e3ap: add E3 agent configuration and CMake target

Add the E3AP CMake target, which links the external libe3 library
discovered via pkg-config, and the E3Configuration parser that reads
the link and transport selection from the gNB configuration file and
validates the supported link/transport combinations.

libe3 is kept external and is only required when E3_AGENT is enabled.
Signed-off-by: Andrea Lacava <thecave003@gmail.com>

openair2/CMakeLists.txt

@@ -7,7 +7,7 @@ if(E2_AGENT)
 endif()
 if(E3_AGENT)
   message(STATUS "Add E3 Agent capabilities")
-  #add_subdirectory(E3AP)
+  add_subdirectory(E3AP)
 endif()
 add_subdirectory(F1AP)
 add_subdirectory(LAYER2)

openair2/E3AP/CMakeLists.txt

+# SPDX-License-Identifier: LicenseRef-CSSL-1.0
+
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(CLIBE3 REQUIRED libe3)
+
+if(NOT CLIBE3_FOUND)
+    message(FATAL_ERROR "libe3 not found and required for E3 Agent")
+endif()
+
+message(STATUS "Using for E3AP libe3 version: ${CLIBE3_VERSION}")
+
+include_directories(${CLIBE3_INCLUDE_DIRS})
+
+# Set default encoding format if not specified
+if(NOT DEFINED E3_ENCODING_FORMAT)
+    set(E3_ENCODING_FORMAT "ASN1" CACHE STRING "E3AP encoding format (ASN1 or JSON)")
+endif()
+
+# Validate encoding format
+if(NOT E3_ENCODING_FORMAT MATCHES "^(ASN1|JSON)$")
+    message(FATAL_ERROR "Invalid E3_ENCODING_FORMAT: ${E3_ENCODING_FORMAT}. Must be ASN1 or JSON")
+endif()
+
+message(STATUS "E3AP encoding format: ${E3_ENCODING_FORMAT}")
+
+add_library(e3ap config/e3_config.c)
+
+# target_link_libraries(e3ap PUBLIC OCP_ITTI) # TODO
+
+# Set encoding format compile definitions - both string value and format flags
+target_compile_definitions(e3ap PRIVATE E3_ENCODING_FORMAT="${E3_ENCODING_FORMAT}")
+
+if(E3_ENCODING_FORMAT STREQUAL "ASN1")
+    target_compile_definitions(e3ap PRIVATE E3_ASN1_FORMAT)
+    target_link_libraries(e3ap PUBLIC ${CLIBE3_LIBRARIES})
+elseif(E3_ENCODING_FORMAT STREQUAL "JSON")
+    target_compile_definitions(e3ap PRIVATE E3_JSON_FORMAT)
+    pkg_check_modules(JSON_C REQUIRED json-c)
+    if(NOT JSON_C_FOUND)
+        message(FATAL_ERROR "JSON-C not found and required for JSON encoding, install it with apt-get install libjson-c-dev")
+    endif()
+    target_link_libraries(e3ap PUBLIC ${CLIBE3_LIBRARIES} ${JSON_C_LIBRARIES})
+    target_include_directories(e3ap PUBLIC ${JSON_C_INCLUDE_DIRS})
+endif()

openair2/E3AP/config/e3_config.c

+/*
+ * SPDX-License-Identifier: LicenseRef-CSSL-1.0
+ */
+
+#include "e3_config.h"
+#include "common/utils/LOG/log.h"
+#include "common/config/config_paramdesc.h"
+#include "common/config/config_userapi.h"
+
+#define E3CONFIG_SECTION "E3Configuration"
+
+#define simOpt PARAMFLAG_NOFREE | PARAMFLAG_CMDLINE_NOPREFIXENABLED
+
+/* String-to-integer mappings for link, transport, and encoding.
+ * Values must match the libe3 e3_config_t enum ordering. */
+// clang-format off
+#define E3_LINK_OKSTRINGS      {"zmq",  "posix"}
+#define E3_LINK_VALUES         {E3_LINK_ZMQ, E3_LINK_POSIX}
+#define E3_TRANSPORT_OKSTRINGS {"sctp", "tcp", "ipc"}
+#define E3_TRANSPORT_VALUES    {E3_TRANSPORT_SCTP, E3_TRANSPORT_TCP, E3_TRANSPORT_IPC}
+#define E3_ENCODING_OKSTRINGS  {"asn1", "json"}
+#define E3_ENCODING_VALUES     {E3_ENCODING_ASN1, E3_ENCODING_JSON}
+
+#define E3_LINK_IDX      0
+#define E3_TRANSPORT_IDX 1
+#define E3_ENCODING_IDX  2
+// clang-format on
+
+void e3_readconfig(e3_cmdline_config_t *config)
+{
+  /* Temporary string storage for the string→int parameters. */
+  char *s_link = NULL, *s_transport = NULL, *s_encoding = NULL;
+
+  // clang-format off
+  paramdef_t e3_params[] = {
+    /* optname             helpstr                                   paramflags  value                           defval      type          numelt */
+    {"link",              "Link layer for E3 (zmq|posix)",           simOpt, .strptr  = &s_link,               .defstrval = "posix", TYPE_STRING,  0},
+    {"transport",         "Transport layer for E3 (sctp|tcp|ipc)",   simOpt, .strptr  = &s_transport,          .defstrval = "ipc",   TYPE_STRING,  0},
+    {"encoding",          "Encoding format for E3 (asn1|json)",      simOpt, .strptr  = &s_encoding,           .defstrval = "asn1",  TYPE_STRING,  0},
+    {"setup_port",        "E3 setup port (0=libe3 default)",         simOpt, .u16ptr  = &config->setup_port,      .defuintval = 0, TYPE_UINT16, 0},
+    {"subscriber_port",   "E3 subscriber port (0=libe3 default)",    simOpt, .u16ptr  = &config->subscriber_port, .defuintval = 0, TYPE_UINT16, 0},
+    {"publisher_port",    "E3 publisher port (0=libe3 default)",     simOpt, .u16ptr  = &config->publisher_port,  .defuintval = 0, TYPE_UINT16, 0},
+  };
+
+  checkedparam_t e3_checks[] = {
+    {.s3a = {config_checkstr_assign_integer, E3_LINK_OKSTRINGS,      E3_LINK_VALUES,      2}},
+    {.s3a = {config_checkstr_assign_integer, E3_TRANSPORT_OKSTRINGS, E3_TRANSPORT_VALUES, 3}},
+    {.s3a = {config_checkstr_assign_integer, E3_ENCODING_OKSTRINGS,  E3_ENCODING_VALUES,  2}},
+    {.s5 = {NULL}},
+    {.s5 = {NULL}},
+    {.s5 = {NULL}},
+  };
+  // clang-format on
+
+  config_set_checkfunctions(e3_params, e3_checks, sizeofArray(e3_params));
+
+  int ret = config_get(config_get_if(), e3_params, sizeofArray(e3_params), E3CONFIG_SECTION);
+  AssertFatal(ret >= 0, "E3Configuration: config_get failed\n");
+
+  config->link_layer = config_get_processedint(config_get_if(), &e3_params[E3_LINK_IDX]);
+  config->transport_layer = config_get_processedint(config_get_if(), &e3_params[E3_TRANSPORT_IDX]);
+  config->encoding = config_get_processedint(config_get_if(), &e3_params[E3_ENCODING_IDX]);
+  /* setup_port, subscriber_port, publisher_port written directly by config_get via u16ptr */
+
+  LOG_I(E3AP,
+        "E3 configuration: link=%d transport=%d encoding=%d setup_port=%u subscriber_port=%u publisher_port=%u\n",
+        config->link_layer,
+        config->transport_layer,
+        config->encoding,
+        config->setup_port,
+        config->subscriber_port,
+        config->publisher_port);
+}

openair2/E3AP/config/e3_config.h

+/*
+ * SPDX-License-Identifier: LicenseRef-CSSL-1.0
+ */
+
+#ifndef E3_CONFIG_H
+#define E3_CONFIG_H
+
+#include <stdint.h>
+
+/* link_layer values (match libe3 e3_config_t; -1 = libe3 default) */
+#define E3_LINK_ZMQ 0
+#define E3_LINK_POSIX 1
+
+/* transport_layer values (match libe3 e3_config_t; -1 = libe3 default) */
+#define E3_TRANSPORT_SCTP 0
+#define E3_TRANSPORT_TCP 1
+#define E3_TRANSPORT_IPC 2
+
+/* encoding values (match libe3 e3_config_t; -1 = libe3 default) */
+#define E3_ENCODING_ASN1 0
+#define E3_ENCODING_JSON 1
+
+typedef struct {
+  int link_layer; /* E3_LINK_{ZMQ,POSIX}; -1 = libe3 default */
+  int transport_layer; /* E3_TRANSPORT_{SCTP,TCP,IPC}; -1 = libe3 default */
+  int encoding; /* E3_ENCODING_{ASN1,JSON}; -1 = libe3 default */
+  uint16_t setup_port; /* 0 = libe3 default (9990) */
+  uint16_t subscriber_port; /* 0 = libe3 default */
+  uint16_t publisher_port; /* 0 = libe3 default */
+} e3_cmdline_config_t;
+
+/**
+ * @brief Read E3 configuration from the OAI config file
+ * @param config Pointer to configuration structure to fill
+ */
+void e3_readconfig(e3_cmdline_config_t *config);
+
+#endif // E3_CONFIG_H