Manual Pages  — ETHERS

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

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES NOTES NIS INTERACTION SEE ALSO HISTORY BUGS

Standard C Library (libc, -lc)

#include <sys/types.h>

#include <sys/socket.h>

#include <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);

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 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 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 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.

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.

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.

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

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.