#ifndef _NTRTL_H
NTSYSAPI
NTSTATUS
NTAPI
RtlIpv6AddressToStringExW(
_In_ PCIN6_ADDR Address,
_In_ ULONG ScopeId,
_In_ USHORT Port,
_Out_writes_to_(*AddressStringLength, *AddressStringLength) PWSTR AddressString,
_Inout_ PULONG AddressStringLength
);
View code on GitHub
This function is documented in Windows SDK.