Re: [dpdk-dev] [PATCH 4/5] mbuf: add a pktmbuf copy routine

["Morten Brørup" <mb@smartsharesystems.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
> Sent: Saturday, September 28, 2019 2:38 AM
> 
> This is a commonly used operation that surprisingly the
> DPDK has not supported. The new rte_pktmbuf_copy does a
> deep copy of packet. This is a complete copy including
> meta-data.
> 
> It handles the case where the source mbuf comes from a pool
> with larger data area than the destination pool. The routine
> also has options for skipping data, or truncating at a fixed
> length.

Great initiative, and the offset/length params makes it even better!

> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>  lib/librte_mbuf/rte_mbuf.c           | 70 ++++++++++++++++++++++++++++
>  lib/librte_mbuf/rte_mbuf.h           | 26 +++++++++++
>  lib/librte_mbuf/rte_mbuf_version.map |  1 +
>  3 files changed, 97 insertions(+)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 12d0258a120d..6888d6bd5dfc 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -324,6 +324,76 @@ rte_pktmbuf_linearize(struct rte_mbuf *mbuf)
>  	return 0;
>  }
> 
> +/* Create a deep copy of mbuf */
> +struct rte_mbuf *
> +rte_pktmbuf_copy(const struct rte_mbuf *m, struct rte_mempool *mp,
> +		 uint32_t off, uint32_t len)
> +{
> +	const struct rte_mbuf *seg = m;
> +	struct rte_mbuf *mc, *m_last, **prev;
> +
> +	if (unlikely(off >= m->pkt_len))
> +		return NULL;
> +
> +	mc = rte_pktmbuf_alloc(mp);
> +	if (unlikely(mc == NULL))
> +		return NULL;
> +
> +	if (len > m->pkt_len - off)
> +		len = m->pkt_len - off;
> +
> +	/* clone meta data from original */
> +	mc->port = m->port;
> +	mc->vlan_tci = m->vlan_tci;
> +	mc->vlan_tci_outer = m->vlan_tci_outer;
> +	mc->tx_offload = m->tx_offload;
> +	mc->hash = m->hash;
> +	mc->packet_type = m->packet_type;
> +	mc->timestamp = m->timestamp;

At the dynamic mbuf presentation at DPDK Userspace, it was mentioned that the last 8 bytes of the mbuf could be used by applications. Consider if their values should be copied too, and thus if they should be explicitly define in the mbuf, e.g. dynfield[1,2] like in the dynamic mbuf patch. I don't have an opinion on this, I'm just bringing it to your attention.


Med venlig hilsen / kind regards
- Morten Brørup