getsourcefilter function (ws2tcpip.h)

Article
10/13/2021

The getsourcefilter inline function retrieves the multicast filter state for an IPv4 or IPv6 socket.

Syntax

int getsourcefilter(
  [in]      SOCKET              Socket,
  [in]      ULONG               Interface,
  [in]      const SOCKADDR      *Group,
  [in]      int                 GroupLength,
  [out]     MULTICAST_MODE_TYPE *FilterMode,
  [in, out] ULONG               *SourceCount,
  [out]     SOCKADDR_STORAGE    *SourceList
);

Parameters

[in] Socket

A descriptor that identifies a multicast socket.

[in] Interface

The interface index of the multicast interface.

[in] Group

A pointer to the socket address of the multicast group.

[in] GroupLength

The length, in bytes, of the socket address pointed to by the Group parameter.

[out] FilterMode

A pointer to a value to receive the multicast filter mode for the multicast group address when the function returns.

[in, out] SourceCount

On input, a pointer to a value that indicates the maximum number of source addresses that will fit in the buffer pointed to by the SourceList parameter.

On output, a pointer to a value that indicates the total number of source addresses associated with the multicast filter.

[out] SourceList

A pointer to a buffer to receive the list of IP addresses associated with the multicast filter.

If SourceCount is zero on input, a NULL pointer may be supplied.

Return value

On success, getsourcefilter returns NO_ERROR (0). Any nonzero return value indicates failure and a specific error code can be retrieved by calling WSAGetLastError.

Error code	Meaning
WSAENOBUFS	Insufficient buffer space is available.
WSAENOTSOCK	The descriptor is not a socket.

Remarks

The getsourcefilter inline function is used to retrieve the multicast filter state for an IPv4 or IPv6 socket.

If the app does not know the size of the source list beforehand, it can make a guess (zero, for example). If upon completion, the SourceCount parameter holds a larger value, the operation can be repeated with a large enough buffer.

On return, the SourceCount parameter is always updated to be the total number of sources in the filter, while the buffer pointed to by the SourceList parameter will hold as many source addresses as fit, up to the minimum of the array size passed in as the original SourceCount value and the total number of sources in the filter.

This function is part of socket interface extensions for multicast source filters defined in RFC 3678. An app can use these functions to retrieve and set the multicast source address filters associated with a socket.

Windows Phone 8: This function is supported for Windows Phone Store apps on Windows Phone 8 and later.

Windows 8.1 and Windows Server 2012 R2: This function is supported for Windows Store apps on Windows 8.1, Windows Server 2012 R2, and later.

Requirements

Requirement	Value
Minimum supported client	Windows 8.1, Windows Vista [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps \| UWP apps]
Target Platform	Windows
Header	ws2tcpip.h
Library	Ws2_32.lib
DLL	Ws2_32.dll