get IP address(es), gateway(s) and metric of all currently enabled network interfaces on windows

getip.c

#define _WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#include <Windows.h>
#include <stdio.h>

#pragma comment(lib, "iphlpapi.lib")
#pragma comment(lib, "Ws2_32.lib")

#define BUFFER_SIZE 15000
#define RETRIES 3

static const char *printAddress(SOCKET_ADDRESS *in)
{
    /* BUG this returns static string, is not re-entrant, and assumes printing SOCKET_ADDRESS is ipv4 */
    static char buf[MAX_PATH];
    return inet_ntop(AF_INET, &((SOCKADDR_IN *)in->lpSockaddr)->sin_addr, buf, sizeof(buf));
}

static const char *printFriendlyName(WCHAR *in)
{
    /* BUG this returns static string, is not re-entrant, and will fail if input string is longer than MAX_PATH
    *  however it's sufficient for demo purposes */
    static char buf[MAX_PATH];
    memset(buf, 0, sizeof(buf));
    WideCharToMultiByte(CP_UTF8, 0, in, -1, buf, MAX_PATH, NULL, NULL);

    return buf;
}

int listInterfaces(void)
{
    ULONG flags = GAA_FLAG_INCLUDE_PREFIX | GAA_FLAG_INCLUDE_GATEWAYS, family = AF_INET;
    PIP_ADAPTER_ADDRESSES addrs = NULL;
    ULONG bufsiz = BUFFER_SIZE;
    DWORD rv = 0;
    int i = 0;

    PIP_ADAPTER_ADDRESSES addr = NULL;
    PIP_ADAPTER_GATEWAY_ADDRESS gateway = NULL;
    PIP_ADAPTER_UNICAST_ADDRESS unicast = NULL;

    do {
        addrs = (IP_ADAPTER_ADDRESSES *)malloc(bufsiz);
        /* all broken */
        if (addrs == NULL)
            return -1;

        /* actually get all adapters info */
        rv = GetAdaptersAddresses(family, flags, NULL, addrs, &bufsiz);

        if (rv == ERROR_BUFFER_OVERFLOW) {
            free(addrs);
            addrs = NULL;
            /* try to increase buffer by 2x */
            bufsiz += BUFFER_SIZE;
        } else
            break;
    } while ((rv == ERROR_BUFFER_OVERFLOW) && (++i < RETRIES));

    /* walk the returned structure */
    addr = addrs;
    while (addr) {
        /* skip useless interfaces: not running/up, no gateway, no ip assigned */
        if ((addr->OperStatus != IfOperStatusUp) || !addr->FirstGatewayAddress || !addr->FirstUnicastAddress) {
            addr = addr->Next;
            continue;
        }

        /* pretty print */

        printf("{\n  interface: '%s',\n", printFriendlyName(addr->FriendlyName));
        printf("  metric: %u,\n", addr->Ipv4Metric);
        printf("  gateway: { ");
        gateway = addr->FirstGatewayAddress;
        for (i = 0; gateway != NULL; i++) {
            printf("'%s'", printAddress(&gateway->Address));
            gateway = gateway->Next;
            if (gateway != NULL)
                printf(", ");
            else
                printf(" ");
        }
        printf("},\n");

        printf("  ip: { ");
        unicast = addr->FirstUnicastAddress;
        for (i = 0; unicast != NULL; i++) {
            printf("'%s'", printAddress(&unicast->Address));
            unicast = unicast->Next;
            if (unicast != NULL)
                printf(", ");
            else
                printf(" ");
        }
        printf("},\n");

        printf("  model: '%wS',\n", addr->Description);

        if (addr->PhysicalAddressLength != 0) {
            printf("  mac_address: '");
            for (i = 0; i < (int)addr->PhysicalAddressLength; i++) {
                if (i == (addr->PhysicalAddressLength - 1))
                    printf("%.2X", (int)addr->PhysicalAddress[i]);
                else
                    printf("%.2X:", (int)addr->PhysicalAddress[i]);
            }
            printf("',\n");
        }
        printf("}\n");

        addr = addr->Next;
    }

    return 0;
}

int main(int argc, char **argv)
{
    SetConsoleOutputCP(65001);
    listInterfaces();
}

output.txt

{
  interface: 'イーサネット',
  metric: 25,
  gateway: { '192.168.14.1' },
  ip: { '192.168.14.88' },
  model: 'Intel(R) 82574L Gigabit Network Connection',
  mac_address: '00:0C:29:XX:XX:XX',
}