[multi-asic] Fixed systemd-sonic-generator for multi-asic (#7954)

Why I did it

systemd-sonic-generator limits multi-asic unit file instances to 10 (single digit instance number 0 - 10). This limitation needs to be removed to handle more than 10 asics.
MAX_NUM_TARGETS and MAX_NUM_INSTALL_LINES limits to 15 which is not sufficient for systems with more than 15 asics.
Inside get_unit_files(), strcmp produce incorrect results due to non null terminated string being compared.

 Added build UT support for systemd-sonic-generator

src/systemd-sonic-generator/.gitignore

@@ -1,4 +1,5 @@
 systemd-sonic-generator
+ssg_test
 debian/*
 !debian/changelog
 !debian/compat

src/systemd-sonic-generator/Makefile

@@ -1,5 +1,9 @@
 CC=gcc
-CFLAGS=-std=gnu99
+CFLAGS=-std=gnu99 -D_GNU_SOURCE
+
+CPP=g++
+CPPFLAGS=-std=c++11 -D_GNU_SOURCE
+LFLAGS=-lpthread -lboost_filesystem -lboost_system -lgtest
 
 BINARY = systemd-sonic-generator
 MAIN_TARGET = $(BINARY)_1.0.0_$(CONFIGURED_ARCH).deb
@@ -20,3 +24,18 @@ install: $(BINARY)
 	mkdir -p $(DESTDIR)/lib/systemd
 	mkdir -p $(DESTDIR)/lib/systemd/system-generators
 	cp ./systemd-sonic-generator $(DESTDIR)/lib/systemd/system-generators
+
+.PHONY: test
+test: ssg_test
+	./ssg_test
+
+ssg_test: ssg-test.cc systemd-sonic-generator.o
+	$(CPP) $(CPPFLAGS) -o $@ $^ $(LFLAGS)
+
+systemd-sonic-generator.o: systemd-sonic-generator.c
+	$(CC) $(CFLAGS) -D_SSG_UNITTEST -o $@ -c $^
+
+clean:
+	rm -f ./systemd-sonic-generator
+	rm -f ./systemd-sonic-generator.o
+	rm -f ./ssg_test

src/systemd-sonic-generator/debian/rules

@@ -8,7 +8,6 @@ PACKAGEVERSION = $(VERSION)
 	dh $@
 
 override_dh_auto_clean:
-override_dh_auto_test:
 override_dh_auto_build:
 override_dh_auto_install:
 	make systemd-sonic-generator

src/systemd-sonic-generator/ssg-test.cc

@@ -0,0 +1,550 @@
+/*------------------------------------------------------------------
+ * ssg-test.cc - systemd-sonic-generator Unit Test
+ *
+ * Initial: Apr 2021
+ *
+ * Copyright (c) 2021 by Cisco Systems, Inc.
+ *------------------------------------------------------------------
+ */
+#include <mutex>
+#include <string>
+#include <sys/stat.h>
+#include <gtest/gtest.h>
+#include <boost/filesystem.hpp>
+#include <boost/format.hpp>
+#include "systemd-sonic-generator.h"
+
+namespace fs = boost::filesystem;
+
+namespace SSGTest {
+#define IS_MULTI_ASIC(x)  ((x) > 1)
+#define IS_SINGLE_ASIC(x) ((x) <= 1)
+#define NUM_UNIT_FILES 6
+
+/*
+ * This test class uses following directory hierarchy for input and output
+ * data for systemd-sonic-generator.
+ *
+ *    tests/ssg-test/   --- Test data directory
+ *             |
+ *             |---generated_services.conf
+ *             |---machine.conf (systemd-sonic-generator fetch platform from here)
+ *             |---systemd/
+ *             |       |--- *.service (Test unit files are copied from
+ *             |                       tests/testfiles/ to here)
+ *             |----test_platform/  (test platform)
+ *             |       |---asic.conf
+ *             |
+ *             |----generator/   (Output Directory)
+ *
+ */
+const std::string TEST_ROOT_DIR = "tests/ssg-test/";
+const std::string TEST_UNIT_FILE_PREFIX = TEST_ROOT_DIR + "systemd/";
+const std::string TEST_ASIC_CONF_FORMAT = TEST_ROOT_DIR + "%s/asic.conf";
+const std::string TEST_MACHINE_CONF = TEST_ROOT_DIR + "machine.conf";
+
+const std::string TEST_PLATFORM_DIR = TEST_ROOT_DIR + "test_platform/";
+const std::string TEST_ASIC_CONF = TEST_PLATFORM_DIR + "asic.conf";
+
+const std::string TEST_OUTPUT_DIR = TEST_ROOT_DIR + "generator/";
+
+const std::string TEST_CONFIG_FILE = TEST_ROOT_DIR + "generated_services.conf";
+
+const std::string TEST_UNIT_FILES = "tests/testfiles/";
+
+/* Input data for generated_services.conf */
+const std::vector<std::string> generated_services = {
+    "multi_inst_a.service",     /* Single instance of a  multi asic service a */
+    "multi_inst_a@.service",    /* Multi-instance of a multi asic service a */
+    "multi_inst_b@.service",    /* Multi-instance of a multi asic service b */
+    "single_inst.service",      /* A single instance service */
+    "test.service",             /* A single instance test service
+                                   to test dependency creation */
+    "test.timer",               /* A timer service */
+};
+
+static std::mutex g_ssg_test_mutex;
+
+class SystemdSonicGeneratorFixture : public testing::Test {
+  protected:
+    /* Save global variables before running tests */
+    virtual void SetUp() {
+        /* one test runs at a time */
+        g_ssg_test_mutex.lock();
+
+        unit_file_prefix_ = g_unit_file_prefix;
+        config_file_ = g_config_file;
+        machine_config_file_ = g_machine_config_file;
+        asic_conf_format_ = g_asic_conf_format;
+    }
+
+    /* Restore global vars */
+    virtual void TearDown() {
+        g_unit_file_prefix = unit_file_prefix_;
+        g_config_file = config_file_;
+        g_machine_config_file = machine_config_file_;
+        g_asic_conf_format = asic_conf_format_;
+
+        g_ssg_test_mutex.unlock();
+    }
+
+  private:
+    const char* unit_file_prefix_;
+    const char* config_file_;
+    const char* machine_config_file_;
+    const char* asic_conf_format_;
+};
+
+/* 
+ * class SsgFunctionTest
+ * Implements functions to execute functional level tests.
+ */
+class SsgFunctionTest : public SystemdSonicGeneratorFixture {
+  protected:
+    /* This function generates the generated_services.conf file */
+    void generate_generated_services_conf() {
+        FILE* fp = fopen(TEST_CONFIG_FILE.c_str(), "w");
+        ASSERT_NE(fp, nullptr);
+        for (std::string str : generated_services) {
+            fputs(str.c_str(), fp);
+            fputs("\n", fp);
+        }
+        fclose(fp);
+    }
+
+    /* copy files from src_dir to dest_dir */
+    void copyfiles(const char* src_dir, const char* dest_dir) {
+        // Iterate through the source directory
+        for (fs::directory_iterator file(src_dir);
+                 file != fs::directory_iterator(); ++file) {
+            try {
+                fs::path current(file->path());
+                if(!fs::is_directory(current)) {
+                    /* Copy file */
+                    fs::copy_file( current, dest_dir / current.filename());
+                }
+            }
+            catch(fs::filesystem_error const & e) {
+                std:: cerr << e.what() << '\n';
+            }
+        }
+    }
+
+    /* Save global variables before running tests */
+    virtual void SetUp() {
+        FILE* fp;
+        SystemdSonicGeneratorFixture::SetUp();
+
+        /* Setup Input and Output directories and files */ 
+        fs::path path{TEST_UNIT_FILE_PREFIX.c_str()};
+        fs::create_directories(path);
+        path = fs::path(TEST_OUTPUT_DIR.c_str());
+        fs::create_directories(path);
+        path = fs::path(TEST_PLATFORM_DIR.c_str());
+        fs::create_directories(path);
+        fp = fopen(TEST_MACHINE_CONF.c_str(), "w");
+        ASSERT_NE(fp, nullptr);
+        fputs("onie_platform=test_platform", fp);
+        fclose(fp);
+        generate_generated_services_conf();
+        copyfiles(TEST_UNIT_FILES.c_str(), TEST_UNIT_FILE_PREFIX.c_str());
+    }
+
+    /* Restore global vars */
+    virtual void TearDown() {
+        /* Delete ssg_test directory */
+        EXPECT_TRUE(fs::exists(TEST_ROOT_DIR.c_str()));
+        fs::path path{TEST_ROOT_DIR.c_str()};
+        fs::remove_all(path);
+
+        SystemdSonicGeneratorFixture::TearDown();
+    }
+
+  private:
+};
+
+/* 
+ * class SsgMainTest
+ * Implements functions to test ssg_main routine.
+ */
+class SsgMainTest : public SsgFunctionTest {
+  protected:
+    /* Retrun true if string belongs to a multi instance service */
+    bool is_multi_instance(const std::string str) {
+        return (str.find("@") != std::string::npos) ? true : false;
+    }
+
+    /* Returns true if it is a timer service */
+    bool is_timer_service(const std::string str) {
+        return (str.find(".timer") != std::string::npos) ? true : false;
+    }
+
+    /* Find a string in a file */
+    bool find_string_in_file(std::string str,
+                             std::string file_name,
+                             int num_asics) {
+        bool found = false;
+            std::string line;
+
+            std::ifstream file(TEST_UNIT_FILE_PREFIX + file_name);
+            while (getline(file, line) && !found) {
+                if (str == line) {
+                    found = true;
+                }
+            }
+        return found;
+    }
+
+    /* This function validates if a given dependency list for an unit file
+     * exists in the unit file as per expected_result. The items in the list
+     * should exist if expected_result is true.
+     */
+    void validate_output_dependency_list(std::vector<std::string> strs,
+                              std::string target,
+                              bool expected_result,
+                              int num_asics) {
+        for (std::string str : strs) {
+            bool finished = false;
+            for (int i = 0 ; i < num_asics && !finished; ++i) {
+                auto str_t = str;
+                if (is_multi_instance(str)) {
+                    /* insert instance id in string */
+                    str_t  = (boost::format{str} % i).str();
+                } else {
+                    /* Run once for single instance */
+                    finished = true;
+                }
+                EXPECT_EQ(find_string_in_file(str_t, target, num_asics),
+                        expected_result)
+                        << "Error validating " + str_t + " in " + target;
+            }
+        }
+    }
+
+    /* This function validates if unit file paths in the provided
+     * list strs exists or not as per expected_result. The unit files
+     * should exist if expected_result is true.
+     */
+    void validate_output_unit_files(std::vector<std::string> strs,
+                              std::string target,
+                              bool expected_result,
+                              int num_asics) {
+        for (std::string str : strs) {
+            bool finished = false;
+            for (int i = 0 ; i < num_asics && !finished; ++i) {
+                auto str_t = str;
+                if (is_multi_instance(str)) {
+                    /* insert instance id in string */
+                    str_t  = (boost::format{str} % i).str();
+                } else {
+                    /* Run once for single instance */
+                    finished = true;
+                }
+                fs::path path{TEST_OUTPUT_DIR + target + "/" + str_t};
+                EXPECT_EQ(fs::exists(path), expected_result)
+                    << "Failed validation: " << path;
+            }
+        }
+    }
+
+    /*
+     * This function validates the generated dependencies in a Unit File.
+     */
+    void validate_depedency_in_unit_file(int num_asics) {
+        std::string test_service = "test.service";
+
+        /* Validate Unit file dependency creation for multi instance
+         * services. These entries should be present for multi asic 
+         * system but not present for single asic system.
+         */
+        validate_output_dependency_list(multi_asic_dependency_list,
+            test_service, IS_MULTI_ASIC(num_asics), num_asics);
+
+        /* Validate Unit file dependency creation for single instance
+         * services. These entries should not be present for multi asic
+         * system but present for single asic system.
+         */
+        validate_output_dependency_list(single_asic_dependency_list,
+            test_service, IS_SINGLE_ASIC(num_asics), num_asics);
+
+        /* Validate Unit file dependency creation for single instance
+         * common services. These entries should not be present for multi
+         * and single asic system.
+         */
+        validate_output_dependency_list(common_dependency_list,
+            test_service, true, num_asics);
+    }
+
+    /*
+     * This function validates the list of generated Service Unit Files.
+     */
+    void validate_service_file_generated_list(int num_asics) {
+        std::string test_target = "multi-user.target.wants";
+        validate_output_unit_files(multi_asic_service_list,
+            test_target, IS_MULTI_ASIC(num_asics), num_asics);
+        validate_output_unit_files(single_asic_service_list,
+            test_target, IS_SINGLE_ASIC(num_asics), num_asics);
+        validate_output_unit_files(common_service_list,
+            test_target, true, num_asics);
+    }
+
+    /* ssg_main test routine.
+     * input: num_asics    number of asics
+     */
+    void ssg_main_test(int num_asics) {
+        FILE* fp;
+        std::vector<char*> argv_;
+        std::vector<std::string> arguments = {
+                    "ssg_main",
+                    TEST_OUTPUT_DIR.c_str()
+                };
+        std::string num_asic_str = "NUM_ASIC=" + std::to_string(num_asics);
+
+        std::string unit_file_path = fs::current_path().string() + "/" +TEST_UNIT_FILE_PREFIX;
+        g_unit_file_prefix = unit_file_path.c_str();
+        g_config_file = TEST_CONFIG_FILE.c_str();
+        g_machine_config_file = TEST_MACHINE_CONF.c_str();
+        g_asic_conf_format = TEST_ASIC_CONF_FORMAT.c_str();
+
+        /* Set NUM_ASIC value in asic.conf */
+        fp = fopen(TEST_ASIC_CONF.c_str(), "w");
+        ASSERT_NE(fp, nullptr);
+        fputs(num_asic_str.c_str(), fp);
+        fclose(fp);
+
+        /* Create argv list for ssg_main. */
+        for (const auto& arg : arguments) {
+            argv_.push_back((char*)arg.data());
+        }
+        argv_.push_back(nullptr);
+
+        /* Call ssg_main */
+        EXPECT_EQ(ssg_main(argv_.size(), argv_.data()), 0);
+
+        /* Validate systemd service template creation. */
+        validate_service_file_generated_list(num_asics);
+
+        /* Validate Test Unit file for dependency creation. */
+        validate_depedency_in_unit_file(num_asics);
+    }
+
+    /* Save global variables before running tests */
+    virtual void SetUp() {
+        SsgFunctionTest::SetUp();
+    }
+
+    /* Restore global vars */
+    virtual void TearDown() {
+        SsgFunctionTest::TearDown();
+    }
+
+
+  private:
+    static const std::vector<std::string> single_asic_service_list;
+    static const std::vector<std::string> multi_asic_service_list;
+    static const std::vector<std::string> common_service_list;
+    static const std::vector<std::string> single_asic_dependency_list;
+    static const std::vector<std::string> multi_asic_dependency_list;
+    static const std::vector<std::string> common_dependency_list;
+};
+
+/*
+ * The following list defines the Service unit files symlinks generated by
+ * Systemd sonic generator for single and multi asic systems. The test case
+ * use these lists to check for presence/absence of unit files based on 
+ * num_asics value.
+ */
+
+/* Systemd service Unit file list for single asic only system */
+const std::vector<std::string>
+SsgMainTest::single_asic_service_list = {
+    "multi_inst_b.service",
+};
+
+/* Systemd service Unit file list for multi asic only system.
+ * %1% is formatter for boost::format API and replaced by asic num.
+ */
+const std::vector<std::string>
+SsgMainTest::multi_asic_service_list = {
+    "multi_inst_a@%1%.service",
+    "multi_inst_b@%1%.service",
+};
+
+/* Common Systemd service Unit file list for single and multi asic system. */
+const std::vector<std::string>
+SsgMainTest::common_service_list = {
+    "multi_inst_a.service",
+    "single_inst.service",
+    "test.service",
+
+};
+
+/*
+ * The following list defines the systemd dependencies in a unit file to be
+ * varified for single and multi asic systems. Based on num_asics and type of
+ * service listed as dependency in Unit file, systemd sonic generator modifies
+ * the original unit file, if required, for multi asic system.
+ * For example: if test.service file defines a dependency "After=multi_inst_a.service",
+ *              as multi_inst_a.service is a multi instance service,
+ *              for a system with 2 asics, systemd sonic generator shall modify 
+ *              test.service to include following dependency strings:
+ *              "After=multi_inst_a@0.service"
+ *              After=multi_inst_a@1.service"
+ */
+
+/* Systemd service Unit file dependency entries for Single asic system. */
+const std::vector<std::string>
+SsgMainTest::single_asic_dependency_list = {
+    "After=multi_inst_a.service multi_inst_b.service",
+};
+
+/* Systemd service Unit file dependency entries for multi asic system. */
+const std::vector<std::string>
+SsgMainTest::multi_asic_dependency_list = {
+    "After=multi_inst_a@%1%.service",
+    "After=multi_inst_b@%1%.service",
+};
+
+/* Common Systemd service Unit file dependency entries for single and multi asic
+ * systems.
+ */
+const std::vector<std::string>
+SsgMainTest::common_dependency_list = {
+    "Before=single_inst.service",
+};
+
+/* Test get functions for global vasr*/
+TEST_F(SystemdSonicGeneratorFixture, get_global_vars) {
+    EXPECT_EQ(g_unit_file_prefix, nullptr);
+    EXPECT_STREQ(get_unit_file_prefix(), UNIT_FILE_PREFIX);
+    g_unit_file_prefix = TEST_UNIT_FILE_PREFIX.c_str();
+    EXPECT_STREQ(get_unit_file_prefix(), TEST_UNIT_FILE_PREFIX.c_str());
+
+    EXPECT_EQ(g_config_file, nullptr);
+    EXPECT_STREQ(get_config_file(), CONFIG_FILE);
+    g_config_file = TEST_CONFIG_FILE.c_str();
+    EXPECT_STREQ(get_config_file(), TEST_CONFIG_FILE.c_str());
+
+    EXPECT_EQ(g_machine_config_file, nullptr);
+    EXPECT_STREQ(get_machine_config_file(), MACHINE_CONF_FILE);
+    g_machine_config_file = TEST_MACHINE_CONF.c_str();
+    EXPECT_STREQ(get_machine_config_file(), TEST_MACHINE_CONF.c_str());
+
+    EXPECT_EQ(g_asic_conf_format, nullptr);
+    EXPECT_STREQ(get_asic_conf_format(), ASIC_CONF_FORMAT);
+    g_asic_conf_format = TEST_ASIC_CONF_FORMAT.c_str();
+    EXPECT_STREQ(get_asic_conf_format(), TEST_ASIC_CONF_FORMAT.c_str());
+}
+
+TEST_F(SystemdSonicGeneratorFixture, global_vars) {
+    EXPECT_EQ(g_unit_file_prefix, nullptr);
+    EXPECT_STREQ(get_unit_file_prefix(), UNIT_FILE_PREFIX);
+
+    EXPECT_EQ(g_config_file, nullptr);
+    EXPECT_STREQ(get_config_file(), CONFIG_FILE);
+
+    EXPECT_EQ(g_machine_config_file, nullptr);
+    EXPECT_STREQ(get_machine_config_file(), MACHINE_CONF_FILE);
+}
+
+/* TEST machine/unit/config if file is missing */
+TEST_F(SsgFunctionTest, missing_file) {
+    EXPECT_TRUE(fs::exists(TEST_MACHINE_CONF.c_str()));
+    EXPECT_TRUE(fs::exists(TEST_UNIT_FILE_PREFIX.c_str()));
+    EXPECT_TRUE(fs::exists(TEST_OUTPUT_DIR.c_str()));
+    EXPECT_TRUE(fs::exists(TEST_PLATFORM_DIR.c_str()));
+}
+
+/* TEST insert_instance_number() */
+TEST_F(SsgFunctionTest, insert_instance_number) {
+    char input[] = "test@.service";
+    for (int i = 0; i <= 100; ++i) {
+        std::string out = "test@" + std::to_string(i) + ".service";
+        char* ret = insert_instance_number(input, i);
+        ASSERT_NE(ret, nullptr);
+        EXPECT_STREQ(ret, out.c_str());
+    }
+}
+
+/* TEST get_num_of_asic() */
+TEST_F(SsgFunctionTest, get_num_of_asic) {
+    FILE* fp;
+
+    g_machine_config_file = TEST_MACHINE_CONF.c_str();
+    g_asic_conf_format = TEST_ASIC_CONF_FORMAT.c_str();
+
+    fp = fopen(TEST_ASIC_CONF.c_str(), "w");
+    ASSERT_NE(fp, nullptr);
+    fputs("NUM_ASIC=1", fp);
+    fclose(fp);
+    EXPECT_EQ(get_num_of_asic(), 1);
+
+    fp = fopen(TEST_ASIC_CONF.c_str(), "w");
+    ASSERT_NE(fp, nullptr);
+    fputs("NUM_ASIC=10", fp);
+    fclose(fp);
+    EXPECT_EQ(get_num_of_asic(), 10);
+
+    fp = fopen(TEST_ASIC_CONF.c_str(), "w");
+    ASSERT_NE(fp, nullptr);
+    fputs("NUM_ASIC=40", fp);
+    fclose(fp);
+    EXPECT_EQ(get_num_of_asic(), 40);
+}
+
+/* TEST get_unit_files()*/
+TEST_F(SsgFunctionTest, get_unit_files) {
+    g_unit_file_prefix = TEST_UNIT_FILE_PREFIX.c_str();
+    g_config_file = TEST_CONFIG_FILE.c_str();
+    char* unit_files[NUM_UNIT_FILES];
+    int num_unit_files = get_unit_files(unit_files);
+    EXPECT_EQ(num_unit_files, NUM_UNIT_FILES);
+    for (std::string service : generated_services) {
+        bool found = false;
+        for (auto& unit_file : unit_files) {
+            if(unit_file == service) {
+                found = true;
+                break;
+            }
+        }
+        EXPECT_TRUE(found) << "unit file not found: " << service;
+    }
+}
+
+/* TEST ssg_main() argv error */
+TEST_F(SsgMainTest, ssg_main_argv) {
+        FILE* fp;
+        std::vector<char*> argv_;
+        std::vector<std::string> arguments = {
+                    "ssg_main",
+                };
+
+        /* Create argv list for ssg_main. */
+        for (const auto& arg : arguments) {
+            argv_.push_back((char*)arg.data());
+        }
+
+        /* Call ssg_main */
+        EXPECT_EQ(ssg_main(argv_.size(), argv_.data()), 1);
+}
+
+/* TEST ssg_main() single asic */
+TEST_F(SsgMainTest, ssg_main_single_npu) {
+    ssg_main_test(1);
+}
+
+/* TEST ssg_main() multi(10) asic */
+TEST_F(SsgMainTest, ssg_main_10_npu) {
+    ssg_main_test(10);
+}
+
+/* TEST ssg_main() multi(40) asic */
+TEST_F(SsgMainTest, ssg_main_40_npu) {
+    ssg_main_test(40);
+}
+}
+
+int main(int argc, char** argv) {
+    testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}

src/systemd-sonic-generator/systemd-sonic-generator.c

@@ -9,14 +9,36 @@
 #include <sys/stat.h>
 #include <linux/limits.h>
 
-#define MAX_NUM_TARGETS 15
+#define MAX_NUM_TARGETS 48
-#define MAX_NUM_INSTALL_LINES 15
+#define MAX_NUM_INSTALL_LINES 48
 #define MAX_NUM_UNITS 128
 #define MAX_BUF_SIZE 512
 
-static const char* UNIT_FILE_PREFIX = "/usr/lib/systemd/system/";
+const char* UNIT_FILE_PREFIX = "/usr/lib/systemd/system/";
-static const char* CONFIG_FILE = "/etc/sonic/generated_services.conf";
+const char* CONFIG_FILE = "/etc/sonic/generated_services.conf";
-static const char* MACHINE_CONF_FILE = "/host/machine.conf";
+const char* MACHINE_CONF_FILE = "/host/machine.conf";
+const char* ASIC_CONF_FORMAT = "/usr/share/sonic/device/%s/asic.conf";
+
+const char* g_unit_file_prefix = NULL;
+const char* get_unit_file_prefix() {
+    return (g_unit_file_prefix) ? g_unit_file_prefix : UNIT_FILE_PREFIX;
+}
+
+const char* g_config_file = NULL;
+const char* get_config_file() {
+    return (g_config_file) ? g_config_file : CONFIG_FILE;
+}
+
+const char* g_machine_config_file = NULL;
+const char* get_machine_config_file() {
+    return (g_machine_config_file) ? g_machine_config_file : MACHINE_CONF_FILE;
+}
+
+const char* g_asic_conf_format = NULL;
+const char* get_asic_conf_format() {
+    return (g_asic_conf_format) ? g_asic_conf_format : ASIC_CONF_FORMAT;
+}
+
 static int num_asics;
 static char** multi_instance_services;
 static int num_multi_inst;
@@ -128,7 +150,7 @@ static int get_install_targets_from_line(char* target_string, char* install_type
         strcat(final_target, install_type);
 
         free(target);
-        
+
         targets[num_targets + existing_targets] = strdup(final_target);
         num_targets++;
     }
@@ -152,12 +174,12 @@ static void replace_multi_inst_dep(char *src) {
     ssize_t nread;
     bool section_done = false;
     char tmp_file_path[PATH_MAX];
-    
+
     /* Assumes that the service files has 3 sections,
      * in the order: Unit, Service and Install.
-     * Assumes that the timer file has 3 sectiosn, 
+     * Assumes that the timer file has 3 sections,
      * in the order: Unit, Timer and Install.
-     * Read service dependency from Unit and Install 
+     * Read service dependency from Unit and Install
      * sections, replace if dependent on multi instance
      * service.
      */
@@ -166,7 +188,7 @@ static void replace_multi_inst_dep(char *src) {
     fp_tmp = fopen(tmp_file_path, "w");
 
     while ((nread = getline(&line, &len, fp_src)) != -1 ) {
-        if ((strstr(line, "[Service]") != NULL) || 
+        if ((strstr(line, "[Service]") != NULL) ||
             (strstr(line, "[Timer]") != NULL)) {
             section_done = true;
             fputs(line,fp_tmp);
@@ -188,7 +210,7 @@ static void replace_multi_inst_dep(char *src) {
                 } else {
                     service_name = strdup(word);
                     service_name = strtok_r(service_name, ".", &save_ptr2);
-                    type = strtok_r(NULL, " ", &save_ptr2);
+                    type = strtok_r(NULL, "\n", &save_ptr2);
                     if (is_multi_instance_service(word)) {
                         for(i = 0; i < num_asics; i++) {
                             snprintf(buf, MAX_BUF_SIZE, "%s=%s@%d.%s\n",
@@ -215,7 +237,7 @@ static void replace_multi_inst_dep(char *src) {
     rename(tmp_file_path, src);
 }
 
-static int get_install_targets(char* unit_file, char* targets[]) {
+int get_install_targets(char* unit_file, char* targets[]) {
     /***
     Returns install targets for a unit file
 
@@ -234,7 +256,7 @@ static int get_install_targets(char* unit_file, char* targets[]) {
     char *instance_name;
     char *dot_ptr;
 
-    strcpy(file_path, UNIT_FILE_PREFIX);
+    strcpy(file_path, get_unit_file_prefix());
     strcat(file_path, unit_file);
 
     instance_name = strdup(unit_file);
@@ -280,7 +302,7 @@ static int get_install_targets(char* unit_file, char* targets[]) {
 }
 
 
-static int get_unit_files(char* unit_files[]) {
+int get_unit_files(char* unit_files[]) {
     /***
     Reads a list of unit files to be installed from /etc/sonic/generated_services.conf
     ***/
@@ -289,18 +311,19 @@ static int get_unit_files(char* unit_files[]) {
     size_t len = 0;
     ssize_t read;
     char *pos;
+    const char* config_file = get_config_file();
 
-    fp = fopen(CONFIG_FILE, "r");
+    fp = fopen(config_file, "r");
 
     if (fp == NULL) {
-        fprintf(stderr, "Failed to open %s\n", CONFIG_FILE);
+        fprintf(stderr, "Failed to open %s\n", config_file);
         exit(EXIT_FAILURE);
     }
 
     int num_unit_files = 0;
     num_multi_inst = 0;
 
-    multi_instance_services = malloc(MAX_NUM_UNITS * sizeof(char *));
+    multi_instance_services = calloc(MAX_NUM_UNITS, sizeof(char *));
 
     while ((read = getline(&line, &len, fp)) != -1) {
         if (num_unit_files >= MAX_NUM_UNITS) {
@@ -312,7 +335,7 @@ static int get_unit_files(char* unit_files[]) {
         /* Get the multi-instance services */
         pos = strchr(line, '@');
         if (pos != NULL) {
-            multi_instance_services[num_multi_inst] = malloc(strlen(line)*sizeof(char));
+            multi_instance_services[num_multi_inst] = calloc(strlen(line), sizeof(char));
             strncpy(multi_instance_services[num_multi_inst], line, pos-line);
             num_multi_inst++;
         }
@@ -334,40 +357,32 @@ static int get_unit_files(char* unit_files[]) {
 }
 
 
-static char* insert_instance_number(char* unit_file, int instance) {
+char* insert_instance_number(char* unit_file, int instance) {
     /***
     Adds an instance number to a systemd template name
 
     E.g. given unit_file='example@.service', instance=3,
-    returns a pointer to 'example@1.service'
+    returns a pointer to 'example@3.service'
     ***/
-    char* prefix;
-    char* suffix;
-    char* instance_string;
     char* instance_name;
-    char* temp_unit_file;
+    int   ret;
-
+    int   prefix_len;
-    instance_string = malloc(2 * sizeof(char));
+    const char *suffix = strchr(unit_file, '@');
-    snprintf(instance_string, 2, "%d", instance);
+    if (!suffix) {
-
+        fprintf(stderr, "Invalid unit file %s for instance %d\n", unit_file, instance);
-    instance_name = malloc(strlen(unit_file) + 2);
-
-    if (instance_name == NULL) {
-        fprintf(stderr, "Error creating instance %d of %s\n", instance, unit_file);
         return NULL;
     }
 
-    temp_unit_file = strdup(unit_file);
+    /***
-    prefix = strtok(temp_unit_file, "@");
+    suffix is "@.service", set suffix=".service"
-    suffix = strtok(NULL, "@");
+    prefix_len is length of "example@"
-
+    ***/
-    strcpy(instance_name, prefix);
+    prefix_len = ++suffix - unit_file;
-    strcat(instance_name, "@");
+    ret = asprintf(&instance_name, "%.*s%d%s", prefix_len, unit_file, instance, suffix);
-    strcat(instance_name, instance_string);
+    if (ret == -1) {
-    strcat(instance_name, suffix);
+        fprintf(stderr, "Error creating instance %d of %s\n", instance, unit_file);
-
+        return NULL;
-    free(instance_string);
+    }
-    free(temp_unit_file);
 
     return instance_name;
 }
@@ -381,7 +396,7 @@ static int create_symlink(char* unit, char* target, char* install_dir, int insta
     char* unit_instance;
     int r;
 
-    strcpy(src_path, UNIT_FILE_PREFIX);
+    strcpy(src_path, get_unit_file_prefix());
     strcat(src_path, unit);
 
     if (instance < 0) {
@@ -462,7 +477,7 @@ static int install_unit_file(char* unit_file, char* target, char* install_dir) {
 
     assert(unit_file);
     assert(target);
-            
+
 
     if ((num_asics > 1) && strstr(unit_file, "@") != NULL) {
 
@@ -476,16 +491,16 @@ static int install_unit_file(char* unit_file, char* target, char* install_dir) {
             }
 
             r = create_symlink(unit_file, target_instance, install_dir, i);
-            if (r < 0) 
+            if (r < 0)
                 fprintf(stderr, "Error installing %s for target %s\n", unit_file, target_instance);
-            
+
             free(target_instance);
 
-        } 
+        }
     }
     else {
         r = create_symlink(unit_file, target, install_dir, -1);
-        if (r < 0) 
+        if (r < 0)
             fprintf(stderr, "Error installing %s for target %s\n", unit_file, target);
     }
 
@@ -493,7 +508,7 @@ static int install_unit_file(char* unit_file, char* target, char* install_dir) {
 }
 
 
-static int get_num_of_asic() {
+int get_num_of_asic() {
     /***
     Determines if the current platform is single or multi-ASIC
     ***/
@@ -507,11 +522,12 @@ static int get_num_of_asic() {
     char asic_file[512];
     char* str_num_asic;
     int num_asic = 1;
+    const char* machine_config_file = get_machine_config_file();
 
-    fp = fopen(MACHINE_CONF_FILE, "r");
+    fp = fopen(machine_config_file, "r");
 
     if (fp == NULL) {
-        fprintf(stderr, "Failed to open %s\n", MACHINE_CONF_FILE);
+        fprintf(stderr, "Failed to open %s\n", machine_config_file);
         exit(EXIT_FAILURE);
     }
 
@@ -524,10 +540,9 @@ static int get_num_of_asic() {
             break;
         }
     }
-
     fclose(fp);
     if(platform != NULL) {
-        snprintf(asic_file, 512, "/usr/share/sonic/device/%s/asic.conf", platform);
+        snprintf(asic_file, 512, get_asic_conf_format(), platform);
         fp = fopen(asic_file, "r");
         if (fp != NULL) {
             while ((nread = getline(&line, &len, fp)) != -1) {
@@ -549,8 +564,7 @@ static int get_num_of_asic() {
 
 }
 
-
+int ssg_main(int argc, char **argv) {
-int main(int argc, char **argv) {
     char* unit_files[MAX_NUM_UNITS];
     char install_dir[PATH_MAX];
     char* targets[MAX_NUM_TARGETS];
@@ -567,10 +581,8 @@ int main(int argc, char **argv) {
     }
 
     num_asics = get_num_of_asic();
-
     strcpy(install_dir, argv[1]);
     strcat(install_dir, "/");
-
     num_unit_files = get_unit_files(unit_files);
 
     // For each unit file, get the installation targets and install the unit
@@ -610,3 +622,10 @@ int main(int argc, char **argv) {
 
     return 0;
 }
+
+
+#ifndef _SSG_UNITTEST
+int main(int argc, char **argv) {
+   return ssg_main(argc, argv);
+}
+#endif

src/systemd-sonic-generator/systemd-sonic-generator.h

@@ -0,0 +1,35 @@
+/*------------------------------------------------------------------
+ * systemd-sonic-generator.h - Header file
+ *
+ * Initial: Apr 2021
+ *
+ * Copyright (c) 2021 by Cisco Systems, Inc.
+ *------------------------------------------------------------------
+ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* expose global vars for testing purpose */
+extern const char* UNIT_FILE_PREFIX;
+extern const char* CONFIG_FILE;
+extern const char* MACHINE_CONF_FILE;
+extern const char* ASIC_CONF_FORMAT;
+extern const char* g_unit_file_prefix;
+extern const char* g_config_file;
+extern const char* g_machine_config_file;
+extern const char* g_asic_conf_format;
+
+/* C-functions under test */
+extern const char* get_unit_file_prefix();
+extern const char* get_config_file();
+extern const char* get_machine_config_file();
+extern const char* get_asic_conf_format();
+extern char* insert_instance_number(char* unit_file, int instance);
+extern int ssg_main(int argc, char** argv);
+extern int get_num_of_asic();
+extern int get_install_targets(char* unit_file, char* targets[]);
+extern int get_unit_files(char* unit_files[]);
+#ifdef __cplusplus
+}
+#endif

src/systemd-sonic-generator/tests/testfiles/multi_inst_a.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Multi Instance A Test service
+StartLimitIntervalSec=1200
+StartLimitBurst=3
+[Service]
+User=root
+ExecStop=/usr/bin/test.sh stop
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/multi_inst_a@.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Multi INstance A test Service
+
+After=multi_inst_a.service
+StartLimitIntervalSec=1200
+StartLimitBurst=3
+[Service]
+User=root
+ExecStop=/usr/bin/test.sh stop %i
+Restart=always
+RestartSec=30
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/multi_inst_b.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Multi instance b Test service
+
+Requires=multi_inst_a.service
+StartLimitIntervalSec=1200
+StartLimitBurst=3
+[Service]
+User=root
+ExecStop=/usr/bin/test.sh stop
+Restart=always
+RestartSec=30
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/multi_inst_b@.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Multi instance b Test service
+Requires=multi_inst_a@%i.service
+StartLimitIntervalSec=1200
+StartLimitBurst=3
+[Service]
+User=root
+ExecStart=/usr/local/bin/test.sh wait %i
+Restart=always
+RestartSec=30
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/single_inst.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Platform monitor container
+Requires=multi_inst_a.service
+StartLimitIntervalSec=1200
+StartLimitBurst=3
+[Service]
+ExecStart=/usr/bin/test.sh wait
+Restart=always
+RestartSec=30
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/test.service

@@ -0,0 +1,10 @@
+[Unit]
+Description=Multi ASIC Test service
+After=multi_inst_a.service multi_inst_b.service
+Before=single_inst.service
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/bin/test.sh start
+[Install]
+WantedBy=multi-user.target

src/systemd-sonic-generator/tests/testfiles/test.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Test Timer service
+After=multi_inst_b.service
+[Timer]
+OnUnitActiveSec=0 sec
+OnBootSec=3min 30 sec
+Unit=snmp.service
+[Install]
+WantedBy=timers.target
+WantedBy=multi_inst_b.service