[ovs-dev] [PATCH v8 02/13] dp-packet: Init specific mbuf fields.

[Eelco Chaudron]

On 11 Jun 2018, at 18:21, Tiago Lam wrote:

> 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>
> ---
>  lib/dp-packet.h | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h
> index 596cfe6..82e45ad 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -626,13 +626,15 @@ 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. */
> + * The DPDK rte library will still otherwise manage the mbuf. */
>  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;
> +    mbuf->next = NULL;

Are we sure this is all we need? Asking as rte_pktmbuf_reset() cleans of 
some more field, so want to make sure we hit all the corner cases. 
Unfortunately, we can not use it here due to the sanity check.

>  #endif
>  }
>
> -- 
> 2.7.4