Reporting Bugs¶

Although every situation is different, this section describes how to collect data which will help make efficient use of everyone’s time when dealing with vpp bugs.

Before you press the Jira button to create a bug report - or email vpp-dev@lists.fd.io - please ask yourself whether there’s enough information for someone else to understand and to reproduce the issue given a reasonable amount of effort. Unicast emails to maintainers, committers, and the project PTL are strongly discouraged.

A good strategy for clear-cut bugs: file a detailed Jira ticket, and then send a short description of the issue to vpp-dev@lists.fd.io, perhaps from the Jira ticket description. It’s fine to send email to vpp-dev@lists.fd.io to ask a few questions before filing Jira tickets.

Data to include in bug reports¶

Image version and operating environment¶

Please make sure to include the vpp image version and command-line arguments.

$ sudo bash
# vppctl show version verbose cmdline
Version:                  v18.07-rc0~509-gb9124828
Compiled by:              vppuser
Compile host:             vppbuild
Compile date:             Fri Jul 13 09:05:37 EDT 2018
Compile location:         /scratch/vpp-showversion
Compiler:                 GCC 7.3.0
Current PID:              5211
Command line arguments:
  /scratch/vpp-showversion/build-root/install-vpp_debug-native/vpp/bin/vpp
  unix
  interactive

With respect to the operating environment: if misbehavior involving a specific VM / container / bare-metal environment is involved, please describe the environment in detail:

Linux Distro (e.g. Ubuntu 18.04.2 LTS, CentOS-7, etc.)
NIC type(s) (ixgbe, i40e, enic, etc. etc.), vhost-user, tuntap
NUMA configuration if applicable

Please note the CPU architecture (x86_86, aarch64), and hardware platform.

When practicable, please report issues against released software, or unmodified master/latest software.

“Show” command output¶

Every situation is different. If the issue involves a sequence of debug CLI command, please enable CLI command logging, and send the sequence involved. Note that the debug CLI is a developer’s tool - no warranty express or implied - and that we may choose not to fix debug CLI bugs.

Please include “show error” [error counter] output. It’s often helpful to “clear error”, send a bit of traffic, then “show error” particularly when running vpp on noisy networks.

Please include ip4 / ip6 / mpls FIB contents (“show ip fib”, “show ip6 fib”, “show mpls fib”, “show mpls tunnel”).

Please include “show hardware”, “show interface”, and “show interface address” output

Here is a consolidated set of commands that are generally useful before/after sending traffic. Before sending traffic:

vppctl clear hardware
vppctl clear interface
vppctl clear error
vppctl clear run

Send some traffic and then issue the following commands.

vppctl show version verbose
vppctl show hardware
vppctl show interface address
vppctl show interface
vppctl show run
vppctl show error

Here are some protocol specific show commands that may also make sense. Only include those features which have been configured.

vppctl show l2fib
vppctl show bridge-domain

vppctl show ip fib
vppctl show ip neighbors

vppctl show ip6 fib
vppctl show ip6 neighbors

vppctl show mpls fib
vppctl show mpls tunnel

Network Topology¶

Please include a crisp description of the network topology, including L2 / IP / MPLS / segment-routing addressing details. If you expect folks to reproduce and debug issues, this is a must.

At or above a certain level of topological complexity, it becomes problematic to reproduce the original setup.

Packet Tracer Output¶

If you capture packet tracer output which seems relevant, please include it.

vppctl trace add dpdk-input 100  # or similar

send-traffic

vppctl show trace

Capturing post-mortem data¶

It should go without saying, but anyhow: please put post-mortem data in obvious, accessible places. Time wasted trying to acquire accounts, credentials, and IP addresses simply delays problem resolution.

Please remember to add post-mortem data location information to Jira tickets.

Syslog Output¶

The vpp signal handler typically writes a certain amount of data in /var/log/syslog before exiting. Make sure to check for evidence, e.g via “grep /usr/bin/vpp /var/log/syslog” or similar.

Binary API Trace¶

If the issue involves a sequence of control-plane API messages - even a very long sequence - please enable control-plane API tracing. Control-plane API post-mortem traces end up in /tmp/api_post_mortem.<pid>.

Please remember to put post-mortem binary api traces in accessible places.

These API traces are especially helpful in cases where the vpp engine is throwing traffic on the floor, e.g. for want of a default route or similar.

Make sure to leave the default stanza “… api-trace { on } … ” in the vpp startup configuration file /etc/vpp/startup.conf, or to include it in the command line arguments passed by orchestration software.

Core Files¶

Production systems, as well as long-running pre-production soak-test systems, must arrange to collect core images. There are various ways to configure core image capture, including e.g. the Ubuntu “corekeeper” package. In a pinch, the following very basic sequence will capture usable vpp core files in /tmp/dumps.

# mkdir -p /tmp/dumps
# sysctl -w debug.exception-trace=1
# sysctl -w kernel.core_pattern="/tmp/dumps/%e-%t"
# ulimit -c unlimited
# echo 2 > /proc/sys/fs/suid_dumpable

If you start VPP from systemd, you also need to edit /lib/systemd/system/vpp.service and uncomment the “LimitCORE=infinity” line before restarting VPP.

Vpp core files often appear enormous, but they are invariably sparse. Gzip compresses them to manageable sizes. A multi-GByte corefile often compresses to 10-20 Mbytes.

When decompressing a vpp core file, we suggest using “dd” as shown to create a sparse, uncompressed core file:

$ zcat vpp_core.gz | dd conv=sparse of=vpp_core

Please remember to put compressed core files in accessible places.

Make sure to leave the default stanza “… unix { … full-coredump … } … ” in the vpp startup configuration file /etc/vpp/startup.conf, or to include it in the command line arguments passed by orchestration software.

Core files from Private Images¶

Core files from private images require special handling. If it’s necessary to go that route, copy the exact Debian packages (or RPMs) which correspond to the core file to the same public place as the core file. A no-excuses-allowed, hard-and-fast requirement.

In particular:

libvppinfra_<version>_<arch>.deb # vppinfra library
libvppinfra-dev_<version>_<arch>.deb # vppinfra library development pkg
vpp_<version>_<arch>.deb         # the vpp executable
vpp-dbg_<version>_<arch>.deb     # debug symbols
vpp-dev_<version>_<arch>.deb     # vpp development pkg
vpp-lib_<version>_<arch>.deb     # shared libraries
vpp-plugin-core_<version>_<arch>.deb # core plugins
vpp-plugin-dpdk_<version>_<arch>.deb # dpdk plugin

For reference, please include git commit-ID, branch, and git repo information [for repos other than gerrit.fd.io] in the Jira ticket.

Note that git commit-ids are crypto sums of the head [latest] merged patch. They say nothing whatsoever about local workspace modifications, branching, or the git repo in question.

Even given a byte-for-byte identical source tree, it’s easy to build dramatically different binary artifacts. All it takes is a different toolchain version.

On-the-fly Core File Compression¶

Depending on operational requirements, it’s possible to compress corefiles as they are generated. Please note that it takes several seconds’ worth of wall-clock time to compress a vpp core file on the fly, during which all packet processing activities are suspended.

To create compressed core files on the fly, create the following script, e.g. in /usr/local/bin/compressed_corefiles, owned by root, executable:

#!/bin/sh
exec /bin/gzip -f - >"/tmp/dumps/core-$1.$2.gz"

Adjust the kernel core file pattern as shown:

sysctl -w kernel.core_pattern="|/usr/local/bin/compressed_corefiles %e %t"

Core File Summary¶

Bottom line: please follow core file handling instructions to the letter. It’s not complicated. Simply copy the exact Debian packages or RPMs which correspond to core files to accessible locations.

If we go through the setup process only to discover that the image and core files don’t match, it will simply delay resolution of the issue; to say nothing of irritating the person who just wasted their time.