1getsockopt(3SOCKET) Sockets Library Functions getsockopt(3SOCKET)
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6 getsockopt, setsockopt - get and set options on sockets
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9 cc [ flag ... ] file ... -lsocket -lnsl [ library ... ]
10 #include <sys/types.h>
11 #include <sys/socket.h>
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13 int getsockopt(int s, int level, int optname, void *optval,
14 int *optlen);
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17 int setsockopt(int s, int level, int optname, const void *optval,
18 int optlen);
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22 The getsockopt() and setsockopt() functions manipulate options associ‐
23 ated with a socket. Options may exist at multiple protocol levels; they
24 are always present at the uppermost "socket" level.
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27 The level argument specifies the protocol level at which the option
28 resides. To manipulate options at the socket level, specify the level
29 argument as SOL_SOCKET. To manipulate options at the protocol level,
30 supply the appropriate protocol number for the protocol controlling the
31 option. For example, to indicate that an option will be interpreted by
32 the TCP, set level to the protocol number of TCP, as defined in the
33 <netinet/in.h> header, or as determined by using getprotoby‐
34 name(3SOCKET). Some socket protocol families may also define additional
35 levels, such as SOL_ROUTE. Only socket-level options are described
36 here.
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39 The parameters optval and optlen are used to access option values for
40 setsockopt(). For getsockopt(), they identify a buffer in which the
41 value(s) for the requested option(s) are to be returned. For getsock‐
42 opt(), optlen is a value-result parameter, initially containing the
43 size of the buffer pointed to by optval, and modified on return to
44 indicate the actual size of the value returned. Use a 0 optval if no
45 option value is to be supplied or returned.
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48 The optname and any specified options are passed uninterpreted to the
49 appropriate protocol module for interpretation. The include file
50 <sys/socket.h> contains definitions for the socket-level options
51 described below. Options at other protocol levels vary in format and
52 name.
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55 Most socket-level options take an int for optval. For setsockopt(), the
56 optval parameter should be non-zero to enable a boolean option, or zero
57 if the option is to be disabled. SO_LINGER uses a struct linger parame‐
58 ter that specifies the desired state of the option and the linger
59 interval. struct linger is defined in <sys/socket.h>. struct linger
60 contains the following members:
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62 l_onoff on = 1/off = 0
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65 l_linger linger time, in seconds
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69 The following options are recognized at the socket level. Except as
70 noted, each may be examined with getsockopt() and set with setsock‐
71 opt().
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73 SO_DEBUG enable/disable recording of debugging information
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76 SO_REUSEADDR enable/disable local address reuse
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79 SO_KEEPALIVE enable/disable keep connections alive
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82 SO_DONTROUTE enable/disable routing bypass for outgoing messages
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85 SO_LINGER linger on close if data is present
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88 SO_BROADCAST enable/disable permission to transmit broadcast mes‐
89 sages
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92 SO_OOBINLINE enable/disable reception of out-of-band data in band
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95 SO_SNDBUF set buffer size for output
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98 SO_RCVBUF set buffer size for input
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101 SO_DGRAM_ERRIND application wants delayed error
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104 SO_TIMESTAMP enable/disable reception of timestamp with datagrams
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107 SO_EXCLBIND enable/disable exclusive binding of the socket
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110 SO_TYPE get the type of the socket (get only)
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113 SO_ERROR get and clear error on the socket (get only)
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116 SO_MAC_EXEMPT get or set mandatory access control on the socket.
117 This option is available only when the system is
118 configured with Trusted Extensions.
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121 SO_ALLZONES bypass zone boundaries (privileged).
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124 SO_DOMAIN get the domain used in the socket (get only)
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127 SO_PROTOTYPE for socket in domains PF_INET and PF_INET6, get the
128 underlying protocol number used in the socket. For
129 socket in domain PF_ROUTE, get the address family
130 used in the socket.
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134 The SO_DEBUG option enables debugging in the underlying protocol mod‐
135 ules. The SO_REUSEADDR option indicates that the rules used in validat‐
136 ing addresses supplied in a bind(3SOCKET) call should allow reuse of
137 local addresses. The SO_KEEPALIVE option enables the periodic transmis‐
138 sion of messages on a connected socket. If the connected party fails to
139 respond to these messages, the connection is considered broken and
140 threads using the socket are notified using a SIGPIPE signal. The
141 SO_DONTROUTE option indicates that outgoing messages should bypass the
142 standard routing facilities. Instead, messages are directed to the
143 appropriate network interface according to the network portion of the
144 destination address.
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147 The SO_LINGER option controls the action taken when unsent messages are
148 queued on a socket and a close(2) is performed. If the socket promises
149 reliable delivery of data and SO_LINGER is set, the system will block
150 the thread on the close() attempt until it is able to transmit the data
151 or until it decides it is unable to deliver the information (a timeout
152 period, termed the linger interval, is specified in the setsockopt()
153 call when SO_LINGER is requested). If SO_LINGER is disabled and a
154 close() is issued, the system will process the close() in a manner that
155 allows the thread to continue as quickly as possible.
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158 The option SO_BROADCAST requests permission to send broadcast datagrams
159 on the socket. With protocols that support out-of-band data, the
160 SO_OOBINLINE option requests that out-of-band data be placed in the
161 normal data input queue as received; it will then be accessible with
162 recv() or read() calls without the MSG_OOB flag.
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165 The SO_SNDBUF and SO_RCVBUF options adjust the normal buffer sizes
166 allocated for output and input buffers, respectively. The buffer size
167 may be increased for high-volume connections or may be decreased to
168 limit the possible backlog of incoming data. The maximum buffer size
169 for UDP is determined by the value of the ndd variable udp_max_buf. The
170 maximum buffer size for TCP is determined the value of the ndd variable
171 tcp_max_buf. Use the ndd(1M) utility to determine the current default
172 values. See the Solaris Tunable Parameters Reference Manual for infor‐
173 mation on setting the values of udp_max_buf and tcp_max_buf. At
174 present, lowering SO_RCVBUF on a TCP connection after it has been
175 established has no effect.
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178 By default, delayed errors (such as ICMP port unreachable packets) are
179 returned only for connected datagram sockets. The SO_DGRAM_ERRIND
180 option makes it possible to receive errors for datagram sockets that
181 are not connected. When this option is set, certain delayed errors
182 received after completion of a sendto() or sendmsg() operation will
183 cause a subsequent sendto() or sendmsg() operation using the same des‐
184 tination address (to parameter) to fail with the appropriate error. See
185 send(3SOCKET).
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188 If the SO_TIMESTAMP option is enabled on a SO_DGRAM or a SO_RAW socket,
189 the recvmsg(3XNET) call will return a timestamp in the native data for‐
190 mat, corresponding to when the datagram was received.
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193 The SO_EXCLBIND option is used to enable or disable the exclusive bind‐
194 ing of a socket. It overrides the use of the SO_REUSEADDR option to re‐
195 use an address on bind(3SOCKET). The actual semantics of the
196 SO_EXCLBIND option depend on the underlying protocol. See tcp(7P) or
197 udp(7P) for more information.
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200 The SO_TYPE and SO_ERROR options are used only with getsockopt(). The
201 SO_TYPE option returns the type of the socket, for example,
202 SOCK_STREAM. It is useful for servers that inherit sockets on startup.
203 The SO_ERROR option returns any pending error on the socket and clears
204 the error status. It may be used to check for asynchronous errors on
205 connected datagram sockets or for other asynchronous errors.
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208 The SO_MAC_EXEMPT option is used to toggle socket behavior with unla‐
209 beled peers. A socket that has this option enabled can communicate with
210 an unlabeled peer if it is in the global zone or has a label that domi‐
211 nates the default label of the peer. Otherwise, the socket must have a
212 label that is equal to the default label of the unlabeled peer. Calling
213 setsockopt() with this option returns an EACCES error if the process
214 lacks the NET_MAC_AWARE privilege or if the socket is bound. The
215 SO_MAC_EXEMPT option is available only when the system is configured
216 with Trusted Extensions.
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219 The SO_ALLZONES option can be used to bypass zone boundaries between
220 shared-IP zones. Normally, the system prevents a socket from being
221 bound to an address that is not assigned to the current zone. It also
222 prevents a socket that is bound to a wildcard address from receiving
223 traffic for other zones. However, some daemons which run in the global
224 zone might need to send and receive traffic using addresses that belong
225 to other shared-IP zones. If set before a socket is bound, SO_ALLZONES
226 causes the socket to ignore zone boundaries between shared-IP zones and
227 permits the socket to be bound to any address assigned to the shared-IP
228 zones. If the socket is bound to a wildcard address, it receives traf‐
229 fic intended for all shared-IP zones and behaves as if an equivalent
230 socket were bound in each active shared-IP zone. Applications that use
231 the SO_ALLZONES option to initiate connections or send datagram traffic
232 should specify the source address for outbound traffic by binding to a
233 specific address. There is no effect from setting this option in an
234 exclusive-IP zone. Setting this option requires the sys_net_config
235 privilege. See zones(5).
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238 If successful, getsockopt() and setsockopt() return 0. Otherwise, the
239 functions return −1 and set errno to indicate the error.
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242 The getsockopt() and setsockopt() calls succeed unless:
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244 EBADF The argument s is not a valid file descriptor.
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247 ENOMEM There was insufficient memory available for the opera‐
248 tion to complete.
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251 ENOPROTOOPT The option is unknown at the level indicated.
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254 ENOSR There were insufficient STREAMS resources available
255 for the operation to complete.
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258 ENOTSOCK The argument s is not a socket.
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261 ENOBUFS SO_SNDBUF or SO_RCVBUF exceeds a system limit.
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264 EINVAL Invalid length for IP_OPTIONS.
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267 EHOSTUNREACH Invalid address for IP_MULTICAST_IF.
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270 EINVAL Not a multicast address for IP_ADD_MEMBERSHIP and
271 IP_DROP_MEMBERSHIP.
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274 EADDRNOTAVAIL Bad interface address for IP_ADD_MEMBERSHIP and
275 IP_DROP_MEMBERSHIP.
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278 EADDRINUSE Address already joined for IP_ADD_MEMBERSHIP.
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281 ENOENT Address not joined for IP_DROP_MEMBERSHIP.
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284 EPERM No permissions.
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287 EACCES Permission denied.
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290 EINVAL The specified option is invalid at the specified
291 socket level, or the socket has been shut down.
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295 See attributes(5) for descriptions of the following attributes:
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300 ┌─────────────────────────────┬─────────────────────────────┐
301 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
302 ├─────────────────────────────┼─────────────────────────────┤
303 │MT-Level │Safe │
304 └─────────────────────────────┴─────────────────────────────┘
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307 ndd(1M), close(2), ioctl(2), read(2), bind(3SOCKET), getprotoby‐
308 name(3SOCKET), recv(3SOCKET), recvmsg(3XNET), send(3SOCKET),
309 socket(3SOCKET), socket.h(3HEAD), attributes(5), zones(5), tcp(7P),
310 udp(7P)
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313 Solaris Tunable Parameters Reference Manual
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317SunOS 5.11 27 Jan 2009 getsockopt(3SOCKET)