net: macb: initialize checksum when using checksum offloading
I'm still struggling to get this fix right..
Changes since v2:
- do not blindly modify SKB contents according to Dave's legitimate
objection
Changes since v1:
- dropped disabling HW checksum offload for Zynq
- initialize checksum similar to net/ethernet/freescale/fec_main.c
-- >8 --
MACB/GEM needs the checksum field initialized to 0 to get correct
results on transmit in all cases, e.g. on Zynq, UDP packets with
payload <= 2 otherwise contain a wrong checksums.
Signed-off-by: Helmut Buchsbaum <helmut.buchsbaum@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 89c0cfa..d954a97b 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -1323,6 +1323,24 @@
return 0;
}
+static inline int macb_clear_csum(struct sk_buff *skb)
+{
+ /* no change for packets without checksum offloading */
+ if (skb->ip_summed != CHECKSUM_PARTIAL)
+ return 0;
+
+ /* make sure we can modify the header */
+ if (unlikely(skb_cow_head(skb, 0)))
+ return -1;
+
+ /* initialize checksum field
+ * This is required - at least for Zynq, which otherwise calculates
+ * wrong UDP header checksums for UDP packets with UDP data len <=2
+ */
+ *(__sum16 *)(skb_checksum_start(skb) + skb->csum_offset) = 0;
+ return 0;
+}
+
static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
u16 queue_index = skb_get_queue_mapping(skb);
@@ -1362,6 +1380,11 @@
return NETDEV_TX_BUSY;
}
+ if (macb_clear_csum(skb)) {
+ dev_kfree_skb_any(skb);
+ return NETDEV_TX_OK;
+ }
+
/* Map socket buffer for DMA transfer */
if (!macb_tx_map(bp, queue, skb)) {
dev_kfree_skb_any(skb);