Getting wrong IP addresses - delphi

Question

I'm trying to auto-detect and report on IPv6 availability for Delphi socket programming.
For "localhost", the following code is returning "1700::" for IPv6 and "2.0.0.0" for IPv4. This address is for simple testing, and should be returning ::1 or 127.0.0.1 for my machine. I'm not getting any socket API errors in the calling code, so I'm trying to figure out what I'm doing wrong when attempting to convert "localhost" to the various IP addresses. I'm using Indy headers.
The type declarations are:
TLSocketAddress = record
case Integer of
AF_INET:
(IPv4: TSockAddrIn);
AF_INET6:
(IPv6: TSockAddrIn6);
end;
TLIpInfo = record
private
function GetFamily: TProtocolFamily;
public
Address : TLSocketAddress;
HostName: string;
Machine: string;
IP6 : string;
IP4 : string;
Port : integer;
Error : integer;
property Family : TProtocolFamily read GetFamily;
end;
and the retrieval routine is:
function GetIpInfo(
const AHostName : string;
const APort : integer
): TLIpInfo;
var
nameRet : PAnsiChar;
ptr : Pointer;
Hints : TAddrInfoW;
AddrInfo : PAddrInfoW;
NextInfo : PAddrInfoW;
RetVal : Integer;
ip,
machine : string;
namelen : integer;
begin
ZeroMemory(#Result, SizeOf(Result));
FillChar(Hints, SizeOf(Hints), 0);
Hints.ai_family := AF_UNSPEC;
AddrInfo := nil;
RetVal := GetAddrInfo(PWideChar(AHostName), nil, #Hints, #AddrInfo);
if RetVal = 0 then
try
Result.HostName := AHostName;
Result.Port := APort;
NextInfo := AddrInfo;
while NextInfo <> nil do
begin
if (NextInfo.ai_family = AF_INET) or (NextInfo.ai_family = AF_INET6) then
begin
if (Result.Machine = '') then
begin
SetLength(machine, NI_MAXHOST);
RetVal := GetNameInfo(NextInfo.ai_addr, NextInfo.ai_addrlen,
PChar(machine), NI_MAXHOST, nil, 0, 0);
if (RetVal <> 0) then
begin
NextInfo := NextInfo.ai_next;
continue;
end;
Result.Machine := PChar(machine);
end;
if NextInfo.ai_family = AF_INET then
begin
ptr := PSockAddrIn(NextInfo.ai_addr);
namelen := INET_ADDRSTRLEN;
SetLength(ip, namelen);
end
else
begin
ptr := PSockAddrIn6(NextInfo.ai_addr);
namelen := INET6_ADDRSTRLEN;
SetLength(ip, namelen);
end;
nameRet := inet_ntop(NextInfo.ai_family, ptr, PChar(ip), namelen);
if (nameRet = nil) then
begin
NextInfo := NextInfo.ai_next;
continue;
end;
if (NextInfo.ai_family = AF_INET6) then
Result.IP6 := PChar(ip)
else
Result.IP4 := PChar(ip);
end;
NextInfo := NextInfo.ai_next;
end;
finally
FreeAddrInfo(AddrInfo);
end;
end;

Answer 1

I know it may be too late for the author, but i struggled today with the same problem and noticed that you pass a pointer to the entire ADDRINFO structure to inet_ntop, however you should only be passing the pointer to the binary address.
So call to intet_ntop for IPv4 addresses should be:
inet_ntop(NextInfo.ai_family, #PSockAddrIn(NextInfo.ai_addr).sin_addr, PChar(ip), namelen)
and for IPv6 should be:
inet_ntop(NextInfo.ai_family, #PSockAddrIn6(NextInfo.ai_addr).sin6_addr, PChar(ip), namelen)