1<sys/socket.h>(0P) POSIX Programmer's Manual <sys/socket.h>(0P)
2
6 sys/socket.h - main sockets header
7
9 #include <sys/socket.h>
10
12 The <sys/socket.h> header shall define the type socklen_t, which is an
13 integer type of width of at least 32 bits; see APPLICATION USAGE.
14 The <sys/socket.h> header shall define the unsigned integer type
16 sa_family_t.
17 The <sys/socket.h> header shall define the sockaddr structure that
19 includes at least the following members:
20 sa_family_t sa_family Address family.
23 char sa_data[] Socket address (variable-length data).
24 The sockaddr structure is used to define a socket address which is used
26 in the bind(), connect(), getpeername(), getsockname(), recvfrom(), and
27 sendto() functions.
28 The <sys/socket.h> header shall define the sockaddr_storage structure.
30 This structure shall be:
31 * Large enough to accommodate all supported protocol-specific address
33 structures
34 * Aligned at an appropriate boundary so that pointers to it can be
36 cast as pointers to protocol-specific address structures and used to
37 access the fields of those structures without alignment problems
38 The sockaddr_storage structure shall contain at least the following
40 members:
41 sa_family_t ss_family
44 When a sockaddr_storage structure is cast as a sockaddr structure, the
46 ss_family field of the sockaddr_storage structure shall map onto the
47 sa_family field of the sockaddr structure. When a sockaddr_storage
48 structure is cast as a protocol-specific address structure, the ss_fam‐
49 ily field shall map onto a field of that structure that is of type
50 sa_family_t and that identifies the protocol's address family.
51 The <sys/socket.h> header shall define the msghdr structure that
53 includes at least the following members:
54 void *msg_name Optional address.
57 socklen_t msg_namelen Size of address.
58 struct iovec *msg_iov Scatter/gather array.
59 int msg_iovlen Members in msg_iov.
60 void *msg_control Ancillary data; see below.
61 socklen_t msg_controllen Ancillary data buffer len.
62 int msg_flags Flags on received message.
63 The msghdr structure is used to minimize the number of directly sup‐
65 plied parameters to the recvmsg() and sendmsg() functions. This struc‐
66 ture is used as a value- result parameter in the recvmsg() function and
67 value only for the sendmsg() function.
68 The iovec structure shall be defined as described in <sys/uio.h> .
70 The <sys/socket.h> header shall define the cmsghdr structure that
72 includes at least the following members:
73 socklen_t cmsg_len Data byte count, including the cmsghdr.
76 int cmsg_level Originating protocol.
77 int cmsg_type Protocol-specific type.
78 The cmsghdr structure is used for storage of ancillary data object
80 information.
81 Ancillary data consists of a sequence of pairs, each consisting of a
83 cmsghdr structure followed by a data array. The data array contains the
84 ancillary data message, and the cmsghdr structure contains descriptive
85 information that allows an application to correctly parse the data.
86 The values for cmsg_level shall be legal values for the level argument
88 to the getsockopt() and setsockopt() functions. The system documenta‐
89 tion shall specify the cmsg_type definitions for the supported proto‐
90 cols.
91 Ancillary data is also possible at the socket level. The <sys/socket.h>
93 header defines the following macro for use as the cmsg_type value when
94 cmsg_level is SOL_SOCKET:
95 SCM_RIGHTS
97 Indicates that the data array contains the access rights to be
98 sent or received.
99 The <sys/socket.h> header defines the following macros to gain access
102 to the data arrays in the ancillary data associated with a message
103 header:
104 CMSG_DATA(cmsg)
106 If the argument is a pointer to a cmsghdr structure, this macro
108 shall return an unsigned character pointer to the data array
109 associated with the cmsghdr structure.
110 CMSG_NXTHDR(mhdr,cmsg)
112 If the first argument is a pointer to a msghdr structure and the
114 second argument is a pointer to a cmsghdr structure in the
115 ancillary data pointed to by the msg_control field of that
116 msghdr structure, this macro shall return a pointer to the next
117 cmsghdr structure, or a null pointer if this structure is the
118 last cmsghdr in the ancillary data.
119 CMSG_FIRSTHDR(mhdr)
121 If the argument is a pointer to a msghdr structure, this macro
123 shall return a pointer to the first cmsghdr structure in the
124 ancillary data associated with this msghdr structure, or a null
125 pointer if there is no ancillary data associated with the msghdr
126 structure.
127 The <sys/socket.h> header shall define the linger structure that
130 includes at least the following members:
131 int l_onoff Indicates whether linger option is enabled.
134 int l_linger Linger time, in seconds.
135 The <sys/socket.h> header shall define the following macros, with dis‐
137 tinct integer values:
138 SOCK_DGRAM
140 Datagram socket.
141 SOCK_RAW
143 Raw Protocol Interface.
144 SOCK_SEQPACKET
146 Sequenced-packet socket.
147 SOCK_STREAM
149 Byte-stream socket.
150 The <sys/socket.h> header shall define the following macro for use as
153 the level argument of setsockopt() and getsockopt().
154 SOL_SOCKET
156 Options to be accessed at socket level, not protocol level.
157 The <sys/socket.h> header shall define the following macros, with dis‐
160 tinct integer values, for use as the option_name argument in getsock‐
161 opt() or setsockopt() calls:
162 SO_ACCEPTCONN
164 Socket is accepting connections.
165 SO_BROADCAST
167 Transmission of broadcast messages is supported.
168 SO_DEBUG
170 Debugging information is being recorded.
171 SO_DONTROUTE
173 Bypass normal routing.
174 SO_ERROR
176 Socket error status.
177 SO_KEEPALIVE
179 Connections are kept alive with periodic messages.
180 SO_LINGER
182 Socket lingers on close.
183 SO_OOBINLINE
185 Out-of-band data is transmitted in line.
186 SO_RCVBUF
188 Receive buffer size.
189 SO_RCVLOWAT
191 Receive ``low water mark''.
192 SO_RCVTIMEO
194 Receive timeout.
195 SO_REUSEADDR
197 Reuse of local addresses is supported.
198 SO_SNDBUF
200 Send buffer size.
201 SO_SNDLOWAT
203 Send ``low water mark''.
204 SO_SNDTIMEO
206 Send timeout.
207 SO_TYPE
209 Socket type.
210 The <sys/socket.h> header shall define the following macro as the maxi‐
213 mum backlog queue length which may be specified by the backlog field of
214 the listen() function:
215 SOMAXCONN
217 The maximum backlog queue length.
218 The <sys/socket.h> header shall define the following macros, with dis‐
221 tinct integer values, for use as the valid values for the msg_flags
222 field in the msghdr structure, or the flags parameter in recvfrom(),
223 recvmsg(), sendmsg(), or sendto() calls:
224 MSG_CTRUNC
226 Control data truncated.
227 MSG_DONTROUTE
229 Send without using routing tables.
230 MSG_EOR
232 Terminates a record (if supported by the protocol).
233 MSG_OOB
235 Out-of-band data.
236 MSG_PEEK
238 Leave received data in queue.
239 MSG_TRUNC
241 Normal data truncated.
242 MSG_WAITALL
244 Attempt to fill the read buffer.
245 The <sys/socket.h> header shall define the following macros, with dis‐
248 tinct integer values:
249 AF_INET
251 Internet domain sockets for use with IPv4 addresses.
252 AF_INET6
254 Internet domain sockets for use with IPv6 addresses.
255 AF_UNIX
257 UNIX domain sockets.
258 AF_UNSPEC
260 Unspecified.
261 The <sys/socket.h> header shall define the following macros, with dis‐
264 tinct integer values:
265 SHUT_RD
267 Disables further receive operations.
268 SHUT_RDWR
270 Disables further send and receive operations.
271 SHUT_WR
273 Disables further send operations.
274 The following shall be declared as functions and may also be defined as
277 macros. Function prototypes shall be provided.
278 int accept(int, struct sockaddr *restrict, socklen_t *restrict);
281 int bind(int, const struct sockaddr *, socklen_t);
282 int connect(int, const struct sockaddr *, socklen_t);
283 int getpeername(int, struct sockaddr *restrict, socklen_t *restrict);
284 int getsockname(int, struct sockaddr *restrict, socklen_t *restrict);
285 int getsockopt(int, int, int, void *restrict, socklen_t *restrict);
286 int listen(int, int);
287 ssize_t recv(int, void *, size_t, int);
288 ssize_t recvfrom(int, void *restrict, size_t, int,
289 struct sockaddr *restrict, socklen_t *restrict);
290 ssize_t recvmsg(int, struct msghdr *, int);
291 ssize_t send(int, const void *, size_t, int);
292 ssize_t sendmsg(int, const struct msghdr *, int);
293 ssize_t sendto(int, const void *, size_t, int, const struct sockaddr *,
294 socklen_t);
295 int setsockopt(int, int, int, const void *, socklen_t);
296 int shutdown(int, int);
297 int socket(int, int, int);
298 int sockatmark(int);
299 int socketpair(int, int, int, int[2]);
300 Inclusion of <sys/socket.h> may also make visible all symbols from
302 <sys/uio.h>.
303 The following sections are informative.
305
307 To forestall portability problems, it is recommended that applications
308 not use values larger than 2**31 -1 for the socklen_t type.
309 The sockaddr_storage structure solves the problem of declaring storage
311 for automatic variables which is both large enough and aligned enough
312 for storing the socket address data structure of any family. For exam‐
313 ple, code with a file descriptor and without the context of the address
314 family can pass a pointer to a variable of this type, where a pointer
315 to a socket address structure is expected in calls such as getpeer‐
316 name(), and determine the address family by accessing the received con‐
317 tent after the call.
318 The example below illustrates a data structure which aligns on a 64-bit
320 boundary. An implementation-defined field _ss_align following _ss_pad1
321 is used to force a 64-bit alignment which covers proper alignment good
322 enough for needs of at least sockaddr_in6 (IPv6) and sockaddr_in (IPv4)
323 address data structures. The size of padding field _ss_pad1 depends on
324 the chosen alignment boundary. The size of padding field _ss_pad2
325 depends on the value of overall size chosen for the total size of the
326 structure. This size and alignment are represented in the above example
327 by implementation-defined (not required) constants _SS_MAXSIZE (chosen
328 value 128) and _SS_ALIGNMENT (with chosen value 8). Constants
329 _SS_PAD1SIZE (derived value 6) and _SS_PAD2SIZE (derived value 112) are
330 also for illustration and not required. The implementation-defined def‐
331 initions and structure field names above start with an underscore to
332 denote implementation private name space. Portable code is not expected
333 to access or reference those fields or constants.
334 /*
337 * Desired design of maximum size and alignment.
338 */
339 #define _SS_MAXSIZE 128
340 /* Implementation-defined maximum size. */
341 #define _SS_ALIGNSIZE (sizeof(int64_t))
342 /* Implementation-defined desired alignment. */
343 /*
346 * Definitions used for sockaddr_storage structure paddings design.
347 */
348 #define _SS_PAD1SIZE (_SS_ALIGNSIZE - sizeof(sa_family_t))
349 #define _SS_PAD2SIZE (_SS_MAXSIZE - (sizeof(sa_family_t)+ \
350 _SS_PAD1SIZE + _SS_ALIGNSIZE))
351 struct sockaddr_storage {
352 sa_family_t ss_family; /* Address family. */
353 /*
354 * Following fields are implementation-defined.
355 */
356 char _ss_pad1[_SS_PAD1SIZE];
357 /* 6-byte pad; this is to make implementation-defined
358 pad up to alignment field that follows explicit in
359 the data structure. */
360 int64_t _ss_align; /* Field to force desired structure
361 storage alignment. */
362 char _ss_pad2[_SS_PAD2SIZE];
363 /* 112-byte pad to achieve desired size,
364 _SS_MAXSIZE value minus size of ss_family
365 __ss_pad1, __ss_align fields is 112. */
366 };
367
369 None.
370
372 None.
373
375 <sys/uio.h>, the System Interfaces volume of IEEE Std 1003.1-2001,
376 accept(), bind(), connect(), getpeername(), getsockname(), getsock‐
377 opt(), listen(), recv(), recvfrom(), recvmsg(), send(), sendmsg(),
378 sendto(), setsockopt(), shutdown(), socket(), socketpair()
379
381 Portions of this text are reprinted and reproduced in electronic form
382 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
383 -- Portable Operating System Interface (POSIX), The Open Group Base
384 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
385 Electrical and Electronics Engineers, Inc and The Open Group. In the
386 event of any discrepancy between this version and the original IEEE and
387 The Open Group Standard, the original IEEE and The Open Group Standard
388 is the referee document. The original Standard can be obtained online
389 at http://www.opengroup.org/unix/online.html .
390IEEE/The Open Group 2003 <sys/socket.h>(0P)