CLI Sample Application

CLI stands for “Command Line Interface”.

This chapter describes the CLI sample application that is part of the Data Plane Development Kit (DPDK). The CLI is a workalike replacement for cmdline library in DPDK and has a simpler programming interface and programming model.

The primary goal of CLI is to allow the developer to create commands quickly and with very little compile or runtime configuration. Using standard Unix* like constructs which are very familar to the developer. Allowing the developer to construct a set of commands for development or deployment of the application.

The CLI design uses a directory like design instead of a single level command line interface. Allowing the developer to use a directory style solution to controlling a DPDK application. The directory style design is nothing new, but it does have some advantages.

One advantage allows the directory path for the command to be part of the information used in executing the command. The next advantage is creating directories to make a hierarchy of commands, plus allowing whole directroy trees to dynamically come and go as required by the developer.

Some of the advantages are:

  • CLI has no global variable other then the single thread variable called this_cli which can only be accessed from the thread which created the CLI instance.
  • CLI supports commands, files, aliases, directories.
    • The alias command is just a string using a simple substitution support for other commands similar to the bash shell like alias commands.
    • Files can be static or dynamic information, can be changed on the fly and saved for later. The file is backed with a simple function callback to allow the developer to update the content or not.
  • Added support for color and cursor movement APIs similar to Pktgen if needed by the developer.
  • It is a work alike replacement for cmdline library. Both cmdline and CLI can be used in the same application if care is taken.
  • Uses a simple fake like directory layout for command and files. Allowing for command hierarchy as path to the command can allow for specific targets to be identified without having to state it on the command line.
  • Has auto-complete for commands, similar to Unix/Linux autocomplete and provides support for command option help as well.
  • Callback functions for commands are simply just argc/argv like functions.
    • The CLI does not convert arguments for the user, it is up to the developer to decode the argv[] values.
    • Most of the arguments converted in the current cmdline are difficult to use or not required as the developer just picks string type and does the conversion himself.
  • Dynamically be able to add and remove commands, directories, files and aliases, does not need to be statically compiled into the application.
  • No weird structures in the code and reduces the line count for testpmd from 12K to 4.5K lines. I convert testpmd to have both CMDLINE and CLI with a command line option.
  • Two methods to parse command lines, first is the standard argc/argv method in the function.
    • The second method is to use a map of strings with simple printf like formatting to detect which command line the user typed.
    • An ID value it returned to the used to indicate which mapping string was found to make the command line to be used in a switch statement.
  • Environment variable support using the env command or using an API.
  • Central help support if needed (optional).

Overview

The CLI sample application is a simple application that demonstrates the use of the command line interface in the DPDK. This application is a readline-like interface that can be used to control a DPDK application.

One of the advantages of CLI over Cmdline is it is dynamic, which means nodes or items can be added and removed on the fly. Which allows adding new directories, file or commands as needed or removing these items at runtime. The CLI has no global modifiable variable as the one global pointer is a thread based variable. Which allows the developer to have multiple CLI commands per thread if needed.

Another advantage is the calling of the backend function to support a command is very familar to developers as it is basically just a argc/argv style command and the developer gets the complete command line.

One other advantage is the use of MAP structures, to help identify commands quickly plus allowing the developer to define new versions of commands and be able to identify these new versions using a simple identifier value. Look at the sample application to see a simple usage.

Another advantage of CLI is how simple it is to add new directroies, files and commands for user development. The basic concept is for the developer to use standard Unix like designs. To add a command a developer needs to add an entry to the cli_tree_t structure and create a function using the following prototype:

int user_cmd(int argc, char **argv);

The argc/argv is exactly like the standard usage in a Unix* system, which allows for using getopt() and other standard functions. The Cmdline structures and text conversions were defined at compile time in most cases. In CLI the routine is passed the argc/argv information to convert these options as needed. The cli variable being a thread Local Storage (TLS) all user routines a CLI routine only need to access the thread variable to eliminate needing a global variable to reference the specific CLI instance and passing the value in the API.

The user can also set environment variables using the env command. These variables are also parsed in the command line a direct substitution is done.

The CLI system also has support for simple files along with alias like commands. These alias commands are fixed strings which are executed instead of a function provided by the developer. If the user has more arguments these are appended to the alias string and processed as if typed on the command line.

Note

The CLI library was designed to be used in production code and the Cmdline was not validated to the same standard as other DPDK libraries. The goal is to provide a production CLI design.

The CLI sample application supports some of the features of the Cmdline library such as, completion, cut/paste and some other special bindings that make configuration and debug faster and easier.

The CLI design uses some very simple VT100 control strings for displaying data and accepting input from the user. Some of the control strings are used to clear the screen or line and position the cursor on a VT100 compatible terminal. The CLI screen code also supports basic color and many other VT100 commands.

The application also shows how the CLI application can be extended to handle a list of commands and user input.

The example presents a simple command prompt DPDK-cli:/> similar to a Unix* shell command along with a directory like file system.

Some of the default commands contained under /sbin directory are:

  • ls: list the current or provided directory files/commands.
  • cd: Change directory command.
  • pwd: print out the current working directory.
  • history: List the current command line history if enabled.
  • more: A simple command to page contents of files.
  • help: display a the help screen.
  • quit: exit the CLI application, also Ctrl-x will exit as well.
  • mkdir: add a directory to the current directory.
  • delay: wait for a given number of microseconds.
  • sleep: wait for a given number of seconds.
  • rm: remove a directory, file or command. Removing a file will delete the data.
  • cls: clear the screen and redisplay the prompt.
  • version: Display the current DPDK version being used.
  • path: display the current search path for executable commands.
  • cmap: Display the current system core and socket information.
  • hugepages: Display the current hugepage information.
  • sizes: a collection system structure and buffer sizes for debugging.
  • copyright: a file containing DPDK copyright information.
  • env: a command show/set/modify the environment variables.

Some example commands under /bin directory are:

  • ll: an alias command to display long ls listing ls -l
  • h: alias command for history
  • hello: a simple Hello World! command.
  • show: has a number of commands using the map feature.

Under the /data directory is:

  • pci: a simple example file for displaying the lspci command in CLI.

Note

To terminate the application, use Ctrl-x or the command quit.

Auto completion

CLI does support auto completion at the file or directory level, meaning the arguments to commands are not expanded as was done in Cmdline code. The CLI auto completion works similar to the standard Unix* system by expanding commands and directory paths. In normal Unix* like commands the user needs to execute the command asking for the help information and CLI uses this method.

Special command features

Using the ‘!’ followed by a number from the history list of commands you can execute that command again. Using the UP/Down arrows the user can quickly find and execute or modify a previous command in history.

The user can also execute host level commands if enabled using the ‘@’ prefix to a command line e.g. @ls or @lspci or ... line is passed to popen or system function to be executed and the output displayed on the console if any output. To disable set CONFIG_RTE_CLI_HOST_COMMANDS=n in configuration file.

Compiling the Application

  1. Go to example directory:
export RTE_SDK=/path/to/rte_sdk
cd ${RTE_SDK}/examples/cli
  1. Set the target (a default target is used if not specified). For example:
    export RTE_TARGET=x86_64-native-linuxapp-gcc

Refer to the *DPDK Getting Started Guide* for possible RTE_TARGET values.
  1. Build the application:
make

Running the Application

To run the application in linuxapp environment, issue the following command:

$ ./build/cli

Note

The example cli application does not require to be run as superuser as it does not startup DPDK by calling rte_eal_init() routine. Which means it also does not use DPDK features except for a few routines not requiring EAL initialization.

Refer to the DPDK Getting Started Guide for general information on running applications and the Environment Abstraction Layer (EAL) options.

Explanation

The following sections provide some explanation of the code.

EAL Initialization and cmdline Start

The first task is the initialization of the Environment Abstraction Layer (EAL), if required for the application.

int
main(int argc, char **argv)
{
    if (cli_create_with_tree(init_tree) ==0) {
        cli_start(NULL, 0); /* NULL is some init message done only once */
                            /* 0 means do not use color themes */
        cli_destroy();
    }
    ...

The cli_start() function returns when the user types Ctrl-x or uses the quit command in this case, the application exits. The cli_create() call takes four arguments and each has a default value if not provided. The API used here is the cli_create_with_tree(), which uses defaults for three of the arguments.

/**
* Create the CLI engine
*
* @param prompt_func
*   Function pointer to call for displaying the prompt.
* @param tree_func
*   The user supplied function to init the tree or can be NULL. If NULL then
*   a default tree is initialized with basic commands.
* @param nb_entries
*   Total number of commands, files, aliases and directories. If 0 then use
*   the default number of nodes. If -1 then unlimited number of nodes.
* @param nb_hist
*   The number of lines to keep in history. If zero then turn off history.
*   If the value is CLI_DEFAULT_HISTORY use CLI_DEFAULT_HIST_LINES
* @return
*   0 on success or -1
*/
int cli_create(cli_prompt_t prompt_func, cli_tree_t tree_func,
                    int nb_entries, uint32_t nb_hist);

The cli_create_with_tree() has only one argument which is the structure to use in order to setup the initial directory structure. Also the wrapper function int cli_create_with_defaults(void) can be used as well.

Consult the cli.h header file for the default values. Also the alias node is a special alias file to allow for aliasing a command to another command.

The tree init routine is defined like:

static struct cli_tree my_tree[] = {
    c_dir("/data"),
    c_file("pci", pci_file, "display lspci information"),
    c_dir("/bin"),
    c_cmd("hello", hello_cmd, "Hello-World!!"),
    c_alias("h", "history", "display history commands"),
    c_alias("ll", "ls -l", "long directory listing alias"),
    c_end()
};

static int
init_tree(void)
{
    /*
     * Root is created already and using system default cmds and dirs, the
     * developer is not required to use the system default cmds/dirs.
     */
    if (cli_default_tree_init())
        return -1;

        /* Using NULL here to start at root directory */
    if (cli_add_tree(NULL, my_tree))
        return -1;

        cli_help_add("Show", show_map, show_help);

        return cli_add_bin_path("/bin");
}

The above structure is used to create the tree structure at initialization time. The struct cli_tree or cli_tree_t typedef can be used to setup a new directory tree or argument the default tree.

The elements are using a set of macros c_dir, c_file, c_cmd, c_alias and c_end. These macros help fill out the cli_tree_t structure for the given type of item.

The developer can create his own tree structure with any commands that are needed and/or call the cli_default_tree_init() routine to get the default structure of commands. If the developer does not wish to call the default CLI routine, then he must call the cli_create_root() function first before adding other nodes. Other nodes can be added and removed at anytime.

CLI Map command support

The CLI command has two types of support to handle arguments normal argc/argv and the map system. As shown above the developer creates a directory tree and attaches a function to a command. The function takes the CLI pointer plus the argc/argv arguments and the developer can just parse the arguments to decode the command arguments. Sometimes you have multiple commands or different versions of a command being handled by a single routine, this is were the map support comes into play.

The map support defines a set of struct cli_map map[]; to help detect the correct command from the user. In the list of cli_map structures a single structure contains two items a developer defined index value and a command strings. The index value is used on the function to identify the specific type of command found in the list. The string is a special printf like string to help identify the command typed by the user. One of the first things todo in the command routine is to call the cli_mapping() function passing in the CLI pointer and the argc/argv values.The two method can be used at the same time.

The cli_mapping() command matches up the special format string with the values in the argc/argv array and returns the developer supplied index value or really the pointer the struct cli_map instance.

Now the developer can use the cli_map.index value in a switch() statement to locate the command the user typed or if not found a return of -1.

Example:

static int
hello_cmd(int argc, char **argv)
{
    int i, opt;

    optind = 1;
    while((opt = getopt(argc, argv, "?")) != -1) {
        switch(opt) {
            case '?': cli_usage(); return 0;
            default:
                break;
        }
    }

    cli_printf("Hello command said: Hello World!! ");
    for(i = 1; i < argc; i++)
        cli_printf("%s ", argv[i]);
    cli_printf("\n");

    return 0;
}

static int
pci_file(struct cli_node *node, char *buff, int len, uint32_t opt)
{
        if (is_file_open(opt)) {
                FILE *f;

                if (node->file_data && (node->fflags & CLI_FREE_DATA))
                        free(node->file_data);

                node->file_data = malloc(32 * 1024);
                if (!node->file_data)
                        return -1;
                node->file_size = 32 * 1024;
                node->fflags = CLI_DATA_RDONLY | CLI_FREE_DATA;

                f = popen("lspci", "r");
                if (!f)
                        return -1;

                node->file_size = fread(node->file_data, 1, node->file_size, f);

                pclose(f);
        return 0;
    }
    return cli_file_handler(node, buff, len, opt);
}

static struct cli_map show_map[] = {
        { 10, "show %P" },
        { 20, "show %P mac %m" },
        { 30, "show %P vlan %d mac %m" },
        { 40, "show %P %|vlan|mac" },
        { -1, NULL }
};

static const char *show_help[] = {
        "show <portlist>",
        "show <portlist> mac <ether_addr>",
        "show <portlist> vlan <vlanid> mac <ether_addr>",
        "show <portlist> [vlan|mac]",
        NULL
};

static int
show_cmd(int argc, char **argv)
{
        struct cli_map *m;
        uint32_t portlist;
        struct ether_addr mac;

        m = cli_mapping(Show_info.map, argc, argv);
        if (!m)
                return -1;

        switch(m->index) {
                case 10:
                        rte_parse_portlist(argv[1], &portlist);
                        cli_printf("   Show Portlist: %08x\n", portlist);
                        break;
                case 20:
                        rte_parse_portlist(argv[1], &portlist);
                        rte_ether_aton(argv[3], &mac);
                        cli_printf("   Show Portlist: %08x, MAC: "
                                        "%02x:%02x:%02x:%02x:%02x:%02x\n",
                                           portlist,
                                           mac.addr_bytes[0],
                                           mac.addr_bytes[1],
                                           mac.addr_bytes[2],
                                           mac.addr_bytes[3],
                                           mac.addr_bytes[4],
                                           mac.addr_bytes[5]);
                        break;
                case 30:
                        rte_parse_portlist(argv[1], &portlist);
                        rte_ether_aton(argv[5], &mac);
                        cli_printf("   Show Portlist: %08x vlan %d MAC: "
                                        "%02x:%02x:%02x:%02x:%02x:%02x\n",
                                           portlist,
                                           atoi(argv[3]),
                                           mac.addr_bytes[0],
                                           mac.addr_bytes[1],
                                           mac.addr_bytes[2],
                                           mac.addr_bytes[3],
                                           mac.addr_bytes[4],
                                           mac.addr_bytes[5]);
                        break;
                case 40:
                        rte_parse_portlist(argv[1], &portlist);
                        rte_ether_aton("1234:4567:8901", &mac);
                        cli_printf("   Show Portlist: %08x %s: ",
                                           portlist, argv[2]);
                        if (argv[2][0] == 'm')
                                cli_printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
                                           mac.addr_bytes[0],
                                           mac.addr_bytes[1],
                                           mac.addr_bytes[2],
                                           mac.addr_bytes[3],
                                           mac.addr_bytes[4],
                                           mac.addr_bytes[5]);
                        else
                                cli_printf("%d\n", 101);
                        break;
                default:
                        cli_help_show_group("Show");
                        return -1;
        }
        return 0;
}

static struct cli_tree my_tree[] = {
        c_dir("/data"),
        c_file("pci",   pci_file,       "display lspci information"),
        c_dir("/bin"),
        c_cmd("show",   show_cmd,       "show mapping options"),
        c_cmd("hello",  hello_cmd,      "Hello-World!!"),
        c_alias("h",    "history",      "display history commands"),
        c_alias("ll",   "ls -l",        "long directory listing alias"),
        c_end()
};

Here is the cli_tree for this example, note it has a lot more commands. The show_cmd or show command is located a number of lines down. This cli_tree creates in the /bin directory a number of commands, which one is the show command. The show command has four different formats if you look at the show_map[].

The user types one of these commands and cli_mapping() attempts to locate the correct entry in the list. You will also notice another structure called pcap_help, which is an array of strings giving a cleaner and longer help description of each of the commands.

These two structure show_map/show_help can be added to the cli_help system to provide help for a command using a simple API.

or we can use the cli_help_show_all() API to show all added help information.

cli_help_show_all(NULL);

The following is from Pktgen source code to add more help to the global help for the system.

cli_help_add("Title", NULL, title_help);
cli_help_add("Page", page_map, page_help);
cli_help_add("Enable", enable_map, enable_help);
cli_help_add("Set", set_map, set_help);
cli_help_add("Range", range_map, range_help);
cli_help_add("Sequence", seq_map, seq_help);
cli_help_add("PCAP", pcap_map, pcap_help);
cli_help_add("Start", start_map, start_help);
cli_help_add("Debug", debug_map, debug_help);
cli_help_add("Misc", misc_map, misc_help);
cli_help_add("Theme", theme_map, theme_help);
cli_help_add("Status", NULL, status_help);

Understanding the CLI system

The command line interface is defined as a fake directory tree with executables, directories and files. The user uses shell like standard commands to move about the directory and execute commands. The CLI is not a powerful as the Bash shell, but has a number of similar concepts.

Our fake directory tree has a ‘/’ or root directory which is created when cli_create() is called along with the default sbin directory. The user starts out at the root directory ‘/’ and is allowed to cd to other directories, which could contain more executables, aliases or directories. The max number of directory levels is limited to the number of nodes given at startup.

The default directory tree starts out as just root (/) and a sbin directory. Also it contains a file called copyright in root, which can be displayed using the default ‘more copyright’ command.

A number of default commands are predefined in the /sbin directory and are defined above. Other bin directories can be added to the system if needed, but a limit of CLI_MAX_BINS is defined in the cli.h header file.

The CLI structure is created at run time adding directories, commands and aliases as needed, which is different from the cmdline interface in DPDK today.

The basic concept for a command is similar to a standard Linux executable, meaning the command when executed it is passed the command line in a argc/argv format to be parsed by the function. The function is attached to a command file in the directory tree and is executed when the user types the name of the function along with it arguments. Some examples of the default commands can be seen in the lib/librte_cli/cli_cmds.c file.