Re: [PATCH] pktgen: Clone skb to avoid corruption of skbs in ndo_start_xmit methods

Ben Greear
2011-07-20T16:33:50Z

On 07/20/2011 08:18 AM, Neil Horman wrote:
> On Wed, Jul 20, 2011 at 06:24:15AM +0200, Eric Dumazet wrote:
>> Le mardi 19 juillet 2011 à 22:07 -0400, Neil Horman a écrit :
>>>>
>>> I think this is a good idea. It lets pktgen dynamically make the clone/share
>>> decision dynamically and only impacts performance for those systems.
>>>
>>
>> Just let pktgen refuse to use clone_skb command for these devices.
>>
> copy that, This is by no means final, but what do you think of this? If its
> agreeable to you, Ben, et al. I can add this to my local tree and start auditing
> all the drivers that may need to have the flag set.
>
> Regards
> Neil
>
>
> diff --git a/include/linux/if.h b/include/linux/if.h
> index 3bc63e6..ae904fe 100644
> --- a/include/linux/if.h
> +++ b/include/linux/if.h
> @@ -76,6 +76,7 @@
> #define IFF_BRIDGE_PORT 0x4000 /* device used as bridge port */
> #define IFF_OVS_DATAPATH 0x8000 /* device used as Open vSwitch
> * datapath port */
> +#define IFF_CANT_SHARE_SKB 0x10000 /* Device can't share skbs in tx path */
>
> #define IF_GET_IFACE 0x0001 /* for querying only */
> #define IF_GET_PROTO 0x0002
> diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> index f76079c..bf6d88d 100644
> --- a/net/core/pktgen.c
> +++ b/net/core/pktgen.c
> @@ -1071,6 +1071,9 @@ static ssize_t pktgen_if_write(struct file *file,
> if (len< 0)
> return len;
>
> + if (pkt_dev->priv_flags& IFF_CANT_SHARE_SKB)
> + return -EOPNOTSUPP;
> +
> i += len;
> pkt_dev->clone_skb = value;
>

Please only return an error if value > 1.

Also, if there is any place where user can configure pkt_dev,
you would want code there to check for the CANT_SHARE_SKB flag
and force clone_skb to zero if user changes to a different
device that cannot share skbs.

Thanks,
Ben

--
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc http://www.candelatech.com