diff mbox

[RFC] 8139cp: properly support change of MTU values

Message ID 1354046932-13606-1-git-send-email-jogreene@redhat.com
State RFC, archived
Delegated to: David Miller
Headers show

Commit Message

John Greene Nov. 27, 2012, 8:08 p.m. UTC 
The 8139cp driver has a change_mtu function that has not been
enabled since the dawn of the git repository. However, the
generic eth_change_mtu is not used in its place, so that
invalid MTU values can be set on the interface.

Original patch salvages the broken code for the single case of
setting the MTU while the interface is down, which is safe
and also includes the range check.  Now enhanced to support up
or down interface.

Original patch from
http://lkml.indiana.edu/hypermail/linux/kernel/1202.2/00770.html

Testing: has been test on virtual 8139cp setup without issue,
awaiting real hardware and retest again, but wanted to post now.

Signed-Off-By: "John Greene" <jogreene@redhat.com>
CC: "David S. Miller" <davem@davemloft.net>
---
 drivers/net/ethernet/realtek/8139cp.c | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

Comments

Rami Rosen Nov. 28, 2012, 7:23 a.m. UTC | #1 
Hi,

In cp_change_mtu(), there is the following check:
...
if (new_mtu < CP_MIN_MTU || new_mtu > CP_MAX_MTU)
		return -EINVAL;
...
Later on, we set dev->mtu to new_mtu.

The CP_MIN_MTU is defined to be 60; shouldn't it be 68 ?


The reason for 68 is (RFC 791,  Internet Protocol,
http://www.ietf.org/rfc/rfc791.txt):
"Every internet module must be able to forward a datagram of 68 octets
without further fragmentation.  This is because an internet  header
may be up to 60 octets, and the minimum fragment is 8 octets."

See also the generic Ethernet () method in eth_change_mtu() (net/ethernet/eth.c)

int eth_change_mtu(struct net_device *dev, int new_mtu)
{
	if (new_mtu < 68 || new_mtu > ETH_DATA_LEN)
		return -EINVAL;
	dev->mtu = new_mtu;
	return 0;
}


regards,
Rami Rosen

http://ramirose.wix.com/ramirosen

On Tue, Nov 27, 2012 at 10:08 PM, John Greene <jogreene@redhat.com> wrote:
> The 8139cp driver has a change_mtu function that has not been
> enabled since the dawn of the git repository. However, the
> generic eth_change_mtu is not used in its place, so that
> invalid MTU values can be set on the interface.
>
> Original patch salvages the broken code for the single case of
> setting the MTU while the interface is down, which is safe
> and also includes the range check.  Now enhanced to support up
> or down interface.
>
> Original patch from
> http://lkml.indiana.edu/hypermail/linux/kernel/1202.2/00770.html
>
> Testing: has been test on virtual 8139cp setup without issue,
> awaiting real hardware and retest again, but wanted to post now.
>
> Signed-Off-By: "John Greene" <jogreene@redhat.com>
> CC: "David S. Miller" <davem@davemloft.net>
> ---
>  drivers/net/ethernet/realtek/8139cp.c | 22 +++-------------------
>  1 file changed, 3 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/net/ethernet/realtek/8139cp.c b/drivers/net/ethernet/realtek/8139cp.c
> index 6cb96b4..7847c83 100644
> --- a/drivers/net/ethernet/realtek/8139cp.c
> +++ b/drivers/net/ethernet/realtek/8139cp.c
> @@ -1226,12 +1226,9 @@ static void cp_tx_timeout(struct net_device *dev)
>         spin_unlock_irqrestore(&cp->lock, flags);
>  }
>
> -#ifdef BROKEN
>  static int cp_change_mtu(struct net_device *dev, int new_mtu)
>  {
>         struct cp_private *cp = netdev_priv(dev);
> -       int rc;
> -       unsigned long flags;
>
>         /* check for invalid MTU, according to hardware limits */
>         if (new_mtu < CP_MIN_MTU || new_mtu > CP_MAX_MTU)
> @@ -1244,22 +1241,11 @@ static int cp_change_mtu(struct net_device *dev, int new_mtu)
>                 return 0;
>         }
>
> -       spin_lock_irqsave(&cp->lock, flags);
> -
> -       cp_stop_hw(cp);                 /* stop h/w and free rings */
> -       cp_clean_rings(cp);
> -
> +       /* network IS up, close it, reset MTU, and come up again. */
> +       cp_close(dev);
>         dev->mtu = new_mtu;
> -       cp_set_rxbufsize(cp);           /* set new rx buf size */
> -
> -       rc = cp_init_rings(cp);         /* realloc and restart h/w */
> -       cp_start_hw(cp);
> -
> -       spin_unlock_irqrestore(&cp->lock, flags);
> -
> -       return rc;
> +       return cp_open(dev);
>  }
> -#endif /* BROKEN */
>
>  static const char mii_2_8139_map[8] = {
>         BasicModeCtrl,
> @@ -1835,9 +1821,7 @@ static const struct net_device_ops cp_netdev_ops = {
>         .ndo_start_xmit         = cp_start_xmit,
>         .ndo_tx_timeout         = cp_tx_timeout,
>         .ndo_set_features       = cp_set_features,
> -#ifdef BROKEN
>         .ndo_change_mtu         = cp_change_mtu,
> -#endif
>
>  #ifdef CONFIG_NET_POLL_CONTROLLER
>         .ndo_poll_controller    = cp_poll_controller,
> --
> 1.7.11.7
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
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John Greene Nov. 28, 2012, 6 p.m. UTC | #2 
On 11/28/2012 02:23 AM, Rami Rosen wrote:
> Hi,
>
> In cp_change_mtu(), there is the following check:
> ...
> if (new_mtu < CP_MIN_MTU || new_mtu > CP_MAX_MTU)
> 		return -EINVAL;
> ...
> Later on, we set dev->mtu to new_mtu.
>
> The CP_MIN_MTU is defined to be 60; shouldn't it be 68 ?
>
>
> The reason for 68 is (RFC 791,  Internet Protocol,
> http://www.ietf.org/rfc/rfc791.txt):
> "Every internet module must be able to forward a datagram of 68 octets
> without further fragmentation.  This is because an internet  header
> may be up to 60 octets, and the minimum fragment is 8 octets."
>
> See also the generic Ethernet () method in eth_change_mtu() (net/ethernet/eth.c)
>
> int eth_change_mtu(struct net_device *dev, int new_mtu)
> {
> 	if (new_mtu < 68 || new_mtu > ETH_DATA_LEN)
> 		return -EINVAL;
> 	dev->mtu = new_mtu;
> 	return 0;
> }
>
>
> regards,
> Rami Rosen
>
> http://ramirose.wix.com/ramirosen
>
> On Tue, Nov 27, 2012 at 10:08 PM, John Greene <jogreene@redhat.com> wrote:
>> The 8139cp driver has a change_mtu function that has not been
>> enabled since the dawn of the git repository. However, the
>> generic eth_change_mtu is not used in its place, so that
>> invalid MTU values can be set on the interface.
>>
>> Original patch salvages the broken code for the single case of
>> setting the MTU while the interface is down, which is safe
>> and also includes the range check.  Now enhanced to support up
>> or down interface.
>>
>> Original patch from
>> http://lkml.indiana.edu/hypermail/linux/kernel/1202.2/00770.html
>>
>> Testing: has been test on virtual 8139cp setup without issue,
>> awaiting real hardware and retest again, but wanted to post now.
>>
>> Signed-Off-By: "John Greene" <jogreene@redhat.com>
>> CC: "David S. Miller" <davem@davemloft.net>commit c3f214170cd1abb89290815c3894b945a86894fe
Author: John Greene <jogreene@redhat.com>
Date:   Mon Nov 26 16:05:06 2012 -0500

     8139cp: properly support change of MTU values

>> ---
>>   drivers/net/ethernet/realtek/8139cp.c | 22 +++-------------------
>>   1 file changed, 3 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/realtek/8139cp.c b/drivers/net/ethernet/realtek/8139cp.c
>> index 6cb96b4..7847c83 100644
>> --- a/drivers/net/ethernet/realtek/8139cp.c
>> +++ b/drivers/net/ethernet/realtek/8139cp.c
>> @@ -1226,12 +1226,9 @@ static void cp_tx_timeout(struct net_device *dev)
>>          spin_unlock_irqrestore(&cp->lock, flags);
>>   }
>>
>> -#ifdef BROKEN
>>   static int cp_change_mtu(struct net_device *dev, int new_mtu)
>>   {
>>          struct cp_private *cp = netdev_priv(dev);
>> -       int rc;
>> -       unsigned long flags;
>>
>>          /* check for invalid MTU, according to hardware limits */
>>          if (new_mtu < CP_MIN_MTU || new_mtu > CP_MAX_MTU)
>> @@ -1244,22 +1241,11 @@ static int cp_change_mtu(struct net_device *dev, int new_mtu)
>>                  return 0;
>>          }
>>
>> -       spin_lock_irqsave(&cp->lock, flags);
>> -
>> -       cp_stop_hw(cp);                 /* stop h/w and free rings */
>> -       cp_clean_rings(cp);
>> -
>> +       /* network IS up, close it, reset MTU, and come up again. */
>> +       cp_close(dev);
>>          dev->mtu = new_mtu;
>> -       cp_set_rxbufsize(cp);           /* set new rx buf size */
>> -
>> -       rc = cp_init_rings(cp);         /* realloc and restart h/w */
>> -       cp_start_hw(cp);
>> -
>> -       spin_unlock_irqrestore(&cp->lock, flags);
>> -
>> -       return rc;
>> +       return cp_open(dev);
>>   }
>> -#endif /* BROKEN */
>>
>>   static const char mii_2_8139_map[8] = {
>>          BasicModeCtrl,
>> @@ -1835,9 +1821,7 @@ static const struct net_device_ops cp_netdev_ops = {
>>          .ndo_start_xmit         = cp_start_xmit,
>>          .ndo_tx_timeout         = cp_tx_timeout,
>>          .ndo_set_features       = cp_set_features,
>> -#ifdef BROKEN
>>          .ndo_change_mtu         = cp_change_mtu,
>> -#endif
>>
>>   #ifdef CONFIG_NET_POLL_CONTROLLER
>>          .ndo_poll_controller    = cp_poll_controller,
>> --
>> 1.7.11.7
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe netdev" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
Good catch Rami.  Thanks.

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diff mbox

Patch

diff --git a/drivers/net/ethernet/realtek/8139cp.c b/drivers/net/ethernet/realtek/8139cp.c
index 6cb96b4..7847c83 100644
--- a/drivers/net/ethernet/realtek/8139cp.c
+++ b/drivers/net/ethernet/realtek/8139cp.c
@@ -1226,12 +1226,9 @@  static void cp_tx_timeout(struct net_device *dev)
 	spin_unlock_irqrestore(&cp->lock, flags);
 }
 
-#ifdef BROKEN
 static int cp_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct cp_private *cp = netdev_priv(dev);
-	int rc;
-	unsigned long flags;
 
 	/* check for invalid MTU, according to hardware limits */
 	if (new_mtu < CP_MIN_MTU || new_mtu > CP_MAX_MTU)
@@ -1244,22 +1241,11 @@  static int cp_change_mtu(struct net_device *dev, int new_mtu)
 		return 0;
 	}
 
-	spin_lock_irqsave(&cp->lock, flags);
-
-	cp_stop_hw(cp);			/* stop h/w and free rings */
-	cp_clean_rings(cp);
-
+	/* network IS up, close it, reset MTU, and come up again. */
+	cp_close(dev);
 	dev->mtu = new_mtu;
-	cp_set_rxbufsize(cp);		/* set new rx buf size */
-
-	rc = cp_init_rings(cp);		/* realloc and restart h/w */
-	cp_start_hw(cp);
-
-	spin_unlock_irqrestore(&cp->lock, flags);
-
-	return rc;
+	return cp_open(dev);
 }
-#endif /* BROKEN */
 
 static const char mii_2_8139_map[8] = {
 	BasicModeCtrl,
@@ -1835,9 +1821,7 @@  static const struct net_device_ops cp_netdev_ops = {
 	.ndo_start_xmit		= cp_start_xmit,
 	.ndo_tx_timeout		= cp_tx_timeout,
 	.ndo_set_features	= cp_set_features,
-#ifdef BROKEN
 	.ndo_change_mtu		= cp_change_mtu,
-#endif
 
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller	= cp_poll_controller,