Using AddIpAddress()/DeleteIpAddress() with info from GetAdaptersAddresses() - c

Question

I need to change the IP address and submask of a specific network interface from a C/C++ program. In Windows documentation, I have found that I should use AddIPAddress()/DeleteIpAddress() from the Windows API. However, DeleteIpAddress(), for instance, requires a NTEContext as a parameter. I have found an example that uses GetAdaptersInfo() to get the index of the interface and context. However, the page also explicitly states that:
On Windows XP and later:  Use the GetAdaptersAddresses function instead of GetAdaptersInfo.
But, while GetAdaptersInfo() populates an IP_ADAPTER_INFO struct in which the index/NTEcontext are present, GetAdaptersAddresses() provides an IP_ADAPTER_ADDRESSES struct in which there are no such members.
What should I do with the newer GetAdaptersAddresses() function to get the index/context for interfaces?

Answer 1

Based on https://learn.microsoft.com/en-us/windows/win32/iphlp/managing-network-adapters, you should be able to use the following:
GetAdapterIndex
GetPerAdapterInfo
IP_PER_ADAPTER_INFO_W2KSP1
IP_ADDR_STRING
Something like this should work:
ULONG IfIndex = 0;
/* check error returned */ GetAdapterIndex(AdapterName, &IfIndex);
IP_PER_ADAPTER_INFO/*_W2KSP1?*/ PerAdapterInfo;
ULONG OutBufLen = sizeof(PerAdapterInfo);
/* check error returned */ GetPerAdapterInfo(IfIndex, &PerAdapterInfo, &OutBufLen);
/* check error returned */ DeleteIPAddress(PerAdapterInfo.DnsServerList.Context);
P.S. For older versions of Windows, this might work: https://microsoft.public.vb.winapi.narkive.com/TW7rVsdu/how-to-obtain-ntecontext-for-use-in-deleteipaddress-without-first-calling-addipaddress

Answer 2

This example retrieves the IP_ADAPTER_ADDRESSES structure for the adapters associated with the system and prints some members for each adapter interface.
The following example retrieves the IP address table to determine the interface index for the first adapter, then adds the IP address specified on command line to the first adapter. The IP address that was added is then deleted.
I combined the two programs and modified the code.
It can output network card description, IP address, MAC address and DNS address. Also, it can add the IP address to the first adapter and delete the same address.
Caution:
The DeleteIPAddress() function deletes an IP address previously added using AddIPAddress().
If you just only use AddIPAddress() to add an IP address, after that you need to delete it manually.
This picture shows the IP added, and you can delete the added IP by “edit” on the left side.
Here is the code:
#pragma comment (lib, "Ws2_32.lib")
// Link with Iphlpapi.lib
#pragma comment(lib, "IPHLPAPI.lib")
#include<WinSock2.h>
#include<WS2tcpip.h>
#include<iostream>
#include<IPHlpApi.h>
using namespace std;
#pragma warning(disable:4996)
int main()
{
PIP_ADAPTER_ADDRESSES pAddresses = nullptr;
IP_ADAPTER_DNS_SERVER_ADDRESS* pDnServer = nullptr;
ULONG outBufLen = 0;
DWORD dwRetVal = 10;
char buff[128];
DWORD bufflen = 128;
int i;
PMIB_IPADDRTABLE pIPAddrTable;
DWORD dwSize =128;
UINT iaIPAddress;
UINT imIPMask;
ULONG NTEContext = 0;
ULONG NTEInstance = 0;
LPVOID lpMsgBuf;
pIPAddrTable = (MIB_IPADDRTABLE*)VirtualAlloc(&dwSize, sizeof(PMIB_IPADDRTABLE), MEM_RESERVE, NULL);
pIPAddrTable = (MIB_IPADDRTABLE*)malloc(150 * sizeof(MIB_IPADDRTABLE));
GetAdaptersAddresses(AF_UNSPEC, 0, NULL, pAddresses, &outBufLen);
pAddresses = (IP_ADAPTER_ADDRESSES*)malloc(outBufLen);
if ((dwRetVal = GetAdaptersAddresses(AF_INET, GAA_FLAG_SKIP_ANYCAST, NULL, pAddresses, &outBufLen)) == NO_ERROR) {
while (pAddresses) {
printf("%S, %.2x-%.2x-%.2x-%.2x-%.2x-%.2x: \n",
pAddresses->FriendlyName,
pAddresses->PhysicalAddress[0], pAddresses->PhysicalAddress[1],
pAddresses->PhysicalAddress[2], pAddresses->PhysicalAddress[3],
pAddresses->PhysicalAddress[4], pAddresses->PhysicalAddress[5]);
PIP_ADAPTER_UNICAST_ADDRESS pUnicast = pAddresses->FirstUnicastAddress;
pDnServer = pAddresses->FirstDnsServerAddress;
if (pDnServer)
{
sockaddr_in* sa_in = (sockaddr_in*)pDnServer->Address.lpSockaddr;
printf("DNS:%s\n", inet_ntop(AF_INET, &(sa_in->sin_addr), buff, bufflen));
}
if (pAddresses->OperStatus == IfOperStatusUp)
{
printf("Status: active\n");
}
else
{
printf("Status: deactive\n");
}
for (i = 0; pUnicast != NULL; i++)
{
if (pUnicast->Address.lpSockaddr->sa_family == AF_INET)
{
sockaddr_in* sa_in = (sockaddr_in*)pUnicast->Address.lpSockaddr;
printf("IPV4 Unicast Address:%s\n", inet_ntop(AF_INET, &(sa_in->sin_addr), buff, bufflen));
}
else if (pUnicast->Address.lpSockaddr->sa_family == AF_INET6)
{
sockaddr_in6* sa_in6 = (sockaddr_in6*)pUnicast->Address.lpSockaddr;
printf("IPV6:%s\n", inet_ntop(AF_INET6, &(sa_in6->sin6_addr), buff, bufflen));
}
else
{
printf("\tUNSPEC");
}
pUnicast = pUnicast->Next;
}
printf("Number of Unicast Addresses: %d\n", i);
pAddresses = pAddresses->Next;
}
}
else {
LPVOID lpMsgBuf;
printf("Call to GetAdaptersAddresses failed.\n");
if (FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dwRetVal,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR)&lpMsgBuf,
0,
NULL)) {
printf("\tError: %s", lpMsgBuf);
}
}
if (GetIpAddrTable(pIPAddrTable, &dwSize, 0) == ERROR_INSUFFICIENT_BUFFER)
{
GlobalFree(pIPAddrTable);
}
// Make a second call to GetIpAddrTable to get the
// actual data we want
if ((dwRetVal = GetIpAddrTable(pIPAddrTable, &dwSize, 0)) == NO_ERROR) {
printf("\t Address: %d\n", pIPAddrTable->table[0].dwAddr);
printf("\t Mask: %d\n", pIPAddrTable->table[0].dwMask);
printf("\t Index: %d\n", pIPAddrTable->table[0].dwIndex);
printf("\t BCast: %d\n", pIPAddrTable->table[0].dwBCastAddr);
printf("\t Reasm: %d\n", pIPAddrTable->table[0].dwReasmSize);
}
else {
printf("Call to GetIpAddrTable failed.\n");
}
// IP and mask we will be adding
iaIPAddress = inet_addr("192.168.0.27");
imIPMask = inet_addr("255.255.255.0");
if ((dwRetVal = AddIPAddress(iaIPAddress,
imIPMask,
pIPAddrTable->table[0].dwIndex,
&NTEContext, &NTEInstance)) == NO_ERROR)
{
printf("\tIP address added.\n");
}
else {
printf("Error adding IP address.\n");
if (FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dwRetVal,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR)&lpMsgBuf,
0,
NULL))
{
printf(" Error: %d");
}
LocalFree(lpMsgBuf);
}
if ((dwRetVal = DeleteIPAddress(NTEContext)) == NO_ERROR)
{
printf("\t IP Address Deleted.\n");
}
else {
printf("\t Call to DeleteIPAddress failed.\n");
}
free(pAddresses);
VirtualFree(&dwSize, 0, MEM_RELEASE);
return 0;
}