INET_NET(3)

🦋 INET_NET(3) 🦋

A Library Functions Manual moment, bestie — this is the INET_NET(3) page, and it’s all about internet network number manipulation routines. 💅

🌸 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 💖

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

inet_net_pton() does the reverse slay: it converts a presentation format Internet network number — that is, the printable form held in a character string — into 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. The size argument 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, periodt:

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 least significant two bytes of the Internet network number.

When a two part number is supplied, the last part is interpreted as a 24-bit quantity and placed in the least significant three bytes of the Internet network number.

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.

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That’s the whole page, bestie — brought to you by Debian, dated November 9, 2021, and filed under the iconic INET_NET(3) banner. 💅✨🎀