dns_client.c

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/*
 * Copyright 2023 Morse Micro
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#include <string.h>
#include "mmosal.h"
#include "mmwlan.h"
#include "mmconfig.h"
 
#include "mmipal.h"
#include "netdb.h"
#include "sys/socket.h"
 
#include "mm_app_common.h"
 
#define DEFAULT_LOOKUP  "www.morsemicro.com"
 
#ifndef DNS_MAX_NAME_LENGTH
#define DNS_MAX_NAME_LENGTH (256)
#endif
 
 
static void dns_lookup(const char *hostname, int ai_family)
{
    /*
     * Hints is optional and can be specified as NULL in getaddrinfo()
     * if you just want to lookup an IP. But if you intend to use the returned data
     * to actually connect (as you would in a real use case), then you need to specify
     * hints so that the correct protocol and ports are returned in addr_list below.
     */
    struct addrinfo hints = { 0 };
    hints.ai_family = ai_family;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
 
    struct addrinfo *addr_list, *cur;
    int ret = getaddrinfo(hostname, NULL, &hints, &addr_list);
    if (ret == 0)
    {
        /*
         * Enumerate all addresses returned.
         * Technically this API can return multiple addresses including combinations
         * of IPv4 and IPv6 addresses (depending on the hints given).
         */
        for (cur = addr_list; cur != NULL; cur = cur->ai_next)
        {
            /*
             * In a typical use case, you can directly use the first element in addr_list
             * to open a socket and connect as shown below:
             *
             * int fd = socket(addr_list->ai_family, addr_list->ai_socktype, addr_list->ai_protocol);
             * connect(fd, addr_list->ai_addr, addr_list->ai_addrlen);
             *
             * However in this example we want to print the list of IP addeesses found
             * so we enumerate the addr_list, and do some conversions to convert and print the
             * IP addresses.
             */
 
            char addr_str[MMIPAL_IPADDR_STR_MAXLEN];
            const char *result = NULL;
 
            if (cur->ai_family == AF_INET)
            {
#if MMIPAL_IPV4_ENABLED
                const struct sockaddr_in *sockaddr = (const struct sockaddr_in *)cur->ai_addr;
                result = inet_ntop(cur->ai_family, &sockaddr->sin_addr,
                                   addr_str, sizeof(addr_str));
#endif
            }
#if MMIPAL_IPV6_ENABLED
            else if (cur->ai_family == AF_INET6)
            {
                const struct sockaddr_in6 *sockaddr = (const struct sockaddr_in6 *)cur->ai_addr;
                result = inet_ntop(cur->ai_family, &sockaddr->sin6_addr,
                                   addr_str, sizeof(addr_str));
            }
#endif
 
            if (result != NULL)
            {
                printf("    %s\n", result);
            }
            else
            {
                printf("Error: Failed to convert IP address to string\n");
            }
        }
        freeaddrinfo(addr_list);
    }
    else
    {
        const char *family_str;
        switch (ai_family)
        {
        case AF_INET:
            family_str = "IPv4";
            break;
 
        case AF_INET6:
            family_str = "IPv6";
            break;
 
        default:
            family_str = "??";
            break;
        }
 
        printf("Could not resolve %s address for hostname %s! (Error code %d)\n",
               family_str, hostname, ret);
    }
}
 
 
void app_init(void)
{
    static char hostname[DNS_MAX_NAME_LENGTH + 1];
 
    printf("\n\nMorse DNS client Demo (Built " __DATE__ " " __TIME__ ")\n\n");
 
    /* Initialize and connect to Wi-Fi, blocks till connected */
    app_wlan_init();
    app_wlan_start();
 
    /* Get the hostname to lookup, if not provided use the default */
    strncpy(hostname, DEFAULT_LOOKUP, sizeof(hostname));
    (void)mmconfig_read_string("dns.lookup", hostname, sizeof(hostname));
 
    printf("Hostname %s resolves to:\n", hostname);
    dns_lookup(hostname, AF_INET);
    dns_lookup(hostname, AF_INET6);
 
    /* Disconnect from Wi-Fi */
    app_wlan_stop();
}