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NXDN: Add conditions to invalidate Superframe SACCH sequences;

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Invalidate entire SACCH superframe in storage if CRC error on individual SACCH or if next SR value (part of frame) is not the expected value;

Set initial nxdn_part_of_frame value to 3 - Ideal sequence is 1/1 NSF to 1/4 SF SACCH; also set to 3 on misc frame types (CAC, FACCH2, etc)
This commit is contained in:
lwvmobile
2026-02-03 01:43:12 -05:00
parent 5af38d3563
commit d7ce5e4cae
2 changed files with 60 additions and 14 deletions
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4
src/dsd_main.c
View File

@@ -417,7 +417,7 @@
// state->p25_vc_freq[1] = 0;
//new nxdn stuff
state->nxdn_part_of_frame = 0;
state->nxdn_part_of_frame = 3;
state->nxdn_ran = 0;
state->nxdn_sf = 0;
memset (state->nxdn_sacch_frame_segcrc, 1, sizeof(state->nxdn_sacch_frame_segcrc)); //init on 1, bad CRC all
@@ -1202,7 +1202,7 @@
state->tg_hold = 0;
//new nxdn stuff
state->nxdn_part_of_frame = 0;
state->nxdn_part_of_frame = 3;
state->nxdn_ran = 0;
state->nxdn_sf = 0;
memset (state->nxdn_sacch_frame_segcrc, 1, sizeof(state->nxdn_sacch_frame_segcrc)); //init on 1, bad CRC all

70
src/nxdn_deperm.c
View File

@@ -374,6 +374,16 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
check = check | viterbi_bits[i+26];
}
//if the crc is bad, its possible the SR value for part of frame is bad, so
//its better to invalidate all SACCH frames in storage to prevent
//random data splicing passing to the sacch assembly for decode
if (crc != check)
{
//reset the sacch field
memset (state->nxdn_sacch_frame_segment, 1, sizeof(state->nxdn_sacch_frame_segment));
memset (state->nxdn_sacch_frame_segcrc, 1, sizeof(state->nxdn_sacch_frame_segcrc));
}
//FIRST! If part of a non_superframe, and CRC is good, send directly to NXDN_Elements_Content_decode
if (state->nxdn_sacch_non_superframe == TRUE)
{
@@ -381,14 +391,12 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
else fprintf (stderr, " ");
//needed for DES and AES
state->nxdn_part_of_frame = 0;
// state->nxdn_part_of_frame = 0; //might be needed for VCALL_IV ks gen, but first voice should be in a SF SACCH PF 1/4
uint8_t nsf_sacch[26];
memset (nsf_sacch, 0, sizeof(nsf_sacch));
for (int i = 0; i < 26; i++)
{
nsf_sacch[i] = viterbi_bits[i+8];
}
if (crc == check)
{
@@ -396,7 +404,18 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
state->nxdn_last_ran = ran;
}
fprintf (stderr, "PF 1/1");
//indicate whether or not this individual sacch is valid
if (crc == check)
{
state->nxdn_part_of_frame = 3; //set to 3 so that a starting SF SACCH sequence check will be okay
fprintf (stderr, "PF 1/1");
}
else
{
state->nxdn_part_of_frame = 0; //will not be an expected next value
fprintf (stderr, "PF X/1");
}
if (state->nxdn_cipher_type == 1 && state->R != 0) state->payload_miN = state->R; //reset scrambler seed
else if (state->forced_alg_id == 1 && state->R != 0) state->payload_miN = state->R; //force reset scrambler seed
@@ -444,6 +463,24 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
else if (sf == 0) part_of_frame = 3;
else part_of_frame = 0;
//sequence check, if not expected next part of frame,
//or the first frame, then invalidate all sacch fields
uint8_t valid_sequence = 0;
// if (part_of_frame == ((state->nxdn_part_of_frame+1)%4) )
if (crc == check && (part_of_frame == ((state->nxdn_part_of_frame+1)%4)) )
valid_sequence = 1;
else if (crc == check && part_of_frame == 0)
valid_sequence = 1;
//its better to invalidate all SACCH frames in storage to prevent
//random data splicing passing to the sacch assembly for decode
if (valid_sequence == 0)
{
//reset the sacch field
memset (state->nxdn_sacch_frame_segment, 1, sizeof(state->nxdn_sacch_frame_segment));
memset (state->nxdn_sacch_frame_segcrc, 1, sizeof(state->nxdn_sacch_frame_segcrc));
}
//needed for DES and AES
state->nxdn_part_of_frame = part_of_frame;
@@ -452,7 +489,13 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
else fprintf (stderr, " ");
fprintf (stderr, "%s", KNRM);
fprintf (stderr, "PF %d/4", part_of_frame+1);
//indicate whether or not this individual sacch is valid or in sequence
if (crc == check && valid_sequence == 1)
fprintf (stderr, "PF %d/4", part_of_frame+1);
else if (crc == check && part_of_frame == 0)
fprintf (stderr, "PF %d/4", part_of_frame+1);
else fprintf (stderr, "PF X/4");
if (part_of_frame == 0)
{
if (state->nxdn_cipher_type == 1 && state->R != 0) state->payload_miN = state->R; //reset scrambler seed
@@ -516,18 +559,15 @@ void nxdn_sacch(dsd_opts * opts, dsd_state * state, uint8_t * bits)
//Hand off to LEH NXDN_SACCH_Full_decode
if (part_of_frame == 3)
{
NXDN_SACCH_Full_decode (opts, state);
}
if (opts->payload == 1)
{
fprintf (stderr, "\n");
fprintf (stderr, " SACCH SF Segment #%d ", part_of_frame+1);
for (int i = 0; i < 4; i++)
{
fprintf (stderr, "[%02X]", viterbi_bytes[i]);
}
if (crc != check) fprintf (stderr, " CRC ERR - %02X %02X", crc, check);
}
@@ -646,6 +686,7 @@ void nxdn_cac(dsd_opts * opts, dsd_state * state, uint8_t * bits)
fprintf (stderr, " (CRC ERR)");
fprintf (stderr, "%s", KNRM);
}
else state->nxdn_part_of_frame = 3; //reset expected SF SACCH PF to 3 if trunking and no sync break
//check for accumulative cac failures and reset if multiple errors pile up
if (crc != 0) cac_fail++;
@@ -1266,15 +1307,20 @@ void nxdn_facch2_udch(dsd_opts * opts, dsd_state * state, uint8_t * bits, uint8_
check = check | viterbi_bits[i+184];
}
// int sf = (viterbi_bits[0] << 1) | viterbi_bits[1]; //not sure why an SF field if there is no SACCH, unless UDCH data is segmented this way?
int sf = (viterbi_bits[0] << 1) | viterbi_bits[1]; //not sure why an SF field if there is no SACCH, unless UDCH data is segmented this way?
int ran = (viterbi_bits[2] << 5) | (viterbi_bits[3] << 4) | (viterbi_bits[4] << 3) | (viterbi_bits[5] << 2) | (viterbi_bits[6] << 1) | viterbi_bits[7];
if (crc == check)
{
state->nxdn_last_ran = ran;
fprintf (stderr, " RAN %02d ", state->nxdn_last_ran);
// fprintf (stderr, "PF %d/4", 4-sf); //on FACCh2 sample, was 4/4 sf = 0;
// fprintf (stderr, "PF %d/4", 4-sf); //on FACCH2 sample, was 4/4 sf = 0;
state->nxdn_part_of_frame = 3 - sf; //this, or hardset 3?
}
else
{
fprintf (stderr, " ");
state->nxdn_part_of_frame = 0; //should be invalid, pretty sure all FACCH2 are set to sf 0 (pf 3)
}
else fprintf (stderr, " ");
fprintf (stderr, "%s", KYEL);
if (type == 0) fprintf (stderr, " UDCH");