From d9e4afe64c0cf5b573094d3f7d0e13673aaa59e6 Mon Sep 17 00:00:00 2001
From: Mark Pizzolato <mark@infocomm.com>
Date: Tue, 28 Feb 2012 12:09:05 -0800
Subject: [PATCH] Fixed internal loopback packet processing.  We should only
 respond to loopback packets addressed to the physical MAC address OR the
 Broadcast address OR a Multicast address we're listening to (we may receive
 other loopback packets if we're in promiscuous mode but we should not respond
 to them).

---
 PDP11/pdp11_xq.c | 10 ++++++++++
 PDP11/pdp11_xu.c | 11 +++++++++++
 2 files changed, 21 insertions(+)

diff --git a/PDP11/pdp11_xq.c b/PDP11/pdp11_xq.c
index c4eb46e7..f3b3ce1f 100644
--- a/PDP11/pdp11_xq.c
+++ b/PDP11/pdp11_xq.c
@@ -1689,6 +1689,16 @@ t_stat xq_process_loopback(CTLR* xq, ETH_PACK* pack)
         physical_address = &xq->var->setup.macs[0];
       else
         physical_address = &xq->var->mac;
+
+  /* The only packets we should be responding to are ones which 
+     we received due to them being directed to our physical MAC address, 
+     OR the Broadcast address OR to a Multicast address we're listening to 
+     (we may receive others if we're in promiscuous mode, but shouldn't 
+     respond to them) */
+  if ((0 == (pack->msg[0]&1)) &&           /* Multicast or Broadcast */
+      (0 != memcmp(physical_address, pack->msg, sizeof(ETH_MAC))))
+      return SCPE_NOFNC;
+
   memcpy (&response.msg[0], &response.msg[offset+2], sizeof(ETH_MAC));
   memcpy (&response.msg[6], physical_address, sizeof(ETH_MAC));
   offset += 8 - 16; /* Account for the Ethernet Header and Offset value in this number  */
diff --git a/PDP11/pdp11_xu.c b/PDP11/pdp11_xu.c
index 36e97ca0..05bccaed 100644
--- a/PDP11/pdp11_xu.c
+++ b/PDP11/pdp11_xu.c
@@ -416,6 +416,17 @@ t_stat xu_process_loopback(CTLR* xu, ETH_PACK* pack)
   /* create forward response packet */
   memcpy (&response, pack, sizeof(ETH_PACK));
   memcpy (physical_address, xu->var->setup.macs[0], sizeof(ETH_MAC));
+
+  /* The only packets we should be responding to are ones which 
+     we received due to them being directed to our physical MAC address, 
+     OR the Broadcast address OR to a Multicast address we're listening to 
+     (we may receive others if we're in promiscuous mode, but shouldn't 
+     respond to them) */
+  if ((0 == (pack->msg[0]&1)) &&           /* Multicast or Broadcast */
+      (0 != memcmp(physical_address, pack->msg, sizeof(ETH_MAC))))
+      return SCPE_NOFNC;
+
+
   memcpy (&response.msg[0], &response.msg[offset+2], sizeof(ETH_MAC));
   memcpy (&response.msg[6], physical_address, sizeof(ETH_MAC));
   offset += 8;