Add a comment, update existing comments, fix the company name.

At least on the document we cite here, the company's name is "VSS
Monitoring",not "VSS-Monitoring".

Perhaps this dissector should be disabled by default, so people don't
get shown bogus VSS Monitoring trailers when the packet just has
one or two bytes of padding at the end.

Change-Id: I367fab67d9e0cc294a668ee8532d46c02feffbfa
Reviewed-on: https://code.wireshark.org/review/33138
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 15 insertions, 8 deletions

diff --git a/epan/dissectors/packet-vssmonitoring.c b/epan/dissectors/packet-vssmonitoring.c
index 01aa70238f..04a4fc9718 100644
--- a/epan/dissectors/packet-vssmonitoring.c
+++ b/epan/dissectors/packet-vssmonitoring.c
@@ -1,7 +1,7 @@
 /* packet-vssmonitoring.c
- * Routines for dissection of VSS-monitoring timestamp and portstamp
+ * Routines for dissection of VSS Monitoring timestamp and portstamp
  *
- * Copyright VSS-Monitoring 2011
+ * Copyright VSS Monitoring 2011
  *
  * 20111205 - First edition by Sake Blok (sake.blok@SYN-bit.nl)
  *
@@ -74,7 +74,7 @@ dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void
    *
    * See
    *
-   *    http://www.vssmonitoring.com/portals/application_note/Port%20and%20Time%20Stamping.pdf
+   *    https://web.archive.org/web/20160402091604/http://www.vssmonitoring.com/resources/feature-brief/Port-and-Time-Stamping.pdf
    *
    * (although that speaks of 2-byte port stamps as being for a "future
    * release").
@@ -104,6 +104,13 @@ dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void
   if ( (trailer_len & 3) == 0 && trailer_len < 8 )
     return 0;
 
+  /*
+   * If we have a time stamp, check it for validity.
+   *
+   * Unfortunately, the port stamp can be zero, so this means that a
+   * one-byte or two-byte all-zero trailer that's just padding can be
+   * misinterpreted as a VSS monitoring trailer.
+   */
   if ( trailer_len >= 8 ) {
     vssmonitoring_time.secs  = tvb_get_ntohl(tvb, offset);
     vssmonitoring_time.nsecs = tvb_get_ntohl(tvb, offset + 4);
@@ -190,17 +197,17 @@ proto_register_vssmonitoring(void)
     { &hf_vssmonitoring_time, {
         "Time Stamp", "vssmonitoring.time",
         FT_ABSOLUTE_TIME, ABSOLUTE_TIME_LOCAL, NULL, 0x0,
-        "VSS-Monitoring Time Stamp", HFILL }},
+        "VSS Monitoring Time Stamp", HFILL }},
 
     { &hf_vssmonitoring_clksrc, {
         "Clock Source", "vssmonitoring.clksrc",
         FT_UINT8, BASE_DEC, VALS(clksrc_vals), 0x0,
-        "VSS-Monitoring Clock Source", HFILL }},
+        "VSS Monitoring Clock Source", HFILL }},
 
     { &hf_vssmonitoring_srcport, {
         "Src Port", "vssmonitoring.srcport",
         FT_UINT16, BASE_DEC, NULL, 0x0,
-        "VSS-Monitoring Source Port", HFILL }}
+        "VSS Monitoring Source Port", HFILL }}
   };
 
   static gint *ett[] = {
@@ -209,7 +216,7 @@ proto_register_vssmonitoring(void)
 
   module_t *vssmonitoring_module;
 
-  proto_vssmonitoring = proto_register_protocol("VSS-Monitoring ethernet trailer", "VSS-Monitoring", "vssmonitoring");
+  proto_vssmonitoring = proto_register_protocol("VSS Monitoring Ethernet trailer", "VSS Monitoring", "vssmonitoring");
   proto_register_field_array(proto_vssmonitoring, hf, array_length(hf));
   proto_register_subtree_array(ett, array_length(ett));
 
@@ -221,7 +228,7 @@ proto_register_vssmonitoring(void)
 void
 proto_reg_handoff_vssmonitoring(void)
 {
-  heur_dissector_add("eth.trailer", dissect_vssmonitoring, "VSS-Monitoring ethernet trailer", "vssmonitoring_eth", proto_vssmonitoring, HEURISTIC_ENABLE);
+  heur_dissector_add("eth.trailer", dissect_vssmonitoring, "VSS Monitoring ethernet trailer", "vssmonitoring_eth", proto_vssmonitoring, HEURISTIC_ENABLE);
 }
 
 /*