[SC92031] Using padto turned driver into an IPv6-only interface

IPv4 would work with this driver only with static arp table entries,
the patch  reverts a padto introduced in

 commit 26a17b7bbb36a8552d531bc1ad08472fb5aa3007
 sc92031: start transmit return value bugfix

The padto does not work because the driver code evaluates `len' later on and
there are cases where skb->len is not updated accordingly.

This was observed with ARP frames (skb->len = 42 bytes, !skb_cloned(),
skb_tailroom = 84 bytes). Then in skb_pad(), the first condition is true, where
skb->len is not updated. As a consequence, the driver uses 42 bytes instead of
the 60 bytes, and the ARP frame never makes it onto the wire.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/net/sc92031.c b/drivers/net/sc92031.c
index f64a860029b7..b4b63805ee8f 100644
--- a/drivers/net/sc92031.c
+++ b/drivers/net/sc92031.c
@@ -953,9 +953,6 @@ static int sc92031_start_xmit(struct sk_buff *skb, struct net_device *dev)
         unsigned entry;
         u32 tx_status;
 
-        if (skb_padto(skb, ETH_ZLEN))
-                return NETDEV_TX_OK;
-
         if (unlikely(skb->len > TX_BUF_SIZE)) {
                 dev->stats.tx_dropped++;
                 goto out;
@@ -975,6 +972,11 @@ static int sc92031_start_xmit(struct sk_buff *skb, struct net_device *dev)
         skb_copy_and_csum_dev(skb, priv->tx_bufs + entry * TX_BUF_SIZE);
 
         len = skb->len;
+        if (unlikely(len < ETH_ZLEN)) {
+                memset(priv->tx_bufs + entry * TX_BUF_SIZE + len,
+                                0, ETH_ZLEN - len);
+                len = ETH_ZLEN;
+        }
 
         wmb();