Use always RFN when handling RACH indications
The previous code was really confusing, passing full FNs as RFNs under
certain external conditions, and then assuming the RFN input of
rfn_to_fn() function could actually be a FN.
As a result, we had a lot of code behaving slightly different depending
on whether the incomding FN from pcuif was filled in by a BSC or a BTS.
Avoid this b ehavior differentiation and always assume the most
restricted one, aka RFN.
Change-Id: Ib3b5702168195b595711cd0ff32c211b9aba429d
diff --git a/src/bts.cpp b/src/bts.cpp
index d4bb35f..8d6f156 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -52,7 +52,6 @@
#include <errno.h>
#include <string.h>
-#define RFN_MODULUS 42432
#define RFN_THRESHOLD RFN_MODULUS / 2
extern void *tall_pcu_ctx;
@@ -744,25 +743,13 @@
uint32_t m_cur_rfn;
uint32_t fn_rounded;
- /* make sure RFN does not exceed the maximum possible value of a valid
- * GSM frame number. */
- OSMO_ASSERT(rfn < GSM_MAX_FN);
-
- /* Note: If a BTS is sending in a rach request it will be fully aware
- * of the frame number. If the PCU is used in a BSC-co-located setup.
- * The BSC will forward the incoming RACH request. The RACH request
- * only contains the relative frame number (Fn % 42432) in its request
- * reference. This PCU implementation has to fit both scenarios, so
- * we need to assume that Fn is a relative frame number. */
-
/* Ensure that all following calculations are performed with the
* relative frame number */
- if (rfn >= RFN_MODULUS)
- return rfn;
+ OSMO_ASSERT(rfn < RFN_MODULUS);
/* Compute an internal relative frame number from the full internal
frame number */
- m_cur_rfn = bts->cur_fn % RFN_MODULUS;
+ m_cur_rfn = fn2rfn(bts->cur_fn);
/* Compute a "rounded" version of the internal frame number, which
* exactly fits in the RFN_MODULUS raster */
diff --git a/src/bts.h b/src/bts.h
index 7dd8547..7a67f76 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -196,7 +196,7 @@
uint16_t ra;
uint8_t trx_nr;
uint8_t ts_nr;
- uint32_t rfn;
+ uint16_t rfn;
int16_t qta;
};
diff --git a/src/pcu_l1_if.cpp b/src/pcu_l1_if.cpp
index aadc640..cda7af7 100644
--- a/src/pcu_l1_if.cpp
+++ b/src/pcu_l1_if.cpp
@@ -630,7 +630,7 @@
.ra = 0x00,
.trx_nr = trx_nr,
.ts_nr = ts_nr,
- .rfn = fn,
+ .rfn = fn2rfn(fn),
.qta = qta,
};
@@ -640,11 +640,22 @@
static int pcu_rx_rach_ind(struct gprs_rlcmac_bts *bts, const struct gsm_pcu_if_rach_ind *rach_ind)
{
int rc = 0;
- int current_fn = bts_current_frame_number(bts);
+ uint32_t current_fn = bts_current_frame_number(bts);
+ uint16_t rfn;
- LOGP(DL1IF, LOGL_INFO, "RACH request received: sapi=%d "
- "qta=%d, ra=0x%02x, fn=%u, cur_fn=%d, is_11bit=%d\n", rach_ind->sapi, rach_ind->qta,
- rach_ind->ra, rach_ind->fn, current_fn, rach_ind->is_11bit);
+ /* Note: If a BSC is sending a RACH req to us, it is actually forwarding it to
+ * us from BTS as a result of receiving an RFN (Fn % 42432) over RSL
+ * (see 3GPP TS 48.058, section 9.3.19).
+ * If a BTS is sending a RACH req to us, it may contain a full FN
+ * (current osmo-bts does that) instead of an RFN.
+ * For consistency, and taking into account the BSC case limitations,
+ * work always with RFNs here:
+ */
+ rfn = fn2rfn(rach_ind->fn);
+
+ LOGP(DL1IF, LOGL_INFO,
+ "RACH request received: sapi=%d qta=%d, ra=0x%02x, fn=%u (rfn=%u), cur_fn=%d, is_11bit=%d\n",
+ rach_ind->sapi, rach_ind->qta, rach_ind->ra, rach_ind->fn, rfn, current_fn, rach_ind->is_11bit);
if (OSMO_UNLIKELY(rach_ind->fn > GSM_TDMA_HYPERFRAME - 1)) {
LOGP(DL1IF, LOGL_ERROR, "RACH request contains fn=%u that exceeds valid limits (0-%u) -- ignored!\n",
@@ -658,7 +669,7 @@
.ra = rach_ind->ra,
.trx_nr = rach_ind->trx_nr,
.ts_nr = rach_ind->ts_nr,
- .rfn = rach_ind->fn,
+ .rfn = rfn,
.qta = rach_ind->qta,
};
diff --git a/src/pcu_utils.h b/src/pcu_utils.h
index 1c698ca..a6beab0 100644
--- a/src/pcu_utils.h
+++ b/src/pcu_utils.h
@@ -84,6 +84,12 @@
return x & -x;
}
+#define RFN_MODULUS 42432
+static inline uint16_t fn2rfn(uint32_t fn)
+{
+ return fn % RFN_MODULUS;
+}
+
/* Used to store a C++ class in a llist used by C code */
struct llist_item {
struct llist_head list; /* item used by llist */
diff --git a/tests/tbf/TbfTest.cpp b/tests/tbf/TbfTest.cpp
index bbd6821..ae8b56f 100644
--- a/tests/tbf/TbfTest.cpp
+++ b/tests/tbf/TbfTest.cpp
@@ -80,7 +80,7 @@
.ra = ra,
.trx_nr = 0,
.ts_nr = 0,
- .rfn = Fn,
+ .rfn = fn2rfn(Fn),
.qta = qta,
};