NAME

inet_net_ntop, inet_net_pton — Internet network number manipulation routines

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

char *
inet_net_ntop(int af, const void *src, int bits, char *dst, size_t size);

int
inet_net_pton(int af, const char *src, void *dst, size_t size);

DESCRIPTION

The inet_net_ntop() function converts an Internet network number from network format (usually a struct in_addr or some other binary form, in network byte order) to CIDR presentation format (suitable for external display purposes). bits is the number of bits in src that are the network number. It returns NULL if a system error occurs (in which case, errno will have been set), or it returns a pointer to the destination string.

The 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 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 errno will have been set. It will be set to ENOENT if the Internet network number was not valid).

The currently supported values for af are AF_INET and AF_INET6. size is the size of the result buffer dst.

NETWORK NUMBERS (IP VERSION 4)

Internet network numbers may be specified in one of the following forms:

a.b.c.d/bits 
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 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 Intel 386, 486 and Pentium processors) the bytes referred to above appear as “d.c.b.a”. That is, little-endian bytes are ordered from right to left.

When a three part number is specified, the last part is interpreted as a 16-bit quantity and placed in the right-most two bytes of the Internet network number. This makes the three part number format convenient for specifying Class B network numbers as “128.net.host”.

When a two part number is supplied, the last part is interpreted as a 24-bit quantity and placed in the right most three bytes of the Internet network number. This makes the two part number format convenient for specifying Class A network numbers as “net.host”.

When only one part is given, the value is stored directly in the Internet network number 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; otherwise, the number is interpreted as decimal).

SEE ALSO

byteorder(3), inet(3), networks(5)

HISTORY

The inet_net_ntop and inet_net_pton functions appeared in BIND 4.9.4 and thence NetBSD 1.3. Support for AF_INET6 appeared in NetBSD 1.6.