| 1 |
28 |
unneback |
<!-- Copyright (C) 2003 Red Hat, Inc. -->
|
| 2 |
|
|
<!-- This material may be distributed only subject to the terms -->
|
| 3 |
|
|
<!-- and conditions set forth in the Open Publication License, v1.0 -->
|
| 4 |
|
|
<!-- or later (the latest version is presently available at -->
|
| 5 |
|
|
<!-- http://www.opencontent.org/openpub/). -->
|
| 6 |
|
|
<!-- Distribution of the work or derivative of the work in any -->
|
| 7 |
|
|
<!-- standard (paper) book form is prohibited unless prior -->
|
| 8 |
|
|
<!-- permission is obtained from the copyright holder. -->
|
| 9 |
|
|
<HTML
|
| 10 |
|
|
><HEAD
|
| 11 |
|
|
><TITLE
|
| 12 |
|
|
>getsockopt</TITLE
|
| 13 |
|
|
><meta name="MSSmartTagsPreventParsing" content="TRUE">
|
| 14 |
|
|
<META
|
| 15 |
|
|
NAME="GENERATOR"
|
| 16 |
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
|
| 17 |
|
|
"><LINK
|
| 18 |
|
|
REL="HOME"
|
| 19 |
|
|
TITLE="eCos Reference Manual"
|
| 20 |
|
|
HREF="ecos-ref.html"><LINK
|
| 21 |
|
|
REL="UP"
|
| 22 |
|
|
TITLE="TCP/IP Library Reference"
|
| 23 |
|
|
HREF="tcpip-library-reference.html"><LINK
|
| 24 |
|
|
REL="PREVIOUS"
|
| 25 |
|
|
TITLE="getsockname"
|
| 26 |
|
|
HREF="net-common-tcpip-manpages-getsockname.html"><LINK
|
| 27 |
|
|
REL="NEXT"
|
| 28 |
|
|
TITLE="ioctl"
|
| 29 |
|
|
HREF="net-common-tcpip-manpages-ioctl.html"></HEAD
|
| 30 |
|
|
><BODY
|
| 31 |
|
|
CLASS="SECT1"
|
| 32 |
|
|
BGCOLOR="#FFFFFF"
|
| 33 |
|
|
TEXT="#000000"
|
| 34 |
|
|
LINK="#0000FF"
|
| 35 |
|
|
VLINK="#840084"
|
| 36 |
|
|
ALINK="#0000FF"
|
| 37 |
|
|
><DIV
|
| 38 |
|
|
CLASS="NAVHEADER"
|
| 39 |
|
|
><TABLE
|
| 40 |
|
|
SUMMARY="Header navigation table"
|
| 41 |
|
|
WIDTH="100%"
|
| 42 |
|
|
BORDER="0"
|
| 43 |
|
|
CELLPADDING="0"
|
| 44 |
|
|
CELLSPACING="0"
|
| 45 |
|
|
><TR
|
| 46 |
|
|
><TH
|
| 47 |
|
|
COLSPAN="3"
|
| 48 |
|
|
ALIGN="center"
|
| 49 |
|
|
>eCos Reference Manual</TH
|
| 50 |
|
|
></TR
|
| 51 |
|
|
><TR
|
| 52 |
|
|
><TD
|
| 53 |
|
|
WIDTH="10%"
|
| 54 |
|
|
ALIGN="left"
|
| 55 |
|
|
VALIGN="bottom"
|
| 56 |
|
|
><A
|
| 57 |
|
|
HREF="net-common-tcpip-manpages-getsockname.html"
|
| 58 |
|
|
ACCESSKEY="P"
|
| 59 |
|
|
>Prev</A
|
| 60 |
|
|
></TD
|
| 61 |
|
|
><TD
|
| 62 |
|
|
WIDTH="80%"
|
| 63 |
|
|
ALIGN="center"
|
| 64 |
|
|
VALIGN="bottom"
|
| 65 |
|
|
>Chapter 38. TCP/IP Library Reference</TD
|
| 66 |
|
|
><TD
|
| 67 |
|
|
WIDTH="10%"
|
| 68 |
|
|
ALIGN="right"
|
| 69 |
|
|
VALIGN="bottom"
|
| 70 |
|
|
><A
|
| 71 |
|
|
HREF="net-common-tcpip-manpages-ioctl.html"
|
| 72 |
|
|
ACCESSKEY="N"
|
| 73 |
|
|
>Next</A
|
| 74 |
|
|
></TD
|
| 75 |
|
|
></TR
|
| 76 |
|
|
></TABLE
|
| 77 |
|
|
><HR
|
| 78 |
|
|
ALIGN="LEFT"
|
| 79 |
|
|
WIDTH="100%"></DIV
|
| 80 |
|
|
><DIV
|
| 81 |
|
|
CLASS="SECT1"
|
| 82 |
|
|
><H1
|
| 83 |
|
|
CLASS="SECT1"
|
| 84 |
|
|
><A
|
| 85 |
|
|
NAME="NET-COMMON-TCPIP-MANPAGES-GETSOCKOPT">getsockopt</H1
|
| 86 |
|
|
><TABLE
|
| 87 |
|
|
BORDER="5"
|
| 88 |
|
|
BGCOLOR="#E0E0F0"
|
| 89 |
|
|
WIDTH="70%"
|
| 90 |
|
|
><TR
|
| 91 |
|
|
><TD
|
| 92 |
|
|
><PRE
|
| 93 |
|
|
CLASS="SCREEN"
|
| 94 |
|
|
>GETSOCKOPT(2) System Calls Manual GETSOCKOPT(2)
|
| 95 |
|
|
|
| 96 |
|
|
NAME
|
| 97 |
|
|
getsockopt, setsockopt - get and set options on sockets
|
| 98 |
|
|
|
| 99 |
|
|
SYNOPSIS
|
| 100 |
|
|
#include <sys/types.h>
|
| 101 |
|
|
#include <sys/socket.h>
|
| 102 |
|
|
|
| 103 |
|
|
int
|
| 104 |
|
|
getsockopt(int s, int level, int optname, void *optval,
|
| 105 |
|
|
socklen_t *optlen);
|
| 106 |
|
|
|
| 107 |
|
|
int
|
| 108 |
|
|
setsockopt(int s, int level, int optname, const void *optval,
|
| 109 |
|
|
socklen_t optlen);
|
| 110 |
|
|
|
| 111 |
|
|
DESCRIPTION
|
| 112 |
|
|
getsockopt() and setsockopt() manipulate the options associated with a
|
| 113 |
|
|
socket. Options may exist at multiple protocol levels; they are always
|
| 114 |
|
|
present at the uppermost ``socket'' level.
|
| 115 |
|
|
|
| 116 |
|
|
When manipulating socket options the level at which the option resides
|
| 117 |
|
|
and the name of the option must be specified. To manipulate options at
|
| 118 |
|
|
the socket level, level is specified as SOL_SOCKET. To manipulate
|
| 119 |
|
|
options at any other level the protocol number of the appropriate proto-
|
| 120 |
|
|
col controlling the option is supplied. For example, to indicate that an
|
| 121 |
|
|
option is to be interpreted by the TCP protocol, level should be set to
|
| 122 |
|
|
the protocol number of TCP; see getprotoent(3).
|
| 123 |
|
|
|
| 124 |
|
|
The parameters optval and optlen are used to access option values for
|
| 125 |
|
|
setsockopt(). For getsockopt() they identify a buffer in which the value
|
| 126 |
|
|
for the requested option(s) are to be returned. For getsockopt(), optlen
|
| 127 |
|
|
is a value-result parameter, initially containing the size of the buffer
|
| 128 |
|
|
pointed to by optval, and modified on return to indicate the actual size
|
| 129 |
|
|
of the value returned. If no option value is to be supplied or returned,
|
| 130 |
|
|
optval may be NULL.
|
| 131 |
|
|
|
| 132 |
|
|
optname and any specified options are passed uninterpreted to the appro-
|
| 133 |
|
|
priate protocol module for interpretation. The include file
|
| 134 |
|
|
<sys/socket.h> contains definitions for socket level options, described
|
| 135 |
|
|
below. Options at other protocol levels vary in format and name; consult
|
| 136 |
|
|
the appropriate entries in section 4 of the manual.
|
| 137 |
|
|
|
| 138 |
|
|
Most socket-level options utilize an int parameter for optval. For
|
| 139 |
|
|
setsockopt(), the parameter should be non-zero to enable a boolean
|
| 140 |
|
|
option, or zero if the option is to be disabled. SO_LINGER uses a struct
|
| 141 |
|
|
linger parameter, defined in <sys/socket.h>, which specifies the desired
|
| 142 |
|
|
state of the option and the linger interval (see below). SO_SNDTIMEO and
|
| 143 |
|
|
SO_RCVTIMEO use a struct timeval parameter, defined in <sys/time.h>.
|
| 144 |
|
|
|
| 145 |
|
|
The following options are recognized at the socket level. Except as
|
| 146 |
|
|
noted, each may be examined with getsockopt() and set with setsockopt().
|
| 147 |
|
|
|
| 148 |
|
|
SO_DEBUG enables recording of debugging information
|
| 149 |
|
|
SO_REUSEADDR enables local address reuse
|
| 150 |
|
|
SO_REUSEPORT enables duplicate address and port bindings
|
| 151 |
|
|
SO_KEEPALIVE enables keep connections alive
|
| 152 |
|
|
SO_DONTROUTE enables routing bypass for outgoing messages
|
| 153 |
|
|
SO_LINGER linger on close if data present
|
| 154 |
|
|
SO_BROADCAST enables permission to transmit broadcast messages
|
| 155 |
|
|
SO_OOBINLINE enables reception of out-of-band data in band
|
| 156 |
|
|
SO_SNDBUF set buffer size for output
|
| 157 |
|
|
SO_RCVBUF set buffer size for input
|
| 158 |
|
|
SO_SNDLOWAT set minimum count for output
|
| 159 |
|
|
SO_RCVLOWAT set minimum count for input
|
| 160 |
|
|
SO_SNDTIMEO set timeout value for output
|
| 161 |
|
|
SO_RCVTIMEO set timeout value for input
|
| 162 |
|
|
SO_TYPE get the type of the socket (get only)
|
| 163 |
|
|
SO_ERROR get and clear error on the socket (get only)
|
| 164 |
|
|
|
| 165 |
|
|
SO_DEBUG enables debugging in the underlying protocol modules.
|
| 166 |
|
|
SO_REUSEADDR indicates that the rules used in validating addresses sup-
|
| 167 |
|
|
plied in a bind(2) call should allow reuse of local addresses.
|
| 168 |
|
|
SO_REUSEPORT allows completely duplicate bindings by multiple processes
|
| 169 |
|
|
if they all set SO_REUSEPORT before binding the port. This option per-
|
| 170 |
|
|
mits multiple instances of a program to each receive UDP/IP multicast or
|
| 171 |
|
|
broadcast datagrams destined for the bound port. SO_KEEPALIVE enables
|
| 172 |
|
|
the periodic transmission of messages on a connected socket. Should the
|
| 173 |
|
|
connected party fail to respond to these messages, the connection is con-
|
| 174 |
|
|
sidered broken and processes using the socket are notified via a SIGPIPE
|
| 175 |
|
|
signal when attempting to send data. SO_DONTROUTE indicates that outgo-
|
| 176 |
|
|
ing messages should bypass the standard routing facilities. Instead,
|
| 177 |
|
|
messages are directed to the appropriate network interface according to
|
| 178 |
|
|
the network portion of the destination address.
|
| 179 |
|
|
|
| 180 |
|
|
SO_LINGER controls the action taken when unsent messages are queued on
|
| 181 |
|
|
socket and a close(2) is performed. If the socket promises reliable
|
| 182 |
|
|
delivery of data and SO_LINGER is set, the system will block the process
|
| 183 |
|
|
on the close(2) attempt until it is able to transmit the data or until it
|
| 184 |
|
|
decides it is unable to deliver the information (a timeout period mea-
|
| 185 |
|
|
sured in seconds, termed the linger interval, is specified in the
|
| 186 |
|
|
setsockopt() call when SO_LINGER is requested). If SO_LINGER is disabled
|
| 187 |
|
|
and a close(2) is issued, the system will process the close in a manner
|
| 188 |
|
|
that allows the process to continue as quickly as possible.
|
| 189 |
|
|
|
| 190 |
|
|
The option SO_BROADCAST requests permission to send broadcast datagrams
|
| 191 |
|
|
on the socket. Broadcast was a privileged operation in earlier versions
|
| 192 |
|
|
of the system. With protocols that support out-of-band data, the
|
| 193 |
|
|
SO_OOBINLINE option requests that out-of-band data be placed in the nor-
|
| 194 |
|
|
mal data input queue as received; it will then be accessible with recv(2)
|
| 195 |
|
|
or read(2) calls without the MSG_OOB flag. Some protocols always behave
|
| 196 |
|
|
as if this option is set. SO_SNDBUF and SO_RCVBUF are options to adjust
|
| 197 |
|
|
the normal buffer sizes allocated for output and input buffers, respec-
|
| 198 |
|
|
tively. The buffer size may be increased for high-volume connections, or
|
| 199 |
|
|
may be decreased to limit the possible backlog of incoming data. The
|
| 200 |
|
|
system places an absolute limit on these values.
|
| 201 |
|
|
|
| 202 |
|
|
SO_SNDLOWAT is an option to set the minimum count for output operations.
|
| 203 |
|
|
Most output operations process all of the data supplied by the call,
|
| 204 |
|
|
delivering data to the protocol for transmission and blocking as neces-
|
| 205 |
|
|
sary for flow control. Nonblocking output operations will process as
|
| 206 |
|
|
much data as permitted subject to flow control without blocking, but will
|
| 207 |
|
|
process no data if flow control does not allow the smaller of the low
|
| 208 |
|
|
water mark value or the entire request to be processed. A select(2) or
|
| 209 |
|
|
poll(2) operation testing the ability to write to a socket will return
|
| 210 |
|
|
true only if the low water mark amount could be processed. The default
|
| 211 |
|
|
value for SO_SNDLOWAT is set to a convenient size for network efficiency,
|
| 212 |
|
|
often 1024. SO_RCVLOWAT is an option to set the minimum count for input
|
| 213 |
|
|
operations. In general, receive calls will block until any (non-zero)
|
| 214 |
|
|
amount of data is received, then return with the smaller of the amount
|
| 215 |
|
|
available or the amount requested. The default value for SO_RCVLOWAT is
|
| 216 |
|
|
1. If SO_RCVLOWAT is set to a larger value, blocking receive calls nor-
|
| 217 |
|
|
mally wait until they have received the smaller of the low water mark
|
| 218 |
|
|
value or the requested amount. Receive calls may still return less than
|
| 219 |
|
|
the low water mark if an error occurs, a signal is caught, or the type of
|
| 220 |
|
|
data next in the receive queue is different than that returned.
|
| 221 |
|
|
|
| 222 |
|
|
SO_SNDTIMEO is an option to set a timeout value for output operations.
|
| 223 |
|
|
It accepts a struct timeval parameter with the number of seconds and
|
| 224 |
|
|
microseconds used to limit waits for output operations to complete. If a
|
| 225 |
|
|
send operation has blocked for this much time, it returns with a partial
|
| 226 |
|
|
count or with the error EWOULDBLOCK if no data was sent. In the current
|
| 227 |
|
|
implementation, this timer is restarted each time additional data are
|
| 228 |
|
|
delivered to the protocol, implying that the limit applies to output por-
|
| 229 |
|
|
tions ranging in size from the low water mark to the high water mark for
|
| 230 |
|
|
output. SO_RCVTIMEO is an option to set a timeout value for input opera-
|
| 231 |
|
|
tions. It accepts a struct timeval parameter with the number of seconds
|
| 232 |
|
|
and microseconds used to limit waits for input operations to complete.
|
| 233 |
|
|
In the current implementation, this timer is restarted each time addi-
|
| 234 |
|
|
tional data are received by the protocol, and thus the limit is in effect
|
| 235 |
|
|
an inactivity timer. If a receive operation has been blocked for this
|
| 236 |
|
|
much time without receiving additional data, it returns with a short
|
| 237 |
|
|
count or with the error EWOULDBLOCK if no data were received.
|
| 238 |
|
|
|
| 239 |
|
|
Finally, SO_TYPE and SO_ERROR are options used only with getsockopt().
|
| 240 |
|
|
SO_TYPE returns the type of the socket, such as SOCK_STREAM; it is useful
|
| 241 |
|
|
for servers that inherit sockets on startup. SO_ERROR returns any pend-
|
| 242 |
|
|
ing error on the socket and clears the error status. It may be used to
|
| 243 |
|
|
check for asynchronous errors on connected datagram sockets or for other
|
| 244 |
|
|
asynchronous errors.
|
| 245 |
|
|
|
| 246 |
|
|
RETURN VALUES
|
| 247 |
|
|
A 0 is returned if the call succeeds, -1 if it fails.
|
| 248 |
|
|
|
| 249 |
|
|
ERRORS
|
| 250 |
|
|
The call succeeds unless:
|
| 251 |
|
|
|
| 252 |
|
|
[EBADF] The argument s is not a valid descriptor.
|
| 253 |
|
|
|
| 254 |
|
|
[ENOTSOCK] The argument s is a file, not a socket.
|
| 255 |
|
|
|
| 256 |
|
|
[ENOPROTOOPT] The option is unknown at the level indicated.
|
| 257 |
|
|
|
| 258 |
|
|
[EFAULT] The address pointed to by optval is not in a valid
|
| 259 |
|
|
part of the process address space. For getsockopt(),
|
| 260 |
|
|
this error may also be returned if optlen is not in a
|
| 261 |
|
|
valid part of the process address space.
|
| 262 |
|
|
|
| 263 |
|
|
SEE ALSO
|
| 264 |
|
|
connect(2), ioctl(2), poll(2), select(2), poll(2), socket(2),
|
| 265 |
|
|
getprotoent(3), protocols(5)
|
| 266 |
|
|
|
| 267 |
|
|
BUGS
|
| 268 |
|
|
Several of the socket options should be handled at lower levels of the
|
| 269 |
|
|
system.
|
| 270 |
|
|
|
| 271 |
|
|
HISTORY
|
| 272 |
|
|
The getsockopt() system call appeared in 4.2BSD.
|
| 273 |
|
|
|
| 274 |
|
|
BSD February 15, 1999 BSD
|
| 275 |
|
|
</PRE
|
| 276 |
|
|
></TD
|
| 277 |
|
|
></TR
|
| 278 |
|
|
></TABLE
|
| 279 |
|
|
></DIV
|
| 280 |
|
|
><DIV
|
| 281 |
|
|
CLASS="NAVFOOTER"
|
| 282 |
|
|
><HR
|
| 283 |
|
|
ALIGN="LEFT"
|
| 284 |
|
|
WIDTH="100%"><TABLE
|
| 285 |
|
|
SUMMARY="Footer navigation table"
|
| 286 |
|
|
WIDTH="100%"
|
| 287 |
|
|
BORDER="0"
|
| 288 |
|
|
CELLPADDING="0"
|
| 289 |
|
|
CELLSPACING="0"
|
| 290 |
|
|
><TR
|
| 291 |
|
|
><TD
|
| 292 |
|
|
WIDTH="33%"
|
| 293 |
|
|
ALIGN="left"
|
| 294 |
|
|
VALIGN="top"
|
| 295 |
|
|
><A
|
| 296 |
|
|
HREF="net-common-tcpip-manpages-getsockname.html"
|
| 297 |
|
|
ACCESSKEY="P"
|
| 298 |
|
|
>Prev</A
|
| 299 |
|
|
></TD
|
| 300 |
|
|
><TD
|
| 301 |
|
|
WIDTH="34%"
|
| 302 |
|
|
ALIGN="center"
|
| 303 |
|
|
VALIGN="top"
|
| 304 |
|
|
><A
|
| 305 |
|
|
HREF="ecos-ref.html"
|
| 306 |
|
|
ACCESSKEY="H"
|
| 307 |
|
|
>Home</A
|
| 308 |
|
|
></TD
|
| 309 |
|
|
><TD
|
| 310 |
|
|
WIDTH="33%"
|
| 311 |
|
|
ALIGN="right"
|
| 312 |
|
|
VALIGN="top"
|
| 313 |
|
|
><A
|
| 314 |
|
|
HREF="net-common-tcpip-manpages-ioctl.html"
|
| 315 |
|
|
ACCESSKEY="N"
|
| 316 |
|
|
>Next</A
|
| 317 |
|
|
></TD
|
| 318 |
|
|
></TR
|
| 319 |
|
|
><TR
|
| 320 |
|
|
><TD
|
| 321 |
|
|
WIDTH="33%"
|
| 322 |
|
|
ALIGN="left"
|
| 323 |
|
|
VALIGN="top"
|
| 324 |
|
|
>getsockname</TD
|
| 325 |
|
|
><TD
|
| 326 |
|
|
WIDTH="34%"
|
| 327 |
|
|
ALIGN="center"
|
| 328 |
|
|
VALIGN="top"
|
| 329 |
|
|
><A
|
| 330 |
|
|
HREF="tcpip-library-reference.html"
|
| 331 |
|
|
ACCESSKEY="U"
|
| 332 |
|
|
>Up</A
|
| 333 |
|
|
></TD
|
| 334 |
|
|
><TD
|
| 335 |
|
|
WIDTH="33%"
|
| 336 |
|
|
ALIGN="right"
|
| 337 |
|
|
VALIGN="top"
|
| 338 |
|
|
>ioctl</TD
|
| 339 |
|
|
></TR
|
| 340 |
|
|
></TABLE
|
| 341 |
|
|
></DIV
|
| 342 |
|
|
></BODY
|
| 343 |
|
|
></HTML
|
| 344 |
|
|
>
|
