setsockopt - Set socket options
#include <sys/socket.h>
int setsockopt(
int socket,
int level,
int option_name,
const void *option_value,
socklen_t option_len );
[XNS4.0] The definition of the setsockopt() function in
XNS4.0uses a size_t data type instead of a socklen_t data
type as specified in XNS5.0 (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 );
Interfaces documented on this reference page conform to
industry standards as follows:
setsockopt(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the file descriptor for the socket. 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.
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: Permits sending of broadcast messages. This
option takes an int value. [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. [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.
[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. Turns on recording of debugging
information. This option enables or disables debugging in
the underlying protocol modules. This option takes an int
value. 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. 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.
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. Leaves received out-ofband
data (data marked urgent) in line. This option takes
an int value. Sets receive buffer size. This option takes
an int value. Reports the minimum number of bytes (lowwater
mark) for socket receive operations. The default is
1. If the value is set to a larger value, blocking receive
calls wait until they receive either the low water mark
value or the requested value (whichever is smaller). The
calls might return less than the water mark if an error
occurs, a signal is received, or type of data in the
receive queue is different than that returned. This
option takes an int value. Sets receive time out. This
option takes a struct timeval value, defined in the
sys/time.h header file, to specify the amount of time
towait for a receive operation to complete. If a receive
operation has blocke for the specified amount of time
without receiving additional data, it returns with a partial
error count or errno set to [EAGAIN] or [EWOULDBLOCK].
The default is 0 (zero), which indicates that a
receive operation will not time out. [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. 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. [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. [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. Sets send buffer size. This
option takes an int value. Sets the minimum number of
bytes (low-water mark) for socket transmit operations.
Non-blocking transmit operations process no data if flow
control does not allow either the send low water mark
value or the entire request (whichever is smaller) to be
processed. This option takes an int value. Sets send time
out. This option takes a struct timeval value, defined in
the sys/time.h header file, to specify the amount of time
a transmit function blocks when flow control prevents the
transmission of data. If a transmit operation blocks for
this amount of time without transmitting data, it returns
with a partial error count or errno set to [EAGAIN] or
[EWOULDBLOCK]. The default is 0 (zero), which indicates
that a transmit operation will not time out. [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.
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). The option_len parameter
contains the size of the buffer pointed to by the
option_value parameter.
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.
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.
If the setsockopt() function fails, errno may be set to
one of the following values: [POSIX] The calling process
does not have appropriate permissions. The socket parameter
is not valid. The send and receive timeout values are
too large to fit in the timeout fields of the socket
structure. The option_len parameter is not valid. The
socket is already connected; the specified option cannot
be set when the socket is in the connected state. The
option_value parameter is not in a readable part of the
user address space. Insufficient resources are available
in the system to complete the call. The system did not
have sufficient memory to fulfill the request. The option
is unknown. The available STREAMS resources were insufficient
for the operation to complete. The socket parameter
refers to a file, not a socket.
Functions: bind(2), endprotoent(3), getsockopt(2), getprotobynumber(3), getprotoent(3), setprotoent(3), socket(2).
Network Information: ip(7), tcp(7).
Standards: standards(5).
Network Programmer's Guide
setsockopt(2)
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