[dpdk-dev] [PATCH 2/5] gso/lib: add TCP/IPv4 GSO support

[Jiayu Hu]

Hi Konstantin,

On Wed, Aug 30, 2017 at 09:38:33AM +0800, Ananyev, Konstantin wrote:
> 
> 
> > -----Original Message-----
> > From: Hu, Jiayu
> > Sent: Thursday, August 24, 2017 3:16 PM
> > To: dev at dpdk.org
> > Cc: Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Ananyev, Konstantin <konstantin.ananyev at intel.com>; Tan, Jianfeng
> > <jianfeng.tan at intel.com>; Hu, Jiayu <jiayu.hu at intel.com>
> > Subject: [PATCH 2/5] gso/lib: add TCP/IPv4 GSO support
> > 
> > This patch adds GSO support for TCP/IPv4 packets. Supported packets
> > may include a single VLAN tag. TCP/IPv4 GSO assumes that all input
> > packets have correct checksums, and doesn't update checksums for output
> > packets (the responsibility for this lies with the application).
> > Additionally, TCP/IPv4 GSO doesn't process IP fragmented packets.
> > 
> > TCP/IPv4 GSO uses two chained MBUFs, one direct MBUF and one indrect
> > MBUF, to organize an output packet. Note that we refer to these two
> > chained MBUFs as a two-segment MBUF. The direct MBUF stores the packet
> > header, while the indirect mbuf simply points to a location within the
> > original packet's payload. Consequently, use of the GSO library requires
> > multi-segment MBUF support in the TX functions of the NIC driver.
> > 
> > If a packet is GSOed, TCP/IPv4 GSO reduces its MBUF refcnt by 1. As a
> > result, when all of its GSOed segments are freed, the packet is freed
> > automatically.
> > 
> > Signed-off-by: Jiayu Hu <jiayu.hu at intel.com>
> > Signed-off-by: Mark Kavanagh <mark.b.kavanagh at intel.com>
> > ---
> >  int
> >  rte_gso_segment(struct rte_mbuf *pkt,
> >  		struct rte_gso_ctx gso_ctx,
> >  		struct rte_mbuf **pkts_out,
> > -		uint16_t nb_pkts_out __rte_unused)
> > +		uint16_t nb_pkts_out)
> >  {
> > +	struct rte_mempool *direct_pool, *indirect_pool;
> > +	struct rte_mbuf *pkt_seg;
> > +	uint16_t nb_segments, gso_size;
> > +
> >  	if (pkt == NULL || pkts_out == NULL || gso_ctx.direct_pool ==
> >  			NULL || gso_ctx.indirect_pool == NULL)
> >  		return -EINVAL;
> 
> Probably we don't need to check gso_ctx values for each incoming packet.
> If you feel it is necessary - create  new function rte_gso_ctx_check() that
> could be performed just once per ctx.
> 
> > 
> > -	return 1;
> > +	if ((gso_ctx.gso_types & RTE_GSO_TCP_IPV4) == 0 ||
> > +			gso_ctx.gso_size >= pkt->pkt_len ||
> > +			gso_ctx.gso_size == 0)
> 
> 
> First and third condition seems redundant.

Yes, we don't need the first and the third check here. Please ingore the redundant
reply in the previous mail.

Thanks,
Jiayu