Ethernet addresses are represented by the following structure:
struct ether_addr {
u_char ether_addr_octet[6];
};
The
ether_ntoa() function converts this structure into an ASCII string of the form ``xx:xx:xx:xx:xx:xx'', consisting of 6 hexadecimal numbers separated by colons. It returns a pointer to a static buffer that is reused for each call. The
ether_aton() converts an ASCII string of the same form and to a structure containing the 6 octets of the address. It returns a pointer to a static structure that is reused for each call.
The
ether_ntohost() and
ether_hostton() functions interrogate the data base mapping host names to Ethernet addresses,
/etc/ethers. The
ether_ntohost() function looks up the given Ethernet address and writes the associated host name into the character buffer passed. The
ether_hostton() function looks up the given host name and writes the associated Ethernet address into the structure passed. Both functions return zero if they find the requested host name or address, and -1 if not. Each call reads
/etc/ethers from the beginning; if a + appears alone on a line in the file, then
ether_hostton() will consult the
ethers.byname YP map, and
ether_ntohost() will consult the
ethers.byaddr YP map.
The
ether_line() function parses a line from the
/etc/ethers file and fills in the passed ``struct ether_addr'' and character buffer with the Ethernet address and host name on the line. It returns zero if the line was successfully parsed and -1 if not.
The
hostname buffer for
ether_line() and
ether_ntohost() should be at least
MAXHOSTNAMELEN + 1 characters long, to prevent a buffer overflow during parsing.