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Dd July 20, 2012
Dt INET_NET 3
Os
Sh NAME
Nm inet_net_ntop ,
Nm inet_net_pton
Nd Internet network number manipulation routines
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In sys/socket.h
In netinet/in.h
In arpa/inet.h
Ft char *
Fn inet_net_ntop "int af" "const void *src" "int bits" "char *dst" "size_t size"
Ft int
Fn inet_net_pton "int af" "const char *src" "void *dst" "size_t size"
Sh DESCRIPTION
The
Fn inet_net_ntop
function converts an Internet network number from network format (usually a
Vt struct in_addr
or some other binary form, in network byte order) to CIDR presentation format
(suitable for external display purposes).
The
Fa bits
argument is the number of bits in
Fa src
that are the network number.
It returns
Dv NULL
if an error occurs (in which case
Va errno
will have been set), or it returns a pointer to the destination string.
Pp
The
Fn inet_net_pton
function converts a presentation format Internet network number (that is,
printable form as held in a character string) to network format (usually a
Vt struct in_addr
or some other internal binary representation, in network byte order).
It returns the number of bits (either computed based on the class, or
specified with /CIDR), or \-1 if a failure occurred
(in which case
Va errno
will have been set).
Pp
The currently supported values for
Fa af
are
Dv AF_INET
and
Dv AF_INET6 .
The
Fa size
argument is the size of the result buffer
Fa dst .
Sh NETWORK NUMBERS (IP VERSION 4)
Internet network numbers may be specified in one of the following forms:
Bd -literal -offset indent
a.b.c.d/bits
a.b.c.d
a.b.c
a.b
a
Ed
Pp
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 network number.
Note that when an Internet network number is viewed as a 32-bit
integer quantity on a system that uses little-endian
byte order (such as the
Tn Intel 386 , 486 ,
and
Tn Pentium
processors) the bytes referred to above appear as
Dq Li d.c.b.a .
That is, little-endian bytes are ordered from right to left.
Pp
When a three part number is specified, the last
part is interpreted as a 16-bit quantity and placed
in the rightmost two bytes of the Internet network number.
This makes the three part number format convenient
for specifying Class B network numbers as
Dq Li 128.net.host .
Pp
When a two part number is supplied, the last part
is interpreted as a 24-bit quantity and placed in
the rightmost three bytes of the Internet network number.
This makes the two part number format convenient
for specifying Class A network numbers as
Dq Li net.host .
Pp
When only one part is given, the value is stored
directly in the Internet network number without any byte
rearrangement.
Pp
All numbers supplied as
Dq parts
in a
Ql \&.
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;
otherwise, the number is interpreted as decimal).
\"
\" .Sh NETWORK NUMBERS (IP VERSION 6)
\" XXX - document this!
\"
Sh ERRORS
The
Fn inet_net_ntop
and
Fn inet_net_pton
functions may fail with
Bl -tag -width Er
It Bq Er EAFNOSUPPORT
The value of
Fa af
was not
Dv AF_INET
or
Dv AF_INET6 .
It Bq Er EMSGSIZE
The conversion of
Fa src
overflows
Fa size
of
Fa dst .
El
Pp
The
Fn inet_net_ntop
function may fail with
Bl -tag -width Er
It Bq Er EINVAL
The
Fa bits
argument contains an invalid number of bits
for the requested address family.
El
Pp
The
Fn inet_net_pton
function may fail with
Bl -tag -width Er
It Bq Er ENOENT
The
Fa src
was not a valid Internet network number.
El
Sh SEE ALSO
Xr byteorder 3 ,
Xr inet 3 ,
Xr networks 5
Sh HISTORY
The
Fn inet_net_ntop
and
Fn inet_net_pton
functions appeared in BIND 4.9.4 and thence
Nx 1.3 .
Support for
Dv AF_INET6
appeared in
Nx 1.6 .

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