Knight rider

Normal sudoku rules apply. Cells seperated by a Knight's move (in chess) cannot contain the same digits. Digits within a circle in a 2x2 must appear within that 2x2 Digits on a grey line read the same forwards as backwards. Digit on the arrow outside the grid is a sum of the digits in that direction. Digits may repeat. Digits seperated by a white dot are consecutive. Digits seperated by a black dot are a 1:2 ratio. Not all dots are given.