Fix inet6_opt_init() to only check extlen when extbuff is not NULL

as per RFC 3542, from DragonFlyBSD via Eitan Adler.

ok bluhm@

1 files changed, 2 insertions, 5 deletions

diff --git a/src/lib/libc/net/ip6opt.c b/src/lib/libc/net/ip6opt.c
index b215f9ac3e..c3609621c2 100644
--- a/src/lib/libc/net/ip6opt.c
+++ b/src/lib/libc/net/ip6opt.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ip6opt.c,v 1.4 2006/12/09 01:12:28 itojun Exp $       */
+/*      $OpenBSD: ip6opt.c,v 1.5 2014/02/07 09:50:04 mpi Exp $  */
 /*      $KAME: ip6opt.c,v 1.18 2005/06/15 07:11:35 keiichi Exp $        */
 
 /*
@@ -383,11 +383,8 @@ inet6_opt_init(void *extbuf, socklen_t extlen)
 {
         struct ip6_ext *ext = (struct ip6_ext *)extbuf;
 
-        if (extlen < 0 || (extlen % 8))
-                return (-1);
-
         if (ext) {
-                if (extlen == 0)
+               if (extlen <= 0 || (extlen % 8))
                         return (-1);
                 ext->ip6e_len = (extlen >> 3) - 1;
         }