csharg

csharg is a Golang module for easy CLI access to the Packetflix capture service deployed to container hosts, such as Edgeshark on Siemens Industrial Edge and also standalone Docker hosts.

csharg is part of the "Edgeshark" project that consist of several repositories:

• Edgeshark Hub repository
• G(h)ostwire discovery service
• Packetflix packet streaming service
• Containershark Extcap plugin for Wireshark
• support modules:
  • 🖝 csharg (CLI) 🖜
  • mobydig
  • ieddata

Usage

csharg can be used in different ways:

• as the standalone CLI program csharg, such as in:

  csharg --host localhost:5001 capture mycontainer | wireshark -k -i -

  For details, see further down below.

• via the Containershark Extcap plugin for Wireshark with a nice Wireshark UI.

• and finally, directly in your own applications and (micro) services by integrating the csharg module without having to care about details of the Packetflix capture service API.

key:

• $ csharg ... denotes a CLI command.
• csharg.New...() denotes a csharg package constructor for connecting to the capture service of container hosts.

Build

To build csharg binary distribution packages for serveral Linux architectures, as well as for Windows (only amd64):

make dist

Afterwards, the dist/ directory contains the built packages and archives. Supported CPU architectures:

• amd64
• arm64

The following package formats are currently supported:

• .apk
• .deb
• .rpm
• .tar.gz

csharg CLI

Commands

This section doesn't aim to be a comprehensive documentation of the cshargCLI, but will give you an idea as to what you might be able to do with the csharg CLI. If in doubt, please use csharg help for up-to-date documentation.

• csharg list: list available capture targets in a Kubernetes cluster.
• csharg capture: capture and live stream network traffic from a capture target, such as a pod, standalone container, et cetera.
• csharg help: ask for help about any of the csharg commands.
• csharg options: list the global command-line options which apply to all commands.
• csharg version: show csharg version.

The CLI --host http://$HOSTNAME[:$PORT] argument specifies hostname (DNS/label or IP address) and optional port number of the Packetflix service on container host. Standard deployments use port :5001. Please note that the port always needs to be specified, unless it is port :80 (or :443 for HTTPS).

To list available capture targets in your container host or local KinD deployment:

• list only stand-alone containers, which are not inside pods: csharg --host ... list containers. Please note that due to the Kubernetes sandbox model with shared network stacks csharg doesn't show or handle the containers inside pods, but only containers that do not belong to any pod.
• list network stacks which neither belong to pods nor stand-alone containers: csharg --host ... list networks (includes bind-mount'ed network stacks).
• list only pods: csharg --host ... list pods (KinD).
• list all capture targets (and we really mean all): csharg -host ... list.

Controlling Capture Target List Output

csharg will list capture targets in tabular format, unless another output format is specified. For example:

$ csharg -host localhost:5001 list
TARGET                                                       TYPE         NODE
accounts-daemon(997)                                         proc         localhost
chrome(79357)                                                proc         localhost
default/nginx                                                pod          localhost
gostwire-gostwire-1                                          docker       localhost
haveged(984)                                                 proc         localhost
kind-control-plane                                           docker       localhost
kube-system/coredns-787d4945fb-787ms                         pod          localhost
kube-system/coredns-787d4945fb-s6drr                         pod          localhost
kube-system/etcd-kind-control-plane                          pod          localhost
kube-system/kindnet-zhgf2                                    pod          localhost
kube-system/kube-apiserver-kind-control-plane                pod          localhost
kube-system/kube-controller-manager-kind-control-plane       pod          localhost
kube-system/kube-proxy-hgbpl                                 pod          localhost
kube-system/kube-scheduler-kind-control-plane                pod          localhost
local-path-storage/local-path-provisioner-75f5b54ffd-xrzg8   pod          localhost
packetflix-packetflix-1                                      docker       localhost
rtkit-daemon(1528)                                           proc         localhost
systemd(1)                                                   proc         localhost

The following output formatting options are available (see also csharg help list):

• -o wide: wide tabular multi-column format.
• -o json: list capture target details in JSON format.
• -o jsonpath=${JSONPATH-EXPRESSION}: print fields defined in the JSONPath expression.
• -o jsonpath-file=$FILENAME: print fields defined in the JSONPath expression from file filename.
• -o yaml: lots of ugly YAML data for the available capture targets.
• -o custom-columns=$SPEC, where $SPEC is a kubectl-like custom columns specification. For instance: -o custom-columns=NAME:.Name,NODE:.NodeName.
• -o custom-columns-file=$FILENAME: use the custom columns format from file filename.
• -o name: simply lists only target names, but no other details.

Please note that --no-headers can be used with the standard format, as well as -o wide, -o custom-columns=..., and -o custom-columns-file=... to hide the column headers.

Capture Live Network Traffic

In the most simple case, just specify a unique capture target name (such as a container name) and then csharg will stream the captured network traffic to stdout in pcapng format (please note the podnamespace/podname notation, with podnamespace being mandatory):

csharg --host localhost:5001 capture container-name

Use option -w filename to write the packet capture stream into the file filename. As it is custom, -w - again writes to stdout (which is the default anyway).

Probably more typical is to feed the live stream directly into Wireshark, this works without having to install the Containershark extcap plugin:

csharg --host localhost:5001 capture special/mypod | wireshark -k -i -

The capture will run until you terminate/interrupt csharg with SIGINT or SIGTERM, for instance, by pressing ^C in your terminal session where you started csharg in the foreground.

By default, captures will capture from all network interfaces of the specified target. Use one or multiple -i/--interface options to specify only those network interfaces you want to capture from:

csharg --host ... capture container container-name -i lo

Filter captures at the source using the --filter option -- the capture filter syntax is Wireshark's dumpcap filter syntax.

Standalone Host: as long as the target name is unique, csharg capture will start a capture even without having to specify the node/host. This makes capturing from a standalone container host especially convenient when using csharg capture ... instead of csharg capture container ....

Look Mum, My First Csharg Program!

Capture five minutes of network traffic on all network interfaces of container "my-container" and write the captured packets into a file named "my-container.pcapng".

package main

import (
    "github.com/siemens/csharg"
    "os"
    "time"
)

func main() {
    // Connect to the host-local Packetflix capture service. Default settings
    // and service time limits (30s) apply. Sensibly, capture  streaming is
    // not time limited.
    st, _ := csharg.NewSharkTankOnHost("http://localhost:5001", nil)
    // Create a new packet capture file...
    f, _ := os.Create("my-container.pcapng")
    defer f.Close()
    // ...and run a network packet capture for five minutes on the container
    // "my-container".
    capt, _ := st.CaptureContainer(f, "my-container", nil)
    capt.StopAfter(5*time.Minute)
}

FAQ

• What does "csharg" mean?

  "csharg" is short for "Container Shark" or "Containershark".

• Shouldn't this be "cshark"?

  Not necessarily, as this is a Go package.

VSCode Tasks

The included csharg.code-workspace defines the following tasks:

• View Go module documentation task: installs pkgsite, if not done already so, then starts pkgsite and opens VSCode's integrated ("simple") browser to show the csharg documentation.

Aux Tasks

• pksite service: auxilliary task to run pkgsite as a background service using scripts/pkgsite.sh. The script leverages browser-sync and nodemon to hot reload the Go module documentation on changes; many thanks to @mdaverde's Build your Golang package docs locally for paving the way. scripts/pkgsite.sh adds automatic installation of pkgsite, as well as the browser-sync and nodemon npm packages for the local user.
• view pkgsite: auxilliary task to open the VSCode-integrated "simple" browser and pass it the local URL to open in order to show the module documentation rendered by pkgsite. This requires a detour via a task input with ID "pkgsite".

Make Targets

• make: lists all targets.
• make clean: removes the build artefacts.
• make dist: builds snapshot packages and archives of the csharg CLI binary.
• make pkgsite: installs x/pkgsite, as well as the browser-sync and nodemon npm packages first, if not already done so. Then runs the pkgsite and hot reloads it whenever the documentation changes.
• make report: installs @gojp/goreportcard if not yet done so and then runs it on the code base.
• make vuln: install (or updates) govuln and then checks the Go sources.

Contributing

Please see CONTRIBUTING.md.

License and Copyright

(c) Siemens AG 2023

SPDX-License-Identifier: MIT