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...
Thanks,
- Greg
>
> return skb;
> }
> @@ -2830,16 +2831,14 @@ static struct sk_buff *fill_packet_ipv4(struct
> net_device *odev,
> mod_cur_headers(pkt_dev);
> queue_map = pkt_dev->cur_queue_map;
>
> - datalen = (odev->hard_header_len + 16) & ~0xf;
> -
> - skb = pktgen_alloc_skb(odev, pkt_dev, datalen);
> + skb = pktgen_alloc_skb(odev, pkt_dev);
> if (!skb) {
> sprintf(pkt_dev->result, "No memory");
> return NULL;
> }
>
> prefetchw(skb->data);
> - skb_reserve(skb, datalen);
> + skb_reserve(skb, 16);
>
> /* Reserve for ethernet and IP header */
> eth = (__u8 *) skb_push(skb, 14);
> @@ -2959,7 +2958,7 @@ static struct sk_buff *fill_packet_ipv6(struct
> net_device *odev,
> mod_cur_headers(pkt_dev);
> queue_map = pkt_dev->cur_queue_map;
>
> - skb = pktgen_alloc_skb(odev, pkt_dev, 16);
> + skb = pktgen_alloc_skb(odev, pkt_dev);
> if (!skb) {
> sprintf(pkt_dev->result, "No memory");
> return NULL;
