ether_ntoa3
Ethernet address conversion and lookup routines
Part of ethers(3).
Usage
#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);
Library
Standard C Library (libc, -lc)
Overview
These functions operate on ethernet addresses using an ether_addr structure, which is defined in the header file ⟨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 ether_addr structures. Likewise, the ether_ntoa() and ether_ntoa_r() functions convert ethernet addresses specified as 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 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.
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.
Releases
87 releases since FreeBSD 2.0.5-RELEASE; the text changed 48 times.