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.
Thank you,
Paolo
