r0 = socket$inet6_udp(0xa, 0x2, 0x0)
setsockopt$inet6_MCAST_JOIN_GROUP(r0, 0x29, 0x2a, &(0x7f0000000080)={0x7c2, {{0xa, 0x0, 0x0, @mcast2}}}, 0x88)