examples: add RD lookup client example

examples/cord_lc/Makefile

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+# name of your application
+APPLICATION = cord_lc
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../..
+
+USEMODULE += gnrc_netdev_default
+USEMODULE += auto_init_gnrc_netif
+USEMODULE += gnrc_ipv6_default
+USEMODULE += gnrc_icmpv6_echo
+
+USEMODULE += cord_lc
+
+USEMODULE += shell
+USEMODULE += shell_commands
+USEMODULE += ps
+
+# The default size of GCOAP_PDU_BUF_SIZE can be too small for the response
+# from the RD server. Use a larger value if the client drops response packet
+# from RD server.
+CFLAGS += -DCONFIG_GCOAP_PDU_BUF_SIZE=512
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+DEVELHELP ?= 1
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

examples/cord_lc/Makefile.ci

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+BOARD_INSUFFICIENT_MEMORY := \
+    arduino-duemilanove \
+    arduino-leonardo \
+    arduino-mega2560 \
+    arduino-nano \
+    arduino-uno \
+    atmega1284p \
+    atmega328p \
+    chronos \
+    derfmega128 \
+    hifive1 \
+    hifive1b \
+    i-nucleo-lrwan1 \
+    im880b \
+    mega-xplained \
+    microduino-corerf \
+    msb-430 \
+    msb-430h \
+    nucleo-f030r8 \
+    nucleo-f031k6 \
+    nucleo-f042k6 \
+    nucleo-f303k8 \
+    nucleo-f334r8 \
+    nucleo-l031k6 \
+    nucleo-l053r8 \
+    stm32f030f4-demo \
+    stm32f0discovery \
+    stm32l0538-disco \
+    telosb \
+    waspmote-pro \
+    wsn430-v1_3b \
+    wsn430-v1_4 \
+    z1 \
+    #

examples/cord_lc/README.md

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+CoRE Resource Directory: Lookup Example
+=========================================
+
+This example application demonstrates the usage of RIOT's Resource Directory
+(RD) lookup module, called `cord_lc`. This module supports the lookup of
+resources and endpoints as defined in
+[draft-ietf-core-resource-directory-20](https://tools.ietf.org/html/draft-ietf-core-resource-directory-23).
+The lookup can be done in two modes: a) raw: result of the lookup is returned
+as is. b) pre-parsed: result of the lookup is parsed and only one link is
+returned for each call.
+
+Usage
+=====
+The examples includes a shell command that you can use to interact with a given
+RD, called `cord_lc`. Simply use that shell command without parameters for
+more information on its usage.

examples/cord_lc/cord_lc_cli.c

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+/*
+ * Copyright (C) 2018 HAW Hamburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     examples
+ * @{
+ *
+ * @file
+ * @brief       Shell command for the cord_lc module
+ *
+ * @author      Aiman Ismail <muhammadaimanbin.ismail@haw-hamburg.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "net/cord/config.h"
+#include "net/cord/lc.h"
+#include "net/gcoap.h"
+#include "net/sock/util.h"
+
+static cord_lc_rd_t rd;
+static sock_udp_ep_t remote;
+static char rdbuf[2 * CONFIG_NANOCOAP_URI_MAX] = {0};
+static unsigned rd_initialized = 0;
+
+static int make_sock_ep(sock_udp_ep_t *ep, const char *addr)
+{
+    ep->port = 0;
+    if (sock_udp_str2ep(ep, addr) < 0) {
+        return -1;
+    }
+    /* if netif not specified in addr */
+    if ((ep->netif == SOCK_ADDR_ANY_NETIF) && (gnrc_netif_numof() == 1)) {
+        /* assign the single interface found in gnrc_netif_numof() */
+        ep->netif = (uint16_t)gnrc_netif_iter(NULL)->pid;
+    }
+    ep->family  = AF_INET6;
+    if (ep->port == 0) {
+        ep->port = COAP_PORT;
+    }
+    return 0;
+}
+
+/**
+ * Parses main arguments for filters.
+ * Returns number of parsed filters
+ */
+static void _parse_filters(clif_attr_t *filters, size_t filter_count,
+                           char **argv) {
+    for (unsigned i = 0; i < filter_count; i++) {
+        clif_attr_t *f = &filters[i];
+        f->key = argv[i];
+        char *key_end = memchr(argv[i], '=', strlen(argv[i]));
+        if (!key_end) {
+            f->key_len = strlen(f->key);
+            f->value = NULL;
+            f->value_len = 0;
+        }
+        else {
+            f->key_len = key_end - f->key;
+            f->value = key_end + 1;
+            f->value_len = strlen(f->value);
+        }
+    }
+}
+
+static void _print_lookup_result(struct cord_lc_result *res) {
+    printf("Found resource/endpoint\n");
+    printf("Target: %.*s\n", res->link.target_len, res->link.target);
+    for (unsigned i = 0; i < res->link.attrs_len; i++) {
+        clif_attr_t *p = &(res->link.attrs[i]);
+        printf("'%.*s': '%.*s'\n", p->key_len, p->key, p->value_len, p->value);
+    }
+}
+
+static void _print_usage(void) {
+    puts("usage: cord_lc <server_addr> "
+         "[-r] { resource | endpoint } [key=value]\n"
+         "Options:\n"
+         "      -r get raw result\n"
+         "example: cord_lc [2001:db8:3::dead:beef]:5683 -r resource count=1 page=2\n"
+         "example: cord_lc [2001:db8:3::dead:beef]:5683 endpoint");
+}
+
+int cord_lc_cli_cmd(int argc, char **argv) {
+    char bufpool[1024] = {0};
+    int raw_mode = 0;
+
+    raw_mode = argc > 3 && !strcmp(argv[2], "-r");
+    if (argc < 3 || (raw_mode && argc < 4)) {
+        _print_usage();
+        return -1;
+    }
+
+    if (!rd_initialized) {
+        int ret = make_sock_ep(&remote, argv[1]);
+        if (ret < 0) {
+            printf("error: unable to parse address\n");
+            return -1;
+        }
+        puts("Performing lookup now, this may take a short while...");
+        ret = cord_lc_rd_init(&rd, rdbuf, sizeof(rdbuf), &remote);
+        if (ret < 0) {
+            printf("error initializing RD server %d", ret);
+            return -1;
+        }
+        rd_initialized = 1;
+    }
+
+    /* parse filters */
+    unsigned filter_start = raw_mode ? 4 : 3;
+    size_t filter_count = argc - filter_start;
+    clif_attr_t filter_array[filter_count];
+    if (filter_count > 0) {
+        _parse_filters(filter_array, filter_count, &argv[filter_start]);
+    }
+    cord_lc_filter_t filters = {
+        .array = filter_array,
+        .len = filter_count,
+        .next = NULL,
+    };
+
+    int retval = 0;
+    if (raw_mode) {
+        if (!strcmp(argv[3], "resource")) {
+            retval = cord_lc_raw(&rd, COAP_FORMAT_LINK, CORD_LC_RES, &filters,
+                                 bufpool, sizeof(bufpool));
+        } else if (!strcmp(argv[3], "endpoint")) {
+            retval = cord_lc_raw(&rd, COAP_FORMAT_LINK, CORD_LC_EP, &filters,
+                                 bufpool, sizeof(bufpool));
+        } else {
+            _print_usage();
+            return -1;
+        }
+        if (retval < 0) {
+            printf("Error during lookup %d\n", retval);
+            return -1;
+        }
+        printf("Lookup result:\n%.*s\n", retval, bufpool);
+    } else if (!strcmp(argv[2], "resource")) {
+        cord_lc_res_t resource;
+        clif_attr_t attrs[5];
+        resource.attrs = attrs;
+        resource.max_attrs = ARRAY_SIZE(attrs);
+        retval =
+            cord_lc_res(&rd, &resource, &filters, bufpool, sizeof(bufpool));
+        if (retval < 0) {
+            printf("Error during lookup %d\n", retval);
+            return -1;
+        }
+        _print_lookup_result(&resource);
+    } else if (!strcmp(argv[2], "endpoint")) {
+        cord_lc_ep_t endpoint;
+        clif_attr_t attrs[5];
+        endpoint.attrs = attrs;
+        endpoint.max_attrs = ARRAY_SIZE(attrs);
+        retval = cord_lc_ep(&rd, &endpoint, &filters, bufpool, sizeof(bufpool));
+        if (retval < 0) {
+            printf("Error during lookup %d\n", retval);
+            return -1;
+        }
+        _print_lookup_result(&endpoint);
+    } else {
+        _print_usage();
+        return -1;
+    }
+    return 0;
+}

examples/cord_lc/main.c

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+/*
+ * Copyright (C) 2018 HAW Hamburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     examples
+ * @{
+ *
+ * @file
+ * @brief       CoRE Resource Directory lookup (cord_lc) example
+ *
+ * @author      Aiman Ismail <muhammadaimanbin.ismail@haw-hamburg.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "shell.h"
+#include "msg.h"
+
+#define MAIN_QUEUE_SIZE     (8)
+static msg_t _main_msg_queue[MAIN_QUEUE_SIZE];
+
+extern int cord_lc_cli_cmd(int argc, char **argv);
+
+static const shell_command_t shell_commands[] = {
+    { "cord_lc", "Cord LC example", cord_lc_cli_cmd },
+    { NULL, NULL, NULL },
+};
+
+int main(void)
+{
+    /* we need a message queue for the thread running the shell in order to
+     * receive potentially fast incoming networking packets */
+    msg_init_queue(_main_msg_queue, MAIN_QUEUE_SIZE);
+
+    puts("CoRE RD lookup client example!\n");
+    char line_buf[SHELL_DEFAULT_BUFSIZE];
+    shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE);
+
+    return 0;
+}