nas/gw/rrc: make LCID for DRB dynamic

- add interface to RRC to allow NAS to query the DRB for a given
  EPS bearer id
- extend interface for NAS to setup GW to also pass LCID of bearer
- in NAS, use this new interface to pass actual LCID of the default
  DRB when creating the TUN device

lib/include/srslte/interfaces/ue_interfaces.h

@@ -102,7 +102,8 @@ public:
 class gw_interface_nas
 {
 public:
-  virtual srslte::error_t setup_if_addr(uint8_t pdn_type, uint32_t ip_addr, uint8_t *ipv6_if_id, char *err_str) = 0;
+  virtual srslte::error_t
+  setup_if_addr(uint32_t lcid, uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_id, char* err_str) = 0;
 };
 
 // GW interface for RRC
@@ -202,6 +203,7 @@ public:
   virtual void set_ue_idenity(asn1::rrc::s_tmsi_s s_tmsi)                                                          = 0;
   virtual bool is_connected() = 0;
   virtual std::string get_rb_name(uint32_t lcid) = 0;
+  virtual uint32_t    get_lcid_for_eps_bearer(const uint32_t& eps_bearer_id) = 0;
 };
 
 // RRC interface for PDCP

srsue/hdr/stack/rrc/rrc.h

@@ -675,6 +675,7 @@ private:
   void add_srb(asn1::rrc::srb_to_add_mod_s* srb_cnfg);
   void add_drb(asn1::rrc::drb_to_add_mod_s* drb_cnfg);
   void release_drb(uint32_t drb_id);
+  uint32_t get_lcid_for_eps_bearer(const uint32_t& eps_bearer_id);
   void add_mrb(uint32_t lcid, uint32_t port);
 
   // Helpers for setting default values

srsue/hdr/stack/upper/gw.h

@@ -58,7 +58,8 @@ public:
   void write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t pdu);
 
   // NAS interface
-  srslte::error_t setup_if_addr(uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_addr, char *err_str);
+  srslte::error_t
+  setup_if_addr(uint32_t lcid, uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_addr, char* err_str);
 
   // RRC interface
   void add_mch_port(uint32_t lcid, uint32_t port);
@@ -80,6 +81,7 @@ private:
   struct ifreq        ifr;
   int32_t             sock;
   bool                if_up;
+  uint32_t            default_lcid = 0;
 
   uint32_t            current_ip_addr;
   uint8_t             current_if_id[8];

srsue/src/stack/rrc/rrc.cc

@@ -3049,6 +3049,17 @@ void rrc::release_drb(uint32_t drb_id)
   }
 }
 
+uint32_t rrc::get_lcid_for_eps_bearer(const uint32_t& eps_bearer_id)
+{
+  // check if this bearer id exists and return it's LCID
+  for (auto& drb : drbs) {
+    if (drb.second.eps_bearer_id == eps_bearer_id) {
+      return drb.first;
+    }
+  }
+  return 0;
+}
+
 void rrc::add_mrb(uint32_t lcid, uint32_t port)
 {
   gw->add_mch_port(lcid, port);

srsue/src/stack/upper/gw.cc

@@ -67,9 +67,7 @@ struct in6_ifreq {
 
 namespace srsue {
 
-#define DRB1_LCID 3
+gw::gw() : if_up(false), default_lcid(0), thread("GW")
-
-gw::gw() : if_up(false), thread("GW")
 {
   current_ip_addr = 0;
 }
@@ -198,7 +196,8 @@ void gw::write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t pdu)
 /*******************************************************************************
   NAS interface
 *******************************************************************************/
-srslte::error_t gw::setup_if_addr(uint8_t pdn_type, uint32_t ip_addr, uint8_t *ipv6_if_addr, char *err_str)
+srslte::error_t
+gw::setup_if_addr(uint32_t lcid, uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_addr, char* err_str)
 {
   srslte::error_t err;
   if(pdn_type == LIBLTE_MME_PDN_TYPE_IPV4 || pdn_type == LIBLTE_MME_PDN_TYPE_IPV4V6 ){
@@ -214,6 +213,8 @@ srslte::error_t gw::setup_if_addr(uint8_t pdn_type, uint32_t ip_addr, uint8_t *i
     }
   }
 
+  default_lcid = lcid;
+
   // Setup a thread to receive packets from the TUN device
   start(GW_THREAD_PRIO);
   return srslte::ERROR_NONE;
@@ -280,10 +281,10 @@ void gw::run_thread()
         if (pkt_len == pdu->N_bytes) {
           gw_log->info_hex(pdu->msg, pdu->N_bytes, "TX PDU");
 
-          while (run_enable && !pdcp->is_lcid_enabled(DRB1_LCID) && attach_wait < ATTACH_WAIT_TOUT) {
+          while (run_enable && !pdcp->is_lcid_enabled(default_lcid) && attach_wait < ATTACH_WAIT_TOUT) {
             if (!attach_wait) {
               gw_log->info(
-                  "LCID=%d not active, requesting NAS attach (%d/%d)\n", DRB1_LCID, attach_wait, ATTACH_WAIT_TOUT);
+                  "LCID=%d not active, requesting NAS attach (%d/%d)\n", default_lcid, attach_wait, ATTACH_WAIT_TOUT);
               if (!nas->attach_request()) {
                 gw_log->warning("Could not re-establish the connection\n");
               }
@@ -299,10 +300,10 @@ void gw::run_thread()
           }
 
           // Send PDU directly to PDCP
-          if (pdcp->is_lcid_enabled(DRB1_LCID)) {
+          if (pdcp->is_lcid_enabled(default_lcid)) {
             pdu->set_timestamp();
             ul_tput_bytes += pdu->N_bytes;
-            pdcp->write_sdu(DRB1_LCID, std::move(pdu), false);
+            pdcp->write_sdu(default_lcid, std::move(pdu), false);
             do {
               pdu = srslte::allocate_unique_buffer(*pool);
               if (!pdu) {

srsue/src/stack/upper/nas.cc

@@ -722,7 +722,11 @@ void nas::parse_attach_accept(uint32_t lcid, unique_byte_buffer_t pdu)
 
       // Setup GW
       char *err_str = NULL;
-      if (gw->setup_if_addr(LIBLTE_MME_PDN_TYPE_IPV4, ip_addr, NULL, err_str)) {
+      if (gw->setup_if_addr(rrc->get_lcid_for_eps_bearer(act_def_eps_bearer_context_req.eps_bearer_id),
+                            LIBLTE_MME_PDN_TYPE_IPV4,
+                            ip_addr,
+                            NULL,
+                            err_str)) {
         nas_log->error("Failed to set gateway address - %s\n", err_str);
       }
     } else if (LIBLTE_MME_PDN_TYPE_IPV6 == act_def_eps_bearer_context_req.pdn_addr.pdn_type){
@@ -749,7 +753,11 @@ void nas::parse_attach_accept(uint32_t lcid, unique_byte_buffer_t pdu)
                        act_def_eps_bearer_context_req.pdn_addr.addr[7]);
       // Setup GW
       char *err_str = NULL;
-      if (gw->setup_if_addr(LIBLTE_MME_PDN_TYPE_IPV6, 0, ipv6_if_id, err_str)) {
+      if (gw->setup_if_addr(rrc->get_lcid_for_eps_bearer(act_def_eps_bearer_context_req.eps_bearer_id),
+                            LIBLTE_MME_PDN_TYPE_IPV6,
+                            0,
+                            ipv6_if_id,
+                            err_str)) {
         nas_log->error("Failed to set gateway address - %s\n", err_str);
       }
     } else if (LIBLTE_MME_PDN_TYPE_IPV4V6 == act_def_eps_bearer_context_req.pdn_addr.pdn_type){ 
@@ -794,7 +802,11 @@ void nas::parse_attach_accept(uint32_t lcid, unique_byte_buffer_t pdu)
                        act_def_eps_bearer_context_req.pdn_addr.addr[11]);
       
       char *err_str = NULL;
-      if (gw->setup_if_addr(LIBLTE_MME_PDN_TYPE_IPV4V6, ip_addr, ipv6_if_id, err_str)) {
+      if (gw->setup_if_addr(rrc->get_lcid_for_eps_bearer(act_def_eps_bearer_context_req.eps_bearer_id),
+                            LIBLTE_MME_PDN_TYPE_IPV4V6,
+                            ip_addr,
+                            ipv6_if_id,
+                            err_str)) {
         nas_log->error("Failed to set gateway address - %s\n", err_str);
       }
     } else {

srsue/test/upper/nas_test.cc

@@ -130,6 +130,7 @@ public:
   uint16_t get_mcc() { return mcc; }
   uint16_t get_mnc() { return mnc; }
   void enable_capabilities() {}
+  uint32_t get_lcid_for_eps_bearer(const uint32_t& eps_bearer_id) { return 0; }
 
 private:
   uint32_t last_sdu_len;
@@ -138,7 +139,10 @@ private:
 
 class gw_dummy : public gw_interface_nas, public gw_interface_pdcp
 {
-  error_t setup_if_addr(uint8_t pdn_type, uint32_t ip_addr, uint8_t *ipv6_if_id, char *err_str) { return ERROR_NONE; }
+  error_t setup_if_addr(uint32_t lcid, uint8_t pdn_type, uint32_t ip_addr, uint8_t* ipv6_if_id, char* err_str)
+  {
+    return ERROR_NONE;
+  }
   void    write_pdu(uint32_t lcid, unique_byte_buffer_t pdu) {}
   void    write_pdu_mch(uint32_t lcid, srslte::unique_byte_buffer_t sdu) {}
 };