inet_ntop反复循环IP

Question

I'm trying to build a tool to gather information about IP addresses based on domain names. I've been using inet_ntop to achieve this and is generally working quite well for most domains. When I try it on sites like google.com or amazon.com the same IP address seems to get printed repeatedly.

Example Output: Host: google.com IPv4: 54.239.17.6 IPv4: 54.239.17.6 IPv4: 54.239.17.6 IPv4: 54.239.17.6 IPv4: 54.239.17.6 IPv4: 54.239.17.6 ....

I was wondering if anyone has experienced this, am I doing something wrong or is this something to do with how the sites are configured.

error = getaddrinfo(domain, "80", &host_info, &host_list);
        // if error exists exit gracefully
        if(error != 0)
        {
            print_conn_err(error);
            return EXIT_FAILURE;
        }
        // print the domain string array
        printf("Host: %s\n", domain);
        // print IP addresses relating to domain name
        printf("IP Address(s):\n");
            for(result = host_list; result != NULL; result = host_list->ai_next)
        {
            void * address;
            char * ip_version;
            // if result is IPv4 address
            if(result->ai_family == AF_INET)
            {
                struct sockaddr_in * ipv4 = (struct sockaddr_in *)result->ai_addr;
                address = &(ipv4->sin_addr);
                ip_version = "IPv4";
            }
            else if(result->ai_family == AF_INET6)
            {
                struct sockaddr_in6 * ipv6 = (struct sockaddr_in6 *)result->ai_addr;
                address = &(ipv6->sin6_addr);
                ip_version = "IPv6";
            }
            else
            {
                printf("%s", "Not a valid IP addresses \n.");
                return EXIT_FAILURE;
            }
            // convert the IP to a string and print it:
            inet_ntop(result->ai_family, address, ip_address, sizeof ip_address);
            printf("  %s: %s\n", ip_version, ip_address);
        }
        freeaddrinfo(result);

One idea I thought of was to check the current IP with the previous IP and break the loop. This seems like quite a hacky solution though.

Answer 1

There's a bug in your code causing this.

for(result = host_list; result != NULL; result = host_list->ai_next)

needs to be

for(result = host_list; result != NULL; result = result->ai_next)

Your freeaddrinfo(result) also must be changed to freeaddrinfo(host_list)