srsue/extnas: implement a simple UNIX domain socket server

Unfortunately, the existing networking API (common/network_utils.h)
lacks the UNIX domain socket support, and it turned to be easier
to implement a simple, single client server using Boost.Asio.

The server runs in its own thread with a blocking Tx queue, and
calls a user definted callback on receipt of any data from client.
Multiple client connections are not supported and will be rejected.

.github/workflows/ccpp.yml

@@ -12,7 +12,7 @@ jobs:
       - name: Build srsLTE on x86 Ubuntu 18.04
         run: |
           sudo apt update
-          sudo apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libconfig++-dev libsctp-dev colordiff ninja-build valgrind
+          sudo apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libasio-dev libconfig++-dev libsctp-dev colordiff ninja-build valgrind
           mkdir build && cd build && cmake -DRF_FOUND=True -GNinja .. && ninja && ctest -T memcheck
   x86_ubuntu16_build:
     name: Build and test on x86 Ubuntu 16.04
@@ -25,7 +25,7 @@ jobs:
       - name: Build srsLTE on x86 Ubuntu 16.04
         run: |
           sudo apt update
-          sudo apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libconfig++-dev libsctp-dev colordiff ninja-build valgrind
+          sudo apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libasio-dev libconfig++-dev libsctp-dev colordiff ninja-build valgrind
           mkdir build && cd build && cmake -DRF_FOUND=True -GNinja .. && ninja && ctest -T memcheck
           
   aarch64_ubuntu18_build:
@@ -44,5 +44,5 @@ jobs:
         run: |
           export CTEST_PARALLEL_LEVEL=$(nproc --all)
           apt update
-          apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libconfig++-dev libsctp-dev ninja-build
-          ls -l && pwd && mkdir build && cd build && cmake -DRF_FOUND=True -GNinja .. && ninja
+          apt install -y build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libasio-dev libconfig++-dev libsctp-dev ninja-build
+          ls -l && pwd && mkdir build && cd build && cmake -DRF_FOUND=True -GNinja .. && ninja

.lgtm.yml

@@ -8,6 +8,7 @@ extraction:
          - libmbedtls-dev
          - libpcsclite-dev
          - libboost-program-options-dev
+         - libasio-dev
          - libconfig++-dev
          - libsctp-dev
          - libuhd-dev

.travis.yml

@@ -3,7 +3,7 @@ sudo: required
 
 before_script:
    - sudo apt-get -qq update
-   - sudo apt-get install -qq build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libconfig++-dev libsctp-dev libczmq-dev libpcsclite-dev rapidjson-dev colordiff ninja-build clang-format-8
+   - sudo apt-get install -qq build-essential cmake libfftw3-dev libmbedtls-dev libpcsclite-dev libboost-program-options-dev libasio-dev libconfig++-dev libsctp-dev libczmq-dev libpcsclite-dev rapidjson-dev colordiff ninja-build clang-format-8
 
 language: cpp
         
@@ -28,4 +28,4 @@ script:
  - cmake -DENABLE_5GNR=True -DENABLE_TTCN3=True -DRF_FOUND=True -G Ninja ..
  - ninja
  - ninja test
- - sudo ninja install
+ - sudo ninja install

CMakeLists.txt

@@ -241,6 +241,7 @@ endif(BUILD_STATIC)
 
 set(BOOST_REQUIRED_COMPONENTS
   program_options
+  system
 )
 if(UNIX AND EXISTS "/usr/lib64")
   list(APPEND BOOST_LIBRARYDIR "/usr/lib64") #fedora 64-bit fix

README.md

@@ -119,7 +119,7 @@ Build Instructions
 
 For example, on Ubuntu, one can install the mandatory build dependencies with:
 ```
-sudo apt-get install cmake libfftw3-dev libmbedtls-dev libboost-program-options-dev libconfig++-dev libsctp-dev
+sudo apt-get install cmake libfftw3-dev libmbedtls-dev libboost-program-options-dev libasio-dev libconfig++-dev libsctp-dev
 ```
 or on Fedora:
 ```

cmake/modules/SRSLTEPackage.cmake

@@ -1,7 +1,7 @@
 SET(CPACK_PACKAGE_DESCRIPTION "srsLTE")
 SET(CPACK_PACKAGE_DESCRIPTION_SUMMARY "LTE library for SDR.")
 SET(CPACK_PACKAGE_NAME "srslte")
-SET(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6 (>= 2.3.6), libgcc1 (>= 1:4.1), libboost-dev (>= 1.35)")
+SET(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6 (>= 2.3.6), libgcc1 (>= 1:4.1), libboost-dev (>= 1.35) libasio-dev")
 
 SET(CPACK_PACKAGE_CONTACT "Ismael Gomez ")
 SET(CPACK_PACKAGE_VENDOR "Software Radio Systems Limited")
@@ -45,12 +45,12 @@ ENDIF()
 ########################################################################
 # Setup CPack Debian
 ########################################################################
-SET(CPACK_DEBIAN_PACKAGE_DEPENDS "libboost-dev")
+SET(CPACK_DEBIAN_PACKAGE_DEPENDS "libboost-dev libasio-dev")
 
 ########################################################################
 # Setup CPack RPM
 ########################################################################
-SET(CPACK_RPM_PACKAGE_REQUIRES "boost-devel")
+SET(CPACK_RPM_PACKAGE_REQUIRES "boost-devel libasio-dev")
 
 ########################################################################
 # Setup CPack NSIS

debian/control

@@ -10,6 +10,7 @@ Build-Depends:
     libfftw3-dev,
     libmbedtls-dev,
     libboost-program-options-dev,
+    libasio-dev,
     libconfig++-dev,
     libsctp-dev,
     libuhd-dev,

srsue/hdr/stack/ue_stack_base.h

@@ -48,6 +48,7 @@ typedef struct {
   std::string nas_level;
   std::string usim_level;
   std::string stack_level;
+  std::string extif_level;
 
   int mac_hex_limit;
   int rlc_hex_limit;
@@ -57,6 +58,7 @@ typedef struct {
   int nas_hex_limit;
   int usim_hex_limit;
   int stack_hex_limit;
+  int extif_hex_limit;
 } stack_log_args_t;
 
 typedef struct {

srsue/hdr/stack/ue_stack_lte.h

@@ -153,6 +153,7 @@ private:
   srslte::log_ref usim_log{"USIM"};
   srslte::log_ref nas_log{"NAS"};
   srslte::log_ref pool_log{"POOL"};
+  srslte::log_ref extif_log{"EXTIF"};
 
   // RAT-specific interfaces
   phy_interface_stack_lte* phy = nullptr;

srsue/hdr/stack/upper/nas_ext.h

@@ -35,6 +35,7 @@
 #include "srsue/hdr/stack/upper/nas.h"
 #include "srsue/hdr/stack/upper/nas_common.h"
 #include "srsue/hdr/stack/upper/nas_ext.h"
+#include "srsue/hdr/stack/upper/nas_extif.h"
 #include "srsue/hdr/stack/upper/nas_metrics.h"
 
 using srslte::byte_buffer_t;
@@ -75,6 +76,9 @@ public:
 
 private:
   nas_ext_args_t cfg = {};
+
+  // Interface to an external NAS entity
+  std::unique_ptr<nas_extif_base> iface;
 };
 
 } // namespace srsue

srsue/hdr/stack/upper/nas_extif.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2020 Software Radio Systems Limited
+ * Author: Vadim Yanitskiy <axilirator@gmail.com>
+ * Sponsored by Positive Technologies
+ *
+ * This file is part of srsLTE.
+ *
+ * srsLTE is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * srsLTE is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * A copy of the GNU Affero General Public License can be found in
+ * the LICENSE file in the top-level directory of this distribution
+ * and at http://www.gnu.org/licenses/.
+ *
+ */
+
+#ifndef SRSUE_NAS_EXTIF_H
+#define SRSUE_NAS_EXTIF_H
+
+#include "srslte/common/common.h"
+#include "srslte/common/log.h"
+#include "srslte/common/logmap.h"
+#include "srslte/common/threads.h"
+
+using srslte::byte_buffer_t;
+
+namespace srsue {
+
+// Abstract class for an external interface
+class nas_extif_base : public srslte::thread
+{
+public:
+  using recv_cb_t = std::function<void(const srslte::byte_buffer_t&)>;
+
+  nas_extif_base(recv_cb_t recv_cb_) :
+    recv_cb(std::move(recv_cb_)),
+    srslte::thread("EXTIF"),
+    if_log{"EXTIF"}
+  { /* empty constructor */ };
+
+  // Interface for nas_ext
+  virtual void close(void)                             = 0;
+  virtual int  write(const srslte::byte_buffer_t& pdu) = 0;
+
+protected:
+  static const int IFACE_THREAD_PRIO = 65;
+  virtual void     run_thread()      = 0;
+  virtual void     stop()            = 0;
+  bool             running           = false;
+
+  recv_cb_t       recv_cb;
+  srslte::log_ref if_log;
+};
+
+} // namespace srsue
+
+#endif // SRSUE_NAS_EXTIF_H

srsue/hdr/stack/upper/nas_extif_unix.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2020 Software Radio Systems Limited
+ * Author: Vadim Yanitskiy <axilirator@gmail.com>
+ * Sponsored by Positive Technologies
+ *
+ * This file is part of srsLTE.
+ *
+ * srsLTE is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * srsLTE is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * A copy of the GNU Affero General Public License can be found in
+ * the LICENSE file in the top-level directory of this distribution
+ * and at http://www.gnu.org/licenses/.
+ *
+ */
+
+#ifndef SRSUE_NAS_EXTIF_UNIX_H
+#define SRSUE_NAS_EXTIF_UNIX_H
+
+#include <boost/asio.hpp>
+
+#include "srslte/common/block_queue.h"
+#include "srslte/common/common.h"
+#include "srslte/common/log.h"
+
+#include "srsue/hdr/stack/upper/nas_extif.h"
+
+namespace srsue {
+
+// UNIX domain socket server
+class nas_extif_unix : public nas_extif_base
+{
+public:
+  nas_extif_unix(recv_cb_t cb_, const std::string& sock_path_);
+
+  void close(void) override;
+  int  write(const srslte::byte_buffer_t& pdu) override;
+
+protected:
+  void run_thread(void) override;
+  void stop(void) override;
+
+private:
+  std::unique_ptr<boost::asio::local::stream_protocol::acceptor> acc;
+  std::unique_ptr<boost::asio::local::stream_protocol::socket>   sock;
+  boost::asio::io_context                                        io_ctx;
+  std::string                                                    sock_path;
+
+  srslte::block_queue<srslte::byte_buffer_t> tx_queue;
+  bool                                       has_connection;
+  uint8_t                                    buf[1024];
+
+  void handle_write(void);
+  void handle_read(void);
+  void accept_conn(void);
+};
+
+} // namespace srsue
+
+#endif // SRSUE_NAS_EXTIF_UNIX_H

srsue/src/main.cc

@@ -166,6 +166,8 @@ static int parse_args(all_args_t* args, int argc, char* argv[])
     ("log.usim_hex_limit", bpo::value<int>(&args->stack.log.usim_hex_limit), "USIM log hex dump limit")
     ("log.stack_level", bpo::value<string>(&args->stack.log.stack_level), "Stack log level")
     ("log.stack_hex_limit", bpo::value<int>(&args->stack.log.stack_hex_limit), "Stack log hex dump limit")
+    ("log.extif_level", bpo::value<string>(&args->stack.log.extif_level), "External interface log level")
+    ("log.extif_hex_limit", bpo::value<int>(&args->stack.log.extif_hex_limit), "External interface log hex dump limit")
 
     ("log.all_level", bpo::value<string>(&args->log.all_level)->default_value("info"), "ALL log level")
     ("log.all_hex_limit", bpo::value<int>(&args->log.all_hex_limit)->default_value(32), "ALL log hex dump limit")
@@ -535,6 +537,9 @@ static int parse_args(all_args_t* args, int argc, char* argv[])
     if (!vm.count("log.stack_level")) {
       args->stack.log.stack_level = args->log.all_level;
     }
+    if (!vm.count("log.extif_level")) {
+      args->stack.log.extif_level = args->log.all_level;
+    }
   }
 
   // Apply all_hex_limit to any unset layers
@@ -566,6 +571,9 @@ static int parse_args(all_args_t* args, int argc, char* argv[])
     if (!vm.count("log.stack_hex_limit")) {
       args->stack.log.stack_hex_limit = args->log.all_hex_limit;
     }
+    if (!vm.count("log.extif_hex_limit")) {
+      args->stack.log.extif_hex_limit = args->log.all_hex_limit;
+    }
   }
 
   // Set sync queue capacity to 1 for ZMQ

srsue/src/stack/ue_stack_lte.cc

@@ -102,6 +102,8 @@ int ue_stack_lte::init(const stack_args_t& args_, srslte::logger* logger_)
   usim_log->set_hex_limit(args.log.usim_hex_limit);
   nas_log->set_level(args.log.nas_level);
   nas_log->set_hex_limit(args.log.nas_hex_limit);
+  extif_log->set_level(args.log.extif_level);
+  extif_log->set_hex_limit(args.log.extif_hex_limit);
 
   // Should we use the built-in NAS implementation
   // TODO: or provide an external interface (RRCTL)?

srsue/src/stack/upper/CMakeLists.txt

@@ -18,7 +18,7 @@
 # and at http://www.gnu.org/licenses/.
 #
 
-set(SOURCES gw.cc nas.cc nas_ext.cc usim_base.cc usim.cc tft_packet_filter.cc)
+set(SOURCES gw.cc nas.cc nas_ext.cc nas_extif.cc usim_base.cc usim.cc tft_packet_filter.cc)
 
 if(HAVE_PCSC)
   list(APPEND SOURCES "pcsc_usim.cc")

srsue/src/stack/upper/nas_ext.cc

@@ -32,6 +32,7 @@
 #include "srsue/hdr/stack/upper/nas.h"
 #include "srsue/hdr/stack/upper/nas_common.h"
 #include "srsue/hdr/stack/upper/nas_ext.h"
+#include "srsue/hdr/stack/upper/nas_extif_unix.h"
 #include "srsue/hdr/stack/upper/nas_metrics.h"
 
 using namespace srslte;
@@ -44,8 +45,12 @@ void nas_ext::init(usim_interface_nas* usim_, rrc_interface_nas* rrc_, gw_interf
   rrc  = rrc_;
   gw   = gw_;
 
-  // TODO: parse the configuration
-  // TODO: init the UNIX domain socket
+  auto rx_cb = [this](const srslte::byte_buffer_t& pdu) {
+    // TODO: parse received payload
+  };
+
+  std::unique_ptr<nas_extif_unix> iface_(new nas_extif_unix(rx_cb, cfg.sock_path));
+  iface = std::move(iface_);
 }
 
 void nas_ext::get_metrics(nas_metrics_t* m)
@@ -57,7 +62,9 @@ void nas_ext::get_metrics(nas_metrics_t* m)
 
 void nas_ext::stop()
 {
-  // TODO: close the UNIX domain socket connection
+  // Close the UNIX domain socket connection
+  iface->close();
+  iface.release();
 }
 
 /*******************************************************************************

srsue/src/stack/upper/nas_extif.cc

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2020 Software Radio Systems Limited
+ * Author: Vadim Yanitskiy <axilirator@gmail.com>
+ * Sponsored by Positive Technologies
+ *
+ * This file is part of srsLTE.
+ *
+ * srsLTE is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * srsLTE is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * A copy of the GNU Affero General Public License can be found in
+ * the LICENSE file in the top-level directory of this distribution
+ * and at http://www.gnu.org/licenses/.
+ *
+ */
+
+#include "srslte/common/common.h"
+#include "srslte/common/log.h"
+
+#include "srsue/hdr/stack/upper/nas_extif_unix.h"
+
+using namespace boost::asio::local;
+
+namespace srsue {
+
+nas_extif_unix::nas_extif_unix(recv_cb_t cb_, const std::string& sock_path_) :
+  nas_extif_base(cb_), sock_path(sock_path_), has_connection(false)
+{
+  if_log->info("Init external NAS interface at '%s'\n", sock_path.c_str());
+
+  // Remove previous binding if present
+  unlink(sock_path.c_str());
+
+  // Set up a UNIX domain socket
+  stream_protocol::endpoint  ep(sock_path);
+  stream_protocol::socket*   sock_ = new stream_protocol::socket(io_ctx);
+  stream_protocol::acceptor* acc_  = new stream_protocol::acceptor(io_ctx, ep);
+
+  // Move ownership to this->acc
+  std::unique_ptr<stream_protocol::acceptor> acc_ptr(acc_);
+  acc = std::move(acc_ptr);
+
+  // Move ownership to this->sock
+  std::unique_ptr<stream_protocol::socket> sock_ptr(sock_);
+  sock = std::move(sock_ptr);
+
+  // Welcome the first connection
+  accept_conn();
+
+  if_log->info("Starting the server...\n");
+  start(IFACE_THREAD_PRIO);
+};
+
+void nas_extif_unix::handle_write(void)
+{
+  srslte::byte_buffer_t pdu;
+
+  if (not tx_queue.try_pop(&pdu))
+    return;
+
+  boost::asio::async_write(*sock, boost::asio::buffer(pdu.msg, pdu.N_bytes),
+      [this](boost::system::error_code ec, std::size_t len)
+      {
+        if (!ec) {
+          if_log->info("Tx %zu bytes to external NAS interface\n", len);
+        } else {
+          if_log->warning("External NAS write() handler got error (ec=%d)\n", ec.value());
+        }
+
+        // Keep writing unless the queue is empty
+        handle_write();
+      });
+}
+
+void nas_extif_unix::handle_read(void)
+{
+  sock->async_read_some(boost::asio::buffer(buf),
+      [this](boost::system::error_code ec, std::size_t len)
+      {
+        if (!ec) {
+          if_log->info("Rx %zu bytes from external NAS interface\n", len);
+
+          // Invoke the Rx callback
+          srslte::byte_buffer_t pdu;
+          pdu.append_bytes(buf, len);
+          recv_cb(pdu);
+
+          // Keep reading
+          handle_read();
+        } else {
+          if_log->info("External NAS interface has lost connection\n");
+          has_connection = false;
+          sock->release();
+        }
+      });
+}
+
+void nas_extif_unix::accept_conn(void)
+{
+  acc->async_accept(
+      [this](boost::system::error_code ec, stream_protocol::socket sock_)
+      {
+        if (!ec) {
+          if (!has_connection) {
+            if_log->info("Accepted connection on external NAS interface\n");
+            *sock = std::move(sock_);
+            has_connection = true;
+            handle_read();
+          } else {
+            if_log->warning("NAS interface already has an active connection, rejecting...\n");
+            boost::asio::write(sock_, boost::asio::buffer("REJECT"));
+          }
+        } else {
+          if_log->warning("External NAS connection handler got error (ec=%d)\n", ec.value());
+        }
+
+        // Keep waiting for a new connection
+        accept_conn();
+      });
+}
+
+void nas_extif_unix::run_thread(void)
+{
+  // This is a blocking call
+  io_ctx.run();
+}
+
+void nas_extif_unix::stop(void)
+{
+  io_ctx.stop();
+  wait_thread_finish();
+}
+
+void nas_extif_unix::close(void)
+{
+  stop();
+}
+
+int nas_extif_unix::write(const srslte::byte_buffer_t& pdu)
+{
+  if (!has_connection) {
+    if_log->error("External NAS entity is not connected\n");
+    return -EIO;
+  }
+
+  tx_queue.push(pdu);
+  handle_write();
+  return 0;
+}
+
+} // namespace srsue