RtlIpv6StringToAddressA function (ip2string.h)

Article
02/09/2023

The RtlIpv6StringToAddress function converts a string representation of an IPv6 address to a binary IPv6 address.

Syntax

NTSYSAPI NTSTATUS RtlIpv6StringToAddressA(
  [in]  PCSTR    S,
  [out] PCSTR    *Terminator,
  [out] in6_addr *Addr
);

Parameters

[in] S

A pointer to a buffer containing the NULL-terminated string representation of the IPv6 address.

[out] Terminator

A parameter that receives a pointer to the character that terminated the converted string. This can be used by the caller to extract more information from the string.

[out] Addr

A pointer where the binary representation of the IPv6 address is to be stored.

Return value

If the function succeeds, the return value is STATUS_SUCCESS.

If the function fails, the return value is one of the following error codes.

Return code	Description
STATUS_INVALID_PARAMETER	An invalid parameter was passed to the function. This error is returned if the string pointed to by the S parameter did not contain a proper string representation of an IPv6 address. This error code is defined in the Ntstatus.h header file.
Other	Use FormatMessage to obtain the message string for the returned error.

Remarks

The RtlIpv6StringToAddress function is used to convert a string representation of the IPv6 address to an IPv6 address returned in network order (bytes ordered from left to right).

RtlIpv6StringToAddress is a convenience function that does not require that the Windows Sockets DLL be loaded to access a function provided in Windows Sockets to perform string to IP address conversion.

The string pointed to by the S parameter must be represented in the form for an IPv6 address string. The basic string representation of an IPv6 address consists of 8 hexadecimal numbers separated by colons. A string of consecutive zero numbers may be replaced with a double-colon. There can only be one double-colon in the string representation of the IPv6 address. The last 32 bits may be represented in IPv4-style dotted-octet notation if the address is an IPv4-compatible address, an IPv4-mapped IPv6 address, or an ISATAP address. For more information, see section 5 of RFC 5942 published by the IETF.

On success, the Terminator parameter points to the character that terminated the string that was converted. This allows an application to pass a string that contains and IP address plus additional information to the RtlIpv6StringToAddress function and then parse the remaining information.

Note Some malformed IPv6 addresses (::::, for example) start with a valid IPv6 address. The RtlIpv6StringToAddress function will return success, having parsed the valid part of the IPv6 address as the double colon (::). The terminator then points to the third colon. To validate that the entire passed-in string is a valid IPv6 address, you need to ensure that the terminator points to the correct character. If the S parameter contains only an IPv6 address, then the terminator should point to the NULL character at the end of the string.

When either UNICODE or _UNICODE is defined, RtlIpv6StringToAddress is defined to RtlIpv6StringToAddressW, the Unicode version of this function. The S and Terminator parameters are defined to the PCWSTR data type.

When both UNICODE and _UNICODE are not defined, RtlIpv6StringToAddress is defined to RtlIpv6StringToAddressA, the ANSI version of this function. The S and Terminator parameters are defined to the PCSTR data type.

The IN6_ADDR structure is defined in the In6addr.h header file.

An import library containing the RtlIpv6StringToAddress function is not included in the Microsoft Windows Software Development Kit (SDK) released for Windows Vista. The RtlIpv6StringToAddress function is included in the Ntdll.lib import library included in the Windows Driver Kit (WDK). An application could also use the GetModuleHandle and GetProcAddress functions to retrieve the function pointer from the Ntdll.dll and call this function.

Note

The ip2string.h header defines RtlIpv6StringToAddress as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2008 [desktop apps \| UWP apps]
Target Platform	Windows
Header	ip2string.h (include Mstcpip.h, Ip2string.h)
Library	ntdll.lib
DLL	ntdll.dll