Martin Mathieson skrev 2011-10-12 20:22:
On Wed, Oct 12, 2011 at 6:42 PM, Guy Harris <g...@alum.mit.edu
<mailto:g...@alum.mit.edu>> wrote:
(Paging LTE experts here....)
On Oct 12, 2011, at 8:02 AM, wme...@wireshark.org
<mailto:wme...@wireshark.org> wrote:
>
http://anonsvn.wireshark.org/viewvc/viewvc.cgi?view=rev&revision=39384
<http://anonsvn.wireshark.org/viewvc/viewvc.cgi?view=rev&revision=39384>
>
> User: wmeier
> Date: 2011/10/12 08:02 AM
>
> Log:
> Fix a benign bug: Use correct proto_tree_add_item() encoding arg.
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Note that the ROHC support in this file has been superceded by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)
From packet-roch.c :-)
*
* Ref:
* http://www.ietf.org/rfc/rfc3095.txt RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and
uncompressed
* http://datatracker.ietf.org/doc/rfc4815/ RObust Header
Compression (ROHC): Corrections and Clarifications to RFC 3095
* http://datatracker.ietf.org/doc/rfc5225/ RObust Header
Compression Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP-Lite
Regards,
Martin
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