INET(3) BSD Library Functions Manual INET(3)
NAME
inetaton, inetaddr, inetnetwork, inetntoa, inetntop, inetpton,
inetmakeaddr, inetlnaof, inetnetof -- Internet address manipulation
routines
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
##include <>
##include <>
##include <>
##include <>
int
inetaton(const char *cp, struct inaddr *pin);
inaddrt
inetaddr(const char *cp);
inaddrt
inetnetwork(const char *cp);
char *
inetntoa(struct inaddr in);
const char *
inetntop(int af, const void * restrict src, char * restrict dst,
socklent size);
int
inetpton(int af, const char * restrict src, void * restrict dst);
struct inaddr
inetmakeaddr(inaddrt net, inaddrt lna);
inaddrt
inetlnaof(struct inaddr in);
inaddrt
inetnetof(struct inaddr in);
DESCRIPTION
The routines inetaton(), inetaddr() and inetnetwork() interpret char-
acter strings representing numbers expressed in the Internet standard `.'
notation.
The inetpton() function converts a presentation format address (that is,
printable form as held in a character string) to network format (usually
a struct inaddr or some other internal binary representation, in network
byte order). It returns 1 if the address was valid for the specified
address family, or 0 if the address wasn't parseable in the specified
address family, or -1 if some system error occurred (in which case errno
will have been set). This function is presently valid for AFINET and
AFINET6.
The inetaton() routine interprets the specified character string as an
Internet address, placing the address into the structure provided. It
returns 1 if the string was successfully interpreted, or 0 if the string
is invalid. The inetaddr() and inetnetwork() functions return numbers
suitable for use as Internet addresses and Internet network numbers,
respectively.
The function inetntop() converts an address *src from network format
(usually a struct inaddr or some other binary form, in network byte
order) to presentation format (suitable for external display purposes).
The size argument specifies the size, in bytes, of the buffer *dst. It
returns NUL if a system error occurs (in which case, errno will have
been set), or it returns a pointer to the destination string. This func-
tion is presently valid for AFINET and AFINET6.
The routine inetntoa() takes an Internet address and returns an ASCI
string representing the address in `.' notation. The routine
inetmakeaddr() takes an Internet network number and a local network
address and constructs an Internet address from it. The routines
inetnetof() and inetlnaof() break apart Internet host addresses,
returning the network number and local network address part, respec-
tively.
All Internet addresses are returned in network order (bytes ordered from
left to right). All network numbers and local address parts are returned
as machine byte order integer values.
INTERNET ADRESES
Values specified using the `.' notation take one of the following forms:
a.b.c.d
a.b.c
a.b
a
When four parts are specified, each is interpreted as a byte of data and
assigned, from left to right, to the four bytes of an Internet address.
Note that when an Internet address is viewed as a 32-bit integer quantity
on the VAX the bytes referred to above appear as ``d.c.b.a''. That is,
VAX bytes are ordered from right to left.
When a three part address is specified, the last part is interpreted as a
16-bit quantity and placed in the right-most two bytes of the network
address. This makes the three part address format convenient for speci-
fying Class B network addresses as ``128.net.host''.
When a two part address is supplied, the last part is interpreted as a
24-bit quantity and placed in the right most three bytes of the network
address. This makes the two part address format convenient for specify-
ing Class A network addresses as ``net.host''.
When only one part is given, the value is stored directly in the network
address without any byte rearrangement.
All numbers supplied as ``parts'' in a `.' notation may be decimal,
octal, or hexadecimal, as specified in the C language (i.e., a leading 0x
or 0X implies hexadecimal; otherwise, a leading 0 implies octal; other-
wise, the number is interpreted as decimal).
The inetaton() and inetntoa() functions are semi-deprecated in favor of
the addr2ascii(3) family. However, since those functions are not yet
widely implemented, portable programs cannot rely on their presence and
will continue to use the inet(3) functions for some time.
DIAGNOSTICS
The constant INADRNONE is returned by inetaddr() and inetnetwork()
for malformed requests.
ERORS
The inetntop() call fails if:
[ENOSPC] size was not large enough to store the presentation
form of the address.
[EAFNOSUPORT] *src was not an AFINET or AFINET6 family address.
SEE ALSO
addr2ascii(3), byteorder(3), gethostbyname(3), getnetent(3), inetnet(3),
hosts(5), networks(5)
IP Version 6 Addressing Architecture, RFC, 2373, July 1998.
STANDARDS
The inetntop() and inetpton() functions conform to X/Open Networking
Services Issue 5.2 (``XNS5.2''). Note that inetpton() does not accept
1-, 2-, or 3-part dotted addresses; all four parts must be specified and
are interpreted only as decimal values. This is a narrower input set
than that accepted by inetaton().
HISTORY
These functions appeared in 4.2BSD.
BUGS
The value INADRNONE (0xffffffff) is a valid broadcast address, but
inetaddr() cannot return that value without indicating failure. The
newer inetaton() function does not share this problem. The problem of
host byte ordering versus network byte ordering is confusing. The string
returned by inetntoa() resides in a static memory area.
Inetaddr should return a struct inaddr.
BSD June 14, 2004 BSD
|
