C でローカル IP アドレスとサブネット マスクを決定する方法

#include <ifaddrs.h>

void GetNetworkInterfaceInfos() {
  struct ifaddrs *ifaddr;
  int status = getifaddrs(&ifaddr);
  if (status != 0) {
    // Error handling
  }

  for (struct ifaddrs *ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
    if (ifa->ifa_addr == NULL) {
      continue;
    }
    if (ifa->ifa_addr->sa_family == AF_INET) { // IPv4 address
      struct sockaddr_in *in = (struct sockaddr_in *)ifa->ifa_addr;
      printf("IP address: %s\n", inet_ntoa(in->sin_addr));

      // Get subnet mask if available
      if (ifa->ifa_netmask != NULL) {
        struct sockaddr_in *mask = (struct sockaddr_in *)ifa->ifa_netmask;
        printf("Subnet mask: %s\n", inet_ntoa(mask->sin_addr));
      }
    } else if (ifa->ifa_addr->sa_family == AF_INET6) { // IPv6 address
      // Handle IPv6 addresses here
    }
  }

  freeifaddrs(ifaddr);
}

#include <iphlpapi.h>

void GetNetworkInterfaceInfos() {
  PIP_ADAPTER_ADDRESSES adapter_addresses;
  ULONG size = 0;
  GetAdaptersAddresses(AF_UNSPEC, 0, NULL, adapter_addresses, &size);
  adapter_addresses = (PIP_ADAPTER_ADDRESSES)HeapAlloc(GetProcessHeap(), 0, size);
  GetAdaptersAddresses(AF_UNSPEC, 0, NULL, adapter_addresses, &size);

  for (PIP_ADAPTER_ADDRESSES adapter = adapter_addresses; adapter; adapter = adapter->Next) {
    printf("IP address: %s\n", adapter->IpAddressList.IpAddress.String);

    // Get subnet mask if available
    if (adapter->SubnetMaskList.IpAddress.String) {
      printf("Subnet mask: %s\n", adapter->SubnetMaskList.IpAddress.String);
    }
  }

  HeapFree(GetProcessHeap(), 0, adapter_addresses);
}