An SIOCGIPMSFILTER IOCTL enables an application to retrieve a list of the IPv4 source addresses that comprise the source filter, with the current mode on a given interface and a multicast group for a socket. The source filter can include or exclude the set of source addresses, depending on the filter mode (MCAST_INCLUDE or MCAST_EXCLUDE), which is defined in the IP_MSFILTER structure of the BPXYIOCC macro.