1netinet_in.h(0P) POSIX Programmer's Manual netinet_in.h(0P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 netinet/in.h — Internet address family
13
15 #include <netinet/in.h>
16
18 The <netinet/in.h> header shall define the following types:
19 in_port_t Equivalent to the type uint16_t as described in <inttypes.h>.
21 in_addr_t Equivalent to the type uint32_t as described in <inttypes.h>.
23 The <netinet_in.h> header shall define the sa_family_t type as
25 described in <sys/socket.h>.
26 The <netinet_in.h> header shall define the uint8_t and uint32_t types
28 as described in <inttypes.h>. Inclusion of the <netinet/in.h> header
29 may also make visible all symbols from <inttypes.h> and <sys/socket.h>.
30 The <netinet/in.h> header shall define the in_addr structure, which
32 shall include at least the following member:
33 in_addr_t s_addr
36 The <netinet/in.h> header shall define the sockaddr_in structure, which
38 shall include at least the following members:
39 sa_family_t sin_family AF_INET.
42 in_port_t sin_port Port number.
43 struct in_addr sin_addr IP address.
44 The sin_port and sin_addr members shall be in network byte order.
46 The sockaddr_in structure is used to store addresses for the Internet
48 address family. Pointers to this type shall be cast by applications to
49 struct sockaddr * for use with socket functions.
50 The <netinet/in.h> header shall define the in6_addr structure, which
52 shall include at least the following member:
53 uint8_t s6_addr[16]
56 This array is used to contain a 128-bit IPv6 address, stored in network
58 byte order.
59 The <netinet/in.h> header shall define the sockaddr_in6 structure,
61 which shall include at least the following members:
62 sa_family_t sin6_family AF_INET6.
65 in_port_t sin6_port Port number.
66 uint32_t sin6_flowinfo IPv6 traffic class and flow information.
67 struct in6_addr sin6_addr IPv6 address.
68 uint32_t sin6_scope_id Set of interfaces for a scope.
69 The sin6_port and sin6_addr members shall be in network byte order.
71 Prior to calling a function in this standard which reads values from a
73 sockaddr_in6 structure (for example, bind() or connect()), the applica‐
74 tion shall ensure that all members of the structure, including any
75 additional non-standard members, if any, are initialized. If the sock‐
76 addr_in6 structure has a non-standard member, and that member has a
77 value other than the value that would result from default initializa‐
78 tion, the behavior of any function in this standard that reads values
79 from the sockaddr_in6 structure is implementation-defined. All func‐
80 tions in this standard that return data in a sockaddr_in6 structure
81 (for example, getaddrinfo() or accept()) shall initialize the structure
82 in a way that meets the above requirements, and shall ensure that each
83 non-standard member, if any, has a value that produces the same behav‐
84 ior as default initialization would in all functions in this standard
85 which read values from a sockaddr_in6 structure.
86 The sin6_scope_id field is a 32-bit integer that identifies a set of
88 interfaces as appropriate for the scope of the address carried in the
89 sin6_addr field. For a link scope sin6_addr, the application shall
90 ensure that sin6_scope_id is a link index. For a site scope sin6_addr,
91 the application shall ensure that sin6_scope_id is a site index. The
92 mapping of sin6_scope_id to an interface or set of interfaces is imple‐
93 mentation-defined.
94 The <netinet/in.h> header shall declare the following external vari‐
96 able:
97 const struct in6_addr in6addr_any
100 This variable is initialized by the system to contain the wildcard IPv6
102 address. The <netinet/in.h> header also defines the IN6ADDR_ANY_INIT
103 macro. This macro must be constant at compile time and can be used to
104 initialize a variable of type struct in6_addr to the IPv6 wildcard
105 address.
106 The <netinet/in.h> header shall declare the following external vari‐
108 able:
109 const struct in6_addr in6addr_loopback
112 This variable is initialized by the system to contain the loopback IPv6
114 address. The <netinet/in.h> header also defines the IN6ADDR_LOOP‐
115 BACK_INIT macro. This macro must be constant at compile time and can be
116 used to initialize a variable of type struct in6_addr to the IPv6 loop‐
117 back address.
118 The <netinet/in.h> header shall define the ipv6_mreq structure, which
120 shall include at least the following members:
121 struct in6_addr ipv6mr_multiaddr IPv6 multicast address.
124 unsigned ipv6mr_interface Interface index.
125 The <netinet/in.h> header shall define the following symbolic constants
127 for use as values of the level argument of getsockopt() and setsock‐
128 opt():
129 IPPROTO_IP Internet protocol.
131 IPPROTO_IPV6 Internet Protocol Version 6.
133 IPPROTO_ICMP Control message protocol.
135 IPPROTO_RAW Raw IP Packets Protocol.
137 IPPROTO_TCP Transmission control protocol.
139 IPPROTO_UDP User datagram protocol.
141 The <netinet/in.h> header shall define the following symbolic constant
143 for use as a local address in the structure passed to bind():
144 INADDR_ANY IPv4 wildcard address.
146 The <netinet/in.h> header shall define the following symbolic constant
148 for use as a destination address in the structures passed to connect(),
149 sendmsg(), and sendto():
150 INADDR_BROADCAST
152 IPv4 broadcast address.
153 The <netinet/in.h> header shall define the following symbolic constant,
155 with the value specified, to help applications declare buffers of the
156 proper size to store IPv4 addresses in string form:
157 INET_ADDRSTRLEN 16. Length of the string form for IP.
159 The htonl(), htons(), ntohl(), and ntohs() functions shall be available
161 as described in <arpa/inet.h>. Inclusion of the <netinet/in.h> header
162 may also make visible all symbols from <arpa/inet.h>.
163 The <netinet/in.h> header shall define the following symbolic constant,
165 with the value specified, to help applications declare buffers of the
166 proper size to store IPv6 addresses in string form:
167 INET6_ADDRSTRLEN
169 46. Length of the string form for IPv6.
170 The <netinet/in.h> header shall define the following symbolic con‐
172 stants, with distinct integer values, for use in the option_name argu‐
173 ment in the getsockopt() or setsockopt() functions at protocol level
174 IPPROTO_IPV6:
175 IPV6_JOIN_GROUP Join a multicast group.
177 IPV6_LEAVE_GROUP
179 Quit a multicast group.
180 IPV6_MULTICAST_HOPS
182 Multicast hop limit.
183 IPV6_MULTICAST_IF
185 Interface to use for outgoing multicast packets.
186 IPV6_MULTICAST_LOOP
188 Multicast packets are delivered back to the local
189 application.
190 IPV6_UNICAST_HOPS
192 Unicast hop limit.
193 IPV6_V6ONLY Restrict AF_INET6 socket to IPv6 communications only.
195 The <netinet/in.h> header shall define the following macros that test
197 for special IPv6 addresses. Each macro is of type int and takes a sin‐
198 gle argument of type const struct in6_addr *:
199 IN6_IS_ADDR_UNSPECIFIED
201 Unspecified address.
202 IN6_IS_ADDR_LOOPBACK
204 Loopback address.
205 IN6_IS_ADDR_MULTICAST
207 Multicast address.
208 IN6_IS_ADDR_LINKLOCAL
210 Unicast link-local address.
211 IN6_IS_ADDR_SITELOCAL
213 Unicast site-local address.
214 IN6_IS_ADDR_V4MAPPED
216 IPv4 mapped address.
217 IN6_IS_ADDR_V4COMPAT
219 IPv4-compatible address.
220 IN6_IS_ADDR_MC_NODELOCAL
222 Multicast node-local address.
223 IN6_IS_ADDR_MC_LINKLOCAL
225 Multicast link-local address.
226 IN6_IS_ADDR_MC_SITELOCAL
228 Multicast site-local address.
229 IN6_IS_ADDR_MC_ORGLOCAL
231 Multicast organization-local address.
232 IN6_IS_ADDR_MC_GLOBAL
234 Multicast global address.
235 The following sections are informative.
237
239 Although applications are required to initialize all members (including
240 any non-standard ones) of a sockaddr_in6 structure, the same is not
241 required for the sockaddr_in structure, since historically many appli‐
242 cations only initialized the standard members. Despite this, applica‐
243 tions are encouraged to initialize sockaddr_in structures in a manner
244 similar to the required initialization of sockaddr_in6 structures.
245 Although it is common practice to initialize a sockaddr_in6 structure
247 using:
248 struct sockaddr_in6 sa;
251 memset(&sa, 0, sizeof sa);
252 this method is not portable according to this standard, because the
254 structure can contain pointer or floating-point members that are not
255 required to have an all-bits-zero representation after default initial‐
256 ization. Portable methods make use of default initialization; for exam‐
257 ple:
258 struct sockaddr_in6 sa = { 0 };
261 or:
263 static struct sockaddr_in6 sa_init;
266 struct sockaddr_in6 sa = sa_init;
267 A future version of this standard may require that a pointer object
269 with an all-bits-zero representation is a null pointer, and that sock‐
270 addr_in6 does not have any floating-point members if a floating-point
271 object with an all-bits-zero representation does not have the value
272 0.0.
273
275 The INADDR_ANY and INADDR_BROADCAST values are byte-order-neutral and
276 thus their byte order is not specified. Many implementations have addi‐
277 tional constants as extensions, such as INADDR_LOOPBACK, that are not
278 byte-order-neutral. Traditionally, these constants are in host byte
279 order, requiring the use of htonl() when using them in a sockaddr_in
280 structure.
281
283 None.
284
286 Section 4.10, Host and Network Byte Orders, <arpa_inet.h>, <int‐
287 types.h>, <sys_socket.h>
288 The System Interfaces volume of POSIX.1‐2017, connect(), getsockopt(),
290 htonl(), sendmsg(), sendto(), setsockopt()
291
293 Portions of this text are reprinted and reproduced in electronic form
294 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
295 table Operating System Interface (POSIX), The Open Group Base Specifi‐
296 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
297 Electrical and Electronics Engineers, Inc and The Open Group. In the
298 event of any discrepancy between this version and the original IEEE and
299 The Open Group Standard, the original IEEE and The Open Group Standard
300 is the referee document. The original Standard can be obtained online
301 at http://www.opengroup.org/unix/online.html .
302 Any typographical or formatting errors that appear in this page are
304 most likely to have been introduced during the conversion of the source
305 files to man page format. To report such errors, see https://www.ker‐
306 nel.org/doc/man-pages/reporting_bugs.html .
307IEEE/The Open Group 2017 netinet_in.h(0P)