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Diffstat (limited to 'lib/libc/sys/getsockopt.2')
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diff --git a/lib/libc/sys/getsockopt.2 b/lib/libc/sys/getsockopt.2 new file mode 100644 index 0000000..46d3d8a --- /dev/null +++ b/lib/libc/sys/getsockopt.2 @@ -0,0 +1,347 @@ +.\" Copyright (c) 1983, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)getsockopt.2 8.3 (Berkeley) 4/19/94 +.\" +.Dd April 19, 1994 +.Dt GETSOCKOPT 2 +.Os BSD 4.3r +.Sh NAME +.Nm getsockopt , +.Nm setsockopt +.Nd get and set options on sockets +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <sys/socket.h> +.Ft int +.Fn getsockopt "int s" "int level" "int optname" "void *optval" "int *optlen" +.Ft int +.Fn setsockopt "int s" "int level" "int optname" "const void *optval" "int optlen" +.Sh DESCRIPTION +.Fn Getsockopt +and +.Fn setsockopt +manipulate the +.Em options +associated with a socket. Options may exist at multiple +protocol levels; they are always present at the uppermost +.Dq socket +level. +.Pp +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, +.Fa level +is specified as +.Dv SOL_SOCKET . +To manipulate options at any +other level the protocol number of the appropriate protocol +controlling the option is supplied. For example, +to indicate that an option is to be interpreted by the +.Tn TCP +protocol, +.Fa level +should be set to the protocol number of +.Tn TCP ; +see +.Xr getprotoent 3 . +.Pp +The parameters +.Fa optval +and +.Fa optlen +are used to access option values for +.Fn setsockopt . +For +.Fn getsockopt +they identify a buffer in which the value for the +requested option(s) are to be returned. For +.Fn getsockopt , +.Fa optlen +is a value-result parameter, initially containing the +size of the buffer pointed to by +.Fa optval , +and modified on return to indicate the actual size of +the value returned. If no option value is +to be supplied or returned, +.Fa optval +may be NULL. +.Pp +.Fa Optname +and any specified options are passed uninterpreted to the appropriate +protocol module for interpretation. +The include file +.Ao Pa sys/socket.h Ac +contains definitions for +socket level options, described below. +Options at other protocol levels vary in format and +name; consult the appropriate entries in +section +4 of the manual. +.Pp +Most socket-level options utilize an +.Fa int +parameter for +.Fa optval . +For +.Fn setsockopt , +the parameter should be non-zero to enable a boolean option, +or zero if the option is to be disabled. +.Dv SO_LINGER +uses a +.Fa struct linger +parameter, defined in +.Ao Pa sys/socket.h Ac , +which specifies the desired state of the option and the +linger interval (see below). +.Dv SO_SNDTIMEO +and +.Dv SO_RCVTIMEO +use a +.Fa struct timeval +parameter, defined in +.Ao Pa sys/time.h Ac . +.Pp +The following options are recognized at the socket level. +Except as noted, each may be examined with +.Fn getsockopt +and set with +.Fn setsockopt . +.Bl -column SO_OOBINLINE -offset indent +.It Dv SO_DEBUG Ta "enables recording of debugging information" +.It Dv SO_REUSEADDR Ta "enables local address reuse" +.It Dv SO_REUSEPORT Ta "enables duplicate address and port bindings" +.It Dv SO_KEEPALIVE Ta "enables keep connections alive" +.It Dv SO_DONTROUTE Ta "enables routing bypass for outgoing messages" +.It Dv SO_LINGER Ta "linger on close if data present" +.It Dv SO_BROADCAST Ta "enables permission to transmit broadcast messages" +.It Dv SO_OOBINLINE Ta "enables reception of out-of-band data in band" +.It Dv SO_SNDBUF Ta "set buffer size for output" +.It Dv SO_RCVBUF Ta "set buffer size for input" +.It Dv SO_SNDLOWAT Ta "set minimum count for output" +.It Dv SO_RCVLOWAT Ta "set minimum count for input" +.It Dv SO_SNDTIMEO Ta "set timeout value for output" +.It Dv SO_RCVTIMEO Ta "set timeout value for input" +.It Dv SO_TYPE Ta "get the type of the socket (get only)" +.It Dv SO_ERROR Ta "get and clear error on the socket (get only)" +.El +.Pp +.Dv SO_DEBUG +enables debugging in the underlying protocol modules. +.Dv SO_REUSEADDR +indicates that the rules used in validating addresses supplied +in a +.Xr bind 2 +call should allow reuse of local addresses. +.Dv SO_REUSEPORT +allows completely duplicate bindings by multiple processes +if they all set +.Dv SO_REUSEPORT +before binding the port. +This option permits multiple instances of a program to each +receive UDP/IP multicast or broadcast datagrams destined for the bound port. +.Dv SO_KEEPALIVE +enables the +periodic transmission of messages on a connected socket. Should the +connected party fail to respond to these messages, the connection is +considered broken and processes using the socket are notified via a +.Dv SIGPIPE +signal when attempting to send data. +.Dv SO_DONTROUTE +indicates that outgoing messages should +bypass the standard routing facilities. Instead, messages are directed +to the appropriate network interface according to the network portion +of the destination address. +.Pp +.Dv SO_LINGER +controls the action taken when unsent messages +are queued on socket and a +.Xr close 2 +is performed. +If the socket promises reliable delivery of data and +.Dv SO_LINGER is set, +the system will block the process on the +.Xr 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 +.Fn setsockopt +call when +.Dv SO_LINGER +is requested). +If +.Dv SO_LINGER +is disabled and a +.Xr close +is issued, the system will process the close in a manner that allows +the process to continue as quickly as possible. +.Pp +The option +.Dv SO_BROADCAST +requests permission to send broadcast datagrams +on the socket. +Broadcast was a privileged operation in earlier versions of the system. +With protocols that support out-of-band data, the +.Dv 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 +.Xr recv +or +.Xr read +calls without the +.Dv MSG_OOB +flag. +Some protocols always behave as if this option is set. +.Dv SO_SNDBUF +and +.Dv SO_RCVBUF +are options to 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 system places an absolute limit on these values. +.Pp +.Dv SO_SNDLOWAT +is an option to set the minimum count for output operations. +Most output operations process all of the data supplied +by the call, delivering data to the protocol for transmission +and blocking as necessary for flow control. +Nonblocking output operations will process as much data as permitted +subject to flow control without blocking, but will process no data +if flow control does not allow the smaller of the low water mark value +or the entire request to be processed. +A +.Xr select 2 +operation testing the ability to write to a socket will return true +only if the low water mark amount could be processed. +The default value for +.Dv SO_SNDLOWAT +is set to a convenient size for network efficiency, often 1024. +.Dv SO_RCVLOWAT +is an option to set the minimum count for input operations. +In general, receive calls will block until any (non-zero) amount of data +is received, then return with the smaller of the amount available or the amount +requested. +The default value for +.Dv SO_RCVLOWAT +is 1. +If +.Dv SO_RCVLOWAT +is set to a larger value, blocking receive calls normally +wait until they have received the smaller of the low water mark value +or the requested amount. +Receive calls may still return less than the low water mark if an error +occurs, a signal is caught, or the type of data next in the receive queue +is different than that returned. +.Pp +.Dv SO_SNDTIMEO +is an option to set a timeout value for output operations. +It accepts a +.Fa struct timeval +parameter with the number of seconds and microseconds +used to limit waits for output operations to complete. +If a send operation has blocked for this much time, +it returns with a partial count +or with the error +.Er EWOULDBLOCK +if no data were sent. +In the current implementation, this timer is restarted each time additional +data are delivered to the protocol, +implying that the limit applies to output portions ranging in size +from the low water mark to the high water mark for output. +.Dv SO_RCVTIMEO +is an option to set a timeout value for input operations. +It accepts a +.Fa struct timeval +parameter with the number of seconds and microseconds +used to limit waits for input operations to complete. +In the current implementation, this timer is restarted each time additional +data are received by the protocol, +and thus the limit is in effect an inactivity timer. +If a receive operation has been blocked for this much time without +receiving additional data, it returns with a short count +or with the error +.Er EWOULDBLOCK +if no data were received. +.Pp +Finally, +.Dv SO_TYPE +and +.Dv SO_ERROR +are options used only with +.Fn getsockopt . +.Dv SO_TYPE +returns the type of the socket, such as +.Dv SOCK_STREAM ; +it is useful for servers that inherit sockets on startup. +.Dv 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. +.Sh RETURN VALUES +A 0 is returned if the call succeeds, -1 if it fails. +.Sh ERRORS +The call succeeds unless: +.Bl -tag -width ENOPROTOOPTAA +.It Bq Er EBADF +The argument +.Fa s +is not a valid descriptor. +.It Bq Er ENOTSOCK +The argument +.Fa s +is a file, not a socket. +.It Bq Er ENOPROTOOPT +The option is unknown at the level indicated. +.It Bq Er EFAULT +The address pointed to by +.Fa optval +is not in a valid part of the process address space. +For +.Fn getsockopt , +this error may also be returned if +.Fa optlen +is not in a valid part of the process address space. +.El +.Sh SEE ALSO +.Xr ioctl 2 , +.Xr socket 2 , +.Xr getprotoent 3 +.Xr protocols 5 +.Sh BUGS +Several of the socket options should be handled at lower levels of the system. +.Sh HISTORY +The +.Nm +system call appeared in +.Bx 4.2 . |
