Development Update 22.44

Overview

This is an interim update (“code drop”) to give the validation team an opportunity to take the DPDK code out for a test drive.

Project Name

Note that the P4-OVS Split Architecture has a new name: P4 Control Plane.

What’s Changed

Highlights

  • Restructured Stratum to support TDI variants

  • Integrated DPDK support from P4-OVS

  • Disabled unsupported port attributes in DPDK

  • Updated OVS to newer release

  • Replaced gnmi_cli with gnmi-ctl in DPDK build

TDI variants

When we compared the Stratum files in P4-OVS with their Tofino equivalents, we found significant changes in the ChassisManager, Hal, Main, and Switch classes, as well as SdeWrapper and YangParseTreePaths.

We addressed the first four classes by creating dpdk and tofino subdirectories under the tdi directories, and giving each target its own implementation of the class.

For SdeWrapper, we refactored tdi_sde_wrapper.cc (~3800 lines) into multiple, smaller source files, isolating the target-specific methods in a single file. We then created separate versions of this file for the DPDK and Tofino targets, and moved them to the target-specific subdirectories

For YangParseTreePaths, we refactored yang_parse_tree_paths.cc (originally ~4100 lines, increasing to ~5600 lines in P4-OVS) into multiple, smaller source files, separating out sections of code that had been heavily modified. We then created alternate versions for DPDK. See Refactoring YangParseTreePaths for details.

This restructuring allowed us to port DPDK code from P4-OVS with minimal impact on the existing Tofino code.

DPDK support

The P4 Control Plane software can now be built for either Tofino or DPDK. Features implemented by Stratum (P4Runtime and OpenConfig) should be on par with P4-OVS.

Additional development work is required to support the kernel monitor and to allow OVS to communicate with infrap4d.

To build DPDK under CMake, you must first set the SDE_INSTALL environment variable to point to the root of the P4-DPDK install tree. Then, from the top-level directory of the networking recipe, enter

./make-all --target=dpdk

to perform the build.

If you are familiar with conventional Stratum builds, you can build the DPDK version of Stratum by setting SDE_INSTALL or DPDK_INSTALL to the root of the P4-DPDK install tree. Then change to the root of the stratum submodule (stratum/stratum under the top of the networking recipe) and enter:

bazel build //stratum/hal/bin/tdi/dpdk:stratum_dpdk --define target=dpdk

You can build the Tofino version by issuing one of the above commands, substituting tofino for dpdk.

DPDK port attributes

The following leaves are not applicable to DPDK, and are no longer supported in the DPDK build:

  • auto-negotiate

  • forwarding-viable

  • hardware-port

  • health-indicator

  • last-change

  • loopback-mode

  • negotiated-port-speed

  • oper-status

  • port-speed

  • system-priority

The following leaves have been renamed, to reduce ambiguity or for consistency with other leaves:

  • host is now host-name

  • hotplug is now qemu-hotplug-mode

  • qemu-vm-mac is now qemu-vm-mac-address

OvS Update

OvS has been updated from January 2022 to a more recent version.

gnmi-ctl

For DPDK builds, we have replaced gnmi_cli with gnmi-ctl, which is the new name for the modified version of gnmi_cli that was part of P4-OVS.

For Tofino builds, we install the unmodified version of gnmi_cli.

Known Issues

  • The Teardown test cases in dpdk_hal_test are currently failing.

  • When tunnel is enabled, it is expected to have total size of the tunnel packet less than or equal to 1514 Bytes. To match this size, user need to adjust overlay network interface MTU size not more than 1450 Bytes. Underlay fragmentation is not support, so we need to make sure packet is with in the MTU size of the underlay port.

  • For any udp/tcp packets from overlay network, if checksum issues are noticed on interfaces which are of type VIRTIO-NET, it is recommended to disable checksum using below command.

    ethtool --offload <netdev-name> rx off tx off

  • pna_tcp_connection_tracking demonstrates the PNA add_on_miss feature and flow aging for auto learn flows. It supports partial implementation of TCP state machine.

Coming Attractions

  • Update Stratum to a more recent version

  • Integrate Kernel Monitor

  • Overhaul DPDK port parameter handling