On Wed, Oct 12, 2011 at 6:42 PM, Guy Harris
<guy@xxxxxxxxxxxx> wrote:
(Paging LTE experts here....)
At least as I read RFC 3095:
UOR-2-TS
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 1 1 0 | TS |
+===+===+===+===+===+===+===+===+
|T=1| M | SN |
+---+---+---+---+---+---+---+---+
| X | CRC |
+---+---+---+---+---+---+---+---+
neither the old code nor the new code are correct - the "M" bit is in the octet after the TS field.
I don't see anything obvious in 3GPP TS 36.323 itself that says the format is different; does something in a later RFC specify something different?
Guy, I'm sure to be missing something, but I don't see what is wrong with the current code, pasted here:
if (T) {
/* UOR-2-TS format */
/* TS */
guint8 ts = tvb_get_guint8(tvb, offset) & 0x1f;
proto_tree_add_uint(tree, hf_pdcp_lte_rohc_ts, tvb, offset, 1, ts);
offset++;
/* Large CID */
if (p_pdcp_info->large_cid_present) {
offset = dissect_large_cid(tree, tvb, offset);
}
/* m */
proto_tree_add_item(tree, hf_pdcp_lte_rohc_m, tvb, offset, 1, ENC_BIG_ENDIAN);
/* TODO: */
}
'offset' is incremented after TS is dissected. The strange +====+=====+ notation indicates that if we have a large CID, thats where it appears.
hf_pdcp_lte_rohc_m has the bitmask 0x40, which is OK.
Note that the ROHC support in this file has been superceded by packet-rohc.c. Its been on my TODO list for a long time that I rip out this implementation and call the one in packet-rohc.c instead (after carefully checking that everything here was already there or merge it across). As far as I know, RFC 3095 is used as-is in PDCP (note that there are corrections/clarifications for this RFC, don't remember where)
Regards,
Martin
