r0 = socket$inet6_udp(0xa, 0x2, 0x0)
setsockopt$inet6_MCAST_MSFILTER(r0, 0x29, 0x12, &(0x7f00000002c0)={0x0, {{0xa, 0x0, 0x0, @mcast1}}}, 0x20000)