[dpdk-dev] [PATCH v3 2/5] gso: add TCP/IPv4 GSO support

[Hu, Jiayu]

Hi Konstantin and Mark,

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Thursday, September 14, 2017 5:36 PM
> To: Hu, Jiayu <jiayu.hu at intel.com>
> Cc: dev at dpdk.org; Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Tan,
> Jianfeng <jianfeng.tan at intel.com>
> Subject: RE: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support
> 
> 
> 
> > -----Original Message-----
> > From: Hu, Jiayu
> > Sent: Thursday, September 14, 2017 10:29 AM
> > To: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> > Cc: dev at dpdk.org; Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Tan,
> Jianfeng <jianfeng.tan at intel.com>
> > Subject: RE: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support
> >
> > Hi Konstantin,
> >
> > > -----Original Message-----
> > > From: Ananyev, Konstantin
> > > Sent: Thursday, September 14, 2017 4:47 PM
> > > To: Hu, Jiayu <jiayu.hu at intel.com>
> > > Cc: dev at dpdk.org; Kavanagh, Mark B <mark.b.kavanagh at intel.com>;
> Tan,
> > > Jianfeng <jianfeng.tan at intel.com>
> > > Subject: RE: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support
> > >
> > > Hi Jiayu,
> > >
> > > > -----Original Message-----
> > > > From: Hu, Jiayu
> > > > Sent: Thursday, September 14, 2017 7:07 AM
> > > > To: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> > > > Cc: dev at dpdk.org; Kavanagh, Mark B <mark.b.kavanagh at intel.com>;
> Tan,
> > > Jianfeng <jianfeng.tan at intel.com>
> > > > Subject: Re: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support
> > > >
> > > > Hi Konstantin,
> > > >
> > > > On Thu, Sep 14, 2017 at 06:10:37AM +0800, Ananyev, Konstantin wrote:
> > > > >
> > > > > Hi Jiayu,
> > > > >
> > > > > > >
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Ananyev, Konstantin
> > > > > > > > Sent: Tuesday, September 12, 2017 12:18 PM
> > > > > > > > To: Hu, Jiayu <jiayu.hu at intel.com>; dev at dpdk.org
> > > > > > > > Cc: Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Tan,
> Jianfeng
> > > <jianfeng.tan at intel.com>
> > > > > > > > Subject: RE: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support
> > > > > > > >
> > > > > > > > > result, when all of its GSOed segments are freed, the packet is
> > > freed
> > > > > > > > > automatically.
> > > > > > > > > diff --git a/lib/librte_gso/rte_gso.c b/lib/librte_gso/rte_gso.c
> > > > > > > > > index dda50ee..95f6ea6 100644
> > > > > > > > > --- a/lib/librte_gso/rte_gso.c
> > > > > > > > > +++ b/lib/librte_gso/rte_gso.c
> > > > > > > > > @@ -33,18 +33,53 @@
> > > > > > > > >
> > > > > > > > >  #include <errno.h>
> > > > > > > > >
> > > > > > > > > +#include <rte_log.h>
> > > > > > > > > +
> > > > > > > > >  #include "rte_gso.h"
> > > > > > > > > +#include "gso_common.h"
> > > > > > > > > +#include "gso_tcp4.h"
> > > > > > > > >
> > > > > > > > >  int
> > > > > > > > >  rte_gso_segment(struct rte_mbuf *pkt,
> > > > > > > > > -		struct rte_gso_ctx gso_ctx __rte_unused,
> > > > > > > > > +		struct rte_gso_ctx gso_ctx,
> > > > > > > > >  		struct rte_mbuf **pkts_out,
> > > > > > > > >  		uint16_t nb_pkts_out)
> > > > > > > > >  {
> > > > > > > > > +	struct rte_mempool *direct_pool, *indirect_pool;
> > > > > > > > > +	struct rte_mbuf *pkt_seg;
> > > > > > > > > +	uint16_t gso_size;
> > > > > > > > > +	uint8_t ipid_delta;
> > > > > > > > > +	int ret = 1;
> > > > > > > > > +
> > > > > > > > >  	if (pkt == NULL || pkts_out == NULL || nb_pkts_out < 1)
> > > > > > > > >  		return -EINVAL;
> > > > > > > > >
> > > > > > > > > -	pkts_out[0] = pkt;
> > > > > > > > > +	if (gso_ctx.gso_size >= pkt->pkt_len ||
> > > > > > > > > +			(pkt->packet_type & gso_ctx.gso_types) !=
> > > > > > > > > +			pkt->packet_type) {
> > > > > > > > > +		pkts_out[0] = pkt;
> > > > > > > > > +		return ret;
> > > > > > > > > +	}
> > > > > > > > > +
> > > > > > > > > +	direct_pool = gso_ctx.direct_pool;
> > > > > > > > > +	indirect_pool = gso_ctx.indirect_pool;
> > > > > > > > > +	gso_size = gso_ctx.gso_size;
> > > > > > > > > +	ipid_delta = gso_ctx.ipid_flag == RTE_GSO_IPID_INCREASE;
> > > > > > > > > +
> > > > > > > > > +	if (is_ipv4_tcp(pkt->packet_type)) {
> > > > > > > >
> > > > > > > > Probably we need here:
> > > > > > > > If (is_ipv4_tcp(pkt->packet_type)  && (gso_ctx->gso_types &
> > > DEV_TX_OFFLOAD_TCP_TSO) != 0) {...
> > > > > > >
> > > > > > > Sorry, actually it probably should be:
> > > > > > > If (pkt->ol_flags & (PKT_TX_TCP_SEG | PKT_TX_IPV4) ==
> PKT_TX_IPV4
> > > &&
> > > > > > >       (gso_ctx->gso_types & DEV_TX_OFFLOAD_TCP_TSO) != 0) {...
> > > > > >
> > > > > > I don't quite understand why the GSO library should be aware if the
> TSO
> > > > > > flag is set or not. Applications can query device TSO capability
> before
> > > > > > they call the GSO library. Do I misundertsand anything?
> > > > > >
> > > > > > Additionally, we don't need to check if the packet is a TCP/IPv4
> packet
> > > here?
> > > > >
> > > > > Well, right now  PMD we doesn't rely on ptype to figure out what type
> of
> > > packet and
> > > > > what TX offload have to be performed.
> > > > > Instead it looks at TX part of ol_flags, and
> > > > > My thought was that as what we doing is actually TSO in SW, it would
> be
> > > good
> > > > > to use the same API here too.
> > > > > Also with that approach, by setting ol_flags properly user can use the
> > > same gso_ctx and still
> > > > > specify what segmentation to perform on a per-packet basis.
> > > > >
> > > > > Alternative way is to rely on ptype to distinguish should segmentation
> be
> > > performed on that package or not.
> > > > > The only advantage I see here is that if someone would like to add
> GSO
> > > for some new protocol,
> > > > > he wouldn't need to introduce new TX flag value for mbuf.ol_flags.
> > > > > Though he still would need to update TX_OFFLOAD_* capabilities and
> > > probably packet_type definitions.
> > > > >
> > > > > So from my perspective first variant (use HW TSO API) is more
> plausible.
> > > > > Wonder what is your and Mark opinions here?
> > > >
> > > > In the first choice, you mean:
> > > > the GSO library uses gso_ctx->gso_types and mbuf->ol_flags to call a
> > > specific GSO
> > > > segmentation function (e.g. gso_tcp4_segment(), gso_tunnel_xxx()) for
> > > each input packet.
> > > > Applications should parse the packet type, and set an exactly correct
> > > DEV_TX_OFFLOAD_*_TSO
> > > > flag to gso_types and ol_flags according to the packet type. That is, the
> > > value of gso_types
> > > > is on a per-packet basis. Using gso_ctx->gso_types and mbuf->ol_flags
> at
> > > the same time
> > > > is because that DEV_TX_OFFLOAD_*_TSO only tells tunnelling type and
> the
> > > inner L4 type, and
> > > > we need to know L3 type by ol_flags. With this design, HW
> segmentation
> > > and SW segmentation
> > > > are indeed consistent.
> > > >
> > > > If I understand it correctly, applications need to set 'ol_flags =
> > > PKT_TX_IPV4' and
> > > > 'gso_types = DEV_TX_OFFLOAD_VXLAN_TNL_TSO' for a
> > > "ether+ipv4+udp+vxlan+ether+ipv4+
> > > > tcp+payload" packet. But PKT_TX_IPV4 just present the inner L3 type for
> > > tunneled packet.
> > > > How about the outer L3 type? Always assume the inner and the outer L3
> > > type are the same?
> > >
> > > It think that for that case you'll have to set in ol_flags:
> > >
> > > PKT_TX_IPV4 | PKT_TX_OUTER_IPV4 | PKT_TX_TUNNEL_VXLAN |
> > > PKT_TX_TCP_SEG
> >
> > OK, so it means PKT_TX_TCP_SEG is also used for tunneled TSO. The
> > GSO library doesn't need gso_types anymore.
> 
> You still might need gso_ctx.gso_types to let user limit what types of
> segmentation
> that particular gso_ctx supports.
> An alternative would be to assume that each gso_ctx supports all
> currently implemented segmentations.
> This is possible too, but probably not very convenient to the user.

Hmm, make sense.

One thing to confirm: the value of gso_types should be DEV_TX_OFFLOAD_*_TSO,
or new macros?

Jiayu
> Konstantin
> 
> >
> > The first choice makes HW and SW segmentation are totally the same.
> > Applications just need to parse the packet and set proper ol_flags, and
> > the GSO library uses ol_flags to decide which segmentation function to use.
> > I think it's better than the second choice which depending on ptype to
> > choose segmentation function.
> >
> > Jiayu
> > >
> > > Konstantin
> > >
> > > >
> > > > Jiayu
> > > > > Konstantin