[PATCHv4 net-next 2/3] sunvnet: allow admin to set sunvnet MTU

[PATCHv4 net-next 2/3] sunvnet: allow admin to set sunvnet MTU

[David L Stevens]

This patch allows an admin to set the MTU on a sunvnet device to arbitrary
values between the minimum (68) and maximum (65535) IPv4 packet sizes.

Signed-off-by: David L Stevens <david.stevens@oracle.com>
---
 drivers/net/ethernet/sun/sunvnet.c |    5 ++++-
 drivers/net/ethernet/sun/sunvnet.h |    2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index a9638c1..5619798 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c
@@ -791,6 +791,9 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (unlikely(!port))
 		goto out_dropped;
 
+	if (skb->len > port->rmtu)
+		goto out_dropped;
+
 	spin_lock_irqsave(&port->vio.lock, flags);
 
 	dr = &port->vio.drings[VIO_DRIVER_TX_RING];
@@ -1038,7 +1041,7 @@ static void vnet_set_rx_mode(struct net_device *dev)
 
 static int vnet_change_mtu(struct net_device *dev, int new_mtu)
 {
-	if (new_mtu != ETH_DATA_LEN)
+	if (new_mtu < 68 || new_mtu > 65535)
 		return -EINVAL;
 
 	dev->mtu = new_mtu;
diff --git a/drivers/net/ethernet/sun/sunvnet.h b/drivers/net/ethernet/sun/sunvnet.h
index 986e04b..809b122 100644
--- a/drivers/net/ethernet/sun/sunvnet.h
+++ b/drivers/net/ethernet/sun/sunvnet.h
@@ -11,7 +11,7 @@
  */
 #define VNET_TX_TIMEOUT			(5 * HZ)
 
-#define VNET_MAXPACKET			1518ULL /* ETH_FRAMELEN + VLAN_HDR */
+#define VNET_MAXPACKET			65553ULL /* 64K-1  +ETH HDR +VLAN HDR*/
 #define VNET_TX_RING_SIZE		512
 #define VNET_TX_WAKEUP_THRESH(dr)	((dr)->pending / 4)
 
-- 
1.7.1

Re: [PATCHv4 net-next 2/3] sunvnet: allow admin to set sunvnet MTU

[David L Stevens]

On 09/15/2014 08:35 PM, David L Stevens wrote:

>   */
>  #define VNET_TX_TIMEOUT			(5 * HZ)
>  
> -#define VNET_MAXPACKET			1518ULL /* ETH_FRAMELEN + VLAN_HDR */
> +#define VNET_MAXPACKET			65553ULL /* 64K-1  +ETH HDR +VLAN HDR*/
>  #define VNET_TX_RING_SIZE		512
>  #define VNET_TX_WAKEUP_THRESH(dr)	((dr)->pending / 4)

While looking at adding TSO support, I've turned up a bug with this.

The transmit buffer mapping should be using a cookie per-page and this increases
the page count (without page alignment) from 2 with a 1500-byte MTU to 10 with a 64K MTU
+ framing and allowing from unaligned buffers.

I think it worked during my testing because the pages were contiguous, but the tx buffer
allocation code is assuming 2 pages (and 2 cookies) max.

So, it's incorrect. I'll fix and repost; please don't apply these yet.

							+-DLS

Re: [PATCHv4 net-next 2/3] sunvnet: allow admin to set sunvnet MTU

[David Miller]

From: David L Stevens <david.stevens@oracle.com>
Date: Tue, 16 Sep 2014 14:51:37 -0400

> So, it's incorrect. I'll fix and repost; please don't apply these
> yet.

Ok, thanks for the heads up.

RE: [PATCHv4 net-next 2/3] sunvnet: allow admin to set sunvnet MTU

[David Laight]

From: David L Stevens
> On 09/15/2014 08:35 PM, David L Stevens wrote:
> 
> >   */
> >  #define VNET_TX_TIMEOUT			(5 * HZ)
> >
> > -#define VNET_MAXPACKET			1518ULL /* ETH_FRAMELEN + VLAN_HDR */
> > +#define VNET_MAXPACKET			65553ULL /* 64K-1  +ETH HDR +VLAN HDR*/

That would be better as the expression (0xffffull + 14 + 4).

> >  #define VNET_TX_RING_SIZE		512
> >  #define VNET_TX_WAKEUP_THRESH(dr)	((dr)->pending / 4)

	David