Difference between revisions of "VPP/Command-line Arguments"

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Revision as of 03:02, 28 April 2016

Introduction

The vpp network stack comes with a command-line interface that can be used for debugging purposes.

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Command-line arguments

The vpp stack can be configured from the command-line in a number of ways. Specific applications built on the stack have been known to require a dozen arguments, depending on requirements. This section describes commonly-used command-line options. These options are parsed by individual bits of code, similar to the action functions of the CLI parser.

You can find command-line argument parsers in the source code by searching for instances of the VLIB_CONFIG_FUNCTION macro. The actual command-line invocation syntax is extremely flexible.

macro invocation: VLIB_CONFIG_FUNCTION (foo_config, "foo")
command-line: "foo { arg1 arg2 arg3 ... }"

When using the command on the command line, surround the list of arguments with curly braces.

NOTE: If you supply a single argument to a specific configuration function, you do not need to surround the argument with curly braces. For example, the following command argument does not have braces:

# /cisco/bin/swt unix interactive
SWT: <start-typing..>

Vpp applications must be able to locate their own executable images. The simplest way to ensure this will work: invoke a vpp application by giving its absolute path. At startup, vpp aplications parse through their own Elf-sections [primarily] to make lists of init, configuration, and exit handlers. In gdb, it's often sufficient to start an application like this:

(gdb) r unix interactive

"unix" parameters

"tuntap" parameters

The "tuntap" driver configures a point-to-point interface between the vpp engine and the local Linux kernel stack. This allows e.g. users to ssh to the host / VM / container via vpp "revenue" interfaces. It's marginally useful, and is currently disabled by default. To [dynamically] create TAP interfaces - the preferred scheme - see the "tap_connect" binary API

Here's a typical multiple parameter invocation:

 tuntap { ethernet have-normal-interface name vpp1 }

"api-trace" parameters

The ability to trace, dump, and replay control-plane API traces makes all the difference in the world when trying to understand what the control-plane has tried to ask the forwarding-plane to do.

Typically, one simply enables the API message trace scheme:

api-trace { on }

"cpu" parameters

Command-line CPU configuration controls the creation of named thread types, and the cpu affinity thereof. As of this writing, the cpu configuration function supports these parameters:

In some cases, it may be necessary to place thread instances manually:

Note that the "main" thread always occupies the lowest core-id specified in the DPDK [process-level] coremask.

Here's a full-bore manual placement example:

/cisco/bin/vpe  unix interactive tuntap disable cpu { main-thread-io coremask-workers 18 coremask-stats 4 } dpdk {coremask 1e}

# taskset -a -p <vpe-pid>
pid 16251's current affinity mask: 2   # main thread
pid 16288's current affinity mask: ffffff # DPDK interrupt thread (not bound to a core)
pid 16289's current affinity mask: 4 # stats thread
pid 16290's current affinity mask: 8 # worker thread 0
pid 16291's current affinity mask: 10 # worker thread 1

"dpdk" parameters

Command line DPDK configuration controls a number of parameters, including device whitelisting, the number of CPUs available for launching dpdk-eal-controlled threads, the number of I/O buffers, and the process affinity mask.

In addition, the DPDK configuration function attempts to support all of the DPDK EAL configuration parameters.

Popular options include:

All of the DPDK EAL options should be available. See .../open-repo/vnet/vnet/devices/dpdk/dpdk.h, look at the set of "foreach_eal_XXX" macros.

"l2tp" parameters

ip6-l2tpv3 configuration controls the method used to locate a specific ip6-l2tpv3 tunnel. The following settings are mutually exclusive

Refer to .../open-repo/vnet/vnet/devices/dpdk/{dpdk.h, init.c} for more details.

"oam" parameters

Oam configuration controls the (ip4-icmp) interval, and number of misses allowed before reporting an oam target down to any registered listener.

"heapsize" parameter

Heapsize configuration controls the size of the main heap. The heap size is configured very early in the boot sequence, before loading plug-ins or doing much of anything else.

"plugin_path" parameter

Plugin_path configuration controls the set of directories searched for vlib plugins. Supply a colon-separated list of (absolute) directory names:

"cj" parameters

The cj thread-safe circular log buffer scheme is occasionally useful when chasing bugs. Calls to it should not be checked in. See .../vlib/vlib/unix/cj.c.

"vhost-user" parameters

Vhost-user configuration parameters control the vhost-user driver.

"l2learn" parameter

Configures the number of L2 (MAC) addresses in the L2 FIB at any one time. Defaults to 1M entries.