UDP-GRO not working

[Hu, Jiayu]

Hi Param,

> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
> Sent: Thursday, June 9, 2022 4:11 PM
> To: Hu, Jiayu <jiayu.hu at intel.com>
> Cc: dev at dpdk.org; olivier.matz at 6wind.com; kraghav at vmware.com;
> kumaraparameshwaran rathinavel <kumaraparamesh92 at gmail.com>
> Subject: Re: UDP-GRO not working
> 
> Jiayu, please could you comment the explanation below?
> 
> 
> 10/03/2022 13:52, kumaraparameshwaran rathinavel:
> > Hi ,
> >
> > I tried using the UDP GRO feature in DPDK recently and it did not see
> > working. I understand the GRO for UDP is applicable only for
> > fragmented packets, there is the following check in gro_udp4.c
> > /*
> > * Don't process non-fragment packet.
> > */
> > if (!is_ipv4_fragment(ipv4_hdr))
> > return -1;
> >
> >
> > There looks to be some conflict in the definition of RTE_PTYPE in
> > rte_mbuf_ptype.h and the usage of this in GRO layer, rte_gro.c
> >
> > The below are the definitions,
> >
> > #define RTE_PTYPE_L4_TCP                    0x00000100
> > #define RTE_PTYPE_L4_UDP                    0x00000200
> > #define RTE_PTYPE_L4_FRAG                   0x00000300
> >
> > Below is the check in GRO layer,
> >
> > #define IS_IPV4_TCP_PKT(ptype) (RTE_ETH_IS_IPV4_HDR(ptype) && \
> >         ((ptype & RTE_PTYPE_L4_TCP) == RTE_PTYPE_L4_TCP) && \
> >         (RTE_ETH_IS_TUNNEL_PKT(ptype) == 0))
> >
> > #define IS_IPV4_UDP_PKT(ptype) (RTE_ETH_IS_IPV4_HDR(ptype) && \
> >         ((ptype & RTE_PTYPE_L4_UDP) == RTE_PTYPE_L4_UDP) && \
> >         (RTE_ETH_IS_TUNNEL_PKT(ptype) == 0))
> >
> > So, for a fragmented UDP packet both RTE_PTYPE_L4_TCP &
> > RTE_PTYPE_L4_UDP would be set and the GRO layer would be unable to
> > interpret the packet type correctly.

Yes, it's an issue. IS_IPV4_TCP_PKT will recognize a UDP/IPv4 fragment as a TCP/IPv4
packet, and the packet will not go into any UDP based gro function. Thanks for pointing
that out.

Thanks,
Jiayu

> >
> > I am using rte_net_get_ptype API before the packet is being sent to
> > the GRO subsystem as the DPDK PMD for the NIC I am using would not set
> > the packet types as required by the GRO subsystem.
> >
> > I would like to contribute a patch for this bug if this indeed is an
> > issue, I was thinking if the GRO subsystem is L4 fragmented then in
> > the GRO layer invoked the appropriate handler, either
> > gro_tcp4_reassemble or gro_ud4_reassemble.
> >
> > Please let me know if I am missing something here.
> >
> > Thanks,
> > Param.
> >
> 
> 
> 
>