- Make a distinction between ethernet padding and an ethernet trailer

- ... and make that distinction configurable for capture files that do not have padding in small frames, but do have trailers
- Add VSS-Monitoring dissector to show by the TAP inserted time- and portstamps



git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@40108 f5534014-38df-0310-8fa8-9805f1628bb7

4 files changed, 270 insertions, 11 deletions

diff --git a/AUTHORS b/AUTHORS
index 3d696d8057..7c241bd9b3 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -2798,6 +2798,7 @@ Sake Blok               <sake [AT] euronet.nl> {
 	Enable printing of all occurrences of fields
 	Follow TCP stream enhancements
         Export SSL Session Keys
+        VSS-Monitoring dissector
 	Miscellaneous enhancements and fixes
 }
 
diff --git a/epan/dissectors/Makefile.common b/epan/dissectors/Makefile.common
index 4745c25ee4..cf15caca45 100644
--- a/epan/dissectors/Makefile.common
+++ b/epan/dissectors/Makefile.common
@@ -1009,6 +1009,7 @@ DISSECTOR_SRC = \
 	packet-vmlab.c		\
 	packet-vnc.c		\
 	packet-vrrp.c		\
+	packet-vssmonitoring.c	\
 	packet-vtp.c		\
 	packet-vuze-dht.c	\
 	packet-vxi11.c		\
diff --git a/epan/dissectors/packet-eth.c b/epan/dissectors/packet-eth.c
index 5e9a377cba..cc98ffa449 100644
--- a/epan/dissectors/packet-eth.c
+++ b/epan/dissectors/packet-eth.c
@@ -43,6 +43,7 @@
 #include <epan/expert.h>
 
 /* Assume all packets have an FCS */
+static gboolean eth_assume_padding = TRUE;
 static gboolean eth_assume_fcs = FALSE;
 static gboolean eth_check_fcs = TRUE;
 /* Interpret packets as FW1 monitor file packets if they look as if they are */
@@ -63,6 +64,7 @@ static int hf_eth_invalid_lentype = -1;
 static int hf_eth_addr = -1;
 static int hf_eth_lg = -1;
 static int hf_eth_ig = -1;
+static int hf_eth_padding = -1;
 static int hf_eth_trailer = -1;
 static int hf_eth_fcs = -1;
 static int hf_eth_fcs_good = -1;
@@ -496,7 +498,12 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
     int trailer_id, tvbuff_t *tvb, tvbuff_t *trailer_tvb, int fcs_len)
 {
   /* If there're some bytes left over, show those bytes as a trailer.
-
+     the trailer can contain:
+     - padding to meet the minimum 64 byte frame length
+     - information inserted by TAPs or other equipment
+     - an optional FCS (optional, because the FCS is usually stripped before
+       the frame is seen by us
+    
      However, if the Ethernet frame was claimed to have had 64 or more
      bytes - i.e., it was at least an FCS worth of data longer than
      the minimum payload size - assume the last 4 bytes of the trailer
@@ -506,16 +513,38 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
 
   if (trailer_tvb && fh_tree) {
     guint trailer_length, trailer_reported_length;
+    guint padding_length = 0;
     gboolean has_fcs = FALSE;
-
-    if (dissector_try_heuristic(eth_trailer_subdissector_list, trailer_tvb,
-        pinfo, tree)) {
-      return;
-    }
+    tvbuff_t *real_trailer_tvb;
 
     trailer_length = tvb_length(trailer_tvb);
     trailer_reported_length = tvb_reported_length(trailer_tvb);
 
+    /* There can not have been padding when the length of the frame (including the 
+       trailer) is less than 60 bytes. */
+    if (eth_assume_padding && pinfo->fd->pkt_len>=60) {
+        /* Calculate the amount of padding needed for a minimum sized frame */
+        if ( (pinfo->fd->pkt_len - trailer_reported_length) < 60 )
+            padding_length = 60 - (pinfo->fd->pkt_len - trailer_reported_length);
+
+        /* Add the padding to the tree, unless it should be treated as 
+           part of the trailer and therefor be handed over to (one of) 
+           the ethernet-trailer dissectors */
+        if (padding_length > 0) {
+            tvb_ensure_bytes_exist(tvb, 0, padding_length);
+            proto_tree_add_item(fh_tree, hf_eth_padding, trailer_tvb, 0,
+                padding_length, FALSE);
+            trailer_length -= padding_length;
+            trailer_reported_length -= padding_length;
+        }
+    }
+    real_trailer_tvb = tvb_new_subset_remaining(trailer_tvb, padding_length);
+
+    /* Call all ethernet trailer dissectors to dissect the trailer.  */
+    if ( dissector_try_heuristic(eth_trailer_subdissector_list, 
+             real_trailer_tvb, pinfo, tree) ) 
+        return;
+    
     if (fcs_len != 0) {
       /* If fcs_len is 4, we assume we definitely have an FCS.
          Otherwise, then, if the frame is big enough that, if we
@@ -555,15 +584,15 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
     }
     if (trailer_length != 0) {
       tvb_ensure_bytes_exist(tvb, 0, trailer_length);
-      proto_tree_add_item(fh_tree, trailer_id, trailer_tvb, 0,
+      proto_tree_add_item(fh_tree, trailer_id, real_trailer_tvb, 0,
         trailer_length, FALSE);
     }
     if (has_fcs) {
-      guint32 sent_fcs = tvb_get_ntohl(trailer_tvb, trailer_length);
+      guint32 sent_fcs = tvb_get_ntohl(real_trailer_tvb, trailer_length);
       if(eth_check_fcs){
         guint32 fcs = crc32_802_tvb(tvb, tvb_length(tvb) - 4);
         if (fcs == sent_fcs) {
-          item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, trailer_tvb,
+          item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, real_trailer_tvb,
                                             trailer_length, 4, sent_fcs,
                                             "Frame check sequence: 0x%08x [correct]", sent_fcs);
           checksum_tree = proto_item_add_subtree(item, ett_eth_fcs);
@@ -574,7 +603,7 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
                                         trailer_length, 2, FALSE);
           PROTO_ITEM_SET_GENERATED(item);
         } else {
-          item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, trailer_tvb,
+          item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, real_trailer_tvb,
                                             trailer_length, 4, sent_fcs,
                                             "Frame check sequence: 0x%08x [incorrect, should be 0x%08x]",
                                             sent_fcs, fcs);
@@ -589,7 +618,7 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
           col_append_str(pinfo->cinfo, COL_INFO, " [ETHERNET FRAME CHECK SEQUENCE INCORRECT]");
         }
       }else{
-        item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, trailer_tvb,
+        item = proto_tree_add_uint_format(fh_tree, hf_eth_fcs, real_trailer_tvb,
                                           trailer_length, 4, sent_fcs,
                                           "Frame check sequence: 0x%08x [validiation disabled]", sent_fcs);
         checksum_tree = proto_item_add_subtree(item, ett_eth_fcs);
@@ -661,6 +690,10 @@ proto_register_eth(void)
         { "Address", "eth.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
             "Source or Destination Hardware Address", HFILL }},
 
+        { &hf_eth_padding,
+        { "Padding", "eth.padding", FT_BYTES, BASE_NONE, NULL, 0x0,
+            "Ethernet Padding", HFILL }},
+
         { &hf_eth_trailer,
         { "Trailer", "eth.trailer", FT_BYTES, BASE_NONE, NULL, 0x0,
             "Ethernet Trailer or Checksum", HFILL }},
@@ -707,6 +740,14 @@ proto_register_eth(void)
     /* Register configuration preferences */
     eth_module = prefs_register_protocol(proto_eth, NULL);
 
+    prefs_register_bool_preference(eth_module, "assume_padding",
+            "Assume short frames which include a trailer contain padding",
+            "Some devices add trailing data to frames. When this setting is checked "
+            "the Ethernet dissector will assume there has been added padding to the "
+            "frame before the trailer was added. Uncheck if a device added a trailer "
+            "before the frame was padded.",
+            &eth_assume_padding);
+
     prefs_register_bool_preference(eth_module, "assume_fcs",
             "Assume packets have FCS",
             "Some Ethernet adapters and drivers include the FCS at the end of a packet, others do not.  "
diff --git a/epan/dissectors/packet-vssmonitoring.c b/epan/dissectors/packet-vssmonitoring.c
new file mode 100644
index 0000000000..1f0ee4c886
--- /dev/null
+++ b/epan/dissectors/packet-vssmonitoring.c
@@ -0,0 +1,216 @@
+/* packet-vssmonitoring.c
+ * Routines for dissection of VSS-monitoring timestamp and portstamp
+ *
+ * Copyright VSS-Monitoring 2011
+ *
+ * 20111205 - First edition by Sake Blok (sake.blok@SYN-bit.nl)
+ *
+ * $Id$
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1998 Gerald Combs
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <stdio.h>
+#include <epan/packet.h>
+#include <epan/prefs.h>
+
+
+#define VSS_NS_MASK     0x3fffffff
+#define CLKSRC_SHIFT    30
+
+#define CLKSRC_LOCAL    0
+#define CLKSRC_NTP      1
+#define CLKSRC_GPS      2
+#define CLKSRC_PTP      3
+
+static const value_string clksrc_vals[] = {
+  { CLKSRC_LOCAL,       "Not Synced" },
+  { CLKSRC_NTP,         "NTP" },
+  { CLKSRC_GPS,         "GPS" },
+  { CLKSRC_PTP,         "PTP" },
+  { 0,                  NULL }
+};
+
+
+static int proto_vssmonitoring = -1;
+
+static int hf_vssmonitoring_time = -1;
+static int hf_vssmonitoring_clksrc = -1;
+static int hf_vssmonitoring_srcport = -1;
+
+static gint ett_vssmonitoring = -1;
+
+static gboolean vssmonitoring_use_heuristics = TRUE;
+
+static int
+dissect_vssmonitoring(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+  proto_tree    *ti = NULL, *item = NULL;
+  proto_tree    *vssmonitoring_tree = NULL;
+  guint         offset = 0;
+
+  guint         trailer_len;
+  nstime_t      vssmonitoring_time;
+  guint8        vssmonitoring_clksrc = 0;
+  guint8        vssmonitoring_srcport = 0;
+
+  struct tm     *tmp;
+
+
+  /* First get the length of the trailer */
+  trailer_len = tvb_reported_length(tvb);
+
+  /* The trailer length is a sum (of any combination) of:
+   * timestamp (8 bytes)
+   * port stamp (1 or 2 bytes)
+   * fcs (4 bytes)
+   * 
+   * This means a trailer length must not be more than 14 bytes
+   */
+  if ( trailer_len > 14 )
+    return 0;
+
+  /* ... and also a 1-byte port stamp can not co-exist with a 2-byte
+   * portstamp
+   */
+  if ( (trailer_len & 3) == 3 )
+    return 0;
+
+  if ( trailer_len & 8 ) {
+    vssmonitoring_time.secs  = tvb_get_ntohl(tvb, offset);
+    vssmonitoring_time.nsecs = tvb_get_ntohl(tvb, offset + 4);
+    vssmonitoring_clksrc     = (guint8)(((guint32)vssmonitoring_time.nsecs) >> CLKSRC_SHIFT);
+    vssmonitoring_time.nsecs &= VSS_NS_MASK;
+
+    /* There are only heuristics for timestamps, the port stamp can be any value */
+    if ( vssmonitoring_use_heuristics ) {
+
+      /* The timestamp will be based on the uptime untill the TAP is completely booted, 
+       * this takes about 60s, but use 1 hour to be sure
+       */
+      if (vssmonitoring_time.secs > 3600) {
+
+        /* Check whether the timestamp in the PCAP header and the VSS-Monitoring 
+         * differ less than 30 days, otherwise, this might not be a VSS-Monitoring
+         * timestamp
+         */
+        if ( vssmonitoring_time.secs > pinfo->fd->abs_ts.secs ) {
+          if ( vssmonitoring_time.secs - pinfo->fd->abs_ts.secs > 2592000 ) /* 30 days */
+            return 0;
+        } else {
+          if ( pinfo->fd->abs_ts.secs - vssmonitoring_time.secs > 2592000 ) /* 30 days */
+            return 0;
+        }
+      }
+
+      /* The nanoseconds field should be less than 1000000000 
+       */
+      if ( vssmonitoring_time.nsecs >= 1000000000 ) 
+        return 0;
+    }
+  }
+
+  /* All systems are go, lets dissect the VSS-Monitoring trailer */
+  if (tree) {
+    ti = proto_tree_add_item(tree, proto_vssmonitoring, 
+             tvb, 0, (trailer_len & 0xb), ENC_NA);
+    vssmonitoring_tree = proto_item_add_subtree(ti, ett_vssmonitoring);
+  }
+
+  /* Do we have a timestamp? */
+  if ( trailer_len & 8 ) {
+    if (tree) {
+      item = proto_tree_add_time(vssmonitoring_tree, hf_vssmonitoring_time, tvb, offset, 8, &vssmonitoring_time);
+      item = proto_tree_add_uint(vssmonitoring_tree, hf_vssmonitoring_clksrc, tvb, offset + 4, 1, vssmonitoring_clksrc);
+
+      tmp = localtime(&vssmonitoring_time.secs);
+      proto_item_append_text(ti, ", Timestamp: %02d:%02d:%02d.%09ld",
+          tmp->tm_hour, tmp->tm_min, tmp->tm_sec,(long)vssmonitoring_time.nsecs);
+    }
+    offset += 8;
+  }
+
+  /* Do we have a portstamp? */
+  if ( trailer_len & 3) {
+    if ( trailer_len & 1) {
+      vssmonitoring_srcport = tvb_get_guint8(tvb, offset);
+      if (tree) 
+        item = proto_tree_add_item(vssmonitoring_tree, hf_vssmonitoring_srcport, tvb, offset, 1, ENC_NA);
+      offset++;
+    } else if ( trailer_len & 2) {
+      vssmonitoring_srcport = tvb_get_ntohs(tvb, offset);
+      if (tree)
+        item = proto_tree_add_item(vssmonitoring_tree, hf_vssmonitoring_srcport, tvb, offset, 2, ENC_NA);
+      offset += 2;
+    }
+    if (tree)
+      proto_item_append_text(ti, ", Source Port: %d", vssmonitoring_srcport);
+  }
+
+  return offset;
+}
+
+void
+proto_register_vssmonitoring(void)
+{
+  static hf_register_info hf[] = {
+    { &hf_vssmonitoring_time, {
+        "Time Stamp", "vssmonitoring.time", 
+        FT_ABSOLUTE_TIME, ABSOLUTE_TIME_LOCAL, NULL, 0x0, 
+        "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 }},
+
+    { &hf_vssmonitoring_srcport, {
+        "Src Port", "vssmonitoring.srcport", 
+        FT_UINT8, BASE_DEC, NULL, 0x0, 
+        "VSS-Monitoring Source Port", HFILL }}
+  };
+
+  static gint *ett[] = {
+    &ett_vssmonitoring
+  };
+
+  module_t *vssmonitoring_module;
+
+  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));
+
+  vssmonitoring_module = prefs_register_protocol(proto_vssmonitoring, NULL);
+
+  prefs_register_bool_preference(vssmonitoring_module, "use_heuristics",
+      "Use heuristics to verify if trailer contains VSS-Monitoring data",
+      "When enabled, Wireshark will do a check on the trailer data to verify"
+      "whether it contains VSS-Monitoring time- and port-stamps.",
+      &vssmonitoring_use_heuristics);
+}
+
+void
+proto_reg_handoff_vssmonitoring(void)
+{
+  heur_dissector_add("eth.trailer", dissect_vssmonitoring, proto_vssmonitoring);
+}