An SIOCSIPMSFILTER IOCTL enables an application to specify or modify a list of IPv4 source addresses on a given interface and to specify or modify 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. The application can join multiple source multicast groups on a single socket; it also can join the same group on multiple interfaces on the same socket. However, there is a maximum limit of 20 groups per single UDP socket and there is a maximum limit of 256 groups per single RAW socket.