[ovs-dev] [PATCH v11 02/14] dp-packet: Init specific mbuf fields.

[Stokes, Ian]

> From: Mark Kavanagh <mark.b.kavanagh at intel.com>
> 
> dp_packets are created using xmalloc(); in the case of OvS-DPDK, it's
> possible the the resultant mbuf portion of the dp_packet contains random
> data. For some mbuf fields, specifically those related to multi-segment
> mbufs and/or offload features, random values may cause unexpected
> behaviour, should the dp_packet's contents be later copied to a DPDK mbuf.
> It is critical therefore, that these fields should be initialized to 0.
> 
> This patch ensures that the following mbuf fields are initialized to
> appropriate values on creation of a new dp_packet:
>    - ol_flags=0
>    - nb_segs=1
>    - tx_offload=0
>    - packet_type=0
>    - next=NULL
> 
> Adapted from an idea by Michael Qiu <qiudayu at chinac.com>:
> https://patchwork.ozlabs.org/patch/777570/
> 
> Co-authored-by: Tiago Lam <tiago.lam at intel.com>
> 
> Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
> Signed-off-by: Tiago Lam <tiago.lam at intel.com>
> Acked-by: Eelco Chaudron <echaudro at redhat.com>
> Acked-by: Flavio Leitner <fbl at sysclose.org>

Thanks Tiago,

This will need a rebase. One minor comment below.
> ---
>  lib/dp-packet.h | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h index ba91e58..b948fe1
> 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -625,14 +625,15 @@ dp_packet_mbuf_rss_flag_reset(struct dp_packet *p
> OVS_UNUSED)  }
> 
>  /* This initialization is needed for packets that do not come
> - * from DPDK interfaces, when vswitchd is built with --with-dpdk.
> - * The DPDK rte library will still otherwise manage the mbuf.
> - * We only need to initialize the mbuf ol_flags. */
> + * from DPDK interfaces, when vswitchd is built with --with-dpdk. */
>  static inline void
>  dp_packet_mbuf_init(struct dp_packet *p OVS_UNUSED)  {  #ifdef
> DPDK_NETDEV
> -    p->mbuf.ol_flags = 0;
> +    struct rte_mbuf *mbuf = &(p->mbuf);
> +    mbuf->ol_flags = mbuf->tx_offload = mbuf->packet_type = 0;
> +    mbuf->nb_segs = 1;

Is it just for ease of access that you cast a pointer to mbuf?

Just looking at the other rte specific functions implemented in the file, they access mbuf via p->mbuf rather than the cast. I would like to keep implementation uniform across functions if possible.

Thanks
Ian

> +    mbuf->next = NULL;
>  #endif
>  }
> 
> --
> 2.7.4