_RESERVED and less than IPPORT_USERRESERVED) will not
result in that port being dedicated (or "locked") for use by
a single node in the cluster. A bind to a privileged
reserved port with a wildcard address (INADDR_ANY or
in6addr_any) will not result in that port being locked. The
source address for outgoing UDP sends or TCP connection
requests will be a local host address (never a cluster alias
address). The SO_CLUA_IN_NOLOCAL and SO_CLUA_IN_NOALIAS
options are mutually exclusive.
SO_CLUA_IN_NOLOCAL
[Tru64 UNIX] In a cluster, specifies that the socket must
receive packets addressed to a cluster alias and will drop
any packets that are not addressed to a cluster alias. The
SO_CLUA_IN_NOLOCAL and SO_CLUA_IN_NOALIAS options are
mutually exclusive.
SO_DONTROUTE
[Tru64 UNIX] Indicates that outgoing messages should bypass
the standard routing facilities. Instead, they are directed
to the appropriate network interface according to the network
portion of the destination address.
SO_KEEPALIVE
Keeps connections active. Enables the periodic transmission
of messages on a connected socket. If the connected socket
fails to respond to these messages, the connection is broken
and processes using that socket are notified with a SIGPIPE
signal.
SO_LINGER
Lingers on a close() function if data is present. This
option controls the action taken when unsent messages queue
on a socket and a close() function is performed. If
SO_LINGER is set, the system blocks the process during the
close() function until it can transmit the data or until the
time expires. If SO_LINGER is not specified and a close()
function is issued, the system handles the call in a way that
allows the process to continue as quickly as possible. This
option takes a struct linger value, defined in the
sys/socket.h header file, to specify the state of the option
and linger interval.
SO_OOBINLINE
Leaves received out-of-band data (data marked urgent) in
line. This option takes an int value.
SO_RCVBUF
Sets receive buffer size. This option takes an int value.
SO_RCVLOWAT
[Tru64 UNIX] Sets receive low-water mark. This option
takes an int value.
SO_RCVTIMEO
[Tru64 UNIX] Sets receive time out. This option takes a
struct timeval value, defined in the sys/time.h header file,
to specify the timeout interval.
SO_RESVPORT
[Tru64 UNIX] In a cluster, an attempt to bind the socket to
a port in the reserved range (512-1024) will fail if the port
is marked static, either by a static entry for the port in
/etc/clua_services or through a call to
clua_registerservice() with the CLUASRV_STATIC option. The
call to bind() will return EADDRINUSE.
SO_REUSEADDR
Specifies that the rules used in validating addresses
supplied by a bind() function should allow reuse of local
addresses. This option takes an int value.
SO_REUSEALIASPORT
[Tru64 UNIX] In a cluster, specifies that the socket can
reuse a locked cluster alias port. When this option is set,
a bind() is distributed clusterwide. A distributed
application can use this side-effect to determine whether or
not a port is in use.
SO_REUSEPORT
[Tru64 UNIX] Allows more than one process to receive UDP
datagrams destined for the same port. The bind system call
binding a process to that port must be preceded by a
setsockopt system call specifying this option.
SO_SNDBUF
Sets send buffer size. This option takes an int value.
SO_SNDLOWAT
[Tru64 UNIX] Sets send low-water mark. This option takes
an int value.
SO_SNDTIMEO
[Tru64 UNIX] Sets send time out. This option takes a
struct timeval value, defined in the sys/time.h header file,
to specify the timeout interval.
SO_USELOOPBACK
[Tru64 UNIX] Valid only for routing sockets. Determines if
a sending socket receives a copy of its own message.
[Tru64 UNIX] Options at other protocol levels vary in format
and name. See the tcp(7) and ip(7) reference pages for more
information on option names relevant for TCP and IP options
respectively.
Note
[Tru64 UNIX] The maximum values for socket level options like
SO_SENDBUF, SO_RCVBUF, SO_SNDLOWAT, and SO_RCVLOWAT are governed by
the protocol limits, as well as its implementation. Use the
getsockopt(2) routine to verify the values for these options after the
socket connection has been established.
option_value
To enable a Boolean option or integer value, set the option_value
parameter to a nonzero value. To disable an option, set the
option_value parameter to 0 (zero).
option_len
The option_len parameter contains the size of the buffer pointed
to by the option_value parameter.
DESCRIPTION
The setsockopt() function sets options associated with a socket. Options
may exist at multiple protocol levels. The SO_ options are always present
at the uppermost socket level.
The setsockopt() function provides an application program with the means to
control a socket communication. An application program can use the
setsockopt() function to enable debugging at the protocol level, allocate
buffer space, control timeouts, or permit socket data broadcasts. The
sys/socket.h file defines all the options available to the setsockopt()
function.
When setting socket options, specify the protocol level at which the option
resides and the name of the option.
Use the option_value and option_len parameters to access option values for
the setsockopt() function. These parameters identify a buffer in which the
value for the requested option or options is returned.
RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
ERRORS
If the setsockopt() function fails, errno may be set to one of the
following values:
[EACCES] [POSIX] The calling process does not have appropriate
permissions.
[EBADF] The socket parameter is not valid.
[EDOM] [POSIX] The send and receive timeout values are too large to fit
in the timeout fields of the socket structure.
[EINVAL] The option_len parameter is not valid.
[EISCONN] [POSIX] The socket is already connected; the specified option
cannot be set when the socket is in the connected state.
[EFAULT] The option_value parameter is not in a readable part of the user
address space.
[ENOBUFS] [POSIX] Insufficient resources are available in the system to
complete the call.
[ENOPROTOOPT]
The option is unknown.
[ENOTSOCK]
The socket parameter refers to a file, not a socket.
RELATED INFORMATION
Functions: bind(2), endprotoent(3), getsockopt(2), getprotobynumber(3),
getprotoent(3), setprotoent(3), socket(2).
Network Information: ip(7), tcp(7).
Standards: standards(5).
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Alphabetical
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