On Sat, 2016-10-01 at 20:05 +0200, Paolo Abeni wrote:
> On Fri, 2016-09-30 at 08:39 -0700, Greg wrote:
> > On Fri, 2016-09-30 at 16:56 +0200, Paolo Abeni wrote:
> > > The commit 879c7220e828 ("net: pktgen: Observe needed_headroom
> > > of the device") increased the 'pkt_overhead' field value by
> > > LL_RESERVED_SPACE.
> > > As a side effect the generated packet size, computed as:
> > >
> > > /* Eth + IPh + UDPh + mpls */
> > > datalen = pkt_dev->cur_pkt_size - 14 - 20 - 8 -
> > > pkt_dev->pkt_overhead;
> > >
> > > is decreased by the same value.
> > > The above changed slightly the behavior of existing pktgen users,
> > > and made the procfs interface somewhat inconsistent.
> > > Fix it by restoring the previous pkt_overhead value and using
> > > LL_RESERVED_SPACE as extralen in skb allocation.
> > > Also, change pktgen_alloc_skb() to only partially reserve
> > > the headroom to allow the caller to prefetch from ll header
> > > start.
> > >
> > > v1 -> v2:
> > > - fixed some typos in the comments
> > >
> > > Fixes: 879c7220e828 ("net: pktgen: Observe needed_headroom of the device")
> > > Suggested-by: Ben Greear <gree...@candelatech.com>
> > > Signed-off-by: Paolo Abeni <pab...@redhat.com>
> > > ---
> > > net/core/pktgen.c | 21 ++++++++++-----------
> > > 1 file changed, 10 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> > > index bbd118b..5219a9e 100644
> > > --- a/net/core/pktgen.c
> > > +++ b/net/core/pktgen.c
> > > @@ -2286,7 +2286,7 @@ out:
> > >
> > > static inline void set_pkt_overhead(struct pktgen_dev *pkt_dev)
> > > {
> > > - pkt_dev->pkt_overhead = LL_RESERVED_SPACE(pkt_dev->odev);
> > > + pkt_dev->pkt_overhead = 0;
> > > pkt_dev->pkt_overhead += pkt_dev->nr_labels*sizeof(u32);
> > > pkt_dev->pkt_overhead += VLAN_TAG_SIZE(pkt_dev);
> > > pkt_dev->pkt_overhead += SVLAN_TAG_SIZE(pkt_dev);
> > > @@ -2777,13 +2777,13 @@ static void pktgen_finalize_skb(struct pktgen_dev
> > > *pkt_dev, struct sk_buff *skb,
> > > }
> > >
> > > static struct sk_buff *pktgen_alloc_skb(struct net_device *dev,
> > > - struct pktgen_dev *pkt_dev,
> > > - unsigned int extralen)
> > > + struct pktgen_dev *pkt_dev)
> > > {
> > > + unsigned int extralen = LL_RESERVED_SPACE(dev);
> > > struct sk_buff *skb = NULL;
> > > - unsigned int size = pkt_dev->cur_pkt_size + 64 + extralen +
> > > - pkt_dev->pkt_overhead;
> > > + unsigned int size;
> > >
> > > + size = pkt_dev->cur_pkt_size + 64 + extralen + pkt_dev->pkt_overhead;
> > > if (pkt_dev->flags & F_NODE) {
> > > int node = pkt_dev->node >= 0 ? pkt_dev->node : numa_node_id();
> > >
> > > @@ -2796,8 +2796,9 @@ static struct sk_buff *pktgen_alloc_skb(struct
> > > net_device *dev,
> > > skb = __netdev_alloc_skb(dev, size, GFP_NOWAIT);
> > > }
> > >
> > > + /* the caller pre-fetches from skb->data and reserves for the mac hdr */
> > > if (likely(skb))
> > > - skb_reserve(skb, LL_RESERVED_SPACE(dev));
> > > + skb_reserve(skb, extralen - 16);
> >
> > Is the 16 here the same as HD_DATA_MOD?
> >
> > Magic numbers...
>
> This magic numbers comes from the current code (the extralen argument),
> this patch just move it around. I can send a v3 using a define for it,
> if really needed, but it seems more a separated clean-up.
Sure, sounds good. Looks like Dave applied it.
- Greg
>
> Thank you,
>
> Paolo
>
