Hi Olivier, > -----Original Message----- > From: Olivier MATZ [mailto:olivier.matz at 6wind.com] > Sent: Thursday, November 6, 2014 9:09 PM > To: Liu, Jijiang > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v8 10/10] app/testpmd:test VxLAN Tx checksum > offload > > Hello Jijiang, > > On 11/06/2014 12:24 PM, Liu, Jijiang wrote: > >> Is it possible to have a more formal definition? For instance, is the > >> following definition below correct? > >> > >> "the PKT_RX_TUNNEL_IPV4_HDR flag CAN be set by a driver if the packet > >> contains a tunneling protocol inside an IPv4 header". > > > > Yes, correct. > > > >> If the definition above is correct, I don't see how this flag can > >> help an application to run faster. There is already a flag telling if > >> there is a valid IPv4 header (PKT_RX_IPV4_HDR). As the > >> PKT_RX_TUNNEL_IPV4_HDR flag does not tell what is ip->proto, the work > >> done by an application to dissect a packet would be exactly the same with > >> or > without this flag. > > > > If the PKT_RX_TUNNEL_IPV4_HDR flag is set, which means driver tell > application that incoming packet is encapsulated packet, and application will > process / analyse the packet according to tunneling format indicated by > packet_type. > > Where is it written that when the PKT_RX_TUNNEL_IPV4_HDR flag is set, the > packet_type is also set? > > To which header packet_type refers to? Inner or Outer? Depends? > > What are the possible values for packet_type? > > Is the PKT_RX_TUNNEL_IPV4_HDR flag set in mbuf related to the commands > rx_vxlan_port add|del? If yes, it should be written in the API! > (assuming this is the right API design) > > When the PKT_RX_TUNNEL_IPV4_HDR flag is set, does PKT_RX_IPV4_HDR or > PKT_RX_VLAN_PKT concerns the inner or outer headers? I hope it still concerns > the first one, else it would break many applications relying on the these > flags. > > As you can see, today, an application cannot use PKT_RX_TUNNEL_IPV4_HDR or > m->packet_type because it is not documented. > > > > In terms of VXLAN packet format (MAC,IPv4,UDP,VXLAN,MAC,IP,TCP,PAY4), if > only the PKT_RX_IPV4_HDR flag is set, and application regard its payload as > "from > VXLAN to PAY4", but actually, the real payload is PAY4. > > > >> Please, can you give an example showing in which conditions this flag > >> can help an application? > > > > http://dpdk.org/ml/archives/dev/2014-October/007151.html > > http://dpdk.org/ml/archives/dev/2014-October/007156.html > > > > We used the PKT_RX_TUNNEL_IPV4_HDR in the two patches to help > application identify incoming packet is tunneling packet. > > As you agreed on "the PKT_RX_TUNNEL_IPV4_HDR flag CAN be set by a driver", > it means that if the flag is not present, the application should do the check > in > software. And there are several reasons why the flag may not be present: > - the packet is not a VxLAN packet As long as it is tunneling packet with IPv4/6 header, the flag should be set by driver.
> - the hw or driver was not able to recognize it (I don't know, maybe > if there are IP options the hw will not recognize it?) > - the hw or driver does not support it (all drivers except i40e) E1000/ixgbe don't support VXLAN packet and another tunneling packet, so driver don't need to set this flag. As to other NICs that support tunneling packet , I don't why HW or driver can't recognize it. > So the application has to provide the software equivalent code to process > PAY4. > > The "csum" testpmd forwarding engine is now a bad example because it is not > able to do the same processing in software or hardware. It now only works with > an i40e driver, which was not the case before. Also, the semantic of the > command > line arguments changed. Before, the meaning was "if the flag is set, process > the > checksum in the NIC, else in SW". > Now, it's "huh... it depends on the flag." Currently, If the packet is non-tunneling packet, I believe the "csum" testpmd forwarding engine also works well as before. we changed the engine as follows, which is compatible with previous implementation. - if (pkt_ol_flags & PKT_RX_IPV4_HDR) { + if (pkt_ol_flags & (PKT_RX_IPV4_HDR | PKT_RX_TUNNEL_IPV4_HDR)) { ... - else if (pkt_ol_flags & PKT_RX_IPV6_HDR) { + } else if (pkt_ol_flags & (PKT_RX_IPV6_HDR | PKT_RX_TUNNEL_IPV6_HDR)) { > I will submit a rework of the csum fowarding engine to clarify its behavior. OK. good. > Regards, > Olivier