Another hand rolled offsetof(), replace with mask2prefixlen from kroute.c

which was copied from bgpd. Found by deraadt@

diff --git a/usr.sbin/ospf6ctl/parser.c b/usr.sbin/ospf6ctl/parser.c
index ef1d0e3..7d076ea 100644 (file)
--- a/usr.sbin/ospf6ctl/parser.c
+++ b/usr.sbin/ospf6ctl/parser.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: parser.c,v 1.8 2010/01/13 11:33:12 jsg Exp $ */
+/*     $OpenBSD: parser.c,v 1.9 2010/07/20 05:26:06 claudio Exp $ */
 
 /*
  * Copyright (c) 2004 Esben Norby <norby@openbsd.org>
@@ -343,17 +343,17 @@ parse_prefix(const char *word, struct in6_addr *addr, u_int8_t *prefixlen)
 u_int8_t
 mask2prefixlen(struct sockaddr_in6 *sa_in6)
 {
-       u_int8_t        l = 0, i, len;
+       u_int8_t        l = 0, *ap, *ep;
 
        /*
         * sin6_len is the size of the sockaddr so substract the offset of
         * the possibly truncated sin6_addr struct.
         */
-       len = sa_in6->sin6_len -
-           (u_int8_t)(&((struct sockaddr_in6 *)NULL)->sin6_addr);
-       for (i = 0; i < len; i++) {
+       ap = (u_int8_t *)&sa_in6->sin6_addr;
+       ep = (u_int8_t *)sa_in6 + sa_in6->sin6_len;
+       for (; ap < ep; ap++) {
                /* this "beauty" is adopted from sbin/route/show.c ... */
-               switch (sa_in6->sin6_addr.s6_addr[i]) {
+               switch (*ap) {
                case 0xff:
                        l += 8;
                        break;