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

Neil Horman
2011-07-20T16:36:56Z

On Wed, Jul 20, 2011 at 09:33:20AM -0700, Ben Greear wrote:
> 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
>
Understood, thank you Ben.
Neil

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