SRSENB: Add SIB7 (GERAN neighbor) support

This adds the required missing bits to the eNB config file parser
to enable minimalistic support of parsing SIB7 configuration.

SIB7 contains GERAN (GSM) neighbor cell information, which is important
if you are operating a combined 2G+4G netowrk and want to assist the UEs
to reselect GSM cells once they move out of LTE coverage.

An example SIB7 section looks as follows:

sib7 = {
    t_resel_geran = 1;
    carrier_freqs_info_list =
    (
        {
            cell_resel_prio = 0;
            ncc_permitted = 255;
            q_rx_lev_min = 0;
            thresh_x_high = 7;
            thresh_x_low = 7;

            start_arfcn = 871;
            band_ind = "dcs1800";
            explicit_list_of_arfcns = ( 873, 875, 877 );
        }

    );
};

Closes: #357

srsenb/hdr/enb.h

@@ -173,6 +173,7 @@ private:
   int  parse_sib2(std::string filename, asn1::rrc::sib_type2_s* data);
   int  parse_sib3(std::string filename, asn1::rrc::sib_type3_s* data);
   int  parse_sib4(std::string filename, asn1::rrc::sib_type4_s* data);
+  int  parse_sib7(std::string filename, asn1::rrc::sib_type7_s* data);
   int  parse_sib9(std::string filename, asn1::rrc::sib_type9_s* data);
   int  parse_sib13(std::string filename, asn1::rrc::sib_type13_r9_s* data);
   int  parse_sibs(all_args_t* args, rrc_cfg_t* rrc_cfg, phy_cfg_t* phy_config_common);

srsenb/src/enb_cfg_parser.cc

@@ -129,6 +129,97 @@ int field_intra_black_cell_list::parse(libconfig::Setting& root)
   return 0;
 }
 
+int field_carrier_freqs_info_list::parse(libconfig::Setting& root)
+{
+  data->carrier_freqs_info_list.resize((uint32_t)root.getLength());
+  data->carrier_freqs_info_list_present = data->carrier_freqs_info_list.size() > 0;
+  if (data->carrier_freqs_info_list.size() > ASN1_RRC_MAX_GNFG) {
+    ERROR("CarrierFreqsInfoGERAN cannot have more than %d entries\n", ASN1_RRC_MAX_GNFG);
+    return -1;
+  }
+  for (uint32_t i = 0; i < data->carrier_freqs_info_list.size(); i++) {
+
+    int cell_resel_prio;
+    if (root[i].lookupValue("cell_resel_prio", cell_resel_prio)) {
+      data->carrier_freqs_info_list[i].common_info.cell_resel_prio_present = true;
+      data->carrier_freqs_info_list[i].common_info.cell_resel_prio = cell_resel_prio;
+    }
+
+    int p_max_geran;
+    if (root[i].lookupValue("p_max_geran", p_max_geran)) {
+      data->carrier_freqs_info_list[i].common_info.p_max_geran_present = true;
+      data->carrier_freqs_info_list[i].common_info.p_max_geran = p_max_geran;
+    }
+
+    field_asn1_bitstring_number<asn1::fixed_bitstring<8>, uint8_t> ncc_permitted("ncc_permitted",
+                                    &data->carrier_freqs_info_list[i].common_info.ncc_permitted);
+    if (ncc_permitted.parse(root[i])) {
+      ERROR("Error parsing `ncc_permitted` in carrier_freqs_info_lsit=%d\n", i);
+      return -1;
+    }
+
+    int q_rx_lev_min = 0;
+    if (!root[i].lookupValue("q_rx_lev_min", q_rx_lev_min)) {
+      ERROR("Missing field `q_rx_lev_min` in carrier_freqs_info_list=%d\n", i);
+      return -1;
+    }
+    data->carrier_freqs_info_list[i].common_info.q_rx_lev_min = q_rx_lev_min;
+
+    int thresh_x_high = 0;
+    if (!root[i].lookupValue("thresh_x_high", thresh_x_high)) {
+      ERROR("Missing field `thresh_x_high` in carrier_freqs_info_list=%d\n", i);
+      return -1;
+    }
+    data->carrier_freqs_info_list[i].common_info.thresh_x_high = thresh_x_high;
+
+    int thresh_x_low = 0;
+    if (!root[i].lookupValue("thresh_x_low", thresh_x_low)) {
+      ERROR("Missing field `thresh_x_low` in carrier_freqs_info_list=%d\n", i);
+      return -1;
+    }
+    data->carrier_freqs_info_list[i].common_info.thresh_x_low = thresh_x_low;
+
+    int start_arfcn = 0;
+    if (root[i].lookupValue("start_arfcn", start_arfcn)) {
+      data->carrier_freqs_info_list[i].carrier_freqs.start_arfcn = start_arfcn;
+    }
+
+    field_asn1_enum_str<asn1::rrc::band_ind_geran_e> band_ind("band_ind",
+                                        &data->carrier_freqs_info_list[i].carrier_freqs.band_ind);
+    if (band_ind.parse(root[i])) {
+      ERROR("Error parsing `band_ind` in carrier_freqs_info_list=%d\n", i);
+      return -1;
+    }
+
+    data->carrier_freqs_info_list[i].carrier_freqs.following_arfcns.set_explicit_list_of_arfcns();
+
+    explicit_list_of_arfcns_l &exp_l =
+	      data->carrier_freqs_info_list[i].carrier_freqs.following_arfcns.explicit_list_of_arfcns();
+    if (root[i].exists("explicit_list_of_arfcns")) {
+      exp_l.resize((uint32_t)root[i]["explicit_list_of_arfcns"].getLength());
+      if (exp_l.size() < 31) { /* SEQUENCE (SIZE (0..31)) OF ARFCN-ValueGERAN */
+        for (uint32_t j = 0; j < exp_l.size(); j++) {
+          int arfcn = root[i]["explicit_list_of_arfcns"][j];
+	  if (arfcn >= 0 && arfcn <= 1024) {
+            exp_l[j] = (short unsigned int)arfcn;
+          } else {
+            fprintf(stderr, "Invalid ARFCN %d in for carrier_freqs_info_list=%d explicit_list_of_arfcns\n", i, j);
+            return -1;
+          }
+        }
+      } else {
+        fprintf(stderr, "Number of ARFCN in explicit_list_of_arfcns exceeds maximum (%d)\n", 31);
+        return -1;
+      }
+    } else {
+      exp_l.resize(0);
+    }
+
+  }
+  return 0;
+}
+
+
 int enb::parse_sib1(std::string filename, sib_type1_s* data)
 {
   parser::section sib1("sib1");
@@ -483,6 +574,24 @@ int enb::parse_sib4(std::string filename, sib_type4_s* data)
   return parser::parse_section(filename, &sib4);
 }
 
+int enb::parse_sib7(std::string filename, sib_type7_s* data)
+{
+  parser::section sib7("sib7");
+
+  sib7.add_field(new parser::field<uint8>("t_resel_geran", &data->t_resel_geran));
+  // TODO: t_resel_geran_sf
+
+  data->carrier_freqs_info_list_present = true;
+  parser::section geran_neigh("carrier_freqs_info_list");
+  sib7.add_subsection(&geran_neigh);
+
+  bool dummy_bool = false;
+  geran_neigh.set_optional(&dummy_bool);
+  geran_neigh.add_field(new field_carrier_freqs_info_list(data));
+
+  return parser::parse_section(filename, &sib7);
+}
+
 int enb::parse_sib9(std::string filename, sib_type9_s* data)
 {
   parser::section sib9("sib9");
@@ -613,6 +722,7 @@ int enb::parse_sibs(all_args_t* args, rrc_cfg_t* rrc_cfg, phy_cfg_t* phy_config_
   sib_type2_s*     sib2  = &rrc_cfg->sibs[1].set_sib2();
   sib_type3_s*     sib3  = &rrc_cfg->sibs[2].set_sib3();
   sib_type4_s*     sib4  = &rrc_cfg->sibs[3].set_sib4();
+  sib_type7_s*     sib7  = &rrc_cfg->sibs[6].set_sib7();
   sib_type9_s*     sib9  = &rrc_cfg->sibs[8].set_sib9();
   sib_type13_r9_s* sib13 = &rrc_cfg->sibs[12].set_sib13_v920();
 
@@ -686,6 +796,13 @@ int enb::parse_sibs(all_args_t* args, rrc_cfg_t* rrc_cfg, phy_cfg_t* phy_config_
     }
   }
 
+  // Generate SIB7 if defined in mapping info
+  if (sib_is_present(sib1->sched_info_list, sib_type_e::sib_type7)) {
+    if (parse_sib7(args->enb_files.sib_config, sib7)) {
+      return -1;
+    }
+  }
+
   // Generate SIB9 if defined in mapping info
   if (sib_is_present(sib1->sched_info_list, sib_type_e::sib_type9)) {
     if (parse_sib9(args->enb_files.sib_config, sib9)) {

srsenb/src/enb_cfg_parser.h

@@ -79,6 +79,20 @@ private:
   asn1::rrc::sib_type4_s* data;
 };
 
+class field_carrier_freqs_info_list : public parser::field_itf
+{
+public:
+  field_carrier_freqs_info_list(asn1::rrc::sib_type7_s* data_) { data = data_; }
+  ~field_carrier_freqs_info_list(){}
+  int parse(Setting &root);
+  const char* get_name() {
+    return "carrier_freqs_info_list";
+  }
+
+private:
+  asn1::rrc::sib_type7_s* data;
+};
+
 class field_sf_mapping : public parser::field_itf
 {
 public: