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Man Pages


Manual Reference Pages  -  ETHERS (3)

NAME

ethers, ether_line, ether_aton, ether_aton_r, ether_ntoa, ether_ntoa_r, ether_ntohost, ether_hostton - Ethernet address conversion and lookup routines

CONTENTS

Library
Synopsis
Description
Return Values
Notes
Nis Interaction
See Also
History
Bugs

LIBRARY


.Lb libc

SYNOPSIS


.In sys/types.h
.In sys/socket.h
.In net/ethernet.h int ether_line const char *l struct ether_addr *e char *hostname struct ether_addr * ether_aton const char *a struct ether_addr * ether_aton_r const char *a struct ether_addr *e char * ether_ntoa const struct ether_addr *n char * ether_ntoa_r const struct ether_addr *n char *buf int ether_ntohost char *hostname const struct ether_addr *e int ether_hostton const char *hostname struct ether_addr *e

DESCRIPTION

These functions operate on ethernet addresses using an
.Vt ether_addr structure, which is defined in the header file
.In net/ethernet.h :
/*
 * The number of bytes in an ethernet (MAC) address.
 */
#define ETHER_ADDR_LEN          6

/* * Structure of a 48-bit Ethernet address. */ struct ether_addr { u_char octet[ETHER_ADDR_LEN]; };

The function ether_line scans l, an ASCII string in ethers(5) format and sets e to the ethernet address specified in the string and h to the hostname. This function is used to parse lines from /etc/ethers into their component parts.

The ether_aton and ether_aton_r functions convert ASCII representation of ethernet addresses into
.Vt ether_addr structures. Likewise, the ether_ntoa and ether_ntoa_r functions convert ethernet addresses specified as
.Vt ether_addr structures into ASCII strings.

The ether_ntohost and ether_hostton functions map ethernet addresses to their corresponding hostnames as specified in the /etc/ethers database. The ether_ntohost function converts from ethernet address to hostname, and ether_hostton converts from hostname to ethernet address.

RETURN VALUES

The ether_line function returns zero on success and non-zero if it was unable to parse any part of the supplied line l. It returns the extracted ethernet address in the supplied
.Vt ether_addr structure e and the hostname in the supplied string h.

On success, ether_ntoa and ether_ntoa_r functions return a pointer to a string containing an ASCII representation of an ethernet address. If it is unable to convert the supplied
.Vt ether_addr structure, it returns a NULL pointer. ether_ntoa stores the result in a static buffer; ether_ntoa_r stores the result in a user-passed buffer.

Likewise, ether_aton and ether_aton_r return a pointer to an
.Vt ether_addr structure on success and a NULL pointer on failure. ether_aton stores the result in a static buffer; ether_aton_r stores the result in a user-passed buffer.

The ether_ntohost and ether_hostton functions both return zero on success or non-zero if they were unable to find a match in the /etc/ethers database.

NOTES

The user must ensure that the hostname strings passed to the ether_line, ether_ntohost and ether_hostton functions are large enough to contain the returned hostnames.

NIS INTERACTION

If the /etc/ethers contains a line with a single + in it, the ether_ntohost and ether_hostton functions will attempt to consult the NIS ethers.byname and ethers.byaddr maps in addition to the data in the /etc/ethers file.

SEE ALSO

ethers(5), yp(8)

HISTORY

This particular implementation of the ethers library functions were written for and first appeared in
.Fx 2.1 . Thread-safe function variants first appeared in
.Fx 7.0 .

BUGS

The ether_aton and ether_ntoa functions returns values that are stored in static memory areas which may be overwritten the next time they are called.

ether_ntoa_r accepts a character buffer pointer, but not a buffer length. The caller must ensure adequate space is available in the buffer in order to avoid a buffer overflow.

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