[ovs-dev] [PATCH v2] dpif-netdev: Check for PKT_RX_RSS_HASH flag.

[Pravin Shelar]

On Wed, Sep 9, 2015 at 8:45 AM, Daniele Di Proietto
<diproiettod at vmware.com> wrote:
> DPDK mbufs contain a valid RSS hash only if PKT_RX_RSS_HASH is
> set in 'ol_flags'.  Otherwise the hash is garbage and doesn't
> relate to the packet.
>
> This fixes an issue with vhost, which, being a virtual NIC, doesn't
> compute the hash.
>
> Reported-by: Dongjun <dongj at dtdream.com>
> Suggested-by: Flavio Leitner <fbl at sysclose.org>
> Signed-off-by: Daniele Di Proietto <diproiettod at vmware.com>
> ---
> v1 -> v2:
>
> * Added a comment above dp_packet_get_rss_hash()
> * Added an OVS_UNUSED attribute on dp_packet_rss_valid()
> ---
>  lib/dp-packet.h   | 13 +++++++++++++
>  lib/dpif-netdev.c |  2 +-
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h
> index e4c2593..5532bee 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -514,6 +514,8 @@ dp_packet_reset_packet(struct dp_packet *b, int off)
>      b->l2_5_ofs = b->l3_ofs = b->l4_ofs = UINT16_MAX;
>  }
>
> +/* Returns the RSS hash of the packet 'p'.  Note that the returned value is
> + * correct only if 'dp_packet_rss_valid(p)' returns true */
>  static inline uint32_t
>  dp_packet_get_rss_hash(struct dp_packet *p)
>  {
> @@ -529,11 +531,22 @@ dp_packet_set_rss_hash(struct dp_packet *p, uint32_t hash)
>  {
>  #ifdef DPDK_NETDEV
>      p->mbuf.hash.rss = hash;
> +    p->mbuf.ol_flags |= PKT_RX_RSS_HASH;
>  #else
>      p->rss_hash = hash;
>  #endif
>  }
>
> +static inline bool
> +dp_packet_rss_valid(struct dp_packet *p OVS_UNUSED)
> +{
> +#ifdef DPDK_NETDEV
> +    return p->mbuf.ol_flags & PKT_RX_RSS_HASH;
> +#else
> +    return true;
> +#endif
> +}
> +
>  #ifdef  __cplusplus
>  }
>  #endif
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index db76290..490ced3 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -3100,7 +3100,7 @@ dpif_netdev_packet_get_rss_hash(struct dp_packet *packet,
>  {
>      uint32_t hash, recirc_depth;
>
> -    hash = dp_packet_get_rss_hash(packet);
> +    hash = dp_packet_rss_valid(packet) ? dp_packet_get_rss_hash(packet) : 0;
>      if (OVS_UNLIKELY(!hash)) {
With new valid hash bit, zero hash should be a valid hash value.

>          hash = miniflow_hash_5tuple(mf, 0);
>          dp_packet_set_rss_hash(packet, hash);
> --
> 2.1.4
>
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