[PATCH net-next v2 06/14] net: stmmac: add GSO MSS checks

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

Add GSO MSS checks to stmmac_features_check().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 031ffb78f40d..b4cc34dd0d76 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4391,12 +4391,19 @@ static size_t stmmac_tso_header_size(struct sk_buff *skb)
  *
  * While IPv4 is limited to MAC+VLAN+IPv4+ext+TCP+ext = 138 bytes, the IPv6
  * extension headers aren't similarly limited.
+ *
+ * Fall back to software GSO for these skbs. Also check that the MSS is >=
+ * the recommended 64 bytes (documented in ETH_DMACxCR register description),
+ * and that a the header plus MSS is not larger than 16383 (documented in
+ * "Building the Descriptor and the packet for the TSO feature").
  */
 static bool stmmac_tso_valid_packet(struct sk_buff *skb)
 {
 	size_t header_len = stmmac_tso_header_size(skb);
+	unsigned int gso_size = skb_shinfo(skb)->gso_size;
 
-	return header_len <= 1023;
+	return header_len <= 1023 && gso_size >= 64 &&
+	       header_len + gso_size < 16383;
 }
 
 /**
-- 
2.47.3