harvey/sys/src/cmd/ip/linklocal.c

/*
 * linklocal - print ipv6 link-local or 6to4 address of a mac address.
 * eui is ieee's extended unique identifier, per rfc2373.
 */

#include <u.h>
#include <libc.h>
#include <ip.h>

enum {
	Mac0mcast	= 1<<0,		/* multicast address */
	Mac0localadm	= 1<<1,		/* locally-administered address, */
	V60globaladm	= 1<<1,		/* but ipv6 reverses the meaning */
};

static char *v4_6to4;

static void
usage(void)
{
	fprint(2, "usage: %s [-t ipv4] ether...\n", argv0);
	exits("usage");
}

void
ea2eui64(uchar *lla, uchar *ea)
{
	*lla++ = *ea++ | V60globaladm;	/* oui (company id) */
	*lla++ = *ea++;			/* " */
	*lla++ = *ea++;			/* " */
	*lla++ = 0xFF;			/* mac-48 in eui-64 (sic) */
	*lla++ = 0xFE;			/* " */
	*lla++ = *ea++;			/* manufacturer-assigned */
	*lla++ = *ea++;			/* " */
	*lla = *ea;			/* " */
}

void
eaip26to4(uchar *lla, uchar *ea, uchar *ipv4)
{
	*lla++ = 0x20;			/* 6to4 address */
	*lla++ = 0x02;			/* " */
	memmove(lla, ipv4, IPv4addrlen);
	lla += IPv4addrlen;
	memset(lla, 0, 2);
	ea2eui64(lla + 2, ea);
}

void
ea2lla(uchar *lla, uchar *ea)
{
	*lla++ = 0xFE;			/* link-local v6 */
	*lla++ = 0x80;			/* " */
	memset(lla, 0, 6);
	ea2eui64(lla + 6, ea);
}

static void
process(char *ether)
{
	uchar ethaddr[6], ipaddr[IPaddrlen], ipv4[IPv4addrlen];

	if (parseether(ethaddr, ether) < 0)
		sysfatal("%s: not an ether address\n", ether);
	if (v4_6to4) {
		v4parseip(ipv4, v4_6to4);
		eaip26to4(ipaddr, ethaddr, ipv4);
	} else
		ea2lla(ipaddr, ethaddr);
	print("%I\n", ipaddr);
}

void
main(int argc, char *argv[])
{
	int i;

	ARGBEGIN {
	case 't':
		v4_6to4 = EARGF(usage());
		break;
	default:
		usage();
		break;
	} ARGEND

	fmtinstall('I', eipfmt);
	if (argc <= 0)
		usage();

	for (i = 0; i < argc; i++)
		process(argv[i]);
	exits(0);
}