ERSPAN: add link to protocol spec and refactoring.

Add link to ERSPAN protocol spec, remove obsolete comments, and
remove unnecessary 'if(tree)' check.

Change-Id: I1b4950777c84d62301c322afdfc876949db0d4ed
Signed-off-by: William Tu <u9012063@gmail.com>
Reviewed-on: https://code.wireshark.org/review/16675
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

diff --git a/epan/dissectors/packet-cisco-erspan.c b/epan/dissectors/packet-cisco-erspan.c
index f97efce73e52db1096ae8c9c5876bf95d89ec079..5d8598f3f7f43f8f531fdf5ac1dc0bed9335a172 100644 (file)
--- a/epan/dissectors/packet-cisco-erspan.c
+++ b/epan/dissectors/packet-cisco-erspan.c
@@ -22,38 +22,14 @@
  * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-/*
- * TODO:
- *     Find out the Unknown values
- *
- * Specs:
- *     No real specs exist. Some general description can be found at:
- *     http://www.cisco.com/en/US/products/hw/routers/ps368/products_configuration_guide_chapter09186a008069952a.html
- *
- *     Some information on ERSPAN type III can be found at:
- *     http://www.cisco.com/en/US/docs/switches/datacenter/nexus1000/sw/4_0_4_s_v_1_3/system_management/configuration/guide/n1000v_system_9span.html
- *
- *     For ERSPAN packets, the "protocol type" field value in the GRE header
- *     is 0x88BE (version 1) or 0x22EB (version 2).
- *
- *     ERSPAN type II is version 1
- *     ERSPAN type III is version 2
- *
- * 0000000: d4c3 b2a1 0200 0400 0000 0000 0000 0000 <-- pcap header
- * 0000010: ffff 0000
- * 0000010:           7100 0000 <-- 0x71 (DLT_TYPE) = linux_cooked_capture (of course not)
- * 0000010:                     7507 f845 11d1 0500 <-- pcap record header
- * 0000020: 7a00 0000 7a00 0000
- * 0000020:                     0000 030a 0000 0000 <-- unknown
- * 0000030: 0000 0000
- * 0000030:           0000 88be <-- GRE header (version 1)
- * 0000030:                     1002 0001 0000 0380 <-- ERSPAN header (01: erspan-id)
- * 0000040: 00d0 b7a7 7480 0015 c721 75c0 0800 4500 <-- Ethernet packet
- * ...
  *
+ * Protocol Spec:
+ *   https://tools.ietf.org/html/draft-foschiano-erspan-01
  *
+ * For ERSPAN packets, the "protocol type" field value in the GRE header
+ * is 0x88BE (version 1) or 0x22EB (version 2).
+ *   ERSPAN type II is version 1
+ *   ERSPAN type III is version 2
  */
 
 #include "config.h"
@@ -168,73 +144,66 @@ dissect_erspan(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _
 
 
        version = tvb_get_ntohs(tvb, offset) >> 12;
-       if (tree) {
-               ti_ver = proto_tree_add_item(erspan_tree, hf_erspan_version, tvb, offset, 2,
-                       ENC_BIG_ENDIAN);
-               if ((version != 1) && (version != 2 )) {
-                       expert_add_info(pinfo, ti_ver, &ei_erspan_version_unknown);
-                       return 2;
-               }
-               proto_tree_add_item(erspan_tree, hf_erspan_vlan, tvb, offset, 2,
-                       ENC_BIG_ENDIAN);
-               offset += 2;
 
-               proto_tree_add_item(erspan_tree, hf_erspan_priority, tvb, offset, 2,
+       ti_ver = proto_tree_add_item(erspan_tree, hf_erspan_version, tvb, offset, 2,
+               ENC_BIG_ENDIAN);
+       if ((version != 1) && (version != 2 )) {
+               expert_add_info(pinfo, ti_ver, &ei_erspan_version_unknown);
+               return 2;
+       }
+       proto_tree_add_item(erspan_tree, hf_erspan_vlan, tvb, offset, 2,
+               ENC_BIG_ENDIAN);
+       offset += 2;
+
+       proto_tree_add_item(erspan_tree, hf_erspan_priority, tvb, offset, 2,
+               ENC_BIG_ENDIAN);
+
+       if (version == 1)
+               proto_tree_add_item(erspan_tree, hf_erspan_encap, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
+       else
+               proto_tree_add_item(erspan_tree, hf_erspan_bso, tvb, offset, 2,
                        ENC_BIG_ENDIAN);
 
-               if (version == 1)
-                       proto_tree_add_item(erspan_tree, hf_erspan_encap, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
-               else
-                       proto_tree_add_item(erspan_tree, hf_erspan_bso, tvb, offset, 2,
-                               ENC_BIG_ENDIAN);
-
-
-               proto_tree_add_item(erspan_tree, hf_erspan_truncated, tvb, offset, 2,
-                       ENC_BIG_ENDIAN);
-               proto_tree_add_item(erspan_tree, hf_erspan_spanid, tvb, offset, 2,
-                       ENC_BIG_ENDIAN);
-               offset += 2;
 
-               if (version == 1) {
-                       proto_tree_add_item(erspan_tree, hf_erspan_index, tvb,
-                               offset, 4, ENC_BIG_ENDIAN);
-                       offset += 4;
-               }
-               else {
-                       proto_tree_add_item(erspan_tree, hf_erspan_timestamp, tvb,
-                               offset, 4, ENC_BIG_ENDIAN);
-                       offset += 4;
+       proto_tree_add_item(erspan_tree, hf_erspan_truncated, tvb, offset, 2,
+               ENC_BIG_ENDIAN);
+       proto_tree_add_item(erspan_tree, hf_erspan_spanid, tvb, offset, 2,
+               ENC_BIG_ENDIAN);
+       offset += 2;
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_sgt, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
-                       offset += 2;
+       if (version == 1) {
+               proto_tree_add_item(erspan_tree, hf_erspan_index, tvb,
+                       offset, 4, ENC_BIG_ENDIAN);
+               offset += 4;
+       }
+       else {
+               proto_tree_add_item(erspan_tree, hf_erspan_timestamp, tvb,
+                       offset, 4, ENC_BIG_ENDIAN);
+               offset += 4;
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_p, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
+               proto_tree_add_item(erspan_tree, hf_erspan_sgt, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
+               offset += 2;
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_ft, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
+               proto_tree_add_item(erspan_tree, hf_erspan_p, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_hw, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
+               proto_tree_add_item(erspan_tree, hf_erspan_ft, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_direction2, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
+               proto_tree_add_item(erspan_tree, hf_erspan_hw, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_gra, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
+               proto_tree_add_item(erspan_tree, hf_erspan_direction2, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
 
-                       proto_tree_add_item(erspan_tree, hf_erspan_o, tvb,
-                               offset, 2, ENC_BIG_ENDIAN);
-                       offset += 2;
-               }
+               proto_tree_add_item(erspan_tree, hf_erspan_gra, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
 
-       }
-       else {
-               offset += 8;
-               if (version == 2)
-                       offset += 12;
+               proto_tree_add_item(erspan_tree, hf_erspan_o, tvb,
+                       offset, 2, ENC_BIG_ENDIAN);
+               offset += 2;
        }
 
        eth_tvb = tvb_new_subset_remaining(tvb, offset);