Apply by doing:
       cd /usr/src/sbin/isakmpd
       patch -p0 < 017_isakmpd.patch

Rebuild and install isakmpd:
       make cleandir
       make obj
       make depend
       make && make install

Restart isakmpd:
       kill `cat /var/run/isakmpd.pid`
       /sbin/isakmpd

Index: message.c
===================================================================
RCS file: /cvs/src/sbin/isakmpd/message.c,v
retrieving revision 1.45
diff -u -u -r1.45 message.c
--- message.c   1 Jul 2001 20:43:39 -0000       1.45
+++ message.c   26 Mar 2002 17:54:43 -0000
@@ -880,9 +880,6 @@
  struct proto tmp_proto;
  struct sa tmp_sa;

-  /* Possibly dump a raw hex image of the message to the log channel.  */
-  message_dump_raw ("message_recv", msg, LOG_MESSAGE);
-
  /* Messages shorter than an ISAKMP header are bad.  */
  if (sz < ISAKMP_HDR_SZ || sz != GET_ISAKMP_HDR_LENGTH (buf))
    {
@@ -890,6 +887,11 @@
      message_drop (msg, ISAKMP_NOTIFY_UNEQUAL_PAYLOAD_LENGTHS, 0, 1, 1);
      return -1;
    }
+
+#ifdef USE_DEBUG
+  /* Possibly dump a raw hex image of the message to the log channel.  */
+  message_dump_raw ("message_recv", msg, LOG_MESSAGE);
+#endif

  /*
   * If the responder cookie is zero, this is a request to setup an ISAKMP SA.