Re: [PATCH] netdev: pktgen xmit packet through vlan interface

[John Fastabend]

On 5/2/2014 6:19 AM, Jesper Dangaard Brouer wrote:
> On Fri,  2 May 2014 15:18:12 +0800
> Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote:
>
> > As http://www.spinics.net/lists/netdev/msg165015.html
> > pktgen generates shared packet through vlan interface will cause
> > oops because of duplicate entering tc queue.
> >
> > Try to solve this problem by means of packet clone instead of sharing.
>
> I really don't like adding this stuff to the fast path of pktgen.
>
> Why would you use pktgen on a VLAN?

Its a good way to test qdiscs. When you run pktgen over the VLAN
you exercise the lower devices qdisc.

Although I never submitted a patch like this because I figured it
was a corner case and we would want to keep the hotpath clean.

> Why don't you use the "vlan_id" feature available in pktgen, and send
> in the lower real device?
>
>
>
> > Signed-off-by: Zhouyi Zhou <yizhouzhou@xxxxxxxxx>
> > ---
> >   net/core/pktgen.c |   20 +++++++++++++++++---
> >   1 files changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> > index 0304f98..ced07fc 100644
> > --- a/net/core/pktgen.c
> > +++ b/net/core/pktgen.c
> > @@ -3297,6 +3297,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> >   	netdev_tx_t (*xmit)(struct sk_buff *, struct net_device *)
> >   		= odev->netdev_ops->ndo_start_xmit;
> >   	struct netdev_queue *txq;
> > +	struct sk_buff *nskb = NULL;
> >   	u16 queue_map;
> >   	int ret;
> >
> > @@ -3347,8 +3348,18 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> >   		pkt_dev->last_ok = 0;
> >   		goto unlock;
> >   	}
> > -	atomic_inc(&(pkt_dev->skb->users));
> > -	ret = (*xmit)(pkt_dev->skb, odev);
> > +
> > +	if (pkt_dev->clone_skb && is_vlan_dev(odev)) {
> > +		nskb = skb_clone(pkt_dev->skb, GFP_ATOMIC);
> > +		ret = -ENOMEM;
> > +		if (nskb)
> > +			ret = (*xmit)(nskb, odev);
> > +		else
> > +			nskb = ERR_PTR(ret);
> > +	} else {
> > +		atomic_inc(&(pkt_dev->skb->users));
> > +		ret = (*xmit)(pkt_dev->skb, odev);
> > +	}
> >
> >   	switch (ret) {
> >   	case NETDEV_TX_OK:
> > @@ -3372,7 +3383,10 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
> >   	case NETDEV_TX_LOCKED:
> >   	case NETDEV_TX_BUSY:
> >   		/* Retry it next time */
> > -		atomic_dec(&(pkt_dev->skb->users));
> > +		if (nskb && !IS_ERR(nskb))
> > +			kfree_skb(nskb);
> > +		else
> > +			atomic_dec(&(pkt_dev->skb->users));
> >   		pkt_dev->last_ok = 0;
> >   	}
> >   unlock:

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