Re: [dpdk-dev] [PATCH 9/9] net/virtio: fix Rx handler when checksum is requested

[Olivier MATZ <olivier.matz@6wind.com>]

Platform description
--------------------

guest (dpdk)
+----------------+
|                |
|                |
|    port0       |
+----------------+
       |
       | virtio
       |
+----------------+
|     tap0       |
|                |
|                |
+----------------+
host (linux, vhost-net)

Host configuration
------------------

Start qemu with:

- a ne2k management interface to avoi any conflict with dpdk
- a virtio net device, connected to a tap interface through vhost-net
- mergeable buffers disabled

  /usr/bin/qemu-system-x86_64 -k fr -daemonize --enable-kvm -m 2G -cpu host \
    -smp 3 -serial telnet::40564,server,nowait -serial null \
    -qmp tcp::44340,server,nowait -monitor telnet::49229,server,nowait \
    -device ne2k_pci,mac=de:ad:de:01:02:03,netdev=user.0,addr=03 \
    -netdev user,id=user.0,hostfwd=tcp::34965-:22 \
    -netdev type=tap,id=vhostnet0,script=no,vhost=on,queues=8 \
    -device virtio-net-pci,mrg_rxbuf=off,netdev=vhostnet0,mq=on,vectors=17 \
    -hda "${VM_PATH}/ubuntu-16.04-template.qcow2" \
    -snapshot -vga none -display none

Guest configuration
-------------------

Compile dpdk:

  cd dpdk.org
  make config T=x86_64-native-linuxapp-gcc
  sed -i 's,CONFIG_RTE_LIBRTE_VIRTIO_DEBUG_INIT=n,CONFIG_RTE_LIBRTE_VIRTIO_DEBUG_INIT=y,' build/.config
  sed -i 's,CONFIG_RTE_LIBRTE_VIRTIO_DEBUG_DRIVER=n,CONFIG_RTE_LIBRTE_VIRTIO_DEBUG_DRIVER=y,' build/.config
  make -j4

Prepare environment:

  mkdir -p /mnt/huge
  mount -t hugetlbfs nodev /mnt/huge
  echo 256 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
  modprobe uio_pci_generic
  python usertools/dpdk-devbind.py -b uio_pci_generic 0000:00:02.0

  ./build/app/testpmd -l 0,1 --log-level 7 -- --total-num-mbufs=16384 \
    -i --port-topology=chained --disable-hw-vlan-filter \
    --enable-rx-cksum --disable-hw-vlan-strip --txqflags=0

Without the fix, simple path is used for rx despite it does not
support rx checksum:

  ...
  PMD: set_rxtx_funcs(): virtio: using simple Rx path on port 0
  PMD: set_rxtx_funcs(): virtio: using standard Tx path on port 0
  ...

Configure testpmd:

  set fwd rxonly
  set verbose 1
  start

Without the fix, the received packets don't have the proper checksum
flags (should be PKT_RX_L4_CKSUM_NONE):

port 0/queue 0: received 1 packets
  src=1A:3F:FB:C6:FF:14 - dst=52:54:00:12:34:56 - type=0x0800 - length=74 - nb_segs=1 - sw ptype: L2_ETHER L3_IPV4 L4_TCP  - l2_len=14 - l3_len=20 - l4_len=40 - Receive queue=0x0
  ol_flags: PKT_RX_L4_CKSUM_UNKNOWN PKT_RX_IP_CKSUM_UNKNOWN

With the fix, standard rx path is used and the flags are correct:

  ...
  PMD: set_rxtx_funcs(): virtio: using standard Rx path on port 0
  PMD: set_rxtx_funcs(): virtio: using standard Tx path on port 0
  ...
  port 0/queue 0: received 1 packets
    src=1A:3F:FB:C6:FF:14 - dst=52:54:00:12:34:56 - type=0x0800 - length=74 - nb_segs=1 - hw ptype: L2_ETHER L3_IPV4 L4_TCP  - sw ptype: L2_ETHER L3_IPV4 L4_TCP  - l2_len=14 - l3_len=20 - l4_len=40 - Receive queue=0x0
    ol_flags: PKT_RX_L4_CKSUM_NONE PKT_RX_IP_CKSUM_UNKNOWN