netdev - Re: [PATCH] pktgen: Clone skb to avoid corruption of skbs in ndo_start

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Date:	Wed, 20 Jul 2011 11:18:27 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ben Greear <greearb@...delatech.com>,
	Jiri Pirko <jpirko@...hat.com>, netdev@...r.kernel.org,
	Alexey Dobriyan <adobriyan@...il.com>,
	"David S. Miller" <davem@...emloft.net>, robert.olsson@....uu.se
Subject: Re: [PATCH] pktgen: Clone skb to avoid corruption of skbs in
 ndo_start_xmit methods

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;
 

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