Index: usr.sbin/rwhod/rwhod.c
===================================================================
--- usr.sbin/rwhod/rwhod.c
+++ usr.sbin/rwhod/rwhod.c
@@ -104,15 +104,20 @@
 
 const struct in6_addr in6addr_whod_group = IN6ADDR_WHOD_GROUP_INIT;
 
-
+int	enable_v4 = 0;
+int	enable_v6 = 0;
 int	insecure_mode;
 int	quiet_mode;
 int	iff_flag = IFF_POINTOPOINT;
 int	multicast_mode = NO_MULTICAST;
 int	multicast_scope;
+
 struct	sockaddr_in multicast_addr =
 	{ sizeof(multicast_addr), AF_INET, 0, { 0 }, { 0 } };
 
+struct  sockaddr_in6 multicast_addr6 =
+	{ sizeof(multicast_addr6), AF_INET6, 0, 0, {{{0}}}, 0 };
+
 /*
  * Sleep interval. Don't forget to change the down time check in ruptime
  * if this is changed.
@@ -134,9 +139,9 @@
 	int		  n_flags;		/* should forward?, interface flags */
 };
 
-struct	neighbor *neighbors;
+struct	neighbor *neighbors = NULL;
 struct	whod mywd;
-in_port_t who_port;
+in_port_t whod_port;
 int	s;
 int	fdp;
 pid_t	pid_child_receiver;
@@ -192,8 +197,8 @@
 int
 main(int argc, char *argv[])
 {
-	int on, err;
-	char *cp;
+	int on, err, ch;
+	char *cp, *endptr;
 	struct addrinfo hints, *res;
 	uid_t unpriv_uid;
 	gid_t unpriv_gid;
@@ -204,36 +209,49 @@
 
 	run_as(&unpriv_uid, &unpriv_gid);
 
-	argv++;
-	argc--;
-	while (argc > 0 && *argv[0] == '-') {
-		if (strcmp(*argv, "-m") == 0) {
-			if (argc > 1 && isdigit(*(argv + 1)[0])) {
-				argv++;
-				argc--;
+	while ((ch = getopt(argc, argv, "46ilpm::")) != -1)
+		switch (ch) {
+		case '4':
+			enable_v4 = 1;
+			break;
+		case '6':
+			enable_v6 = 1;
+			break;
+		case 'i':
+			insecure_mode = 1;
+			break;
+		case 'l':
+			quiet_mode = 1;
+			break;
+		case 'p':
+			iff_flag = 0;
+			break;
+		case 'm':
+			if (optarg != NULL) {
 				multicast_mode  = SCOPED_MULTICAST;
-				multicast_scope = atoi(*argv);
-				if (multicast_scope > MAX_MULTICAST_SCOPE) {
+				multicast_scope = (int)strtol(optarg, &endptr, 10);
+				if (*endptr != '\0') {
+					errx(1, "invalid ttl: %s", endptr);
+				} else if (multicast_scope > MAX_MULTICAST_SCOPE) {
 					errx(1, "ttl must not exceed %u",
 					    MAX_MULTICAST_SCOPE);
 				}
 			} else {
 				multicast_mode = PER_INTERFACE_MULTICAST;
 			}
-		} else if (strcmp(*argv, "-i") == 0) {
-			insecure_mode = 1;
-		} else if (strcmp(*argv, "-l") == 0) {
-			quiet_mode = 1;
-		} else if (strcmp(*argv, "-p") == 0) {
-			iff_flag = 0;
-		} else {
+			break;
+		case '?':
+		default:
 			usage();
 		}
-		argv++;
-		argc--;
-	}
-	if (argc > 0)
-		usage();
+
+	argc -= optind;
+	argv += optind;
+
+	/* if neither -4 nor -6 was specified, enable both */
+	if (enable_v4 == 0 && enable_v6 == 0)
+		enable_v4 = enable_v6 = 1;
+
 #ifndef DEBUG
 	daemon(1, 0);
 #endif
@@ -242,22 +260,24 @@
 
 	memset(&hints, 0, sizeof(hints));
 	hints.ai_protocol = IPPROTO_UDP;
-	hints.ai_family   = AF_UNSPEC;
+	if (enable_v6 == 1)
+		hints.ai_family = AF_INET6;
+	else
+		hints.ai_family = AF_INET;
 	hints.ai_socktype = SOCK_DGRAM;
 
 	err = getaddrinfo(NULL, "who", &hints, &res);
-	if (err) {
+	if (err != 0) {
 		syslog(LOG_ERR, "who/udp: %s", gai_strerror(err));
 		exit(1);
 	}
 
-	if (res->ai_family == AF_INET) {
-		struct sockaddr_in *sin = (struct sockaddr_in *)res->ai_addr;
-		who_port = htons(sin->sin_port);
-	}
-	else if (res->ai_family == AF_INET6) {
+	if (res->ai_family == AF_INET6) {
 		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)res->ai_addr;
-		who_port = htons(sin6->sin6_port);
+		whod_port = htons(sin6->sin6_port);
+	} else if (res->ai_family == AF_INET) {
+		struct sockaddr_in *sin = (struct sockaddr_in *)res->ai_addr;
+		whod_port = htons(sin->sin_port);
 	}
 
 	if (chdir(_PATH_RWHODIR) < 0) {
@@ -280,16 +300,24 @@
 		syslog(LOG_ERR, "socket: %m");
 		exit(1);
 	}
-	if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) < 0) {
-		syslog(LOG_ERR, "setsockopt SO_BROADCAST: %m");
-		exit(1);
-	}
-	
+
+	/*
+	 * ipv6 doesn't support broadcast, but maybe
+	 * multicast at FF02::1 can be used, 2 being scope for link-local
+	 */
+	if (enable_v6 == 0)
+		if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) < 0) {
+			syslog(LOG_ERR, "setsockopt SO_BROADCAST: %m");
+			exit(1);
+		}
 
 	if (bind(s, res->ai_addr, res->ai_addrlen) < 0) {
 		syslog(LOG_ERR, "bind: %m");
 		exit(1);
 	}
+
+	freeaddrinfo(res);
+
 	if (setgid(unpriv_gid) != 0) {
 		syslog(LOG_ERR, "setgid: %m");
 		exit(1);
@@ -328,7 +356,7 @@
 usage(void)
 {
 
-	fprintf(stderr, "usage: rwhod [-i] [-p] [-l] [-m [ttl]]\n");
+	fprintf(stderr, "usage: rwhod [-4] [-6] [-i] [-p] [-l] [-m [ttl]]\n");
 	exit(1);
 }
 
@@ -380,7 +408,7 @@
 void
 receiver_process(void)
 {
-	struct sockaddr_in from;
+	struct sockaddr_storage from;
 	struct stat st;
 	cap_rights_t rights;
 	char path[64];
@@ -389,6 +417,7 @@
 	socklen_t len;
 	int cc, whod;
 	time_t t;
+	char ip[INET6_ADDRSTRLEN];
 
 	len = sizeof(from);
 	dirfd = open(".", O_RDONLY | O_DIRECTORY);
@@ -414,14 +443,26 @@
 				syslog(LOG_WARNING, "recv: %m");
 			continue;
 		}
-		if (from.sin_port != who_port && !insecure_mode) {
-			syslog(LOG_WARNING, "%d: bad source port from %s",
-			    ntohs(from.sin_port), inet_ntoa(from.sin_addr));
-			continue;
+		if (from.ss_family == AF_INET) {
+			struct sockaddr_in *sin = (struct sockaddr_in *)&from;
+			if (sin->sin_port != whod_port && !insecure_mode) {
+				syslog(LOG_WARNING, "%d: bad source port from %s",
+				    ntohs(sin->sin_port),
+				    inet_ntop(from.ss_family, &(sin->sin_addr), ip, sizeof(ip)));
+				continue;
+			}
+		} else if (from.ss_family == AF_INET6) {
+			struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&from;
+			if (sin6->sin6_port != whod_port && !insecure_mode) {
+				syslog(LOG_WARNING, "%d: bad source port from %s",
+				    ntohs(sin6->sin6_port),
+				    inet_ntop(from.ss_family, &(sin6->sin6_addr), ip, sizeof(ip)));
+				continue;
+			}
 		}
+
 		if (cc < WHDRSIZE) {
-			syslog(LOG_WARNING, "short packet from %s",
-			    inet_ntoa(from.sin_addr));
+			syslog(LOG_WARNING, "short packet from %s", ip);
 			continue;
 		}
 		if (wd.wd_vers != WHODVERSION)
@@ -429,8 +470,7 @@
 		if (wd.wd_type != WHODTYPE_STATUS)
 			continue;
 		if (!verify(wd.wd_hostname, sizeof(wd.wd_hostname))) {
-			syslog(LOG_WARNING, "malformed host name from %s",
-			    inet_ntoa(from.sin_addr));
+			syslog(LOG_WARNING, "malformed host name from %s", ip);
 			continue;
 		}
 		(void) snprintf(path, sizeof(path), "whod.%s", wd.wd_hostname);
@@ -629,30 +669,63 @@
 
 	flags = 0;
 	if (multicast_mode != NO_MULTICAST) {
-		multicast_addr.sin_addr.s_addr = htonl(INADDR_WHOD_GROUP);
-		multicast_addr.sin_port = who_port;
+
+		if (enable_v4 == 1) {
+			multicast_addr.sin_addr.s_addr = htonl(INADDR_WHOD_GROUP);
+			multicast_addr.sin_port = whod_port;
+		}
+		if (enable_v6 == 1) {
+			multicast_addr6.sin6_addr = in6addr_whod_group;
+			multicast_addr6.sin6_port = whod_port;
+		}
 	}
 
 	if (multicast_mode == SCOPED_MULTICAST) {
-		struct ip_mreq mreq;
-		unsigned char ttl;
-
-		mreq.imr_multiaddr.s_addr = htonl(INADDR_WHOD_GROUP);
-		mreq.imr_interface.s_addr = htonl(INADDR_ANY);
-		if (setsockopt(so, IPPROTO_IP, IP_ADD_MEMBERSHIP,
-		    &mreq, sizeof(mreq)) < 0) {
-			syslog(LOG_ERR,
-			    "setsockopt IP_ADD_MEMBERSHIP: %m");
-			return (0);
+
+		if (enable_v4 == 1) {
+			struct ip_mreq mreq;
+			uint8_t ttl;
+
+			mreq.imr_multiaddr.s_addr = htonl(INADDR_WHOD_GROUP);
+			mreq.imr_interface.s_addr = htonl(INADDR_ANY);
+			if (setsockopt(so, IPPROTO_IP, IP_ADD_MEMBERSHIP,
+			    &mreq, sizeof(mreq)) < 0) {
+				syslog(LOG_ERR,
+				    "setsockopt IP_ADD_MEMBERSHIP: %m");
+				return (0);
+			}
+			ttl = multicast_scope;
+			if (setsockopt(so, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
+			    sizeof(ttl)) < 0) {
+				syslog(LOG_ERR,
+				    "setsockopt IP_MULTICAST_TTL: %m");
+				return (0);
+			}
+			return (1);
 		}
-		ttl = multicast_scope;
-		if (setsockopt(so, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
-		    sizeof(ttl)) < 0) {
-			syslog(LOG_ERR,
-			    "setsockopt IP_MULTICAST_TTL: %m");
-			return (0);
+		if (enable_v6 == 1) {
+			struct ipv6_mreq mreq6;
+			uint8_t hops;
+
+			mreq6.ipv6mr_multiaddr = in6addr_whod_group;
+			mreq6.ipv6mr_interface = 0; /* choose default multicast interface, same as above in ipv4*/
+
+			if (setsockopt(so, IPPROTO_IPV6, IPV6_JOIN_GROUP,
+			    &mreq6, sizeof(mreq6)) < 0) {
+				syslog(LOG_ERR,
+				    "setsockopt IPV6_ADD_MEMBERSHIP: %m");
+				return (0);
+			}
+			hops = multicast_scope;
+			if (setsockopt(so, IPPROTO_IP, IPV6_MULTICAST_HOPS, &hops,
+			    sizeof(hops)) < 0) {
+				syslog(LOG_ERR,
+				    "setsockopt IPV6_MULTICAST_HOPS: %m");
+				return (0);
+			}
+			return (1);
 		}
-		return (1);
+		//assert(enable_ipv4 == 1 || enable_ipv6 == 1);
 	}
 
 	mib[0] = CTL_NET;
@@ -697,7 +770,7 @@
 #define	PORT_SA(x)	((struct sockaddr_in *)(x))->sin_port
 		if (dstaddr == 0 || dstaddr->sa_family != AF_INET)
 			continue;
-		PORT_SA(dstaddr) = who_port;
+		PORT_SA(dstaddr) = whod_port;
 		for (np = neighbors; np != NULL; np = np->n_next) {
 			if (memcmp(sdl->sdl_data, np->n_name,
 			    sdl->sdl_nlen) == 0 &&