Commit 5a0a92e6 authored May 17, 2008 by Gerrit Renker Committed by Jeff Garzik May 22, 2008

[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 26a17b7b
 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>

parent 789585e9

drivers/net/sc92031.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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();