netinet_in.h(0p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

netinet_in.h(0P)        POSIX Programmer's Manual       netinet_in.h(0P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       netinet/in.h — Internet address family

SYNOPSIS         top

       #include <netinet/in.h>

DESCRIPTION         top

       The <netinet/in.h> header shall define the following types:

       in_port_t Equivalent to the type uint16_t as described in
                 <inttypes.h>.

       in_addr_t Equivalent to the type uint32_t as described in
                 <inttypes.h>.

       The <netinet_in.h> header shall define the sa_family_t type as
       described in <sys/socket.h>.

       The <netinet_in.h> header shall define the uint8_t and uint32_t
       types as described in <inttypes.h>.  Inclusion of the
       <netinet/in.h> header may also make visible all symbols from
       <inttypes.h> and <sys/socket.h>.

       The <netinet/in.h> header shall define the in_addr structure,
       which shall include at least the following member:

           in_addr_t  s_addr

       The <netinet/in.h> header shall define the sockaddr_in structure,
       which shall include at least the following members:

           sa_family_t     sin_family   AF_INET.
           in_port_t       sin_port     Port number.
           struct in_addr  sin_addr     IP address.

       The sin_port and sin_addr members shall be in network byte order.

       The sockaddr_in structure is used to store addresses for the
       Internet address family.  Pointers to this type shall be cast by
       applications to struct sockaddr * for use with socket functions.

       The <netinet/in.h> header shall define the in6_addr structure,
       which shall include at least the following member:

           uint8_t s6_addr[16]

       This array is used to contain a 128-bit IPv6 address, stored in
       network byte order.

       The <netinet/in.h> header shall define the sockaddr_in6
       structure, which shall include at least the following members:

           sa_family_t      sin6_family    AF_INET6.
           in_port_t        sin6_port      Port number.
           uint32_t         sin6_flowinfo  IPv6 traffic class and flow information.
           struct in6_addr  sin6_addr      IPv6 address.
           uint32_t         sin6_scope_id  Set of interfaces for a scope.

       The sin6_port and sin6_addr members shall be in network byte
       order.

       Prior to calling a function in this standard which reads values
       from a sockaddr_in6 structure (for example, bind() or connect()),
       the application shall ensure that all members of the structure,
       including any additional non-standard members, if any, are
       initialized.  If the sockaddr_in6 structure has a non-standard
       member, and that member has a value other than the value that
       would result from default initialization, the behavior of any
       function in this standard that reads values from the sockaddr_in6
       structure is implementation-defined. All functions in this
       standard that return data in a sockaddr_in6 structure (for
       example, getaddrinfo() or accept()) shall initialize the
       structure in a way that meets the above requirements, and shall
       ensure that each non-standard member, if any, has a value that
       produces the same behavior as default initialization would in all
       functions in this standard which read values from a sockaddr_in6
       structure.

       The sin6_scope_id field is a 32-bit integer that identifies a set
       of interfaces as appropriate for the scope of the address carried
       in the sin6_addr field. For a link scope sin6_addr, the
       application shall ensure that sin6_scope_id is a link index. For
       a site scope sin6_addr, the application shall ensure that
       sin6_scope_id is a site index. The mapping of sin6_scope_id to an
       interface or set of interfaces is implementation-defined.

       The <netinet/in.h> header shall declare the following external
       variable:

           const struct in6_addr in6addr_any

       This variable is initialized by the system to contain the
       wildcard IPv6 address. The <netinet/in.h> header also defines the
       IN6ADDR_ANY_INIT macro. This macro must be constant at compile
       time and can be used to initialize a variable of type struct
       in6_addr to the IPv6 wildcard address.

       The <netinet/in.h> header shall declare the following external
       variable:

           const struct in6_addr in6addr_loopback

       This variable is initialized by the system to contain the
       loopback IPv6 address. The <netinet/in.h> header also defines the
       IN6ADDR_LOOPBACK_INIT macro. This macro must be constant at
       compile time and can be used to initialize a variable of type
       struct in6_addr to the IPv6 loopback address.

       The <netinet/in.h> header shall define the ipv6_mreq structure,
       which shall include at least the following members:

           struct in6_addr  ipv6mr_multiaddr  IPv6 multicast address.
           unsigned         ipv6mr_interface  Interface index.

       The <netinet/in.h> header shall define the following symbolic
       constants for use as values of the level argument of getsockopt()
       and setsockopt():

       IPPROTO_IP      Internet protocol.

       IPPROTO_IPV6    Internet Protocol Version 6.

       IPPROTO_ICMP    Control message protocol.

       IPPROTO_RAW     Raw IP Packets Protocol.

       IPPROTO_TCP     Transmission control protocol.

       IPPROTO_UDP     User datagram protocol.

       The <netinet/in.h> header shall define the following symbolic
       constant for use as a local address in the structure passed to
       bind():

       INADDR_ANY      IPv4 wildcard address.

       The <netinet/in.h> header shall define the following symbolic
       constant for use as a destination address in the structures
       passed to connect(), sendmsg(), and sendto():

       INADDR_BROADCAST
                       IPv4 broadcast address.

       The <netinet/in.h> header shall define the following symbolic
       constant, with the value specified, to help applications declare
       buffers of the proper size to store IPv4 addresses in string
       form:

       INET_ADDRSTRLEN 16. Length of the string form for IP.

       The htonl(), htons(), ntohl(), and ntohs() functions shall be
       available as described in <arpa/inet.h>.  Inclusion of the
       <netinet/in.h> header may also make visible all symbols from
       <arpa/inet.h>.

       The <netinet/in.h> header shall define the following symbolic
       constant, with the value specified, to help applications declare
       buffers of the proper size to store IPv6 addresses in string
       form:

       INET6_ADDRSTRLEN
                       46. Length of the string form for IPv6.

       The <netinet/in.h> header shall define the following symbolic
       constants, with distinct integer values, for use in the
       option_name argument in the getsockopt() or setsockopt()
       functions at protocol level IPPROTO_IPV6:

       IPV6_JOIN_GROUP Join a multicast group.

       IPV6_LEAVE_GROUP
                       Quit a multicast group.

       IPV6_MULTICAST_HOPS
                       Multicast hop limit.

       IPV6_MULTICAST_IF
                       Interface to use for outgoing multicast packets.

       IPV6_MULTICAST_LOOP
                       Multicast packets are delivered back to the local
                       application.

       IPV6_UNICAST_HOPS
                       Unicast hop limit.

       IPV6_V6ONLY     Restrict AF_INET6 socket to IPv6 communications
                       only.

       The <netinet/in.h> header shall define the following macros that
       test for special IPv6 addresses. Each macro is of type int and
       takes a single argument of type const struct in6_addr *:

       IN6_IS_ADDR_UNSPECIFIED
             Unspecified address.

       IN6_IS_ADDR_LOOPBACK
             Loopback address.

       IN6_IS_ADDR_MULTICAST
             Multicast address.

       IN6_IS_ADDR_LINKLOCAL
             Unicast link-local address.

       IN6_IS_ADDR_SITELOCAL
             Unicast site-local address.

       IN6_IS_ADDR_V4MAPPED
             IPv4 mapped address.

       IN6_IS_ADDR_V4COMPAT
             IPv4-compatible address.

       IN6_IS_ADDR_MC_NODELOCAL
             Multicast node-local address.

       IN6_IS_ADDR_MC_LINKLOCAL
             Multicast link-local address.

       IN6_IS_ADDR_MC_SITELOCAL
             Multicast site-local address.

       IN6_IS_ADDR_MC_ORGLOCAL
             Multicast organization-local address.

       IN6_IS_ADDR_MC_GLOBAL
             Multicast global address.

       The following sections are informative.

APPLICATION USAGE         top

       Although applications are required to initialize all members
       (including any non-standard ones) of a sockaddr_in6 structure,
       the same is not required for the sockaddr_in structure, since
       historically many applications only initialized the standard
       members. Despite this, applications are encouraged to initialize
       sockaddr_in structures in a manner similar to the required
       initialization of sockaddr_in6 structures.

       Although it is common practice to initialize a sockaddr_in6
       structure using:

           struct sockaddr_in6 sa;
           memset(&sa, 0, sizeof sa);

       this method is not portable according to this standard, because
       the structure can contain pointer or floating-point members that
       are not required to have an all-bits-zero representation after
       default initialization. Portable methods make use of default
       initialization; for example:

           struct sockaddr_in6 sa = { 0 };

       or:

           static struct sockaddr_in6 sa_init;
           struct sockaddr_in6 sa = sa_init;

       A future version of this standard may require that a pointer
       object with an all-bits-zero representation is a null pointer,
       and that sockaddr_in6 does not have any floating-point members if
       a floating-point object with an all-bits-zero representation does
       not have the value 0.0.

RATIONALE         top

       The INADDR_ANY and INADDR_BROADCAST values are byte-order-neutral
       and thus their byte order is not specified. Many implementations
       have additional constants as extensions, such as INADDR_LOOPBACK,
       that are not byte-order-neutral. Traditionally, these constants
       are in host byte order, requiring the use of htonl() when using
       them in a sockaddr_in structure.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Section 4.10, Host and Network Byte Orders, arpa_inet.h(0p),
       inttypes.h(0p), sys_socket.h(0p)

       The System Interfaces volume of POSIX.1‐2017, connect(3p),
       getsockopt(3p), htonl(3p), sendmsg(3p), sendto(3p),
       setsockopt(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                  netinet_in.h(0P)

Pages that refer to this page: arpa_inet.h(0p)netdb.h(0p)sys_un.h(0p)getsockopt(3p)setsockopt(3p)socket(3p)