gw: fix race condition

GW thread was checking the default_eps_bearer variable without
protection. RRC could update it when deleting DRB or receiving RRC
connection release.

srsue/hdr/stack/upper/gw.h

@@ -22,6 +22,7 @@
 #include "srsran/srslog/srslog.h"
 #include "tft_packet_filter.h"
 #include <atomic>
+#include <mutex>
 #include <net/if.h>
 #include <netinet/in.h>
 
@@ -84,6 +85,7 @@ private:
 
   static const int NOT_ASSIGNED          = -1;
   int32_t          default_eps_bearer_id = NOT_ASSIGNED;
+  std::mutex       gw_mutex;
 
   srslog::basic_logger& logger;
 

srsue/src/stack/upper/gw.cc

@@ -165,11 +165,7 @@ void gw::write_pdu_mch(uint32_t lcid, srsran::unique_byte_buffer_t pdu)
 /*******************************************************************************
   NAS interface
 *******************************************************************************/
-int gw::setup_if_addr(uint32_t eps_bearer_id,
-                      uint8_t  pdn_type,
-                      uint32_t ip_addr,
-                      uint8_t* ipv6_if_addr,
-                      char*    err_str)
+int gw::setup_if_addr(uint32_t eps_bearer_id, uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_addr, char* err_str)
 {
   int err;
   if (pdn_type == LIBLTE_MME_PDN_TYPE_IPV4 || pdn_type == LIBLTE_MME_PDN_TYPE_IPV4V6) {
@@ -212,8 +208,7 @@ bool gw::is_running()
   return running;
 }
 
-int gw::apply_traffic_flow_template(const uint8_t&                                 erab_id,
-                                    const LIBLTE_MME_TRAFFIC_FLOW_TEMPLATE_STRUCT* tft)
+int gw::apply_traffic_flow_template(const uint8_t& erab_id, const LIBLTE_MME_TRAFFIC_FLOW_TEMPLATE_STRUCT* tft)
 {
   return tft_matcher.apply_traffic_flow_template(erab_id, tft);
 }
@@ -270,6 +265,8 @@ void gw::run_thread()
       break;
     }
 
+    {
+      std::unique_lock<std::mutex> lock(gw_mutex);
       // Check if IP version makes sense and get packtet length
       struct iphdr*   ip_pkt  = (struct iphdr*)pdu->msg;
       struct ipv6hdr* ip6_pkt = (struct ipv6hdr*)pdu->msg;
@@ -294,7 +291,9 @@ void gw::run_thread()
           if (!register_wait) {
             logger.info("UE is not attached, waiting for NAS attach (%d/%d)", register_wait, REGISTER_WAIT_TOUT);
           }
-        usleep(100000);
+          lock.unlock();
+          std::this_thread::sleep_for(std::chrono::microseconds(100));
+          lock.lock();
           register_wait++;
         }
         register_wait = 0;
@@ -343,13 +342,12 @@ void gw::run_thread()
         idx += N_bytes;
         logger.debug("Entire packet not read from socket. Total Length %d, N_Bytes %d.", ip_pkt->tot_len, pdu->N_bytes);
       }
+    } // end of holdering gw_mutex
   }
   running = false;
   logger.info("GW IP receiver thread exiting.");
 }
 
-
-
 /**************************/
 /* TUN Interface Helpers  */
 /**************************/