[PATCH] via-rhine: zero pad short packets on Rhine I ethernet cards

commit 8828db2ed1908d2a19d61a5d9a63719bb0083d22
tree 9a5434514577287ae691900c0f7dddb47f9d82e2
parent d296e6191afbfc63077da02a1386bcd73bd4c1e0
author Craig Brind <[email protected]> Mon, 24 Apr 2006 23:35:41 +0200
committer Marcelo Tosatti <[email protected]> Sun, 30 Apr 2006 20:37:05 -0300

[PATCH] via-rhine: zero pad short packets on Rhine I ethernet cards

Fixes Rhine I cards disclosing fragments of previously transmitted
frames in new transmissions.

Before transmission, any socket buffer (skb) shorter than the ethernet
minimum length of 60 bytes was zero-padded. On Rhine I cards the data
can later be copied into an aligned transmission buffer without copying
this padding. This resulted in the transmission of the frame with the
extra bytes beyond the provided content leaking the previous contents of
this buffer on to the network.

Now zero-padding is repeated in the local aligned buffer if one is used.

Following a suggestion from the via-rhine maintainer, no attempt is made
here to avoid the duplicated effort of padding the skb if it is known
that an aligned buffer will definitely be used. This is to make the
change "obviously correct" and allow it to be applied to a stable kernel
if necessary. There is no change to the flow of control and the changes
are only to the Rhine I code path.

Signed-off-by: Craig Brind <[email protected]>
Signed-off-by: Roger Luethi <[email protected]>

 drivers/net/via-rhine.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/via-rhine.c b/drivers/net/via-rhine.c
index 0c62b02..91e12bd 100644
--- a/drivers/net/via-rhine.c
+++ b/drivers/net/via-rhine.c
@@ -124,6 +124,7 @@
 
 	LK1.1.19 (Roger Luethi)
 	- Increase Tx threshold for unspecified errors
+	- Craig Brind: Zero padded aligned buffers for short packets
 
 */
 
@@ -1308,10 +1309,14 @@ static int via_rhine_start_tx(struct sk_
 			np->stats.tx_dropped++;
 			return 0;
 		}
+		/* Padding is not copied and so must be redone. */
 		skb_copy_and_csum_dev(skb, np->tx_buf[entry]);
+		if (skb->len < ETH_ZLEN)
+			memset(np->tx_buf[entry] + skb->len, 0,
+			       ETH_ZLEN - skb->len);
 		np->tx_skbuff_dma[entry] = 0;
 		np->tx_ring[entry].addr = cpu_to_le32(np->tx_bufs_dma +
-										  (np->tx_buf[entry] - np->tx_bufs));
+					  (np->tx_buf[entry] - np->tx_bufs));
 	} else {
 		np->tx_skbuff_dma[entry] =
 			pci_map_single(np->pdev, skb->data, skb->len, PCI_DMA_TODEVICE);