From e2d5c2c21d231166d0b98d3dc9cf8877a5aa79cc Mon Sep 17 00:00:00 2001
From: Vadim Yanitskiy <vyanitskiy@ptsecurity.com>
Date: Sun, 26 Jul 2020 04:49:00 +0700
Subject: [PATCH] srsue/extnas: implement forwarding of paging messages

---
 srsue/hdr/stack/upper/rrctl.h    | 14 ++++++++++++++
 srsue/src/stack/upper/nas_ext.cc |  8 +++++++-
 srsue/src/stack/upper/rrctl.cc   | 15 +++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/srsue/hdr/stack/upper/rrctl.h b/srsue/hdr/stack/upper/rrctl.h
index 7fe343c9a..f97d742e6 100644
--- a/srsue/hdr/stack/upper/rrctl.h
+++ b/srsue/hdr/stack/upper/rrctl.h
@@ -38,6 +38,7 @@ namespace proto {
     RRCTL_PLMN_SELECT,
     RRCTL_CONN_ESTABLISH,
     RRCTL_CONN_RELEASE,
+    RRCTL_PAGING,
   };
 
   enum msg_disc {
@@ -84,10 +85,20 @@ namespace proto {
     uint8_t pdu[0];
   } __attribute__((packed));
 
+  struct __mmec_m_tmsi {
+    uint8_t mmec;
+    uint32_t m_tmsi;
+  } __attribute__((packed));
+
+  struct msg_paging_ind {
+    struct __mmec_m_tmsi ueid;
+  } __attribute__((packed));
+
   struct msg {
     struct msg_hdr hdr;
     union {
       struct msg_data data;
+      struct msg_paging_ind paging_ind;
       struct msg_plmn_search_res plmn_search_res;
       struct msg_plmn_select_req plmn_select_req;
       struct msg_conn_establish_req conn_establish_req;
@@ -129,6 +140,9 @@ void enc_data_ind(srslte::byte_buffer_t& buf,
                   const uint8_t *pdu, size_t pdu_len,
                   uint32_t lcid);
 
+void enc_paging_ind(srslte::byte_buffer_t& buf,
+                    srslte::s_tmsi_t* ue_identity);
+
 } // namespace codec
 
 } // namespace rrctl
diff --git a/srsue/src/stack/upper/nas_ext.cc b/srsue/src/stack/upper/nas_ext.cc
index ea804e7ec..d53e649a7 100644
--- a/srsue/src/stack/upper/nas_ext.cc
+++ b/srsue/src/stack/upper/nas_ext.cc
@@ -225,8 +225,14 @@ void nas_ext::left_rrc_connected() {}
 
 bool nas_ext::paging(srslte::s_tmsi_t* ue_identity)
 {
+  srslte::byte_buffer_t msg;
+
   nas_log->info("Received paging from RRC\n");
-  // TODO: send PAGING.ind to the external entity
+
+  rrctl::codec::enc_paging_ind(msg, ue_identity);
+  iface->write(msg);
+
+  // TODO: what are we supposed to return?
   return false;
 }
 
diff --git a/srsue/src/stack/upper/rrctl.cc b/srsue/src/stack/upper/rrctl.cc
index 1fb7847da..ece15bdf2 100644
--- a/srsue/src/stack/upper/rrctl.cc
+++ b/srsue/src/stack/upper/rrctl.cc
@@ -53,6 +53,9 @@ std::string msg_hdr_desc(proto::msg_type type, proto::msg_disc disc, uint16_t le
   case RRCTL_DATA:
     desc += "Data (PDU)";
     break;
+  case RRCTL_PAGING:
+    desc += "Paging";
+    break;
   default:
     desc += "<UNKNOWN>";
   }
@@ -195,6 +198,18 @@ void enc_data_ind(srslte::byte_buffer_t& buf,
   buf.append_bytes(pdu, pdu_len);
 }
 
+void enc_paging_ind(srslte::byte_buffer_t& buf,
+                    srslte::s_tmsi_t* ue_identity)
+{
+  struct proto::msg_paging_ind msg;
+
+  msg.ueid.m_tmsi = htonl(ue_identity->m_tmsi);
+  msg.ueid.mmec = ue_identity->mmec;
+
+  enc_hdr(buf, proto::RRCTL_PAGING, proto::RRCTL_IND, sizeof(msg));
+  buf.append_bytes((const uint8_t*) &msg, sizeof(msg));
+}
+
 } // namespace codec
 
 } // namespace rrctl