getsockopt(3SOCKET)					     Sockets Library Functions					       getsockopt(3SOCKET)

NAME

       getsockopt, setsockopt - get and set options on sockets

SYNOPSIS

       cc [ flag ... ] file ... -lsocket -lnsl [ library ... ]
       #include <sys/types.h>
       #include <sys/socket.h>

       int getsockopt(int s, int level, int optname, void *optval, int *optlen);

       int setsockopt(int s, int level, int optname, const void *optval, int optlen);

DESCRIPTION

       getsockopt()  and  setsockopt() manipulate options associated with a socket. Options may exist at multiple protocol levels; they are always
       present at the uppermost "socket" level.

       When manipulating socket options, the level at which the option resides and the name of the option must be specified. To manipulate options
       at the "socket" level, level is specified as SOL_SOCKET. To manipulate options at any other level, level is the protocol number of the pro-
       tocol that controls the option. For example, to indicate that an option is to be interpreted by the TCP protocol, level is set to  the  TCP
       protocol number .  See getprotobyname(3SOCKET).

       The  parameters	optval and optlen are used to access option values for setsockopt(). For getsockopt(), they identify a buffer in which the
       value(s) for the requested option(s) are to be returned. For getsockopt(), optlen is a value-result  parameter,	initially  containing  the
       size  of  the  buffer  pointed to by optval, and modified on return to indicate the actual size of the value returned. Use a 0 optval if no
       option value is to be supplied or returned.

       optname and any specified options are passed uninterpreted to  the  appropriate	protocol  module  for  interpretation.	The  include  file
       <sys/socket.h> contains definitions for the socket-level options described below. Options at other protocol levels vary in format and name.

       Most  socket-level options take an int for optval. For setsockopt(), the optval parameter should be non-zero to enable a boolean option, or
       zero if the option is to be disabled. SO_LINGER uses a struct linger parameter that specifies the desired  state  of  the  option  and  the
       linger interval. struct linger is defined in <sys/socket.h>. struct linger contains the following members:

       l_onoff		       on = 1/off = 0

       l_linger 	       linger time, in seconds

       The  following  options	are  recognized at the socket level. Except as noted, each may be examined with getsockopt() and set with setsock-
       opt().

       SO_DEBUG 	       enable/disable recording of debugging information

       SO_REUSEADDR	       enable/disable local address reuse

       SO_KEEPALIVE	       enable/disable keep connections alive

       SO_DONTROUTE	       enable/disable routing bypass for outgoing messages

       SO_LINGER	       linger on close if data is present

       SO_BROADCAST	       enable/disable permission to transmit broadcast messages

       SO_OOBINLINE	       enable/disable reception of out-of-band data in band

       SO_SNDBUF	       set buffer size for output

       SO_RCVBUF	       set buffer size for input

       SO_DGRAM_ERRIND	       application wants delayed error

       SO_TYPE		       get the type of the socket (get only)

       SO_ERROR 	       get and clear error on the socket (get only)

       SO_DEBUG enables debugging in the underlying protocol modules. SO_REUSEADDR indicates that the rules used in validating addresses  supplied
       in  a  bind(3SOCKET)  call should allow reuse of local addresses. SO_KEEPALIVE enables the periodic transmission of messages on a connected
       socket. If the connected party fails to respond to these messages, the connection is considered broken and threads  using  the  socket  are
       notified using a SIGPIPE signal. SO_DONTROUTE indicates that outgoing messages should bypass the standard routing facilities. Instead, mes-
       sages are directed to the appropriate network interface according to the network portion of the destination address.

       SO_LINGER controls the action taken when unsent messages are queued on a socket and a close(2) is performed. If the socket  promises  reli-
       able  delivery  of data and SO_LINGER is set, the system will block the thread on the close() attempt until it is able to transmit the data
       or until it decides it is unable to deliver the information (a timeout period, termed the linger interval, is specified in the setsockopt()
       call  when  SO_LINGER is requested). If SO_LINGER is disabled and a close() is issued, the system will process the close() in a manner that
       allows the thread to continue as quickly as possible.

       The option SO_BROADCAST requests permission to send broadcast datagrams on the socket. With protocols that support  out-of-band	data,  the
       SO_OOBINLINE  option  requests  that out-of-band data be placed in the normal data input queue as received; it will then be accessible with
       recv() or read() calls without the MSG_OOB flag.

       SO_SNDBUF and SO_RCVBUF are options that adjust the normal buffer sizes allocated for output and input buffers,	respectively.  The  buffer
       size  may  be  increased for high-volume connections or may be decreased to limit the possible backlog of incoming data. The maximum buffer
       size for UDP is determined by the value	    of the ndd variable udp_max_buf.  The maximum buffer size for TCP is determined the  value	of
       the  ndd  variable tcp_max_buf.	Use the ndd(1M) utility to determine the current default values. See the Solaris Tunable Parameters Refer-
       ence Manual for information on setting the values of udp_max_buf and tcp_max_buf.

       By default, delayed errors (such as ICMP port unreachable packets) are returned only for connected datagram sockets. SO_DGRAM_ERRIND  makes
       it  possible  to receive errors for datagram sockets that are not connected. When this option is set, certain delayed errors received after
       completion of a sendto() or sendmsg() operation will cause a subsequent sendto() or sendmsg() operation using the same destination  address
       (to parameter) to fail with the appropriate error.  See send(3SOCKET).

       Finally,  SO_TYPE  and  SO_ERROR are options used only with getsockopt(). SO_TYPE returns the type of the socket, for example, SOCK_STREAM.
       It is useful for servers that inherit sockets on startup. SO_ERROR returns any pending error on the socket and clears the error status.	It
       may be used to check for asynchronous errors on connected datagram sockets or for other asynchronous errors.

RETURN VALUES

       If successful, getsockopt() and setsockopt() return 0; otherwise, the functions return -1 and set errno to indicate the error.

ERRORS

       The getsockopt() and setsockopt() calls succeed unless:

       EBADF		       The argument s is not a valid file descriptor.

       ENOMEM		       There was insufficient memory available for the operation to complete.

       ENOPROTOOPT	       The option is unknown at the level indicated.

       ENOSR		       There were insufficient STREAMS resources available for the operation to complete.

       ENOTSOCK 	       The argument s is not a socket.

       ENOBUFS		       SO_SNDBUF or SO_RCVBUF exceeds a system limit.

       EINVAL		       Invalid length for IP_OPTIONS.

       EHOSTUNREACH	       Invalid address for IP_MULTICAST_IF.

       EINVAL		       Not a multicast address for IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP.

       EADDRNOTAVAIL	       Bad interface address for IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP.

       EADDRINUSE	       Address already joined for IP_ADD_MEMBERSHIP.

       ENOENT		       Address not joined for IP_DROP_MEMBERSHIP.

       EPERM		       No permissions.

       EINVAL		       The specified option is invalid at the specified socket level, or the socket has been shut down.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ndd(1M), close(2), ioctl(2), read(2), bind(3SOCKET), getprotobyname(3SOCKET), recv(3SOCKET), send(3SOCKET), socket(3SOCKET), attributes(5)

       Solaris Tunable Parameters Reference Manual

SunOS 5.10							    1 Nov 2003						       getsockopt(3SOCKET)