TCP dissector creates invalid packet diagram

Summary

The layout of the TCP header in the packet diagram is incorrect.
This happens for all branches, develop, stable and old-stable.

Sample capture file

Any capture file with TCP packets in it will do.

Steps to reproduce

  1. Load capture file with TCP packets
  2. In Preferences|Layout select Packet Diagram for Pane 2 or 3
  3. Observe TCP header diagram

What is the current bug behavior?

image

What is the expected correct behavior?

  1. The red marked 32-bit area after Acknowledge Number should not be there.
  2. The green-blue marked area should show the flags.
  3. Where the Urgent pointer is should be the window size.
  4. That should be followed by the checksum and then the urgent pointer.

Build information

Version 4.7.0 (v4.7.0rc0-621-g2215b6862a10).

Compile-time info:
 Bit width: 64-bit
  Compiler: GCC 15.2.0
      GLib: 2.86.0
 With:
  +brotli                      +nghttp2 1.64.0
  +Gcrypt 1.11.2               +nghttp3 1.12.0
  +GnuTLS 3.8.10 and PKCS#11   +PCRE2 10.46 2025-08-27
  +Kerberos (MIT)              +POSIX capabilities (Linux)
  +libnl 3                     +Qt 6.9.2
  +libpcap                     +QtDBus
  +libsmi 0.5.0                +QtMultimedia
  +libxml2 2.14.6              +Snappy 1.2.2
  +Lua 5.4.8                   +xxhash 0.8.3
  +LZ4 1.10.0                  +zlib 1.3.1
  +MaxMind                     +Zstandard 1.5.7
 Without:
  -automatic updates  -Minizip            -zlib-ng

Runtime info:
      OS: Linux 6.12.31-amd64
     CPU: Intel(R) Core(TM) i5-4570 CPU @ 3.20GHz (with SSE4.2)
  Memory: 15689 MB of physical memory
    GLib: 2.86.0
  Locale: LC_TYPE=en_US.UTF-8
 Plugins: supported, 22 loaded
 With:
  +brotli 1.1.0                      +nghttp3 1.12.0
  +c-ares 1.34.5                     +PCRE2 10.46 2025-08-27
  +Gcrypt 1.11.2                     +QPA plugin "xcb"
  +GnuTLS 3.8.10                     +Qt 6.9.2
  +libpcap 1.10.5 (with TPACKET_V3)  +Xorg
  +libsmi 0.5.0                      +xxhash 803
  +light display mode                +zlib 1.3.1
  +LZ4 1.10.0                        +Zstandard 1.5.7
  +nghttp2 1.64.0
 Without:
  -HiDPI
Version 4.6.1 (v4.6.1rc0-44-g4636bdbc7eea).

Compile-time info:
 Bit width: 64-bit
  Compiler: GCC 15.2.0
      GLib: 2.86.0
 With:
  +brotli                      +nghttp2 1.64.0
  +Gcrypt 1.11.2               +nghttp3 1.12.0
  +GnuTLS 3.8.10 and PKCS#11   +PCRE2 10.46 2025-08-27
  +Kerberos (MIT)              +POSIX capabilities (Linux)
  +libnl 3                     +Qt 6.9.2
  +libpcap                     +QtDBus
  +libsmi 0.5.0                +QtMultimedia
  +libxml2 2.14.6              +Snappy 1.2.2
  +Lua 5.4.8                   +xxhash 0.8.3
  +LZ4 1.10.0                  +zlib 1.3.1
  +MaxMind                     +Zstandard 1.5.7
 Without:
  -automatic updates  -Minizip            -zlib-ng

Runtime info:
      OS: Linux 6.12.31-amd64
     CPU: Intel(R) Core(TM) i5-4570 CPU @ 3.20GHz (with SSE4.2)
  Memory: 15689 MB of physical memory
    GLib: 2.86.0
  Locale: LC_TYPE=en_US.UTF-8
 Plugins: supported, 21 loaded
 With:
  +brotli 1.1.0                      +nghttp3 1.12.0
  +c-ares 1.34.5                     +PCRE2 10.46 2025-08-27
  +Gcrypt 1.11.2                     +QPA plugin "xcb"
  +GnuTLS 3.8.10                     +Qt 6.9.2
  +libpcap 1.10.5 (with TPACKET_V3)  +Xorg
  +libsmi 0.5.0                      +xxhash 803
  +light display mode                +zlib 1.3.1
  +LZ4 1.10.0                        +Zstandard 1.5.7
  +nghttp2 1.64.0
 Without:
  -HiDPI
Version 4.4.11 (v4.4.11rc0-7-gdc8b7d330e6a).

Compiled (64-bit) using GCC 15.2.0, with GLib 2.86.0, with Qt 6.9.2, with
libpcap, with POSIX capabilities (Linux), with libnl 3, with zlib 1.3.1, without
zlib-ng, with PCRE2, with Lua 5.4.8, with GnuTLS 3.8.10 and PKCS #11 support,
with Gcrypt 1.11.2, with Kerberos (MIT), with MaxMind, with nghttp2 1.64.0, with
nghttp3 1.12.0, with brotli, with LZ4, with Zstandard, with Snappy, with libxml2
2.14.6, with libsmi 0.5.0, without Minizip, with QtMultimedia, with QtDBus,
without automatic updates, with binary plugins.

Running on Linux 6.12.31-amd64, with Intel(R) Core(TM) i5-4570 CPU @ 3.20GHz
(with SSE4.2), with 15689 MB of physical memory, with GLib 2.86.0, with Qt
6.9.2, with libpcap 1.10.5 (with TPACKET_V3), with zlib 1.3.1, with PCRE2 10.46
2025-08-27, with c-ares 1.34.5, with GnuTLS 3.8.10, with Gcrypt 1.11.2, with
nghttp2 1.64.0, with nghttp3 1.12.0, with brotli 1.1.0, with LZ4 1.10.0, with
Zstandard 1.5.7, with libsmi 0.5.0, with light display mode, without HiDPI, with
Xorg, with QPA plugin "xcb", with LC_TYPE=en_US.UTF-8, binary plugins supported.
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