Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

[platform/kernel/linux-starfive.git] / drivers / net / usb / smsc95xx.c

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index a50cb9f..e3d0862 100644 (file)
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -2009,6 +2009,23 @@ static u32 smsc95xx_calc_csum_preamble(struct sk_buff *skb)
        return (high_16 << 16) | low_16;
 }
 
+/* The TX CSUM won't work if the checksum lies in the last 4 bytes of the
+ * transmission. This is fairly unlikely, only seems to trigger with some
+ * short TCP ACK packets sent.
+ *
+ * Note, this calculation should probably check for the alignment of the
+ * data as well, but a straight check for csum being in the last four bytes
+ * of the packet should be ok for now.
+ */
+static bool smsc95xx_can_tx_checksum(struct sk_buff *skb)
+{
+       unsigned int len = skb->len - skb_checksum_start_offset(skb);
+
+       if (skb->len <= 45)
+              return false;
+       return skb->csum_offset < (len - (4 + 1));
+}
+
 static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
                                         struct sk_buff *skb, gfp_t flags)
 {
@@ -2033,7 +2050,7 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
        tx_cmd_a = tx_cmd_b | TX_CMD_A_FIRST_SEG_ | TX_CMD_A_LAST_SEG_;
 
        if (csum) {
-               if (skb->len <= 45) {
+               if (!smsc95xx_can_tx_checksum(skb)) {
                        /* workaround - hardware tx checksum does not work
                         * properly with extremely small packets */
                        long csstart = skb_checksum_start_offset(skb);