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Harald Welte gerrit-no-reply at lists.osmocom.orgHarald Welte has uploaded this change for review. ( https://gerrit.osmocom.org/12788
Change subject: WIP: Implement CSFB "Fast Return" Handling at RR RELEASE
......................................................................
WIP: Implement CSFB "Fast Return" Handling at RR RELEASE
When the MSC sends a BSSMAP CLEAR CMD containing a CSFB Indication IE,
it lets us know that the to-be-released connection related to a CSFB
call.
We as the BSC then subsequently should include the "Cell Selection
Indocator after release of all TCH and SDCCH" IE in the RR RELEASE
message sent to the MS/UE. This IE contains the LTE neighbor cells
that we're configured to broadcast in si2quater.
That in turn will make sure the MS/UE can return very quickly to
the LTE cell.
Change-Id: Ibfbb87e2e16b05032ad1cb91c11fad1b2f76d755
Requires: libosmocore Id4bd7f7543f5b0f4f6f876e283bd065039c37646
Requires: libosmocore I0e101af316438b56d63d43fc2cb16d7caf563d07
---
M include/osmocom/bsc/gsm_data.h
M src/osmo-bsc/bsc_subscr_conn_fsm.c
M src/osmo-bsc/gsm_04_08_rr.c
M src/osmo-bsc/osmo_bsc_bssap.c
4 files changed, 75 insertions(+), 1 deletion(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/88/12788/1
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 9f7ce8d..58c0541 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -557,6 +557,9 @@
/* If a release event is being handled, ignore other ricocheting release events until that
* release handling has concluded. */
bool in_release_handler;
+
+ /* is this release at the end of a CSFB call? */
+ bool is_csfb;
} release;
/* The logical channel type */
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index fc34968..13a5730 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -718,6 +718,8 @@
/* Regular allstate event processing */
switch (event) {
case GSCON_EV_A_CLEAR_CMD:
+ if (conn->lchan)
+ conn->lchan->release.is_csfb = *(bool *)data;
/* MSC tells us to cleanly shut down */
if (conn->fi->state != ST_CLEARING)
osmo_fsm_inst_state_chg(fi, ST_CLEARING, 60, 999);
diff --git a/src/osmo-bsc/gsm_04_08_rr.c b/src/osmo-bsc/gsm_04_08_rr.c
index f1061ef..5c86d53 100644
--- a/src/osmo-bsc/gsm_04_08_rr.c
+++ b/src/osmo-bsc/gsm_04_08_rr.c
@@ -28,7 +28,9 @@
#include <netinet/in.h>
#include <osmocom/core/msgb.h>
+#include <osmocom/core/bitvec.h>
#include <osmocom/gsm/gsm48.h>
+#include <osmocom/gsm/sysinfo.h>
#include <osmocom/bsc/abis_rsl.h>
#include <osmocom/bsc/debug.h>
@@ -40,6 +42,8 @@
#include <osmocom/bsc/assignment_fsm.h>
#include <osmocom/bsc/handover_fsm.h>
#include <osmocom/bsc/gsm_08_08.h>
+#include <osmocom/bsc/gsm_data.h>
+
/* should ip.access BTS use direct RTP streams between each other (1),
* or should OpenBSC always act as RTP relay/proxy in between (0) ? */
@@ -236,6 +240,46 @@
lchan->mr_ms_lv + 1);
}
+
+#define CELL_SEL_IND_AFTER_REL_MAX_BITS (4+MAX_EARFCN_LIST*19)
+#define CELL_SEL_IND_AFTER_REL_MAX_BYTES ((CELL_SEL_IND_AFTER_REL_MAX_BITS/8)+1)
+
+/* Generate a CSN.1 encoded "Cell Selection Indocator after release of all TCH and SDCCH"
+ * as per TF 44.018 version 15.3.0 Table 10.5.2.1e.1. This only generates the "value"
+ * part of the IE, not the tag+length wrapper */
+static int generate_cell_sel_ind_after_rel(uint8_t *out, unsigned int out_len, const struct gsm_bts *bts)
+{
+ struct bitvec bv;
+ unsigned int i;
+
+ bv.data = out;
+ bv.data_len = out_len;
+ bitvec_zero(&bv);
+
+ /* E-UTRAN Description */
+ bitvec_set_uint(&bv, 3, 3);
+ bitvec_set_bit(&bv, 1);
+
+ for (i = 0; i < MAX_EARFCN_LIST; i++) {
+ const struct osmo_earfcn_si2q *e = &bts->si_common.si2quater_neigh_list;
+ if (e->arfcn[i] == OSMO_EARFCN_INVALID)
+ continue;
+
+ if (0/* no more space in bitvec for 19 bits*/)
+ break;
+
+ bitvec_set_uint(&bv, e->arfcn[i], 16);
+ /* No "Measurement Bandwidth" */
+ bitvec_set_bit(&bv, 0);
+ /* No "Not Allowed Cells" */
+ bitvec_set_bit(&bv, 0);
+ /* No "TARGET_PCID" */
+ bitvec_set_bit(&bv, 0);
+ }
+ /* return the number of bytes used */
+ return bitvec_used_bytes(&bv);
+}
+
/* 7.1.7 and 9.1.7: RR CHANnel RELease */
int gsm48_send_rr_release(struct gsm_lchan *lchan)
{
@@ -250,6 +294,14 @@
cause = msgb_put(msg, 1);
cause[0] = GSM48_RR_CAUSE_NORMAL;
+ if (lchan->release.is_csfb) {
+ uint8_t buf[CELL_SEL_IND_AFTER_REL_MAX_BYTES];
+ int len;
+
+ len = generate_cell_sel_ind_after_rel(buf, sizeof(buf), lchan->ts->trx->bts);
+ msgb_tlv_put(msg, GSM48_IE_CELL_SEL_IND_AFTER_REL, len, buf);
+ }
+
DEBUGP(DRR, "Sending Channel Release: Chan: Number: %d Type: %d\n",
lchan->nr, lchan->type);
diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c
index f2ccf2c..ab7f79c 100644
--- a/src/osmo-bsc/osmo_bsc_bssap.c
+++ b/src/osmo-bsc/osmo_bsc_bssap.c
@@ -420,6 +420,23 @@
return gsm48_send_rr_ciph_mode(conn->lchan, include_imeisv);
}
+static int bssmap_handle_clear_cmd(struct gsm_subscriber_connection *conn,
+ struct msgb *msg, unsigned int length)
+{
+ struct tlv_parsed tp;
+ bool is_csfb = false;
+
+ tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l4h + 1, length - 1, 0, 0);
+
+ /* FIXME: Check for mandatory cause IE, and use that in RR RELEASE cause! */
+ if (TLVP_PRESENT(&tp, GSM0808_IE_CSFB_INDICATION))
+ is_csfb = true;
+
+ osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_A_CLEAR_CMD, &is_csfb);
+
+ return 0;
+}
+
/*
* GSM 08.08 § 3.1.14 cipher mode handling. We will have to pick
* the cipher to be used for this. In case we are already using
@@ -867,7 +884,7 @@
switch (msg->l4h[0]) {
case BSS_MAP_MSG_CLEAR_CMD:
- osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_A_CLEAR_CMD, msg);
+ ret = bssmap_handle_clear_cmd(conn, msg, length);
break;
case BSS_MAP_MSG_CIPHER_MODE_CMD:
ret = bssmap_handle_cipher_mode(conn, msg, length);
--
To view, visit https://gerrit.osmocom.org/12788
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Ibfbb87e2e16b05032ad1cb91c11fad1b2f76d755
Gerrit-Change-Number: 12788
Gerrit-PatchSet: 1
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
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