Try 3 of PAL networking hack

siocgifconf.frag.c

// Works on AIX, but doesn't on i because ifr_name is NOT THE DEVICE NAME ON i!
// On i, ifr_name returns the IP address; if_nameindex returns the real OS/400
// names, but SIOCGIFCONF won't, and thus we need a new way to enumerate...
#elif HAVE_SIOCGIFCONF
    // Adapted from Mono's networking-posix.c.
    packetInfo->InterfaceIndex = 0;

    struct ifconf ifc;
    struct ifreq *ifr;
    int fd;
    fd = socket (AF_INET, SOCK_DGRAM, 0);
    if (fd == -1)
        return 1; // just assume 0, like the getifaddrs case

    // heap alloc instead of stack because there's a lot
    memset (&ifc, 0, sizeof (ifc));
    ifc.ifc_len = 1024;
    ifc.ifc_buf = (char *)malloc (1024);
    if (ioctl (fd, SIOCGIFCONF, &ifc) < 0)
        goto done;

    for (ifr = ifc.ifc_req;
        ifr < (struct ifreq*)((char*)(ifc).ifc_req + (ifc).ifc_len);
        ifr = (struct ifreq*)((char*)(ifr) + sizeof (struct ifreq)))
    {
        in_addr_t ipv4;
        sa_family_t family;
        // ifr_link and fd2 are for getting the IP if it's an AF_LINK,
        // and we can't declare them inside of the switch block.
        struct ifreq ifr_link;
        int fd2, if_idx;

        ipv4 = 0;
        if_idx = if_nametoindex(ifr->ifr_name);
        if (!if_idx) // 0 index is error, so a skippable interface
            continue;

        family = ifr->ifr_addr.sa_family;
        if (!(family == AF_INET || family == AF_LINK))
            continue; // we want interfaces that have IPv4 and what could be v4

        switch (family)
        {
        // HACK: AIX has en* interfaces as AF_LINK; you can't get a sockaddr_in
        // out of them without having to perform this extra step
        case AF_LINK:
            strncpy (ifr_link.ifr_name, ifr->ifr_name, IFNAMSIZ);
            fd2 = socket (AF_INET, SOCK_DGRAM, 0);
            if (fd2 != -1)
                if (ioctl(fd2, SIOCGIFADDR, &ifr_link) >= 0)
                    ipv4 = ((struct sockaddr_in*)&ifr_link.ifr_addr)->sin_addr.s_addr;
            close (fd2);
            break;
        case AF_INET:
            ipv4 = ((struct sockaddr_in*)&ifr->ifr_addr)->sin_addr.s_addr;
            break;
        }

        if (ipv4 ==  pktinfo->ipi_addr.s_addr)
        {
            packetInfo->InterfaceIndex = if_idx;
            goto done;
        }
    }

done:
    free (ifc.ifc_buf);
    close (fd);