Apply by doing:
        cd /usr/src
        patch -p0 < 016_bridge.patch

And then rebuild your kernel.

Index: sys/net/if_bridge.c
===================================================================
RCS file: /cvs/src/sys/net/if_bridge.c,v
retrieving revision 1.131
retrieving revision 1.131.2.1
diff -u -p -r1.131 -r1.131.2.1
--- sys/net/if_bridge.c	10 Feb 2004 20:20:01 -0000	1.131
+++ sys/net/if_bridge.c	25 Aug 2004 21:44:41 -0000	1.131.2.1
@@ -2274,9 +2274,9 @@ bridge_ipsec(int dir, int af, int hlen, 
 			splx(s);
 			return (1);
 		} else {
+			splx(s);
  skiplookup:
 			/* XXX do an input policy lookup */
-			splx(s);
 			return (0);
 		}
 	} else { /* Outgoing from the bridge. */
