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net: stmmac: fix dropping of multi-descriptor RX frames

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Packets without the last descriptor set should be dropped early. If we
receive a frame larger than the DMA buffer, the HW will continue using the
next descriptor. Driver mistakes these as individual frames, and sometimes
a truncated frame (without the LD set) may look like a valid packet.

This fixes a strange issue where the system replies to 4098-byte ping
although the MTU/DMA buffer size is set to 4096, and yet at the same
time it's logging an oversized packet.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Aaro Koskinen 2019-03-27 22:35:39 +02:00 committed by David S. Miller
parent 1b746ce8b3
commit 8ac0c24fe1
1 changed files with 5 additions and 0 deletions
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5
drivers/net/ethernet/stmicro/stmmac/enh_desc.c
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@ -201,6 +201,11 @@ static int enh_desc_get_rx_status(void *data, struct stmmac_extra_stats *x,
if (unlikely(rdes0 & RDES0_OWN))
return dma_own;
if (unlikely(!(rdes0 & RDES0_LAST_DESCRIPTOR))) {
stats->rx_length_errors++;
return discard_frame;
}
if (unlikely(rdes0 & RDES0_ERROR_SUMMARY)) {
if (unlikely(rdes0 & RDES0_DESCRIPTOR_ERROR)) {
x->rx_desc++;