falconia has uploaded this change for review.
trau: new function osmo_trau2rtp_ufe()
TRAU frame formats for newer codecs (HR, EFR, AMR) include a UFE
(uplink frame error) indicator bit in the DL direction. TRAUs are
expected to set this bit to active error state (0 for HR/EFR/AMR or
1 for D144 E-TRAU) if frame synchronization is lost in the UL
direction, or if received TRAU-UL frames have bad CRC or invalid
control bits - errors that indicate corruption on terrestrial
circuits or faults in the CCU, rather than radio Rx errors.
In Osmocom implementation, TRAU frame CRC and control bit patterns
are checked during conversion to RTP, as part of the work done by
osmo_trau2rtp() - but there is no separate return indication from
that function that distinguishes these errors from ordinary BFIs
due to radio errors or FACCH stealing etc. Solution: add a new
API function that indicates UFE conditions separately.
Related: OS#6614
Change-Id: I7a90eca296b17b1211e5c2125fb1496cd362e1c9
---
M include/osmocom/trau/trau_rtp.h
M src/trau/trau_rtp_conv.c
2 files changed, 80 insertions(+), 32 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/31/39731/1
diff --git a/include/osmocom/trau/trau_rtp.h b/include/osmocom/trau/trau_rtp.h
index 3631b83..cb6d8e2 100644
--- a/include/osmocom/trau/trau_rtp.h
+++ b/include/osmocom/trau/trau_rtp.h
@@ -32,5 +32,8 @@
int osmo_trau2rtp(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
struct osmo_trau2rtp_state *st);
+int osmo_trau2rtp_ufe(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
+ struct osmo_trau2rtp_state *st, bool *ufe);
+
int osmo_rtp2trau(struct osmo_trau_frame *tf, const uint8_t *rtp, size_t rtp_len,
struct osmo_trau2rtp_state *st);
diff --git a/src/trau/trau_rtp_conv.c b/src/trau/trau_rtp_conv.c
index 8307112..3b52ad9 100644
--- a/src/trau/trau_rtp_conv.c
+++ b/src/trau/trau_rtp_conv.c
@@ -246,7 +246,8 @@
* \param[in] out_len length of out buffer in bytes
* \param[in] tf input TRAU frame in decoded form
* \returns number of bytes generated in 'out'; negative on error. */
-static int trau2rtp_hr16(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf, bool emit_twts002)
+static int trau2rtp_hr16(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
+ bool emit_twts002, bool *ufe)
{
enum osmo_gsm631_sid_class sidc;
int rc;
@@ -274,7 +275,7 @@
* BFI or invalid SID packets. */
if (!emit_twts002 &&
(tf->c_bits[11] || sidc == OSMO_GSM631_SID_CLASS_INVALID))
- goto bad_frame;
+ return 0;
/* BFI turns valid SID into invalid */
if (tf->c_bits[11] && sidc == OSMO_GSM631_SID_CLASS_VALID)
@@ -306,6 +307,8 @@
return GSM_HR_BYTES_RTP_RFC5993;
bad_frame:
+ if (ufe)
+ *ufe = true;
if (emit_twts002) {
out[0] = FT_NO_DATA << 4;
twts002_hr16_set_extra_flags(out, tf);
@@ -343,7 +346,8 @@
* \param[in] emit_twts002 self-explanatory
* \returns number of bytes generated in 'out'; negative on error. */
static int trau2rtp_hr8(uint8_t *out, size_t out_len,
- const struct osmo_trau_frame *tf, bool emit_twts002)
+ const struct osmo_trau_frame *tf, bool emit_twts002,
+ bool *ufe)
{
unsigned xc1_4;
@@ -409,6 +413,8 @@
default:
bad_frame:
/* received garbage, emit BFI with no data */
+ if (ufe)
+ *ufe = true;
if (emit_twts002) {
out[0] = FT_NO_DATA << 4;
twts002_hr8_set_extra_flags(out, tf);
@@ -455,7 +461,8 @@
* \param[in] out_len length of out buffer in bytes
* \param[in] fr input TRAU frame in decoded form
* \returns number of bytes generated in 'out'; negative on error. */
-static int trau2rtp_efr(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf, bool emit_twts001)
+static int trau2rtp_efr(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
+ bool emit_twts001, bool *ufe)
{
size_t req_out_len = emit_twts001 ? GSM_EFR_BYTES+1 : GSM_EFR_BYTES;
int i, j, rc;
@@ -482,6 +489,33 @@
*twts001_hdr |= 0x01;
}
+ /* verify CRC before proceeding with conversion to RTP */
+ efr_parity_bits_1(check_bits, tf->d_bits);
+ rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 26,
+ tf->d_bits + 39);
+ if (rc)
+ goto bad_frame;
+ efr_parity_bits_2(check_bits, tf->d_bits);
+ rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
+ tf->d_bits + 95);
+ if (rc)
+ goto bad_frame;
+ efr_parity_bits_3(check_bits, tf->d_bits);
+ rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
+ tf->d_bits + 148);
+ if (rc)
+ goto bad_frame;
+ efr_parity_bits_4(check_bits, tf->d_bits);
+ rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
+ tf->d_bits + 204);
+ if (rc)
+ goto bad_frame;
+ efr_parity_bits_5(check_bits, tf->d_bits);
+ rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
+ tf->d_bits + 257);
+ if (rc)
+ goto bad_frame;
+
if (tf->c_bits[11] && !emit_twts001) /* BFI without TW-TS-001 */
return 0;
@@ -490,39 +524,14 @@
/* reassemble d-bits */
for (i = 1, j = 4; i < 39; i++, j++)
out[j/8] |= (tf->d_bits[i] << (7-(j%8)));
- efr_parity_bits_1(check_bits, tf->d_bits);
- rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 26,
- tf->d_bits + 39);
- if (rc)
- goto bad_frame;
for (i = 42, j = 42; i < 95; i++, j++)
out[j/8] |= (tf->d_bits[i] << (7-(j%8)));
- efr_parity_bits_2(check_bits, tf->d_bits);
- rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
- tf->d_bits + 95);
- if (rc)
- goto bad_frame;
for (i = 98, j = 95; i < 148; i++, j++)
out[j/8] |= (tf->d_bits[i] << (7-(j%8)));
- efr_parity_bits_3(check_bits, tf->d_bits);
- rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
- tf->d_bits + 148);
- if (rc)
- goto bad_frame;
for (i = 151, j = 145; i < 204; i++, j++)
out[j/8] |= (tf->d_bits[i] << (7-(j%8)));
- efr_parity_bits_4(check_bits, tf->d_bits);
- rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 12,
- tf->d_bits + 204);
- if (rc)
- goto bad_frame;
for (i = 207, j = 198; i < 257; i++, j++)
out[j/8] |= (tf->d_bits[i] << (7-(j%8)));
- efr_parity_bits_5(check_bits, tf->d_bits);
- rc = osmo_crc8gen_check_bits(&gsm0860_efr_crc3, check_bits, 8,
- tf->d_bits + 257);
- if (rc)
- goto bad_frame;
/*
* Many BTS models will emit the previous content of their internal
@@ -557,6 +566,8 @@
return req_out_len;
bad_frame:
+ if (ufe)
+ *ufe = true;
if (emit_twts001) {
*twts001_hdr |= 0x06; /* BFI and No_Data flags */
return 1;
@@ -1656,13 +1667,47 @@
int osmo_trau2rtp(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
struct osmo_trau2rtp_state *st)
{
+ return osmo_trau2rtp_ufe(out, out_len, tf, st, NULL);
+}
+
+/*! convert received TRAU-UL frame to RTP payload, while also flagging
+ * Uplink Frame Errors.
+ * \param[out] out Buffer for the output RTP payload
+ * \param[in] out_len Size of buffer pointed to by \ref out
+ * \param[in] tf Osmo-decoded TRAU frame
+ * \param[in] st State/config structure
+ * \param[out] ufe Must be initialized to false by the user, set to true
+ * by the function if an Uplink Frame Error is detected
+ * \returns length of converted RTP payload if successful; negative on error
+ *
+ * This function is just like plain osmo_trau2rtp(), but it also returns a
+ * secondary output: is the decoded TRAU-UL frame in error in terms of CRC
+ * or invalid control bits? This UFE flag is intended for use by software
+ * implementations of standard TRAU functionality, where a TRAU is expected
+ * to indicate UFE in its DL output if the UL input is corrupted in a way
+ * that is independent of radio Rx errors.
+ *
+ * Caveats:
+ *
+ * - *ufe is only set to true by this function, and is not written to at all
+ * if there is no error - thus the caller must initialize its bool variable
+ * to false before calling this API.
+ *
+ * - UFE checks exist only for HRv1 and EFR speech frames; for all other frame
+ * types, this function never writes to *ufe. (AMR is another frame type
+ * for which TRAU-UL decoding would include a UFE check, but we currently
+ * don't support AMR at all.)
+ */
+int osmo_trau2rtp_ufe(uint8_t *out, size_t out_len, const struct osmo_trau_frame *tf,
+ struct osmo_trau2rtp_state *st, bool *ufe)
+{
switch (tf->type) {
case OSMO_TRAU16_FT_FR:
return trau2rtp_fr(out, out_len, tf, check_twts001(st));
case OSMO_TRAU16_FT_EFR:
- return trau2rtp_efr(out, out_len, tf, check_twts001(st));
+ return trau2rtp_efr(out, out_len, tf, check_twts001(st), ufe);
case OSMO_TRAU16_FT_HR:
- return trau2rtp_hr16(out, out_len, tf, check_twts002(st));
+ return trau2rtp_hr16(out, out_len, tf, check_twts002(st), ufe);
case OSMO_TRAU16_FT_DATA:
return trau2rtp_data_fr(out, out_len, tf);
case OSMO_TRAU16_FT_DATA_HR:
@@ -1670,7 +1715,7 @@
case OSMO_TRAU16_FT_EDATA:
return trau2rtp_edata(out, out_len, tf);
case OSMO_TRAU8_SPEECH:
- return trau2rtp_hr8(out, out_len, tf, check_twts002(st));
+ return trau2rtp_hr8(out, out_len, tf, check_twts002(st), ufe);
case OSMO_TRAU8_DATA:
return trau2rtp_data_hr8(out, out_len, tf);
default:
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