added TSBK dissection
git-svn-id: http://op25.osmocom.org/svn/trunk@51 65a5c917-d112-43f1-993d-58c26a4786be
This commit is contained in:
mossmann
parent
aa884bb19f
commit
4f73e76dbe
|
|
@ -36,11 +36,16 @@
|
|||
void proto_reg_handoff_p25cai(void);
|
||||
tvbuff_t* extract_status_symbols(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
|
||||
tvbuff_t* build_hdu_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset);
|
||||
tvbuff_t* build_tsdu_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset);
|
||||
tvbuff_t* build_termlc_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset);
|
||||
void data_deinterleave(tvbuff_t *tvb, guint8 *deinterleaved, int bit_offset);
|
||||
void trellis_1_2_decode(guint8 *encoded, guint8 *decoded, int offset);
|
||||
guint8 golay_18_6_8_decode(guint32 codeword);
|
||||
guint16 golay_24_12_8_decode(guint32 codeword);
|
||||
void rs_24_12_13_decode(guint8 *codeword, guint8 *decoded);
|
||||
void rs_36_20_17_decode(guint8 *codeword, guint8 *decoded);
|
||||
int find_min(guint8 list[], int len);
|
||||
int count_bits(unsigned int n);
|
||||
|
||||
/* Initialize the protocol and registered fields */
|
||||
static int proto_p25cai = -1;
|
||||
|
|
@ -62,13 +67,18 @@ static int hf_p25cai_ss_parent = -1;
|
|||
static int hf_p25cai_ss = -1;
|
||||
static int hf_p25cai_lc = -1;
|
||||
static int hf_p25cai_lcf = -1;
|
||||
static int hf_p25cai_lbf = -1;
|
||||
static int hf_p25cai_ptbf = -1;
|
||||
static int hf_p25cai_opcode = -1;
|
||||
static int hf_p25cai_args = -1;
|
||||
static int hf_p25cai_crc = -1;
|
||||
|
||||
/* Field values */
|
||||
static const value_string data_unit_ids[] = {
|
||||
{ 0x0, "Header Data Unit" },
|
||||
{ 0x3, "Terminator without Link Control" },
|
||||
{ 0x5, "Logical Link Data Unit 1" },
|
||||
{ 0x7, "Single Block Format Trunking Control Channel Packet" },
|
||||
{ 0x7, "Trunking Signaling Data Unit" },
|
||||
{ 0xA, "Logical Link Data Unit 2" },
|
||||
{ 0xC, "Packet Data Unit" },
|
||||
{ 0xF, "Terminator with Link Control" },
|
||||
|
|
@ -91,7 +101,7 @@ dissect_p25cai(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
|
|||
proto_tree *p25cai_tree, *nid_tree, *du_tree;
|
||||
int offset;
|
||||
tvbuff_t *extracted_tvb, *du_tvb;
|
||||
guint8 duid;
|
||||
guint8 duid, last_block;
|
||||
|
||||
/* If this doesn't look like a P25 CAI frame, give up and return 0 so that
|
||||
* perhaps another dissector can take over.
|
||||
|
|
@ -182,9 +192,27 @@ dissect_p25cai(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
|
|||
case 0x5:
|
||||
du_item = proto_tree_add_item(p25cai_tree, hf_p25cai_ldu1, extracted_tvb, offset, -1, FALSE);
|
||||
break;
|
||||
/* Trunking control channel packet in single block format */
|
||||
/* Trunking Signaling Data Unit */
|
||||
case 0x7:
|
||||
du_item = proto_tree_add_item(p25cai_tree, hf_p25cai_tsbk, extracted_tvb, offset, -1, FALSE);
|
||||
du_tvb = build_tsdu_tvb(extracted_tvb, pinfo, offset);
|
||||
offset = 0;
|
||||
last_block = 0;
|
||||
while (last_block == 0) {
|
||||
last_block = tvb_get_guint8(du_tvb, offset) >> 7;
|
||||
du_item = proto_tree_add_item(p25cai_tree, hf_p25cai_tsbk, du_tvb, offset, 12, FALSE);
|
||||
du_tree = proto_item_add_subtree(du_item, ett_du);
|
||||
proto_tree_add_item(du_tree, hf_p25cai_lbf, du_tvb, offset, 1, FALSE);
|
||||
proto_tree_add_item(du_tree, hf_p25cai_ptbf, du_tvb, offset, 1, FALSE);
|
||||
proto_tree_add_item(du_tree, hf_p25cai_opcode, du_tvb, offset, 1, FALSE);
|
||||
offset += 1;
|
||||
proto_tree_add_item(du_tree, hf_p25cai_mfid, du_tvb, offset, 1, FALSE);
|
||||
offset += 1;
|
||||
proto_tree_add_item(du_tree, hf_p25cai_args, du_tvb, offset, 8, FALSE);
|
||||
offset += 8;
|
||||
/* TODO: more items */
|
||||
proto_tree_add_item(du_tree, hf_p25cai_crc, du_tvb, offset, 2, FALSE);
|
||||
offset += 2;
|
||||
}
|
||||
break;
|
||||
/* Logical Link Data Unit 2 */
|
||||
case 0xA:
|
||||
|
|
@ -300,6 +328,42 @@ build_hdu_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset)
|
|||
return hdu_tvb;
|
||||
}
|
||||
|
||||
/* Build Trunking Signaling Block tvb. */
|
||||
tvbuff_t*
|
||||
build_tsdu_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset)
|
||||
{
|
||||
guint8 *tsdu_buffer, *trellis_buffer;
|
||||
guint8 last_block;
|
||||
int tsdu_offset, tvb_bit_offset;
|
||||
tvbuff_t *tsdu_tvb;
|
||||
|
||||
/* From here on, our tvb offset may not fall on bit boundaries, so we track
|
||||
* it by bits instead of bytes.
|
||||
*/
|
||||
tvb_bit_offset = offset * 8;
|
||||
tsdu_offset = 0;
|
||||
last_block = 0;
|
||||
|
||||
tsdu_buffer = (guint8*)ep_alloc0(36); /* 12 times maximum number of TSBKs (3) */
|
||||
|
||||
while (last_block == 0) {
|
||||
DISSECTOR_ASSERT(tvb_length_remaining(tvb, tvb_bit_offset / 8) >= 25);
|
||||
trellis_buffer = (guint8*)ep_alloc0(25);
|
||||
data_deinterleave(tvb, trellis_buffer, tvb_bit_offset);
|
||||
trellis_1_2_decode(trellis_buffer, tsdu_buffer, tsdu_offset);
|
||||
tvb_bit_offset += 196;
|
||||
last_block = tsdu_buffer[tsdu_offset] >> 7;
|
||||
tsdu_offset += 12;
|
||||
}
|
||||
|
||||
/* Setup a new tvb buffer with the decoded data. */
|
||||
tsdu_tvb = tvb_new_real_data(tsdu_buffer, tsdu_offset, tsdu_offset);
|
||||
tvb_set_child_real_data_tvbuff(tvb, tsdu_tvb);
|
||||
add_new_data_source(pinfo, tsdu_tvb, "data units");
|
||||
|
||||
return tsdu_tvb;
|
||||
}
|
||||
|
||||
/* Build Terminator Data Unit with Link Control tvb. */
|
||||
/* TODO: This one is completely untested. */
|
||||
tvbuff_t*
|
||||
|
|
@ -343,6 +407,73 @@ build_termlc_tvb(tvbuff_t *tvb, packet_info *pinfo, int offset)
|
|||
return termlc_tvb;
|
||||
}
|
||||
|
||||
/* Deinterleave data block. Assumes output buffer is already zeroed. */
|
||||
void
|
||||
data_deinterleave(tvbuff_t *tvb, guint8 *deinterleaved, int bit_offset)
|
||||
{
|
||||
int d, i, j, t;
|
||||
int steps[] = {0, 52, 100, 148};
|
||||
|
||||
/* step through input nibbles to copy to output */
|
||||
for (i = bit_offset, d = 0; i < 45 + bit_offset; i += 4) {
|
||||
for (j = 0; j < 4; j++, d += 4) {
|
||||
/* t = tvb bit index
|
||||
* d = deinterleaved bit index
|
||||
*/
|
||||
t = i + steps[j];
|
||||
deinterleaved[d / 8] |= ((tvb_get_guint8(tvb, t / 8) << (t % 8)) & 0xF0) >> (d % 8);
|
||||
}
|
||||
}
|
||||
t = bit_offset + 48;
|
||||
deinterleaved[24] |= ((tvb_get_guint8(tvb, t / 8) << (t % 8)) & 0xF0);
|
||||
}
|
||||
|
||||
/* 1/2 rate trellis decoder. Assumes output buffer is already zeroed. */
|
||||
void
|
||||
trellis_1_2_decode(guint8 *encoded, guint8 *decoded, int offset)
|
||||
{
|
||||
int i, j, k;
|
||||
int state = 0;
|
||||
guint8 codeword;
|
||||
|
||||
/* Hamming distance */
|
||||
guint8 hd[4];
|
||||
|
||||
/* state transition table, including constellation to dibit pair mapping */
|
||||
guint8 next_words[4][4] = {
|
||||
{0x2, 0xC, 0x1, 0xF},
|
||||
{0xE, 0x0, 0xD, 0x3},
|
||||
{0x9, 0x7, 0xA, 0x4},
|
||||
{0x5, 0xB, 0x6, 0x8}
|
||||
};
|
||||
|
||||
/* step through 4 bit codewords in input */
|
||||
for (i = 0; i < 196; i += 4) {
|
||||
codeword = (encoded[i / 8] >> (4 - (i % 8))) & 0xF;
|
||||
for (k = 0; k < 4; k++)
|
||||
hd[k] = 0;
|
||||
/* try each codeword in a row of the state transition table */
|
||||
for (j = 0; j < 4; j++) {
|
||||
/* find Hamming distance for candidate */
|
||||
hd[j] = count_bits(codeword ^ next_words[state][j]);
|
||||
}
|
||||
/* find the dibit that matches the most codeword bits (minimum Hamming distance) */
|
||||
state = find_min(hd, 4);
|
||||
/* error if minimum can't be found */
|
||||
DISSECTOR_ASSERT(state != -1);
|
||||
/* It also might be nice to report a condition where the minimum is
|
||||
* non-zero, i.e. an error has been corrected. It probably shouldn't
|
||||
* be a permanent failure, though.
|
||||
*
|
||||
* DISSECTOR_ASSERT(hd[state] == 0);
|
||||
*/
|
||||
|
||||
/* append dibit onto output buffer */
|
||||
if (i < 192)
|
||||
decoded[(i / 16) + offset] |= state << (6 - (i / 2) % 8);
|
||||
}
|
||||
}
|
||||
|
||||
/* Error correction decoders
|
||||
*
|
||||
* TODO: For now these are fake. They pull out the original bits without
|
||||
|
|
@ -485,6 +616,31 @@ proto_register_p25cai(void)
|
|||
{ "Link Control Format", "p25cai.lcf",
|
||||
FT_UINT8, BASE_HEX, NULL, 0x0,
|
||||
NULL, HFILL }
|
||||
},
|
||||
{ &hf_p25cai_lbf,
|
||||
{ "Last Block Flag", "p25cai.lbf",
|
||||
FT_BOOLEAN, BASE_NONE, NULL, 0x80,
|
||||
NULL, HFILL }
|
||||
},
|
||||
{ &hf_p25cai_ptbf,
|
||||
{ "Protected Trunking Block Flag", "p25cai.ptbf",
|
||||
FT_BOOLEAN, BASE_NONE, NULL, 0x40,
|
||||
NULL, HFILL }
|
||||
},
|
||||
{ &hf_p25cai_opcode,
|
||||
{ "Opcode", "p25cai.opcode",
|
||||
FT_UINT8, BASE_HEX, NULL, 0x3F,
|
||||
NULL, HFILL }
|
||||
},
|
||||
{ &hf_p25cai_args,
|
||||
{ "Arguments", "p25cai.args",
|
||||
FT_UINT64, BASE_HEX, NULL, 0x0,
|
||||
NULL, HFILL }
|
||||
},
|
||||
{ &hf_p25cai_crc,
|
||||
{ "CRC", "p25cai.crc",
|
||||
FT_UINT16, BASE_HEX, NULL, 0x0,
|
||||
NULL, HFILL }
|
||||
}
|
||||
};
|
||||
|
||||
|
|
@ -534,3 +690,41 @@ proto_reg_handoff_p25cai(void)
|
|||
inited = TRUE;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* Utility functions */
|
||||
|
||||
/* count the number of 1 bits in an int */
|
||||
int
|
||||
count_bits(unsigned int n)
|
||||
{
|
||||
int i = 0;
|
||||
for (i = 0; n != 0; i++)
|
||||
n &= n - 1;
|
||||
return i;
|
||||
}
|
||||
|
||||
/* return the index of the lowest value in a list */
|
||||
int
|
||||
find_min(guint8 list[], int len)
|
||||
{
|
||||
int min = list[0];
|
||||
int index = 0;
|
||||
int unique = 1;
|
||||
int i;
|
||||
|
||||
for (i = 1; i < len; i++) {
|
||||
if (list[i] < min) {
|
||||
min = list[i];
|
||||
index = i;
|
||||
unique = 1;
|
||||
} else if (list[i] == min) {
|
||||
unique = 0;
|
||||
}
|
||||
}
|
||||
/* return -1 if a minimum can't be found */
|
||||
if (!unique)
|
||||
return -1;
|
||||
|
||||
return index;
|
||||
}
|
||||
|
|
|
|||
Reference in New Issue