diff mbox series

[v2,2/2] net: dsa: tag_ksz: dont let the hardware process the layer 4 checksum

Message ID 20210721215642.19866-3-LinoSanfilippo@gmx.de
State New
Headers show
Series Fixes for KSZ DSA switch | expand

Commit Message

Lino Sanfilippo July 21, 2021, 9:56 p.m. UTC 
If the checksum calculation is offloaded to the network device (e.g due to
NETIF_F_HW_CSUM inherited from the DSA master device), the calculated
layer 4 checksum is incorrect. This is since the DSA tag which is placed
after the layer 4 data is considered as being part of the daa and thus
errorneously included into the checksum calculation.
To avoid this, always calculate the layer 4 checksum in software.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
---
 net/dsa/tag_ksz.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

Vladimir Oltean July 21, 2021, 11:37 p.m. UTC | #1 
On Wed, Jul 21, 2021 at 11:56:42PM +0200, Lino Sanfilippo wrote:
> If the checksum calculation is offloaded to the network device (e.g due to
> NETIF_F_HW_CSUM inherited from the DSA master device), the calculated
> layer 4 checksum is incorrect. This is since the DSA tag which is placed
> after the layer 4 data is considered as being part of the daa and thus
> errorneously included into the checksum calculation.
> To avoid this, always calculate the layer 4 checksum in software.
> 
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
> ---

Fixes: 8b8010fb7876 ("dsa: add support for Microchip KSZ tail tagging")
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Florian Fainelli July 22, 2021, 3:55 a.m. UTC | #2 
On 7/21/2021 2:56 PM, Lino Sanfilippo wrote:
> If the checksum calculation is offloaded to the network device (e.g due to
> NETIF_F_HW_CSUM inherited from the DSA master device), the calculated
> layer 4 checksum is incorrect. This is since the DSA tag which is placed
> after the layer 4 data is considered as being part of the daa and thus
> errorneously included into the checksum calculation.
> To avoid this, always calculate the layer 4 checksum in software.
> 
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
diff mbox series

Patch

diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index 53565f48934c..a201ccf2435d 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -53,6 +53,9 @@  static struct sk_buff *ksz8795_xmit(struct sk_buff *skb, struct net_device *dev)
 	u8 *tag;
 	u8 *addr;
 
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
 	/* Tag encoding */
 	tag = skb_put(skb, KSZ_INGRESS_TAG_LEN);
 	addr = skb_mac_header(skb);
@@ -114,6 +117,9 @@  static struct sk_buff *ksz9477_xmit(struct sk_buff *skb,
 	u8 *addr;
 	u16 val;
 
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
 	/* Tag encoding */
 	tag = skb_put(skb, KSZ9477_INGRESS_TAG_LEN);
 	addr = skb_mac_header(skb);
@@ -164,6 +170,9 @@  static struct sk_buff *ksz9893_xmit(struct sk_buff *skb,
 	u8 *addr;
 	u8 *tag;
 
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
 	/* Tag encoding */
 	tag = skb_put(skb, KSZ_INGRESS_TAG_LEN);
 	addr = skb_mac_header(skb);