Order of entries in dissector tables at startup and lua

AMR preferences

As @Anders pointed out, the problem is due to your preference for "AMR dynamic payload type" conflicting with your dissector registration. Set that preference to 0 to prevent AMR from being put into the dissector table for rtp.pt.

Initialization order

Actually, the dissectors are not loaded randomly. Wireshark loads the C dissectors and then the Lua scripts, each of which is always loaded in the same order. Note that preferences are read last during initialization, which is the reason the AMR preference took effect over your Lua dissector.

The Makefile generates dissector-registration code (register.c) based on dissector source. The C dissectors are thus registered in the order seen in this generated code, which is ascending ASCII order.

Then, Lua scripts (which can contain dissectors) are also loaded in ascending ASCII order as follows:

1. ${GLOBAL_CONFIG_DIR}/init.lua
2. ${GLOBAL_PLUGINS_DIR}/**/*.lua
3. ${PERSONAL_CONFIG_DIR}/init.lua
4. ${PERSONAL_PLUGINS_DIR}/**/*.lua

The path variables above can be determined in Wireshark (Help > About > Folders). Example values:

Variable name	Mac OSX value	Windows value
GLOBAL_CONFIG_DIR	/usr/share/wireshark	%WIRESHARK%
GLOBAL_PLUGINS_DIR	/usr/lib/wireshark/plugins/1.7.1	%WIRESHARK%\plugins\1.7.1
PERSONAL_CONFIG_DIR	$HOME/.wireshark	%APPDATA%\Wireshark
PERSONAL_PLUGINS_DIR	$HOME/.wireshark/plugins	%APPDATA%\Wireshark\plugins

Control of initialization order

You can't change the initialization order of the C dissectors unless you modify the code. However, you do have control of Lua script loading, but it requires you to make changes to prevent the scripts from being auto-loaded:

1. Move all Lua scripts outside of ${PERSONAL_PLUGINS_DIR} OR rename them to a different extension (such as ".lua_").
2. Modify ${PERSONAL_CONFIG_DIR}/init.lua to explicitly load the Lua scripts in a specific order.

Example: Let's say I had this directory structure:

~/.wireshark/plugins/
    |-- a.lua
    |-- b.lua
    -- x/
        |-- c.lua
        |-- d.lua
        |-- e.lua
        -- f.lua

...which has a load order of a through f. I want to change the order to "everything in the x directory alphabetically, then b, and a". So, I move the Lua scripts outside of ~/.wireshark/plugins to say, ~/.wireshark/lua/; and I add ~/.wireshark/init.lua, which contains:

-- USER_DIR is initialized in ${GLOBAL_CONFIG_DIR}/init.lua
local basedir = ( USER_DIR or persconffile_path() )..'lua/'
– load all Lua scripts in "~/.wireshark/lua/x" (ascending ASCII order)
local xdir = basedir..'x/'
for f in Dir.open(xdir, ".lua") do
dofile(xdir..f)
end
dofile(basedir..'b.lua')
dofile(basedir..'a.lua')

Assume the contents of each Lua script contains:

print( (require 'debug').getinfo(1).source )

which prints the absolute path to the running script. Now, if I start Wireshark or TShark, I should see the load order from the command line, like so:

$ tshark -v
@/Users/tony/.wireshark/lua/x/c.lua
@/Users/tony/.wireshark/lua/x/d.lua
@/Users/tony/.wireshark/lua/x/e.lua
@/Users/tony/.wireshark/lua/x/f.lua
@/Users/tony/.wireshark/lua/x/z.lua
@/Users/tony/.wireshark/lua/b.lua
@/Users/tony/.wireshark/lua/a.lua
TShark 1.7.1 (SVN Rev Unknown from unknown)

Copyright 1998-2012 Gerald Combs <[email protected]> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Compiled (64-bit) with GLib 2.28.8, with libpcap (version unknown), with libz
1.2.5, without POSIX capabilities, with SMI 0.4.8, with c-ares 1.7.4, with Lua
5.1, with Python 2.7.1, with GnuTLS 2.8.6, with Gcrypt 1.5.0, with MIT Kerberos,
with GeoIP.
Running on Mac OS 10.7.2 (Darwin 11.2.0), with locale en_US.UTF-8, with libpcap
version 1.1.1, with libz 1.2.5.
Built using llvm-gcc 4.2.1 (Based on Apple Inc. build 5658) (LLVM build
2336.1.00).