Hi,
I'm trying to write a new dissector, and failing miserably getting my tree to show, because the tree I'm getting in my dissect_PROTONAME() is always NULL, not sure why.
I'm dissecting over TCP, with (regretfully) my own desegmentation:
packets 1-3 are syn, syn-ack, ack.
packet 4 is a start of a PDU, which is not enough to dissect the PDU, although I'm a getting its header. From the header, I'm taking the complete PDU length and therefore setting pinfo->desegment_len to calculated PDU length - length of what I got already ( with the offset = 0).
This looks nice and correct and indeed seems to be desegmented correctly, BUT:
packet 4 has my COL_PROTOCOL set (why?, I didn't dissect it eventually)
packet 5 doesn't (correct, I've asked for more than it has - it just a TCP segment)
packet 6 has my COL_PROTOCOL set (good) - but the packet isn't dissected there, although now I have the complete data (and TCP desgmentation shows the data is indeed taken from packets 4, 5 ,6 correctly.
This is part of my dissection:
...< get conversation data and state of the protocol>
col_set_str(pinfo->cinfo, COL_PROTOCOL, "Spice");
col_clear(pinfo->cinfo, COL_INFO);
if (tree) { /* WHY IS TREE ALWAYS NULL HERE?! */
ti = proto_tree_add_item(tree, proto_spice, tvb, 0, -1, FALSE);
spice_tree = proto_item_add_subtree(ti, ett_spice);
}
switch (spice_info->next_state) {
case RED_STATE_LINK_CLIENT:
len = tvb_reported_length(tvb);
if (len < 16 && redc_desegment) { /* the header is at least 16 bytes long */
pinfo->desegment_offset = 0;
pinfo->desegment_len = 16 - len;
return len;
}
pdu_len = tvb_get_letohl(tvb, 12) + 16;
if (len < pdu_len && redc_desegment) { /* Did not get all the PDU - request the full length of the PDU */
pinfo->desegment_offset = 0;
pinfo->desegment_len = pdu_len - len;
return len;
}
col_set_str(pinfo->cinfo, COL_INFO, "RED_STATE_LINK_CLIENT");
dissect_spice_link_client_pdu(tvb, pinfo, spice_tree, spice_info);
spice_info->next_state = RED_STATE_LINK_SERVER;
break;
...
I must be missing something obvious here. I just fail to understand what it is. I do know wireshark has two modes, one of which it goes over packets without the tree set, but I don't get when and where.
I've looked at other dissectors and they seem to be doing identical/similar dissection (wrongfully setting the protocol to their own even on segments, btw?).
Thanks in advance,
Yaniv.
