- Close file descriptors on exec

Avoid FD leakage to children.

--- common.c.orig	Sun Jan 10 00:44:14 2016
+++ common.c	Sun Jan 10 00:46:53 2016
@@ -1115,7 +1115,7 @@ getifhwaddr(const char *ifname, char *buf, u_int16_t *
 		(void) snprintf(fname, sizeof (fname), "/dev/%s", ifname);
 	getctl.maxlen = sizeof (getbuf);
 	getctl.buf = (char *)getbuf;
-	if ((fd = open(fname, O_RDWR)) == -1) {
+	if ((fd = open(fname, O_RDWR | O_CLOEXEC)) == -1) {
 		dl_attach_req_t dlar;
 
 		cp = fname + strlen(fname) - 1;
@@ -1131,7 +1131,7 @@ getifhwaddr(const char *ifname, char *buf, u_int16_t *
 		cp++;
 		dlar.dl_ppa = atoi(cp);
 		*cp = '\0';
-		if ((fd = open(fname, O_RDWR)) == -1)
+		if ((fd = open(fname, O_RDWR | O_CLOEXEC)) == -1)
 			return (-1);
 		dlar.dl_primitive = DL_ATTACH_REQ;
 		putctl.len = sizeof (dlar);
@@ -3292,7 +3292,7 @@ ifaddrconf(cmd, ifname, addr, plen, pltime, vltime)
 		return (-1);
 	}
 
-	if ((s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
+	if ((s = socket(PF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP)) < 0) {
 		dprintf(LOG_ERR, FNAME, "can't open a temporary socket: %s",
 		    strerror(errno));
 		return (-1);