diff options
Diffstat (limited to 'drivers/net/usb/smsc95xx.c')
| -rw-r--r-- | drivers/net/usb/smsc95xx.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index a50cb9fd10fb..e3d08626828e 100644 --- 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); |