1 .\" Copyright (c) 1983, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)getsockopt.2 8.4 (Berkeley) 5/2/95
37 .Nd get and set options on sockets
44 .Fn getsockopt "int s" "int level" "int optname" "void * restrict optval" "socklen_t * restrict optlen"
46 .Fn setsockopt "int s" "int level" "int optname" "const void *optval" "socklen_t optlen"
55 associated with a socket.
56 Options may exist at multiple
57 protocol levels; they are always present at the uppermost
61 When manipulating socket options the level at which the
62 option resides and the name of the option must be specified.
63 To manipulate options at the socket level,
67 To manipulate options at any
68 other level the protocol number of the appropriate protocol
69 controlling the option is supplied.
71 to indicate that an option is to be interpreted by the
75 should be set to the protocol number of
85 are used to access option values for
89 they identify a buffer in which the value for the
90 requested option(s) are to be returned.
94 is a value-result argument, initially containing the
95 size of the buffer pointed to by
97 and modified on return to indicate the actual size of
100 to be supplied or returned,
107 and any specified options are passed uninterpreted to the appropriate
108 protocol module for interpretation.
111 contains definitions for
112 socket level options, described below.
113 Options at other protocol levels vary in format and
114 name; consult the appropriate entries in
118 Most socket-level options utilize an
124 the argument should be non-zero to enable a boolean option,
125 or zero if the option is to be disabled.
131 which specifies the desired state of the option and the
132 linger interval (see below).
141 The following options are recognized at the socket level.
142 For protocol-specific options, see protocol manual pages,
147 Except as noted, each may be examined with
151 .Bl -column SO_ACCEPTFILTER -offset indent
152 .It Dv SO_DEBUG Ta "enables recording of debugging information"
153 .It Dv SO_REUSEADDR Ta "enables local address reuse"
154 .It Dv SO_REUSEPORT Ta "enables duplicate address and port bindings"
155 .It Dv SO_KEEPALIVE Ta "enables keep connections alive"
156 .It Dv SO_DONTROUTE Ta "enables routing bypass for outgoing messages"
157 .It Dv SO_LINGER Ta "linger on close if data present"
158 .It Dv SO_BROADCAST Ta "enables permission to transmit broadcast messages"
159 .It Dv SO_OOBINLINE Ta "enables reception of out-of-band data in band"
160 .It Dv SO_SNDBUF Ta "set buffer size for output"
161 .It Dv SO_RCVBUF Ta "set buffer size for input"
162 .It Dv SO_SNDLOWAT Ta "set minimum count for output"
163 .It Dv SO_RCVLOWAT Ta "set minimum count for input"
164 .It Dv SO_SNDTIMEO Ta "set timeout value for output"
165 .It Dv SO_RCVTIMEO Ta "set timeout value for input"
166 .It Dv SO_ACCEPTFILTER Ta "set accept filter on listening socket"
167 .It Dv SO_NOSIGPIPE Ta
168 controls generation of
171 .It Dv SO_TIMESTAMP Ta "enables reception of a timestamp with datagrams"
172 .It Dv SO_BINTIME Ta "enables reception of a timestamp with datagrams"
173 .It Dv SO_ACCEPTCONN Ta "get listening status of the socket (get only)"
174 .It Dv SO_TYPE Ta "get the type of the socket (get only)"
175 .It Dv SO_PROTOCOL Ta "get the protocol number for the socket (get only)"
176 .It Dv SO_PROTOTYPE Ta "SunOS alias for the Linux SO_PROTOCOL (get only)"
177 .It Dv SO_ERROR Ta "get and clear error on the socket (get only)"
178 .It Dv SO_SETFIB Ta "set the associated FIB (routing table) for the socket (set only)"
181 The following options are recognized in
183 .Bl -column SO_LISTENINCQLEN -offset indent
184 .It Dv SO_LABEL Ta "get MAC label of the socket (get only)"
185 .It Dv SO_PEERLABEL Ta "get socket's peer's MAC label (get only)"
186 .It Dv SO_LISTENQLIMIT Ta "get backlog limit of the socket (get only)"
187 .It Dv SO_LISTENQLEN Ta "get complete queue length of the socket (get only)"
188 .It Dv SO_LISTENINCQLEN Ta "get incomplete queue length of the socket (get only)"
189 .It Dv SO_USER_COOKIE Ta "set the 'so_user_cookie' value for the socket (uint32_t, set only)"
190 .It Dv SO_TS_CLOCK Ta "set specific format of timestamp returned by SO_TIMESTAMP"
191 .It Dv SO_MAX_PACING_RATE Ta "set the maximum transmit rate in bytes per second for the socket"
195 enables debugging in the underlying protocol modules.
198 indicates that the rules used in validating addresses supplied
201 system call should allow reuse of local addresses.
204 allows completely duplicate bindings by multiple processes
207 before binding the port.
208 This option permits multiple instances of a program to each
209 receive UDP/IP multicast or broadcast datagrams destined for the bound port.
213 periodic transmission of messages on a connected socket.
215 connected party fail to respond to these messages, the connection is
216 considered broken and processes using the socket are notified via a
218 signal when attempting to send data.
221 indicates that outgoing messages should
222 bypass the standard routing facilities.
223 Instead, messages are directed
224 to the appropriate network interface according to the network portion
225 of the destination address.
228 controls the action taken when unsent messages
229 are queued on socket and a
232 If the socket promises reliable delivery of data and
235 the system will block the process on the
237 attempt until it is able to transmit the data or until it decides it
238 is unable to deliver the information (a timeout period, termed the
239 linger interval, is specified in seconds in the
248 is issued, the system will process the close in a manner that allows
249 the process to continue as quickly as possible.
253 requests permission to send broadcast datagrams
255 Broadcast was a privileged operation in earlier versions of the system.
257 With protocols that support out-of-band data, the
260 requests that out-of-band data be placed in the normal data input queue
261 as received; it will then be accessible with
268 Some protocols always behave as if this option is set.
273 are options to adjust the normal
274 buffer sizes allocated for output and input buffers, respectively.
275 The buffer size may be increased for high-volume connections,
276 or may be decreased to limit the possible backlog of incoming data.
277 The system places an absolute maximum on these values, which is accessible
281 .Dq Li kern.ipc.maxsockbuf .
284 is an option to set the minimum count for output operations.
285 Most output operations process all of the data supplied
286 by the call, delivering data to the protocol for transmission
287 and blocking as necessary for flow control.
288 Nonblocking output operations will process as much data as permitted
289 subject to flow control without blocking, but will process no data
290 if flow control does not allow the smaller of the low water mark value
291 or the entire request to be processed.
294 operation testing the ability to write to a socket will return true
295 only if the low water mark amount could be processed.
296 The default value for
298 is set to a convenient size for network efficiency, often 1024.
301 is an option to set the minimum count for input operations.
302 In general, receive calls will block until any (non-zero) amount of data
303 is received, then return with the smaller of the amount available or the amount
305 The default value for
310 is set to a larger value, blocking receive calls normally
311 wait until they have received the smaller of the low water mark value
312 or the requested amount.
313 Receive calls may still return less than the low water mark if an error
314 occurs, a signal is caught, or the type of data next in the receive queue
315 is different from that which was returned.
318 is an option to set a timeout value for output operations.
321 argument with the number of seconds and microseconds
322 used to limit waits for output operations to complete.
323 If a send operation has blocked for this much time,
324 it returns with a partial count
327 if no data were sent.
328 In the current implementation, this timer is restarted each time additional
329 data are delivered to the protocol,
330 implying that the limit applies to output portions ranging in size
331 from the low water mark to the high water mark for output.
334 is an option to set a timeout value for input operations.
337 argument with the number of seconds and microseconds
338 used to limit waits for input operations to complete.
339 In the current implementation, this timer is restarted each time additional
340 data are received by the protocol,
341 and thus the limit is in effect an inactivity timer.
342 If a receive operation has been blocked for this much time without
343 receiving additional data, it returns with a short count
346 if no data were received.
349 can be used to over-ride the default FIB (routing table) for the given socket.
350 The value must be from 0 to one less than the number returned from
355 can be used to set the uint32_t so_user_cookie field in the socket.
356 The value is an uint32_t, and can be used in the kernel code that
357 manipulates traffic related to the socket.
358 The default value for the field is 0.
359 As an example, the value can be used as the skipto target or
367 which will filter incoming connections
368 on a listening stream socket before being presented for
372 must be called on the socket before
373 trying to install the filter on it,
376 system call will fail.
378 struct accept_filter_arg {
388 .Fa struct accept_filter_arg
389 that will select and configure the
390 .Xr accept_filter 9 .
394 should be filled with the name of the accept filter
395 that the application wishes to place on the listening socket.
396 The optional argument
398 can be passed to the accept
401 to provide additional configuration options at attach time.
404 of NULL will remove the filter.
408 option controls generation of the
411 when writing to a connected socket where the other end has been
412 closed returns with the error
419 option is enabled on a
423 call will return a timestamp corresponding to when the datagram was received.
428 structure points to a buffer that contains a
430 structure followed by a
440 fields have the following values for TIMESTAMP by default:
442 cmsg_len = CMSG_LEN(sizeof(struct timeval));
443 cmsg_level = SOL_SOCKET;
444 cmsg_type = SCM_TIMESTAMP;
450 cmsg_len = CMSG_LEN(sizeof(struct bintime));
451 cmsg_level = SOL_SOCKET;
452 cmsg_type = SCM_BINTIME;
455 Additional timestamp types are available by following
459 which requests a specific timestamp format to be returned instead of
460 .Dv SCM_TIMESTAMP when
461 .Dv SO_TIMESTAMP is enabled.
464 values are recognized in
466 .Bl -column SO_TS_CLOCK -offset indent
467 .It Dv SO_TS_REALTIME_MICRO Ta "realtime (SCM_TIMESTAMP, struct timeval), default"
468 .It Dv SO_TS_BINTIME Ta "realtime (SCM_BINTIME, struct bintime)"
469 .It Dv SO_TS_REALTIME Ta "realtime (SCM_REALTIME, struct timespec)"
470 .It Dv SO_TS_MONOTONIC Ta "monotonic time (SCM_MONOTONIC, struct timespec)"
480 are options used only with
483 returns whether the socket is currently accepting connections,
484 that is, whether or not the
486 system call was invoked on the socket.
488 returns the type of the socket, such as
490 it is useful for servers that inherit sockets on startup.
492 returns the protocol number for the socket, for
498 returns any pending error on the socket and clears
500 It may be used to check for asynchronous errors on connected
501 datagram sockets or for other asynchronous errors.
505 returns the MAC label of the socket.
507 returns the MAC label of the socket's peer.
508 Note that your kernel must be compiled with MAC support.
511 for more information.
513 returns the maximal number of queued connections, as set by
516 returns the number of unaccepted complete connections.
518 returns the number of unaccepted incomplete connections.
520 .Dv SO_MAX_PACING_RATE
521 instruct the socket and underlying network adapter layers to limit the
522 transfer rate to the given unsigned 32-bit value in bytes per second.
526 The call succeeds unless:
531 is not a valid descriptor.
535 is a file, not a socket.
536 .It Bq Er ENOPROTOOPT
537 The option is unknown at the level indicated.
539 The address pointed to by
541 is not in a valid part of the process address space.
544 this error may also be returned if
546 is not in a valid part of the process address space.
550 on a non-listening socket was attempted.
566 .Xr accept_filter 9 ,
573 system calls appeared in
576 Several of the socket options should be handled at lower levels of the system.