diff -Naur /usr/ports/net/xprobe/files/patch-loopback xprobe/files/patch-loopback
--- /usr/ports/net/xprobe/files/patch-loopback	Thu Jan  1 01:00:00 1970
+++ xprobe/files/patch-loopback	Mon Mar 22 17:27:52 2004
@@ -0,0 +1,20 @@
+--- libs-external/USI++/src/datalink.cc.orig	Fri Sep 26 13:40:23 2003
++++ libs-external/USI++/src/datalink.cc	Mon Mar 22 17:26:18 2004
+@@ -249,7 +249,7 @@
+ 
+ 	// loopback
+ 	case DLT_NULL:
+-		d_framelen = 0;
++		d_framelen = 4;
+ 		break;
+ #ifdef DLT_LINUX_SLL
+     case DLT_LINUX_SLL:
+@@ -349,6 +349,8 @@
+                 break;
+ 	case DLT_RAW:
+ 		break;
++	case DLT_NULL:
++		break;	
+ #ifdef DLT_LINUX_SLL
+     case DLT_LINUX_SLL:
+         break;