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Annotation of 43BSDTahoe/man/man2/getsockopt.2, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)getsockopt.2        6.4 (Berkeley) 5/23/86
        !             6: .\"
        !             7: .TH GETSOCKOPT 2 "May 23, 1986"
        !             8: .UC 5
        !             9: .SH NAME
        !            10: getsockopt, setsockopt \- get and set options on sockets
        !            11: .SH SYNOPSIS
        !            12: .nf
        !            13: .ft B
        !            14: #include <sys/types.h>
        !            15: #include <sys/socket.h>
        !            16: .PP
        !            17: .ft B
        !            18: getsockopt(s, level, optname, optval, optlen)
        !            19: int s, level, optname;
        !            20: char *optval;
        !            21: int *optlen;
        !            22: .sp
        !            23: setsockopt(s, level, optname, optval, optlen)
        !            24: int s, level, optname;
        !            25: char *optval;
        !            26: int optlen;
        !            27: .fi
        !            28: .SH DESCRIPTION
        !            29: .I Getsockopt
        !            30: and
        !            31: .I setsockopt
        !            32: manipulate
        !            33: .I options
        !            34: associated with a socket.  Options may exist at multiple
        !            35: protocol levels; they are always present at the uppermost
        !            36: ``socket'' level.
        !            37: .PP
        !            38: When manipulating socket options the level at which the
        !            39: option resides and the name of the option must be specified.
        !            40: To manipulate options at the ``socket'' level,
        !            41: .I level
        !            42: is specified as SOL_SOCKET.  To manipulate options at any
        !            43: other level the protocol number of the appropriate protocol
        !            44: controlling the option is supplied.  For example,
        !            45: to indicate that an option is to be interpreted by the TCP protocol,
        !            46: .I level
        !            47: should be set to the protocol number of TCP; see
        !            48: .IR getprotoent (3N).
        !            49: .PP
        !            50: The parameters
        !            51: .I optval
        !            52: and
        !            53: .I optlen
        !            54: are used to access option values for
        !            55: .IR setsockopt .
        !            56: For
        !            57: .I getsockopt
        !            58: they identify a buffer in which the value for the
        !            59: requested option(s) are to be returned.  For
        !            60: .IR getsockopt ,
        !            61: .I optlen
        !            62: is a value-result parameter, initially containing the
        !            63: size of the buffer pointed to by
        !            64: .IR optval ,
        !            65: and modified on return to indicate the actual size of
        !            66: the value returned.  If no option value is
        !            67: to be supplied or returned,
        !            68: .I optval
        !            69: may be supplied as 0.
        !            70: .PP
        !            71: .I Optname
        !            72: and any specified options are passed uninterpreted to the appropriate
        !            73: protocol module for interpretation.
        !            74: The include file
        !            75: .RI < sys/socket.h >
        !            76: contains definitions for ``socket'' level options, described below.
        !            77: Options at other protocol levels vary in format and
        !            78: name; consult the appropriate entries in section (4P).
        !            79: .PP
        !            80: Most socket-level options take an
        !            81: .I int
        !            82: parameter for
        !            83: .IR optval .
        !            84: For
        !            85: .IR setsockopt ,
        !            86: the parameter should non-zero to enable a boolean option,
        !            87: or zero if the option is to be disabled.
        !            88: SO_LINGER uses a
        !            89: .I struct linger
        !            90: parameter, defined in
        !            91: .RI < sys/socket.h >,
        !            92: which specifies the desired state of the option and the
        !            93: linger interval (see below).
        !            94: .PP
        !            95: The following options are recognized at the socket level.
        !            96: Except as noted, each may be examined with
        !            97: .I getsockopt
        !            98: and set with
        !            99: .IR setsockopt .
        !           100: .PP
        !           101: .RS
        !           102: .ta \w'SO_BROADCAST\ \ \ \ 'u
        !           103: .nf
        !           104: SO_DEBUG       toggle recording of debugging information
        !           105: SO_REUSEADDR   toggle local address reuse
        !           106: SO_KEEPALIVE   toggle keep connections alive
        !           107: SO_DONTROUTE   toggle routing bypass for outgoing messages
        !           108: SO_LINGER      linger on close if data present
        !           109: SO_BROADCAST   toggle permission to transmit broadcast messages
        !           110: SO_OOBINLINE   toggle reception of out-of-band data in band
        !           111: SO_SNDBUF      set buffer size for output
        !           112: SO_RCVBUF      set buffer size for input
        !           113: SO_TYPE        get the type of the socket (get only)
        !           114: SO_ERROR       get and clear error on the socket (get only)
        !           115: .fi
        !           116: .RE
        !           117: .PP
        !           118: SO_DEBUG enables debugging in the underlying protocol modules.
        !           119: SO_REUSEADDR indicates that the rules used in validating addresses supplied
        !           120: in a
        !           121: .IR bind (2)
        !           122: call should allow reuse of local addresses.  SO_KEEPALIVE enables the
        !           123: periodic transmission of messages on a connected socket.  Should the
        !           124: connected party fail to respond to these messages, the connection is
        !           125: considered broken and processes using the socket are notified via a
        !           126: SIGPIPE signal.  SO_DONTROUTE indicates that outgoing messages should
        !           127: bypass the standard routing facilities.  Instead, messages are directed
        !           128: to the appropriate network interface according to the network portion
        !           129: of the destination address.
        !           130: .PP
        !           131: SO_LINGER controls the action taken when unsent messags
        !           132: are queued on socket and a 
        !           133: .IR close (2)
        !           134: is performed.
        !           135: If the socket promises reliable delivery of data and SO_LINGER is set,
        !           136: the system will block the process on the 
        !           137: .I close
        !           138: attempt until it is able to transmit the data or until it decides it
        !           139: is unable to deliver the information (a timeout period, termed the
        !           140: linger interval, is specified in the
        !           141: .IR setsockopt 
        !           142: call when SO_LINGER is requested). 
        !           143: If SO_LINGER is disabled and a 
        !           144: .I close
        !           145: is issued, the system will process the close in a manner that allows
        !           146: the process to continue as quickly as possible.
        !           147: .PP
        !           148: The option SO_BROADCAST requests permission to send broadcast datagrams
        !           149: on the socket.
        !           150: Broadcast was a privileged operation in earlier versions of the system.
        !           151: With protocols that support out-of-band data, the SO_OOBINLINE option
        !           152: requests that out-of-band data be placed in the normal data input queue
        !           153: as received; it will then be accessible with
        !           154: .I recv
        !           155: or
        !           156: .I read
        !           157: calls without the MSG_OOB flag.
        !           158: SO_SNDBUF and SO_RCVBUF are options to adjust the normal
        !           159: buffer sizes allocated for output and input buffers, respectively.
        !           160: The buffer size may be increased for high-volume connections,
        !           161: or may be decreased to limit the possible backlog of incoming data.
        !           162: The system places an absolute limit on these values.
        !           163: Finally, SO_TYPE and SO_ERROR are options used only with
        !           164: .IR setsockopt .
        !           165: SO_TYPE returns the type of the socket, such as SOCK_STREAM;
        !           166: it is useful for servers that inherit sockets on startup.
        !           167: SO_ERROR returns any pending error on the socket and clears
        !           168: the error status.
        !           169: It may be used to check for asynchronous errors on connected
        !           170: datagram sockets or for other asynchronous errors.
        !           171: .SH "RETURN VALUE"
        !           172: A 0 is returned if the call succeeds, \-1 if it fails.
        !           173: .SH ERRORS
        !           174: The call succeeds unless:
        !           175: .TP 20
        !           176: [EBADF]
        !           177: The argument \fIs\fP is not a valid descriptor.
        !           178: .TP 20
        !           179: [ENOTSOCK]
        !           180: The argument \fIs\fP is a file, not a socket.
        !           181: .TP 20
        !           182: [ENOPROTOOPT]
        !           183: The option is unknown at the level indicated.
        !           184: .TP 20
        !           185: [EFAULT]
        !           186: The address pointed to by 
        !           187: .I optval
        !           188: is not in a valid part of the process address space.
        !           189: For
        !           190: .IR getsockopt ,
        !           191: this error may also be returned if
        !           192: .I optlen
        !           193: is not in a valid part of the process address space.
        !           194: .SH "SEE ALSO"
        !           195: ioctl(2), socket(2), getprotoent(3N)
        !           196: .SH BUGS
        !           197: Several of the socket options should be handled at lower levels of the system.

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