tbf: Learn and propagate the TLLI changes due a new P-TMSI

During a routing area update a new P-TMSI was assigned. During
the PACKET CONTROL ACK on the DL we notice the change of TLLI
but didn't propagate this. This means that a Routing Area Update
Complete was only sent after a new RACH request.

Addresses:
<0007> gprs_rlcmac_meas.cpp:103 UL RSSI of TLLI=0x88661bc6: -67 dBm
<0002> bts.cpp:945 Got ACK, but UL TBF is gone TLLI=0xe512eba3
<0007> gprs_rlcmac_meas.cpp:158 DL packet loss of IMSI=274080000004765 / TLLI=0xe512eba3: 0%
<0002> tbf.cpp:668 TBF TFI=0 TLLI=0x88661bc6 T3169 timeout during transsmission
<0002> tbf.cpp:690 - Assignment was on PACCH
<0002> tbf.cpp:694 - No uplink data received yet

1 files changed, 26 insertions, 3 deletions

diff --git a/src/tbf.cpp b/src/tbf.cpp
index fac5aaf8..d78090fb 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -1618,9 +1618,32 @@ void gprs_rlcmac_tbf::update_tlli(uint32_t tlli)
 	if (tlli == m_tlli)
 		return;
 
-#warning "TODO.. find the DL/UL opposite and update the TLLI too"
-	LOGP(DRLCMAC, LOGL_NOTICE, "%s changing tlli to TLLI=0x%08x\n",
-		tbf_name(this), tlli);
+	bool changedUl = false;
+
+	/*
+	 * During a Routing Area Update (due the assignment of a new
+	 * P-TMSI) the tlli can change. We notice this when receiving
+	 * a PACKET CONTROL ACK.
+	 * When we get a TLLI change on the DL we will look if there
+	 * is a UL TBF and change the tlli there as well.
+	 *
+	 * TODO: There could be multiple DL and UL TBFs and we should
+	 * have a proper way to link all the related TBFs so we can do
+	 * a group update.
+	 */
+	if (m_tlli_valid && direction == GPRS_RLCMAC_DL_TBF) {
+		gprs_rlcmac_tbf *ul_tbf;
+		ul_tbf = bts->tbf_by_tlli(m_tlli, GPRS_RLCMAC_UL_TBF);
+
+		if (ul_tbf) {
+			ul_tbf->m_tlli = tlli;
+			changedUl = true;
+		}
+	}
+
+	LOGP(DRLCMAC, LOGL_NOTICE,
+		"%s changing tlli from TLLI=0x%08x TLLI=0x%08x ul_changed=%d\n",
+		tbf_name(this), m_tlli, tlli, changedUl);
 	m_tlli = tlli;
 }