From 303a7cc58fbcb7674155f4060c00192ea2ef638b Mon Sep 17 00:00:00 2001
From: Jaap Keuter <jaap.keuter@xs4all.nl>
Date: Wed, 27 Jan 2021 21:06:11 +0000
Subject: [PATCH] ZVT: Use standard TCP segment reassemble support function

Fixes #17177


(cherry picked from commit 616d44cbb651fd53273946fc04d4653aa69584fb)
---
 epan/dissectors/packet-zvt.c | 66 ++++++++++--------------------------
 1 file changed, 17 insertions(+), 49 deletions(-)

diff --git a/epan/dissectors/packet-zvt.c b/epan/dissectors/packet-zvt.c
index df74277814..7aaec34706 100644
--- a/epan/dissectors/packet-zvt.c
+++ b/epan/dissectors/packet-zvt.c
@@ -34,6 +34,7 @@
 #include <epan/packet.h>
 #include <epan/addr_resolv.h>
 #include <epan/expert.h>
+#include "packet-tcp.h"
 
 /* special characters of the serial transport protocol */
 #define STX 0x02
@@ -948,59 +949,26 @@ dissect_zvt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
     return zvt_len;
 }
 
+static guint get_zvt_message_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)
+{
+    guint len = tvb_get_guint8(tvb, offset+2);
+    if (len == 0xFF)
+        if (tvb_captured_length_remaining(tvb, offset) >= 5)
+            len = tvb_get_letohs(tvb, offset+3) + 5;
+        else
+            len = 0;
+    else
+        len += 3;
+
+    return len;
+}
 
 static int
 dissect_zvt_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 {
-    gint        offset = 0, zvt_len = 0, ret;
-    proto_item *zvt_ti;
-    proto_tree *zvt_tree;
-
-    if (tvb_captured_length(tvb) < ZVT_APDU_MIN_LEN) {
-        if (pinfo->can_desegment) {
-            pinfo->desegment_offset = offset;
-            pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
-            return -1;
-        }
-        return zvt_len;
-    }
-
-    if (!valid_ctrl_field(tvb, 0))
-        return 0; /* reject the packet */
-
-    col_set_str(pinfo->cinfo, COL_PROTOCOL, "ZVT");
-    col_clear(pinfo->cinfo, COL_INFO);
-    zvt_ti = proto_tree_add_protocol_format(tree, proto_zvt,
-            tvb, 0, -1,
-            "ZVT Kassenschnittstelle: Transport Protocol TCP/IP");
-    zvt_tree = proto_item_add_subtree(zvt_ti, ett_zvt);
-
-    while (tvb_captured_length_remaining(tvb, offset) > 0) {
-        ret = dissect_zvt_apdu(tvb, offset, pinfo, zvt_tree);
-        if (ret == 0) {
-            /* not a valid APDU
-               mark the bytes that we consumed and exit, give
-               other dissectors a chance to try the remaining
-               bytes */
-            break;
-        }
-        else if (ret < 0) {
-            /* not enough data - ask the TCP layer for more */
-
-            if (pinfo->can_desegment) {
-                pinfo->desegment_offset = offset;
-                pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
-            }
-            break;
-        }
-        else {
-            offset += ret;
-            zvt_len += ret;
-        }
-    }
-
-    proto_item_set_len(zvt_ti, zvt_len);
-    return zvt_len;
+    tcp_dissect_pdus(tvb, pinfo, tree, TRUE, ZVT_APDU_MIN_LEN,
+                     get_zvt_message_len, dissect_zvt, data);
+    return tvb_captured_length(tvb);
 }
 
 static void