From fe0cd8ca1b82983db24b173bb8518ea646c02d25 Mon Sep 17 00:00:00 2001 From: Nisar Sayed Date: Fri, 19 May 2017 14:00:25 +0000 Subject: [PATCH] smsc95xx: Support only IPv4 TCP/UDP csum offload When TX checksum offload is used, if the computed checksum is 0 the LAN95xx device do not alter the checksum to 0xffff. In the case of ipv4 UDP checksum, it indicates to receiver that no checksum is calculated. Under ipv6, UDP checksum yields a result of zero must be changed to 0xffff. Hence disabling checksum offload for ipv6 packets. Signed-off-by: Nisar Sayed Reported-by: popcorn mix Signed-off-by: David S. Miller --- drivers/net/usb/smsc95xx.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index 765400b62168..2dfca96a63b6 100644 --- a/drivers/net/usb/smsc95xx.c +++ b/drivers/net/usb/smsc95xx.c @@ -681,7 +681,7 @@ static int smsc95xx_set_features(struct net_device *netdev, if (ret < 0) return ret; - if (features & NETIF_F_HW_CSUM) + if (features & NETIF_F_IP_CSUM) read_buf |= Tx_COE_EN_; else read_buf &= ~Tx_COE_EN_; @@ -1279,12 +1279,19 @@ static int smsc95xx_bind(struct usbnet *dev, struct usb_interface *intf) spin_lock_init(&pdata->mac_cr_lock); + /* LAN95xx devices do not alter the computed checksum of 0 to 0xffff. + * RFC 2460, ipv6 UDP calculated checksum yields a result of zero must + * be changed to 0xffff. RFC 768, ipv4 UDP computed checksum is zero, + * it is transmitted as all ones. The zero transmitted checksum means + * transmitter generated no checksum. Hence, enable csum offload only + * for ipv4 packets. + */ if (DEFAULT_TX_CSUM_ENABLE) - dev->net->features |= NETIF_F_HW_CSUM; + dev->net->features |= NETIF_F_IP_CSUM; if (DEFAULT_RX_CSUM_ENABLE) dev->net->features |= NETIF_F_RXCSUM; - dev->net->hw_features = NETIF_F_HW_CSUM | NETIF_F_RXCSUM; + dev->net->hw_features = NETIF_F_IP_CSUM | NETIF_F_RXCSUM; smsc95xx_init_mac_address(dev);