Wireshark-dev: Re: [Wireshark-dev] How can I register a link layer protocol?

From: Armando Vázquez <avr989@xxxxxxxxx>
Date: Sat, 3 Mar 2012 11:47:07 -0600
Thanks ashis!

When I tried this my protocol does not show up as a valid protocol, why is that? I tried using my dissector for the header protocol, but it should also disscet 2 trailer bytes, does that represent a problem ? What should I put in the header size field?

Besides, I've read that using the GUI and editing the DLT_User is the same as using the function dissector_add_uint(), am I right? If so, why isn't working? should I change something else in pcap-common.c or wtap.c or wtap.h?


Armando Vázquez Ramírez


On Sat, Mar 3, 2012 at 6:27 AM, ashish goel <ashish.kumar.goel1@xxxxxxxxx> wrote:
Hi Armando,

The is a way you can do it through wireshark GUI. Go to preferences -> protocols -> DLT_User. Here click on edit and add your protocol on any of the User DLTs(147 - 162). But make sure that that the pcap file you are using must have defined the same DLT value in its global header.

Hope this helps.

Thanks,
Ashish
2012/3/2 Armando Vázquez <avr989@xxxxxxxxx>
Hi guys,

I've read the developers guide, README.developer, wiretap plugin wiki and found no answer. Here is my problem. I'm trying to use Wireshark for dissecting a pcap capture of a protocol that it's not currently defined in wireshark. So I started writing a plugin, but I haven't been able to declare or register this dissector so it is enabled as a link layer dissector. I need to achieve this because this is not a internet protocol, so I need to identify it in this layer.

I've already read this dev-topic (http://www.mail-archive.com/wireshark-dev@xxxxxxxxxxxxx/msg05931.html) but I didn't understand it well.

The dissection part works fine, I've tested it using a pcap and nesting it on top of TCP. I would really appreciate your help. 

Also I've added in wtap.h

#define WTAP_ENCAP_MYPROTOCOL 147

and in wtap.c

static struct encap_type_info encap_table_base[] = {
...
{ "RESERVED 138", "res0" },
{ "RESERVED 139", "res1" },
{ "RESERVED 140", "res2" },
{ "RESERVED 141", "res3" },
{ "RESERVED 142", "res4" },
{ "RESERVED 143", "res5" },
{ "RESERVED 144", "res6" },
{ "RESERVED 145", "res7" },
{ "RESERVED 146", "res8" },

/* WTAP_ENCAP_MYPROTOCOL*/
{ "MY PROTOCOL, "myprotocol" }
};

Here are the register and handoff sections of my code

----------------------------------------------------------------------------------
void proto_register_myprotocol (void)
{
...

myprotocol_dissector_table = register_dissector_table("myprotocol.proto","ACN protocol number", FT_UINT8, BASE_HEX);
proto_register_field_array (proto_myprotocol, hf, array_length (hf));
proto_register_subtree_array (ett, array_length (ett));
register_dissector("myprotocol", dissect_myprotocol, proto_myprotocol);
}

void proto_reg_handoff_myprotocol(void)
{

data_handle = find_dissector("data");
myprotocol_handle = create_dissector_handle(dissect_myprotocol, proto_myprotocol);
dissector_add_uint("wtap_encap", WTAP_ENCAP_MYPROTOCOL, myprotocol_handle);
dissector_add_uint("tcp.port", global_myprotocol_port, myprotocol_handle); // Registering this on top of TCP was only to develop the dissection part, this won't be present in the release version


}

----------------------------------------------------------------------------------


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--
Thanks,
Ashish


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