bugfix,gtpu: send end marker via the forwarding tunnel, when the source enb receives ue ctxt release command. Improve GTPU unit testing

srsenb/src/stack/upper/gtpu.cc

@@ -138,10 +138,14 @@ bool gtpu_tunnel_manager::update_rnti(uint16_t old_rnti, uint16_t new_rnti)
   srsran::bounded_vector<uint32_t, MAX_TUNNELS_PER_UE> to_remove;
   for (lcid_tunnel& bearer : new_rnti_obj) {
     tunnels[bearer.teid].rnti = new_rnti;
-    if (tunnels[bearer.teid].state == tunnel_state::forward_to) {
     // Remove forwarding path
+    if (tunnels[bearer.teid].state == tunnel_state::forward_to) {
       tunnels[bearer.teid].state      = tunnel_state::pdcp_active;
       tunnels[bearer.teid].fwd_tunnel = nullptr;
+      logger.info("Taking down forwarding tunnel for rnti=0x%x, lcid=%d. New default " TEID_IN_FMT,
+                  new_rnti,
+                  bearer.lcid,
+                  bearer.teid);
     } else if (tunnels[bearer.teid].state == tunnel_state::forwarded_from) {
       to_remove.push_back(bearer.teid);
     }
@@ -537,10 +541,19 @@ void gtpu::rem_tunnel(uint32_t teidin)
 
 void gtpu::rem_user(uint16_t rnti)
 {
-  if (tunnels.find_rnti_tunnels(rnti) == nullptr) {
+  const auto* tun_lst = tunnels.find_rnti_tunnels(rnti);
+  if (tun_lst == nullptr) {
     logger.info("Removing user - rnti=0x%x not found.", rnti);
     return;
   }
+  for (gtpu_tunnel_manager::lcid_tunnel tun_elem : *tun_lst) {
+    const gtpu_tunnel* tun = tunnels.find_tunnel(tun_elem.teid);
+    if (tun != nullptr and tun->state == gtpu_tunnel_manager::tunnel_state::forwarded_from) {
+      // In case of forwarding tunnel tx endpoint, send one extra End Marker on removal
+      send_end_marker(tun->teid_in);
+      rem_tunnel(tun->teid_in);
+    }
+  }
   tunnels.remove_rnti(rnti);
 }
 
@@ -553,6 +566,7 @@ void gtpu::handle_end_marker(const gtpu_tunnel& rx_tunnel)
     // TS 36.300, Sec 10.1.2.2.1 - Path Switch upon handover
     // END MARKER should be forwarded to TeNB if forwarding is activated
     send_end_marker(rx_tunnel.fwd_tunnel->teid_in);
+    rem_tunnel(rx_tunnel.fwd_tunnel->teid_in);
   }
 
   // Remove tunnel that received End Marker

srsenb/test/upper/gtpu_test.cc

@@ -205,7 +205,7 @@ void test_gtpu_tunnel_manager()
   TESTASSERT(after_tun->state == gtpu_tunnel_manager::tunnel_state::pdcp_active);
 }
 
-enum class tunnel_test_event { success, wait_end_marker_timeout };
+enum class tunnel_test_event { success, wait_end_marker_timeout, ue_removal_no_marker, reest_senb };
 
 int test_gtpu_direct_tunneling(tunnel_test_event event)
 {
@@ -330,6 +330,25 @@ int test_gtpu_direct_tunneling(tunnel_test_event event)
     for (size_t i = 0; i < gtpu_args.indirect_tunnel_timeout_msec + 1; ++i) {
       task_sched.tic();
     }
+  } else if (event == tunnel_test_event::ue_removal_no_marker) {
+    // TEST: EndMarker may even reach SeNB, but the SeNB receives in tandem the UEContextReleaseCommand and closes
+    //       the user tunnels before the chance to send an EndMarker
+    senb_gtpu.rem_user(0x46);
+    tenb_gtpu.handle_gtpu_s1u_rx_packet(read_socket(tenb_rx_sockets.s1u_fd), senb_sockaddr);
+  } else if (event == tunnel_test_event::reest_senb) {
+    // TEST: UE may start a Reestablishment to the SeNB. In such case, the rnti will be updated, the forwarding tunnel
+    //       taken down, and the previous main tunnel reestablished
+    senb_gtpu.mod_bearer_rnti(0x46, 0x47);
+    std::iota(data_vec.begin(), data_vec.end(), 0);
+    std::shuffle(data_vec.begin(), data_vec.end(), g);
+    pdu = encode_gtpu_packet(data_vec, senb_teid_in, sgw_sockaddr, senb_sockaddr);
+    encoded_data.assign(pdu->msg + 8u, pdu->msg + pdu->N_bytes);
+    senb_pdcp.last_sdu = nullptr;
+    senb_gtpu.handle_gtpu_s1u_rx_packet(std::move(pdu), sgw_sockaddr);
+    TESTASSERT(senb_pdcp.last_sdu != nullptr);
+    TESTASSERT(senb_pdcp.last_sdu->N_bytes == encoded_data.size() and
+               memcmp(senb_pdcp.last_sdu->msg, encoded_data.data(), encoded_data.size()) == 0);
+    return SRSRAN_SUCCESS;
   } else {
     // TEST: EndMarker is forwarded via MME->SeNB->TeNB, and TeNB buffered PDUs are flushed
     pdu = encode_end_marker(senb_teid_in);
@@ -357,6 +376,8 @@ int main(int argc, char** argv)
   srsenb::test_gtpu_tunnel_manager();
   TESTASSERT(srsenb::test_gtpu_direct_tunneling(srsenb::tunnel_test_event::success) == SRSRAN_SUCCESS);
   TESTASSERT(srsenb::test_gtpu_direct_tunneling(srsenb::tunnel_test_event::wait_end_marker_timeout) == SRSRAN_SUCCESS);
+  TESTASSERT(srsenb::test_gtpu_direct_tunneling(srsenb::tunnel_test_event::ue_removal_no_marker) == SRSRAN_SUCCESS);
+  TESTASSERT(srsenb::test_gtpu_direct_tunneling(srsenb::tunnel_test_event::reest_senb) == SRSRAN_SUCCESS);
 
   srslog::flush();