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Add GSMTAP encapsulation of RLP frames in CSD NT mode 

In CSD (Circuit Switched Data) NT (Non-Transparent) mode, there
are RLP (Radio Link Protocol) frames inside the modified V.110.

wireshark alrady has a dissector for this, and we've introduced
a GSMTAP type for RLP some time ago.  So with this patch, we now
generate such GSMTAP RLP frames.

Change-Id: I6a258458822bcb3fe7290a9b9b3d104beecda219
This commit is contained in:
Harald Welte 2023-11-23 19:20:44 +01:00 committed by laforge
parent f60f45e7ab
commit 7786d9b673
5 changed files with 111 additions and 4 deletions
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1
include/osmo-bts/bts.h
View File

@ -377,6 +377,7 @@ struct gsm_bts {
char *local_host;
uint32_t sapi_mask;
uint8_t sapi_acch;
bool rlp;
} gsmtap;
struct osmux_state osmux;

6
include/osmo-bts/lchan.h
View File

@ -287,7 +287,11 @@ struct gsm_lchan {
} dtx_fr_hr_efr;
uint8_t last_cmr;
uint32_t last_fn;
struct {
/* buffers to re-combine RLP frame from multiple Um blocks */
uint8_t rlp_buf_ul[576/8]; /* maximum size of RLP frame */
uint8_t rlp_buf_dl[576/8]; /* maximum size of RLP frame */
} csd;
} tch;
/* 3GPP TS 48.058 § 9.3.37: [0; 255] ok, -1 means invalid*/

83
src/common/l1sap.c
View File

@ -1848,19 +1848,88 @@ static int l1sap_ph_data_ind(struct gsm_bts_trx *trx,
return 1;
}
static void send_ul_rtp_packet_data(struct gsm_lchan *lchan, uint32_t fn,
/* process one MAC block of unpacked bits of a non-transparent CSD channel */
static void gsmtap_csd_rlp_process(struct gsm_lchan *lchan, bool is_uplink,
const struct ph_tch_param *tch_ind,
const uint8_t *data, unsigned int data_len)
{
struct gsm_bts_trx *trx = lchan->ts->trx;
struct gsmtap_inst *inst = trx->bts->gsmtap.inst;
pbit_t *rlp_buf;
int byte_len;
if (!inst || !trx->bts->gsmtap.rlp)
return;
if (lchan->csd_mode != LCHAN_CSD_M_NT)
return;
if (is_uplink)
rlp_buf = lchan->tch.csd.rlp_buf_ul;
else
rlp_buf = lchan->tch.csd.rlp_buf_dl;
/* TCH/F 9.6: 4x60bit block => 240bit RLP frame
* TCH/F 4.8: 2x 2x60bit blocks starting at B0/B2/B4 => 240bit RLP frame
* TCH/H 4.8: 4x60bit block => 240bit RLP frame
* TCH/F 2.4: 2x36bit blocks => transparent only
* TCH/H 2.4: 4x36bit blocks => transparent only
* TCH/F 14.4: 2x 290 bit block (starting with M1=0) => 576-bit RLP frame
*/
if (lchan->type == GSM_LCHAN_TCH_F && lchan->tch_mode == GSM48_CMODE_DATA_6k0) {
/* in this mode we have 120bit MAC blocks; two of them need to be concatenated
* to render a 240-bit RLP frame. The fist block is present in B0/B2/B4.
* The E7 bit is used to indicate the Frame MF0a */
OSMO_ASSERT(data_len == 120);
ubit_t e7 = data[4*7+3];
if (e7 == 0) {
osmo_ubit2pbit_ext(rlp_buf, 0, data, 0, data_len, 1);
return;
} else {
osmo_ubit2pbit_ext(rlp_buf, 120, data, 0, data_len, 1);
byte_len = 240/8;
}
} else if (lchan->type == GSM_LCHAN_TCH_F && lchan->tch_mode == GSM48_CMODE_DATA_14k5) {
/* in this mode we have 290bit MAC blocks containing M1, M2 and 288 data bits;
* two of them need to be concatenated to render a
* 576-bit RLP frame. The start of a RLP frame is
* denoted by a block with M1-bit set to 0. */
OSMO_ASSERT(data_len == 290);
ubit_t m1 = data[0];
if (m1 == 0) {
osmo_ubit2pbit_ext(rlp_buf, 0, data, 2, data_len, 1);
return;
} else {
osmo_ubit2pbit_ext(rlp_buf, 288, data, 2, data_len, 1);
byte_len = 576/8;
}
} else {
byte_len = osmo_ubit2pbit_ext(rlp_buf, 0, data, 0, data_len, 1);
}
gsmtap_send_ex(inst, GSMTAP_TYPE_GSM_RLP, trx->arfcn | is_uplink ? GSMTAP_ARFCN_F_UPLINK : 0,
lchan->ts->nr,
lchan->type == GSM_LCHAN_TCH_H ? GSMTAP_CHANNEL_VOICE_H : GSMTAP_CHANNEL_VOICE_F,
lchan->nr, tch_ind->fn, tch_ind->rssi, 0, rlp_buf, byte_len);
}
static void send_ul_rtp_packet_data(struct gsm_lchan *lchan, const struct ph_tch_param *tch_ind,
const uint8_t *data, uint16_t data_len)
{
uint8_t rtp_pl[RFC4040_RTP_PLEN];
int rc;
gsmtap_csd_rlp_process(lchan, true, tch_ind, data, data_len);
rc = csd_v110_rtp_encode(lchan, &rtp_pl[0], data, data_len);
if (rc < 0)
return;
osmo_rtp_send_frame_ext(lchan->abis_ip.rtp_socket,
&rtp_pl[0], sizeof(rtp_pl),
fn_ms_adj(fn, lchan),
fn_ms_adj(tch_ind->fn, lchan),
lchan->rtp_tx_marker);
/* Only clear the marker bit once we have sent a RTP packet with it */
lchan->rtp_tx_marker = false;
@ -2000,7 +2069,7 @@ static int l1sap_tch_ind(struct gsm_bts_trx *trx, struct osmo_phsap_prim *l1sap,
send_ul_rtp_packet_speech(lchan, fn, msg->data, msg->len);
break;
case RSL_CMOD_SPD_DATA:
send_ul_rtp_packet_data(lchan, fn, msg->data, msg->len);
send_ul_rtp_packet_data(lchan, tch_ind, msg->data, msg->len);
break;
case RSL_CMOD_SPD_SIGN:
return 0; /* drop stale TCH.ind */
@ -2309,6 +2378,10 @@ void l1sap_rtp_rx_cb(struct osmo_rtp_socket *rs, const uint8_t *rtp_pl,
int rc = csd_v110_rtp_decode(lchan, msg->tail,
rtp_pl, rtp_pl_len);
if (rc > 0) {
/* 'fake' tch_ind containing all-zero so gsmtap code can be shared
* between UL and DL */
static const struct ph_tch_param fake_tch_ind = {};
gsmtap_csd_rlp_process(lchan, false, &fake_tch_ind, msg->tail, rc);
msgb_put(msg, rc);
} else {
msgb_free(msg);
@ -2420,6 +2493,10 @@ int l1sap_chan_rel(struct gsm_bts_trx *trx, uint8_t chan_nr)
lchan->ecu_state = NULL;
}
/* reset CSD RLP buffers to avoid any user plane data leaking from
* one previous lchan into a later one */
memset(&lchan->tch.csd, 0, sizeof(lchan->tch.csd));
return l1sap_chan_act_dact_modify(trx, chan_nr, PRIM_INFO_DEACTIVATE,
0);
}

22
src/common/vty.c
View File

@ -447,6 +447,8 @@ static void config_write_bts_single(struct vty *vty, const struct gsm_bts *bts)
sapi_buf = osmo_str_tolower(get_value_string(gsmtap_sapi_names, GSMTAP_CHANNEL_ACCH));
vty_out(vty, " gsmtap-sapi %s%s", sapi_buf, VTY_NEWLINE);
}
if (bts->gsmtap.rlp)
vty_out(vty, " gsmtap-rlp%s", VTY_NEWLINE);
vty_out(vty, " min-qual-rach %d%s", bts->min_qual_rach,
VTY_NEWLINE);
vty_out(vty, " min-qual-norm %d%s", bts->min_qual_norm,
@ -2386,6 +2388,24 @@ DEFUN(cfg_bts_no_gsmtap_sapi, cfg_bts_no_gsmtap_sapi_cmd,
return CMD_SUCCESS;
}
DEFUN(cfg_bts_gsmtap_rlp, cfg_bts_gsmtap_rlp_cmd,
"gsmtap-rlp",
"Enable generation of GSMTAP frames for RLP (non-transparent CSD)\n")
{
struct gsm_bts *bts = vty->index;
bts->gsmtap.rlp = true;
return CMD_SUCCESS;
}
DEFUN(cfg_bts_no_gsmtap_rlp, cfg_bts_no_gsmtap_rlp_cmd,
"no gsmtap-rlp",
NO_STR "Disable generation of GSMTAP frames for RLP (non-transparent CSD)\n")
{
struct gsm_bts *bts = vty->index;
bts->gsmtap.rlp = false;
return CMD_SUCCESS;
}
static struct cmd_node phy_node = {
PHY_NODE,
"%s(phy)# ",
@ -2757,6 +2777,8 @@ int bts_vty_init(void *ctx)
install_element(BTS_NODE, &cfg_bts_gsmtap_sapi_all_cmd);
install_element(BTS_NODE, &cfg_bts_gsmtap_sapi_cmd);
install_element(BTS_NODE, &cfg_bts_no_gsmtap_sapi_cmd);
install_element(BTS_NODE, &cfg_bts_gsmtap_rlp_cmd);
install_element(BTS_NODE, &cfg_bts_no_gsmtap_rlp_cmd);
/* Osmux Node */
install_element(BTS_NODE, &cfg_bts_osmux_cmd);

3
tests/osmo-bts.vty
View File

@ -262,6 +262,8 @@ OsmoBTS(bts)# list
gsmtap-sapi (enable-all|disable-all)
gsmtap-sapi (bcch|ccch|rach|agch|pch|sdcch|tch/f|tch/h|pacch|pdtch|ptcch|cbch|sacch)
no gsmtap-sapi (bcch|ccch|rach|agch|pch|sdcch|tch/f|tch/h|pacch|pdtch|ptcch|cbch|sacch)
gsmtap-rlp
no gsmtap-rlp
osmux
trx <0-254>
...
@ -285,6 +287,7 @@ OsmoBTS(bts)# ?
gsmtap-remote-host Enable GSMTAP Um logging (see also 'gsmtap-sapi')
gsmtap-local-host Enable local bind for GSMTAP Um logging (see also 'gsmtap-sapi')
gsmtap-sapi Enable/disable sending of UL/DL messages over GSMTAP
gsmtap-rlp Enable generation of GSMTAP frames for RLP (non-transparent CSD)
osmux Configure Osmux
trx Select a TRX to configure
...