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How to call VNC / RFB dissector from my lua dissector?

asked 2021-10-17 07:46:31 +0000

I can't find it in Dissector.list()

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answered 2021-10-17 18:36:04 +0000

Chuckc gravatar image

VNC is not registered as a dissector. See end of packet-vnc.c:

#define VNC_PORT_RANGE "5500-5501,5900-5901"
proto_reg_handoff_vnc(void)
{
    vnc_handle = create_dissector_handle(dissect_vnc, proto_vnc);

    dissector_add_uint_range_with_preference("tcp.port", VNC_PORT_RANGE, vnc_handle);
    heur_dissector_add("tcp", test_vnc_protocol, "VNC over TCP", "vnc_tcp", proto_vnc, HEURISTIC_ENABLE);

It's a subdissector to the tcp.port table.
There is an example of getting a subdissector at the end of the Wiki page for Lua/Dissectors:

        local tcp_dissector_table = DissectorTable.get("tcp.port")
        original_http_dissector = tcp_dissector_table:get_dissector(80) 

Here is an example getting the VNC dissector based on the port number 5500:

local tcp_port_table = DissectorTable.get("tcp.port")
local vnc_dissector = tcp_port_table:get_dissector(5500)
print (vnc_dissector)
print "----------"
10/17/2021 1:34:40 PM Console opened
10/17/2021 1:35:08 PM VNC
10/17/2021 1:35:08 PM ----------
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Comments

Is there a reason why it's not registered (and others like it)? Seems like adding the following to proto_register_vnc() would also fix this problem.

register_dissector("vnc", dissect_vnc, proto_vnc);
cmaynard gravatar imagecmaynard ( 2021-10-18 15:56:32 +0000 )edit

A sentence or two in the WSDG and/or README.dissector describing "subdissector" (and "sub-dissector" and "sub-protocol dissector" and "subprotocol dissector") might help to reason why not all dissectors (or in this case, subdissector) are registered in the dissector table.

Chuckc gravatar imageChuckc ( 2021-10-18 17:56:17 +0000 )edit

Thanks! .

meniadin gravatar imagemeniadin ( 2021-10-20 06:51:40 +0000 )edit

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Asked: 2021-10-17 07:46:31 +0000

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Last updated: Oct 17 '21