tbf: Remove TBF chaining (m_new_tbf and m_old_tbf)

Currently a new TBF is chained to an existing older one, either of
the other direction (active or releasing) or of the same direction
(releasing). This does not work properly work if and uplink and a
downlink TBF are being established at the same time while an old TBF
is being released. In that case, one of them is thrown away and the
pending procedure is cancelled.

The chaining is no longer necessary since the GprsMs objects have
been introduced which keep track of the active TBFs.

This commit removes the TBF members m_new_tbf and m_old_tbf and the
related methods and code paths.

Note that a new TBF can replace an older TBF entry of the same
direction within an MS object when it is associated with an MS (e.g.
by TLLI or because it is assigned via another, already associated
TBF). In that case, the old TBF is no longer associated with an MS
object.

Ticket: #1674
Sponsored-by: On-Waves ehf

3 files changed, 15 insertions, 85 deletions

diff --git a/src/bts.cpp b/src/bts.cpp
index f1339774..c7daf8e6 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -482,7 +482,6 @@ void BTS::trigger_dl_ass(
 			"PACCH, because %s exists\n", tbf_name(old_tbf));
 		old_tbf->dl_ass_state = GPRS_RLCMAC_DL_ASS_SEND_ASS;
 
-		old_tbf->set_new_tbf(dl_tbf);
 		old_tbf->was_releasing = old_tbf->state_is(GPRS_RLCMAC_WAIT_RELEASE);
 
 		/* use TA from old TBF */
@@ -498,7 +497,6 @@ void BTS::trigger_dl_ass(
 		/* change state */
 		dl_tbf->set_state(GPRS_RLCMAC_ASSIGN);
 		dl_tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_CCCH);
-		dl_tbf->set_new_tbf(dl_tbf);
 		/* send immediate assignment */
 		dl_tbf->bts->snd_dl_ass(dl_tbf, 0, dl_tbf->imsi());
 		dl_tbf->m_wait_confirm = 1;
@@ -713,11 +711,7 @@ void gprs_rlcmac_pdch::rcv_control_ack(Packet_Control_Acknowledgement_t *packet,
 		return;
 	}
 	tbf->update_tlli(tlli);
-
-	if (tbf->new_tbf())
-		tbf->new_tbf()->update_ms(tlli, GPRS_RLCMAC_UL_TBF);
-	else
-		tbf->update_ms(tlli, GPRS_RLCMAC_UL_TBF);
+	tbf->update_ms(tlli, GPRS_RLCMAC_UL_TBF);
 
 	LOGP(DRLCMAC, LOGL_DEBUG, "RX: [PCU <- BTS] %s Packet Control Ack\n", tbf_name(tbf));
 	tbf->poll_state = GPRS_RLCMAC_POLL_NONE;
@@ -742,7 +736,7 @@ void gprs_rlcmac_pdch::rcv_control_ack(Packet_Control_Acknowledgement_t *packet,
 		tbf->n3105 = 0;
 		tbf->dl_ass_state = GPRS_RLCMAC_DL_ASS_NONE;
 
-		new_tbf = tbf->new_tbf();
+		new_tbf = tbf->ms() ? tbf->ms()->dl_tbf() : NULL;
 		if (!new_tbf) {
 			LOGP(DRLCMAC, LOGL_ERROR, "Got ACK, but DL "
 				"TBF is gone TLLI=0x%08x\n", tlli);
@@ -770,7 +764,7 @@ void gprs_rlcmac_pdch::rcv_control_ack(Packet_Control_Acknowledgement_t *packet,
 		tbf->n3105 = 0;
 		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_NONE;
 
-		new_tbf = tbf->new_tbf();
+		new_tbf = tbf->ms() ? tbf->ms()->ul_tbf() : NULL;
 		if (!new_tbf) {
 			LOGP(DRLCMAC, LOGL_ERROR, "Got ACK, but UL "
 				"TBF is gone TLLI=0x%08x\n", tlli);
@@ -837,7 +831,11 @@ void gprs_rlcmac_pdch::rcv_control_dl_ack_nack(Packet_Downlink_Ack_Nack_t *ack_n
 	if (ack_nack->Exist_Channel_Request_Description) {
 		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
 			"message, so we provide one:\n");
-		tbf->set_new_tbf(tbf_alloc_ul(bts_data(), tbf->trx->trx_no, tbf->ms_class, tbf->tlli(), tbf->ta, tbf));
+
+		/* This call will register the new TBF with the MS on success */
+		tbf_alloc_ul(bts_data(), tbf->trx->trx_no, tbf->ms_class,
+			tbf->tlli(), tbf->ta, tbf);
+
 		/* schedule uplink assignment */
 		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
 	}
@@ -908,7 +906,6 @@ void gprs_rlcmac_pdch::rcv_resource_request(Packet_Resource_Request_t *request,
 		if (!ul_tbf)
 			return;
 
-		ul_tbf->set_new_tbf(ul_tbf);
 		/* set control ts to current MS's TS, until assignment complete */
 		LOGP(DRLCMAC, LOGL_DEBUG, "Change control TS to %d until assinment is complete.\n", ts_no);
 		ul_tbf->control_ts = ts_no;
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 4bafe144..ac0cdf3f 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -89,31 +89,6 @@ void gprs_rlcmac_tbf::assign_imsi(const char *imsi_)
 	m_ms->set_imsi(imsi_);
 }
 
-void gprs_rlcmac_tbf::set_new_tbf(gprs_rlcmac_tbf *tbf)
-{
-	if (m_new_tbf) {
-		if (m_new_tbf == tbf) {
-			LOGP(DRLCMAC, LOGL_INFO,
-				"%s reassigning %s to m_new_tbf\n",
-				tbf_name(this), tbf_name(tbf));
-			return;
-		}
-		if (m_new_tbf != this) {
-			LOGP(DRLCMAC, LOGL_NOTICE,
-				"%s m_new_tbf is already assigned to %s, "
-				"overwriting the old value with %s\n",
-				tbf_name(this), tbf_name(m_new_tbf), tbf_name(tbf));
-		}
-		/* Detach from other TBF */
-		m_new_tbf->m_old_tbf = NULL;
-	}
-	m_new_tbf = tbf;
-	tbf->m_old_tbf = this;
-
-	if (!tbf->ms())
-		tbf->set_ms(ms());
-}
-
 void gprs_rlcmac_tbf::set_ms(GprsMs *ms)
 {
 	if (m_ms == ms)
@@ -227,40 +202,6 @@ void tbf_free(struct gprs_rlcmac_tbf *tbf)
 	else
 		tbf->bts->tbf_dl_freed();
 
-	if (tbf->m_old_tbf) {
-		if (tbf->m_old_tbf == tbf) {
-			/* points to itself, ignore */
-		} else if (tbf->m_old_tbf->m_new_tbf == tbf) {
-			LOGP(DRLCMAC, LOGL_INFO,
-				"%s Old TBF %s still exists, detaching\n",
-				tbf_name(tbf), tbf_name(tbf->m_old_tbf));
-			tbf->m_old_tbf->m_new_tbf = NULL;
-		} else {
-			LOGP(DRLCMAC, LOGL_ERROR, "%s Software error: "
-				"tbf->m_old_tbf->m_new_tbf != tbf\n",
-				tbf_name(tbf));
-		}
-
-		tbf->m_old_tbf = NULL;
-	}
-
-	if (tbf->m_new_tbf) {
-		if (tbf->m_new_tbf == tbf) {
-			/* points to itself, ignore */
-		} else if (tbf->m_new_tbf->m_old_tbf == tbf) {
-			LOGP(DRLCMAC, LOGL_INFO,
-				"%s New TBF %s still exists, detaching\n",
-				tbf_name(tbf), tbf_name(tbf->m_new_tbf));
-			tbf->m_new_tbf->m_old_tbf = NULL;
-		} else {
-			LOGP(DRLCMAC, LOGL_ERROR, "%s Software error: "
-				"tbf->m_new_tbf->m_old_tbf != tbf\n",
-				tbf_name(tbf));
-		}
-
-		tbf->m_new_tbf = NULL;
-	}
-
 	if (tbf->ms())
 		tbf->set_ms(NULL);
 
@@ -668,7 +609,7 @@ int gprs_rlcmac_tbf::rlcmac_diag()
 struct msgb *gprs_rlcmac_tbf::create_dl_ass(uint32_t fn)
 {
 	struct msgb *msg;
-	struct gprs_rlcmac_dl_tbf *new_dl_tbf;
+	struct gprs_rlcmac_dl_tbf *new_dl_tbf = NULL;
 	int poll_ass_dl = 1;
 
 	if (direction == GPRS_RLCMAC_DL_TBF && control_ts != first_common_ts) {
@@ -706,7 +647,9 @@ struct msgb *gprs_rlcmac_tbf::create_dl_ass(uint32_t fn)
 		}
 	}
 
-	new_dl_tbf = static_cast<gprs_rlcmac_dl_tbf *>(m_new_tbf);
+	if (ms())
+		new_dl_tbf = ms()->dl_tbf();
+
 	if (!new_dl_tbf) {
 		LOGP(DRLCMACDL, LOGL_ERROR, "We have a schedule for downlink "
 			"assignment at uplink %s, but there is no downlink "
@@ -758,7 +701,7 @@ struct msgb *gprs_rlcmac_tbf::create_dl_ass(uint32_t fn)
 struct msgb *gprs_rlcmac_tbf::create_ul_ass(uint32_t fn)
 {
 	struct msgb *msg;
-	struct gprs_rlcmac_ul_tbf *new_tbf;
+	struct gprs_rlcmac_ul_tbf *new_tbf = NULL;
 
 	if (poll_state != GPRS_RLCMAC_POLL_NONE) {
 		LOGP(DRLCMACUL, LOGL_DEBUG, "Polling is already "
@@ -772,7 +715,8 @@ struct msgb *gprs_rlcmac_tbf::create_ul_ass(uint32_t fn)
 			return NULL;
 	}
 
-	new_tbf = static_cast<gprs_rlcmac_ul_tbf *>(m_new_tbf);
+	if (ms())
+		new_tbf = ms()->ul_tbf();
 	if (!new_tbf) {
 		LOGP(DRLCMACUL, LOGL_ERROR, "We have a schedule for uplink "
 			"assignment at downlink %s, but there is no uplink "
diff --git a/src/tbf.h b/src/tbf.h
index 0820065f..5ea6d4ef 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -150,9 +150,6 @@ struct gprs_rlcmac_tbf {
 	const char *imsi() const;
 	void assign_imsi(const char *imsi);
 
-	void set_new_tbf(gprs_rlcmac_tbf *tbf);
-	gprs_rlcmac_tbf *new_tbf() const;
-
 	time_t created_ts() const;
 
 	/* attempt to make things a bit more fair */
@@ -176,9 +173,6 @@ struct gprs_rlcmac_tbf {
 	enum gprs_rlcmac_tbf_ul_ass_state ul_ass_state;
 	enum gprs_rlcmac_tbf_ul_ack_state ul_ack_state;
 
-	gprs_rlcmac_tbf *m_new_tbf;
-	gprs_rlcmac_tbf *m_old_tbf; /* reverse pointer for m_new_tbf */
-
 	enum gprs_rlcmac_tbf_poll_state poll_state;
 	uint32_t poll_fn; /* frame number to poll */
 
@@ -297,11 +291,6 @@ inline uint8_t gprs_rlcmac_tbf::tfi() const
 	return m_tfi;
 }
 
-inline gprs_rlcmac_tbf *gprs_rlcmac_tbf::new_tbf() const
-{
-	return m_new_tbf;
-}
-
 inline time_t gprs_rlcmac_tbf::created_ts() const
 {
 	return m_created_ts;