smsc95xx: Fix tx checksum offload for small packets
TX checksum offload does not work properly when transmitting
UDP packets with 0, 1 or 2 bytes of data. This patch works
around the problem by calculating checksums for these packets
in the driver.
Signed-off-by: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index d222d7e..73f9a31 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1189,9 +1189,21 @@
}
if (csum) {
- u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
- skb_push(skb, 4);
- memcpy(skb->data, &csum_preamble, 4);
+ if (skb->len <= 45) {
+ /* workaround - hardware tx checksum does not work
+ * properly with extremely small packets */
+ long csstart = skb->csum_start - skb_headroom(skb);
+ __wsum calc = csum_partial(skb->data + csstart,
+ skb->len - csstart, 0);
+ *((__sum16 *)(skb->data + csstart
+ + skb->csum_offset)) = csum_fold(calc);
+
+ csum = false;
+ } else {
+ u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
+ skb_push(skb, 4);
+ memcpy(skb->data, &csum_preamble, 4);
+ }
}
skb_push(skb, 4);
