21 Nov
2010
21 Nov
'10
9:45 p.m.
Hi all,
I've been looking at receiving CBCH traffic (where I live, 226-01
broadcasts a geographical area name with each cell).
Patches 1/1 and 1/2 are small fixes for the layer23 system information
parser, for storing the required CBCH channel description and mobile
allocation info.
I'll also reply with WIP patches for a small CBCH sniffing l23 app, and
for decoding CBCH in Wireshark. The latter is a quick hack job, as it
only decodes the first block, and it's bodged onto the LAPDm dissector.
Also a question: what would be the best place to integrate CBCH
handling into osmocom-bb? I'm guessing host/layer23/src/common/lapdm.c
would handle block reassembly, then send CBS frames up the stack. Would
any existing messages fit the bill (RSL_MT_UNIT_DATA_IND?) or should we
add a new one?
Cheers,
Alex
Alex Badea (2):
layer23 sysinfo: store chan_nr when decoding CBCH Channel Description
layer23 sysinfo: fix parsing of CBCH Mobile Allocation
src/host/layer23/src/common/sysinfo.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
21 Nov
21 Nov
9:47 p.m.
New subject: [RFC][PATCH wireshark] packet-lapdm: dissect CBS payloads
Hack dissection of Cell Broadcast Service into LAPDm. First-Block payloads
are also dissected directly.
---
packet-lapdm.c | 164 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 163 insertions(+), 1 deletion(-)
diff --git a/epan/dissectors/packet-lapdm.c b/epan/dissectors/packet-lapdm.c
index dbeac85..e1d67b4 100644
--- a/epan/dissectors/packet-lapdm.c
+++ b/epan/dissectors/packet-lapdm.c
@@ -61,12 +61,25 @@
#include <epan/xdlc.h>
#include <epan/reassemble.h>
+#include <epan/asn1.h>
+#include "packet-gsm_map.h"
+#include "packet-gsm_sms.h"
+
static int proto_lapdm = -1;
static int hf_lapdm_address = -1;
static int hf_lapdm_ea = -1;
static int hf_lapdm_cr = -1;
static int hf_lapdm_sapi = -1;
static int hf_lapdm_lpd = -1;
+static int hf_lapdm_cb_lb = -1;
+static int hf_lapdm_cb_seq = -1;
+static int hf_lapdm_cbs_serial_gs = -1;
+static int hf_lapdm_cbs_serial_mcode = -1;
+static int hf_lapdm_cbs_serial_updnum = -1;
+static int hf_lapdm_cbs_msgid = -1;
+static int hf_lapdm_cbs_page_num = -1;
+static int hf_lapdm_cbs_page_cnt = -1;
+static int hf_lapdm_cbs_content = -1;
static int hf_lapdm_control = -1;
static int hf_lapdm_n_r = -1;
@@ -103,6 +116,8 @@ static gint ett_lapdm_control = -1;
static gint ett_lapdm_length = -1;
static gint ett_lapdm_fragment = -1;
static gint ett_lapdm_fragments = -1;
+static gint ett_lapdm_cbs_serial = -1;
+static gint ett_lapdm_cbs_dcs = -1;
static GHashTable *lapdm_fragment_table = NULL;
static GHashTable *lapdm_reassembled_table = NULL;
@@ -121,6 +136,12 @@ static gboolean reassemble_lapdm = TRUE;
#define LAPDM_CR 0x02 /* Command/Response bit */
#define LAPDM_EA 0x01 /* First Address Extension bit */
#define LAPDM_LPD 0x60 /* Link Protocol Discriminator */
+#define LAPDM_LPD_CB 0x20 /* Cell Broadcast LPD */
+#define LAPDM_CB_LB 0x10 /* Cell Broadcast Last Bit */
+#define LAPDM_CB_SEQ 0x0f /* Cell Broadcast sequence number */
+#define LAPDM_CBS_SERIAL_GS 0xc0 /* CBS Serial Number - Geographical Scope */
+#define LAPDM_CBS_SERIAL_MCODE 0x3ffc /* CBS Serial Number - Message Code */
+#define LAPDM_CBS_SERIAL_UPDNUM 0x03 /* CBS Serial Number - Update Number */
/*
* Bits in the length field.
@@ -132,6 +153,7 @@ static gboolean reassemble_lapdm = TRUE;
#define LAPDM_LEN_SHIFT 2
#define LAPDM_HEADER_LEN 3
+#define LAPDM_CB_HEADER_LEN 1
#define LAPDM_SAPI_RR_CC_MM 0
#define LAPDM_SAPI_SMS 3
@@ -179,6 +201,33 @@ static const value_string lapdm_el_vals[] = {
{ 0, NULL }
};
+/* 04.12 section 3.3.1 */
+static const value_string lapdm_lb_vals[] = {
+ { 0, "More blocks" },
+ { 1, "Last block" },
+ { 0, NULL }
+};
+
+/* 04.12 section 3.3.1 */
+static const value_string lapdm_seq_vals[] = {
+ { 0, "First block" },
+ { 1, "Second block" },
+ { 2, "Third block" },
+ { 3, "Fourth block" },
+ { 8, "First schedule block" },
+ { 15, "Null message" },
+ { 0, NULL }
+};
+
+/* 03.41 section 9.3.2.1 */
+static const value_string lapdm_serial_gs_vals[] = {
+ { 0, "Cell wide (immediate)" },
+ { 1, "PLMN wide" },
+ { 2, "Location Area wide" },
+ { 3, "Cell wide" },
+ { 0, NULL }
+};
+
static const fragment_items lapdm_frag_items = {
/* Fragment subtrees */
@@ -209,6 +258,79 @@ lapdm_defragment_init (void)
static void
+dissect_lapdm_cb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+ proto_tree *lapdm_tree, *addr_tree;
+ proto_item *lapdm_ti, *addr_ti;
+ guint8 addr, seq;
+ tvbuff_t *payload;
+ int offset;
+ int length, out_len;
+ gchar msgbuf[88];
+
+ addr = tvb_get_guint8(tvb, 0);
+ if (tree) {
+ lapdm_ti = proto_tree_add_item(tree, proto_lapdm, tvb, 0, LAPDM_CB_HEADER_LEN,
FALSE);
+ lapdm_tree = proto_item_add_subtree(lapdm_ti, ett_lapdm);
+
+ addr_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_address, tvb, 0, 1, addr);
+ addr_tree = proto_item_add_subtree(addr_ti, ett_lapdm_address);
+
+ proto_tree_add_uint(addr_tree, hf_lapdm_lpd, tvb, 0, 1, addr);
+ proto_tree_add_uint(addr_tree, hf_lapdm_cb_lb, tvb, 0, 1, addr);
+ proto_tree_add_uint(addr_tree, hf_lapdm_cb_seq, tvb, 0, 1, addr);
+ } else {
+ lapdm_ti = NULL;
+ lapdm_tree = NULL;
+ }
+
+ col_append_str(pinfo->cinfo, COL_INFO, "CBS ");
+
+ offset = 1;
+
+ /* TODO: reassemble blocks 1-3 */
+ seq = addr & LAPDM_CB_SEQ;
+ if (seq == 0) {
+ proto_item *ti;
+ proto_tree *subtree;
+
+ ti = proto_tree_add_text(lapdm_tree, tvb, offset, 2, "Serial Number");
+ subtree = proto_item_add_subtree(ti, ett_lapdm_cbs_serial);
+
+ proto_tree_add_item(subtree, hf_lapdm_cbs_serial_gs, tvb, offset, 1, FALSE);
+ proto_tree_add_item(subtree, hf_lapdm_cbs_serial_mcode, tvb, offset, 2, FALSE);
+ offset++;
+ proto_tree_add_item(subtree, hf_lapdm_cbs_serial_updnum, tvb, offset, 1, FALSE);
+ offset++;
+
+ proto_tree_add_item(lapdm_tree, hf_lapdm_cbs_msgid, tvb, offset, 2, FALSE);
+ offset += 2;
+
+ ti = proto_tree_add_text(lapdm_tree, tvb, offset, 1, "Data Coding
Scheme");
+ subtree = proto_item_add_subtree(ti, ett_lapdm_cbs_dcs);
+ dissect_cbs_data_coding_scheme(tvb_new_subset(tvb, offset, 1, -1), pinfo,
subtree);
+ offset++;
+
+ proto_tree_add_item(lapdm_tree, hf_lapdm_cbs_page_num, tvb, offset, 1, FALSE);
+ proto_tree_add_item(lapdm_tree, hf_lapdm_cbs_page_cnt, tvb, offset, 1, FALSE);
+ offset++;
+
+ length = tvb_length(tvb) - offset;
+ out_len = gsm_sms_char_7bit_unpack(0, length, sizeof(msgbuf) - 1,
+ tvb_get_ptr(tvb, offset, length), msgbuf);
+ msgbuf[out_len] = '\0';
+ proto_tree_add_string(lapdm_tree, hf_lapdm_cbs_content, tvb, offset, length,
+ gsm_sms_chars_to_utf8(msgbuf, out_len));
+
+ col_append_fstr(pinfo->cinfo, COL_INFO, " [%s]",
gsm_sms_chars_to_utf8(msgbuf, out_len));
+ }
+
+ payload = tvb_new_subset_remaining(tvb, offset);
+ call_dissector(data_handle, payload, pinfo, tree);
+}
+
+
+static void
dissect_lapdm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
proto_tree *lapdm_tree, *addr_tree, *length_tree;
@@ -227,6 +349,11 @@ dissect_lapdm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPDm");
addr = tvb_get_guint8(tvb, 0);
+ if ((addr & LAPDM_LPD) == LAPDM_LPD_CB) {
+ dissect_lapdm_cb(tvb, pinfo, tree);
+ return;
+ }
+
length = tvb_get_guint8(tvb, 2);
cr = addr & LAPDM_CR;
@@ -360,6 +487,39 @@ proto_register_lapdm(void)
{ "SAPI", "lapdm.sapi", FT_UINT8, BASE_DEC,
VALS(lapdm_sapi_vals), LAPDM_SAPI,
"Service access point identifier", HFILL }},
+ { &hf_lapdm_cb_lb,
+ { "LB", "lapdm.cb.lb", FT_UINT8, BASE_DEC,
+ VALS(lapdm_lb_vals), LAPDM_CB_LB, "Last Block bit", HFILL }},
+
+ { &hf_lapdm_cb_seq,
+ { "SEQ", "lapdm.cb.seq", FT_UINT8, BASE_DEC,
+ VALS(lapdm_seq_vals), LAPDM_CB_SEQ, "Sequence Number", HFILL }},
+
+ { &hf_lapdm_cbs_serial_gs,
+ { "GS", "lapdm.cbs.serial.gs", FT_UINT8, BASE_DEC,
+ VALS(lapdm_serial_gs_vals), LAPDM_CBS_SERIAL_GS, "Geographic Scope",
HFILL }},
+ { &hf_lapdm_cbs_serial_mcode,
+ { "Message Code", "lapdm.cbs.serial.mcode", FT_UINT16,
BASE_DEC,
+ NULL, LAPDM_CBS_SERIAL_MCODE, NULL, HFILL }},
+ { &hf_lapdm_cbs_serial_updnum,
+ { "Update Number", "lapdm.cbs.serial.updnum", FT_UINT8,
BASE_DEC,
+ NULL, LAPDM_CBS_SERIAL_MCODE, NULL, HFILL }},
+
+ { &hf_lapdm_cbs_msgid,
+ { "Message Identifier", "lapdm.cbs.msgid", FT_UINT16,
BASE_DEC,
+ NULL, 0, NULL, HFILL }},
+
+ { &hf_lapdm_cbs_page_num,
+ { "Page number", "lapdm.cbs.page.num", FT_UINT8, BASE_DEC,
+ NULL, 0xf0, NULL, HFILL }},
+ { &hf_lapdm_cbs_page_cnt,
+ { "Total pages", "lapdm.cbs.page.cnt", FT_UINT8, BASE_DEC,
+ NULL, 0x0f, NULL, HFILL }},
+
+ { &hf_lapdm_cbs_content,
+ { "Content of Message", "lapdm.cbs.content", FT_STRING,
BASE_NONE,
+ NULL, 0x00, NULL, HFILL }},
+
{ &hf_lapdm_control,
{ "Control Field", "lapdm.control_field", FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }},
@@ -461,7 +621,9 @@ proto_register_lapdm(void)
&ett_lapdm_control,
&ett_lapdm_length,
&ett_lapdm_fragment,
- &ett_lapdm_fragments
+ &ett_lapdm_fragments,
+ &ett_lapdm_cbs_serial,
+ &ett_lapdm_cbs_dcs,
};
module_t *lapdm_module;
11:32 p.m.
New subject: [RFC][PATCH wireshark] packet-lapdm: dissect CBS payloads
Hi Alex,
first of all thanks for your CBCH contribution, it is much apperciated.
To me, the osmocom-bb patches all look fine. I'll let Andreas have a look
at them and decide, since it's mostly his code that is touched by your patches.
Regarding the wireshark patch: I suggest submitting that directly to the
wireshark project. You typically do this by creating a bugzilla ticket and
attaching your patch. It will then be reviewed and hopefully included.
I am not an official wireshark developer either, just contributing patches
here and there. But if you run into any trouble and need some support arguing
for inclusion of your patch, let me know.
Regards,
Harald
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
22 Nov
22 Nov
10:11 a.m.
New subject: [RFC][PATCH wireshark] packet-lapdm: dissect CBS payloads
Hi, thanks everyone for your feedback.
On Mon, Nov 22, 2010 at 12:32 AM, Harald Welte <laforge(a)gnumonks.org> wrote:
Regarding the wireshark patch: I suggest submitting
that directly to the
wireshark project. You typically do this by creating a bugzilla ticket and
attaching your patch. It will then be reviewed and hopefully included.
I plan to do that, but it needs some cleanup first. At the very least, the
CBS-specific dissection should be factored out into another module, since
the messages are also present between CBC <-> BSC <-> BTS. Presumably,
only block reassembly should sit in packet-lapdm.c.
Thanks,
Alex
21 Nov
21 Nov
11:33 p.m.
New subject: [RFC][PATCH wireshark] packet-lapdm: dissect CBS payloads
On 11/21/2010 09:47 PM, Alex Badea wrote:
Hack dissection of Cell Broadcast Service into LAPDm.
First-Block payloads
are also dissected directly.
Cool, could you send a mail to the wireshark-dev and ask them how to proceed
with this kind of patch?
thanks
holger
22 Nov
22 Nov
12:38 a.m.
New subject: [RFC][PATCH wireshark] packet-lapdm: dissect CBS payloads
Hi,
On 21.11.2010 21:47, Alex Badea wrote:
Hack dissection of Cell Broadcast Service into LAPDm.
First-Block payloads
are also dissected directly.
Cool stuff! 262-07 (O2 Germany) transmits the cell location as well.
They are encoded as Gauss-Krüger coordinates, which can be converted
with this script:
http://www.nobbi.com/download/gauss-converter.tar.gz
Works fine and the location matches.
Andreas: This would be a cool addon for cell_log ;)
Regards,
Steve
21 Nov
21 Nov
11:34 p.m.
Alex:
Ah well, this was so non-intrusive that I simply applied the first three
patches of your patchset (excluding the wireshark patch which you should
submit direcly to the wireshark folks)
Andreas: Hope this is fine for you.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
22 Nov
22 Nov
10:38 a.m.
Also a question: what would be the best place to
integrate CBCH
handling into osmocom-bb? I'm guessing host/layer23/src/common/lapdm.c
would handle block reassembly, then send CBS frames up the stack.
I don't know CBCH at all, but a general rule would be:
Is the block reassembly part of LAPDm ? (i.e. GSM 04.06 ?)
- If yes, then it fits in lapdm.c
- If no and nothing else fits, create a new file for it.
Cheers,
Sylvain
8:09 p.m.
On 11/22/2010 11:38 AM, Sylvain Munaut wrote:
Actually, the only link to 04.06 is a note in section 3.2 saying:
Also a
question: what would be the best place to integrate CBCH
handling into osmocom-bb? I'm guessing host/layer23/src/common/lapdm.c
would handle block reassembly, then send CBS frames up the stack.
I don't know CBCH at all, but a general rule would be:
Is the block reassembly part of LAPDm ? (i.e. GSM 04.06 ?)
- If yes, then it fits in lapdm.c
- If no and nothing else fits, create a new file for it. LPD = "0 1" corresponds to the data link
protocol used for SMSCB (see 3GPP TS 04.12).
... whereupon the LPD=01 address field variant is redefined to contain
different bit-fields. This supports the idea that implementation of
SMSCB should be entirely separate from LAPDm.
Thanks,
Alex
4916
days inactive
4917
days old
baseband-devel@lists.osmocom.org
8 comments
5 participants
participants (5)
-
Alex Badea -
Harald Welte -
Holger Hans Peter Freyther -
Steve Markgraf -
Sylvain Munaut