On 02.11.2018 12:06, Tiago Lam wrote:
> From: Mark Kavanagh <[email protected]>
>
> 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
I don't understand why we need this, at least without multi-segs.
malloced packets never reaches dpdk library functions. We're always
re-allocating them. The only exception is the call to egress policer,
but we can clear some fields right before it inside dpdk_do_tx_copy().
We're only using ol_flags, but this field already cleared in current code.
In general, I'd like to drop these 'mbuf' related references in generic
code at all like it done in my recent patch-set:
https://patchwork.ozlabs.org/patch/990181/
Best regards, Ilya Maximets.
>
> Adapted from an idea by Michael Qiu <[email protected]>:
> https://patchwork.ozlabs.org/patch/777570/
>
> Co-authored-by: Tiago Lam <[email protected]>
>
> Signed-off-by: Mark Kavanagh <[email protected]>
> Signed-off-by: Tiago Lam <[email protected]>
> Acked-by: Eelco Chaudron <[email protected]>
> Acked-by: Flavio Leitner <[email protected]>
> ---
> lib/dp-packet.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/lib/dp-packet.h b/lib/dp-packet.h
> index 5b4c9c7..fe34d04 100644
> --- a/lib/dp-packet.h
> +++ b/lib/dp-packet.h
> @@ -498,14 +498,14 @@ dp_packet_mbuf_rss_flag_reset(struct dp_packet *p)
> p->mbuf.ol_flags &= ~PKT_RX_RSS_HASH;
> }
>
> -/* 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. */
> +/* This initialization is needed for packets that do not come from DPDK
> + * interfaces, when vswitchd is built with --with-dpdk. */
> static inline void
> dp_packet_mbuf_init(struct dp_packet *p)
> {
> - p->mbuf.ol_flags = 0;
> + p->mbuf.ol_flags = p->mbuf.tx_offload = p->mbuf.packet_type = 0;
> + p->mbuf.nb_segs = 1;
> + p->mbuf.next = NULL;
> }
>
> static inline bool
>
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