On Wed, 2016-01-20 at 16:27 -0800, Jesse Gross wrote:
> GRO is currently not aware of tunnel metadata generated by lightweight
> tunnels and stored in the dst. This leads to two possible problems:
> * Incorrectly merging two frames that have different metadata.
> * Leaking of allocated metadata from merged frames.
>
> This avoids those problems by comparing the tunnel information before
> merging, similar to how we handle other metadata (such as vlan tags),
> and releasing any state when we are done.
>
> Reported-by: John <john.philli...@hpe.com>
> Fixes: 2e15ea39 ("ip_gre: Add support to collect tunnel metadata.")
> Signed-off-by: Jesse Gross <je...@kernel.org>
> ---
> include/net/dst_metadata.h | 23 +++++++++++++++++++++++
> net/core/dev.c | 9 +++++++--
> 2 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h
> index 6816f0f..c3de935 100644
> --- a/include/net/dst_metadata.h
> +++ b/include/net/dst_metadata.h
> @@ -44,6 +44,29 @@ static inline bool skb_valid_dst(const struct sk_buff *skb)
> return dst && !(dst->flags & DST_METADATA);
> }
>
> +static inline int skb_metadata_dst_cmp(struct sk_buff *skb_a,
> + struct sk_buff *skb_b)
> +{
> + const struct metadata_dst *a = skb_metadata_dst(skb_a);
> + const struct metadata_dst *b = skb_metadata_dst(skb_b);
> +
> + if (!a != !b)
> + return 1;
> +
> + if (!a)
> + return 0;
> +
It is adding 4 conditional test per flow in GRO engine for the fast
path...
With up to 8 flows in GRO (per RX queue), it is a total of 32 added
conditional tests.
You should shortcut to one test :
if (!(skb_a->_skb_refdst | skb_b->_skb_refdst)
return 0;
