[Q] Dissector Sub Items

Hi Forum,

I am trying to write a dissector for a protocol. I cannot figure out how to display a sub tree PLUS box and sub fields.

I have created a simple example of what I have done.

My protocol has UINT16 message length followed FCOD (UNIT8). I want to use this FCODE as a subtree and have a PLUS box and sub fields, but I have been unable to get it to work.

I am expecting to see

+FOO Protocol
    Message Length 1234
    +FCODE
        FLAGS

Thanks

Stuart

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <epan/packet.h>
#define FOO_PORT 2000
static int hf_header_message_length = -1;
static int hf_header_fcode          = -1;
static int hf_fcode_flag            = -1;
static int ett_fooheader = -1;
static int ett_foosegment = -1;
static int proto_foo = -1;
// define protocol names, register structure
void proto_register_foo(void)
{
static hf_register_info hf[] = {
{ &hf_header_message_length,
{ "Message Length", "foo.msglength",
FT_UINT16, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_header_fcode,
{ "Function Code", "foo.FCode",
FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_fcode_flag,
{ "Fcode Flags", "foo.Fcode.flags",
FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }
}
};
static int *ett[] = {
    &amp;ett_fooheader,         //foo header
    &amp;ett_foosegment
};

proto_foo = proto_register_protocol (
    &quot;FOO Potocol&quot;,      // name
    &quot;FOO&quot;,              // short name
    &quot;foo&quot;               // abb ref
    );

proto_register_field_array(proto_foo, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));

}
static void dissect_foo(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
int offset = 0;
guint8 fcode  = 0;

col_set_str(pinfo-&gt;cinfo, COL_PROTOCOL, &quot;FOO&quot;);
// Clear out stuff in the info column
col_clear(pinfo-&gt;cinfo,COL_INFO);

if (tree) { // in case that someone wants to know some details of our protocol
    proto_item *ti = NULL;
    proto_tree *header_tree = NULL;

    ti = proto_tree_add_item(tree, proto_foo, tvb, 0, -1, ENC_NA);  // Grab all the data from the TCP Layer
    header_tree = proto_item_add_subtree(ti, ett_fooheader);

    proto_tree_add_item(header_tree, hf_header_message_length, tvb, offset, 2,  ENC_BIG_ENDIAN);
    offset +=2;

    fcode = tvb_get_guint8(tvb, offset);

    if (fcode = 0x00) {
        proto_tree *sub_tree = NULL;
        sub_tree = proto_item_add_subtree(header_tree, ett_foosegment);
        proto_tree_add_item(sub_tree, hf_fcode_flag, tvb, offset, 1,  ENC_BIG_ENDIAN);
        offset++;
    }
}

}
void proto_reg_handoff_foo(void) {
static dissector_handle_t foo_handle;
foo_handle = create_dissector_handle(dissect_foo, proto_foo);
dissector_add_uint("tcp.port", FOO_PORT, foo_handle);
}