ionic: restrict received packets to mtu size
Make sure the NIC drops packets that are larger than the specified MTU. The front end of the NIC will accept packets larger than MTU and will copy all the data it can to fill up the driver's posted buffers - if the buffers are not long enough the packet will then get dropped. With the Rx SG buffers allocagted as full pages, we are currently setting up more space than MTU size available and end up receiving some packets that are larger than MTU, up to the size of buffers posted. To be sure the NIC doesn't waste our time with oversized packets we need to lie a little in the SG descriptor about how long is the last SG element. At dealloc time, we know the allocation was a page, so the deallocation doesn't care about what length we put in the descriptor. Signed-off-by: Shannon Nelson <snelson@pensando.io> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
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