docs: add VPP Container Testbench example and lab

Adding a "VPP container testbench" (pair of Docker containers plus
helper scripts to test Linux and VPP interfaces). Will be part of a
larger set of labs/exercises/tutorials. Putting this baseline setup up
for review first to see if the community sees use/value in it. If so,
additional exercises using the testbench will be added gradually.

Type: improvement
Signed-off-by: Matthew Giassa <mgiassa@cisco.com>
Change-Id: I582310f7355419e907d575f640482ca49cbb282f

6 files changed, 842 insertions, 0 deletions

diff --git a/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench b/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench
new file mode 100644
index 00000000000..f7e19feebbf
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench
@@ -0,0 +1,82 @@
+#------------------------------------------------------------------------------#
+# @brief:       Dockerfile for building the VPP testbench project.
+# @author:      Matthew Giassa <mgiassa@cisco.com>
+# @copyright:   (C) Cisco 2021.
+#------------------------------------------------------------------------------#
+# Baseline image both client and server inherit from.
+FROM ubuntu:focal as baseline
+
+# System packages.
+RUN apt update -y && \
+    DEBIAN_FRONTEND="noninteractive" apt install -y tzdata termshark && \
+    apt install -y \
+        apt-transport-https \
+        axel \
+        bash \
+        binutils \
+        bridge-utils \
+        ca-certificates \
+        coreutils \
+        curl \
+        gnupg \
+        htop \
+        iftop \
+        iproute2 \
+        iptables \
+        iputils-ping \
+        netcat \
+        net-tools \
+        nload \
+        nmap \
+        procps \
+        python3 \
+        python3-dev \
+        python3-pip \
+        sudo \
+        wget \
+        tcpdump \
+        vim \
+        && \
+    apt clean -y
+# Python packages.
+RUN python3 -m pip install \
+    scapy
+
+# VPP.
+RUN bash -c "curl -L https://packagecloud.io/fdio/master/gpgkey | apt-key add -" && \
+    bash -c "echo \"deb [trusted=yes] https://packagecloud.io/fdio/release/ubuntu focal main\" >> /etc/apt/sources.list.d/99fd.io.list" && \
+    apt update && \
+    apt install -y \
+        vpp \
+        vpp-plugin-core \
+        vpp-plugin-dpdk \
+    && \
+    apt clean -y
+
+# Used by client/server entrypoint scripts.
+ADD vpp_testbench_helpers.sh /
+
+
+#------------------------------------------------------------------------------#
+# Client image.
+FROM baseline as client_img
+# Enable a health probe.
+ARG HEALTHCHECK_PORT=8080
+ENV HEALTHCHECK_PORT_RUNTIME="${HEALTHCHECK_PORT}"
+HEALTHCHECK CMD curl --fail "http://localhost:$HEALTHCHECK_PORT_RUNTIME" || exit 1
+# Image-specific overrides.
+ADD ./entrypoint_client.sh /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]
+
+
+#------------------------------------------------------------------------------#
+# Server image.
+FROM baseline as server_img
+# Enable a health probe.
+ARG HEALTHCHECK_PORT=8080
+ENV HEALTHCHECK_PORT_RUNTIME="${HEALTHCHECK_PORT}"
+HEALTHCHECK CMD curl --fail "http://localhost:$HEALTHCHECK_PORT_RUNTIME" || exit 1
+# Image-specific overrides.
+ADD ./entrypoint_server.sh /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]
+
diff --git a/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench.dockerignore b/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench.dockerignore
new file mode 100644
index 00000000000..0a39eeac666
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/Dockerfile.vpp_testbench.dockerignore
@@ -0,0 +1,14 @@
+#------------------------------------------------------------------------------#
+# @brief:       Dockerfile permit/deny-list for building the VPP testbench
+#               project.
+# @author:      Matthew Giassa <mgiassa@cisco.com>
+# @copyright:   (C) Cisco 2021.
+#------------------------------------------------------------------------------#
+# Ignore everything by default. Permit-list only.
+*
+
+# Entrypoint scripts and other artifacts.
+!entrypoint_client.sh
+!entrypoint_server.sh
+!vpp_testbench_helpers.sh
+
diff --git a/docs/usecases/vpp_testbench/src/Makefile b/docs/usecases/vpp_testbench/src/Makefile
new file mode 100644
index 00000000000..4433edbe4d7
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/Makefile
@@ -0,0 +1,147 @@
+################################################################################
+# @brief:       Makefile for building the VPP testbench example.
+# @author:      Matthew Giassa.
+# @copyright:   (C) Cisco 2021.
+################################################################################
+#------------------------------------------------------------------------------#
+# Constants and settings.
+#------------------------------------------------------------------------------#
+SHELL=/bin/bash
+.DEFAULT_GOAL: all
+
+# Image names.
+# TODO: semver2 format if we want to publish these to a registry.
+DOCKER_CLIENT_IMG               := vpp-testbench-client
+DOCKER_CLIENT_REL               := local
+DOCKER_CLIENT_IMG_FULL          := $(DOCKER_CLIENT_IMG):$(DOCKER_CLIENT_REL)
+DOCKER_SERVER_IMG               := vpp-testbench-server
+DOCKER_SERVER_REL               := local
+DOCKER_SERVER_IMG_FULL          := $(DOCKER_SERVER_IMG):$(DOCKER_SERVER_REL)
+# Docker build-time settings (and run-time settings as well).
+DOCKER_HEALTH_PROBE_PORT        := $(shell bash -c ". vpp_testbench_helpers.sh; host_only_get_docker_health_probe_port")
+
+#------------------------------------------------------------------------------#
+# Functions.
+#------------------------------------------------------------------------------#
+#------------------------------------------------------------------------------#
+# Cleanup running containers, Docker networks, etc.; from previous runs.
+define cleanup_everything
+	# Terminate the containers.
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_kill_testbench_client_container $(DOCKER_CLIENT_IMG_FULL); \
+		host_only_kill_testbench_server_container $(DOCKER_SERVER_IMG_FULL); \
+		"
+
+	# Cleanup Docker bridge network.
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_destroy_docker_networks; \
+		"
+endef
+
+#------------------------------------------------------------------------------#
+# Launch our containers and connect them to a private Docker network for
+# testing.
+define launch_testbench
+	# Create Docker bridge network.
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_create_docker_networks; \
+		"
+
+	# Launch the containers.
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_run_testbench_client_container $(DOCKER_CLIENT_IMG_FULL); \
+		host_only_run_testbench_server_container $(DOCKER_SERVER_IMG_FULL); \
+		"
+
+	# Entrypoint scripts will bring up the various links.
+	# Use "docker ps" to check status of containers, see if their health
+	# probes are working as expected (i.e. "health"), etc.
+endef
+
+#------------------------------------------------------------------------------#
+# Goals.
+#------------------------------------------------------------------------------#
+#------------------------------------------------------------------------------#
+# Default goal.
+.PHONY: all
+all: docker
+	@echo Done.
+
+#------------------------------------------------------------------------------#
+# Build all docker images.
+.PHONY: docker
+docker: Dockerfile.vpp_testbench Dockerfile.vpp_testbench.dockerignore \
+	entrypoint_client.sh entrypoint_server.sh \
+	vpp_testbench_helpers.sh
+	# Client image.
+	DOCKER_BUILDKIT=1 docker build \
+			--file Dockerfile.vpp_testbench \
+			--build-arg HEALTHCHECK_PORT=$(DOCKER_HEALTH_PROBE_PORT) \
+			--tag $(DOCKER_CLIENT_IMG_FULL) \
+			--target client_img \
+			.
+	# Server image.
+	DOCKER_BUILDKIT=1 docker build \
+			--file Dockerfile.vpp_testbench \
+			--build-arg HEALTHCHECK_PORT=$(DOCKER_HEALTH_PROBE_PORT) \
+			--tag $(DOCKER_SERVER_IMG_FULL) \
+			--target server_img \
+			.
+
+#------------------------------------------------------------------------------#
+# Execute end-to-end test via containers.
+.PHONY: test
+test:
+	# Cleanup anything from previous runs.
+	$(call cleanup_everything)
+
+	# Launch our testbench.
+	$(call launch_testbench)
+
+	# Final cleanup.
+	$(call cleanup_everything)
+
+#------------------------------------------------------------------------------#
+# For manually cleaning up a test that fails partway through its execution.
+.PHONY: clean
+clean:
+	$(call cleanup_everything)
+
+#------------------------------------------------------------------------------#
+# For manually launching our testbench for interactive testing.
+.PHONY: start
+start:
+	$(call launch_testbench)
+
+#------------------------------------------------------------------------------#
+# For manually stopping (and cleaning up) our testbench.
+.PHONY: stop
+stop:
+	$(call cleanup_everything)
+
+#------------------------------------------------------------------------------#
+# Create an interactive shell session connected to the client container (for
+# manual testing). Typically preceded by "make start", and concluded with
+# "make stop" after exiting the shell.
+.PHONY: shell_client
+shell_client:
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_shell_client_container; \
+		"
+
+#------------------------------------------------------------------------------#
+# Create an interactive shell session connected to the server container (for
+# manual testing). Typically preceded by "make start", and concluded with
+# "make stop" after exiting the shell.
+.PHONY: shell_server
+shell_server:
+	bash -c "\
+		. vpp_testbench_helpers.sh; \
+		host_only_shell_server_container; \
+		"
+
diff --git a/docs/usecases/vpp_testbench/src/entrypoint_client.sh b/docs/usecases/vpp_testbench/src/entrypoint_client.sh
new file mode 100755
index 00000000000..432c2769730
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/entrypoint_client.sh
@@ -0,0 +1,150 @@
+#!/bin/bash
+################################################################################
+# @brief:       Launcher/entrypoint script plus helper functions for "client
+#               side" container in the VPP testbench.
+# @author:      Matthew Giassa <mgiassa@cisco.com>
+# @copyright:   (C) Cisco 2021.
+################################################################################
+
+################################################################################
+# Dependencies.
+################################################################################
+# Import common settings for server and client. This is supplied via the
+# Dockerfile build.
+# shellcheck disable=SC1091
+. vpp_testbench_helpers.sh
+
+################################################################################
+# Globals.
+################################################################################
+# VPP instance socket.
+export VPP_SOCK=/run/vpp/vpp.testbench-client.sock
+# Alias for vppctl that uses the correct socket name.
+export VPPCTL="vppctl -s ${VPP_SOCK}"
+# Our "Docker bridge network". Don't change this value.
+export NET_IF_DOCKER="eth0"
+# Name of link associated with our VXLAN.
+export LINK_VXLAN_LINUX="vxlan-vid-${VXLAN_ID_LINUX}"
+
+################################################################################
+# Function definitions.
+################################################################################
+#------------------------------------------------------------------------------#
+# @brief:   Alias for vppctl (knowing which API socket to use).
+function vc()
+{
+    vppctl -s "${VPP_SOCK}" "${@}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Used to initialize/configure the client container once it's up and
+#           running.
+function context_create()
+{
+    set -x
+    echo "Running client. Host: $(hostname)"
+    local mtu
+
+    # Setup VXLAN overlay.
+    ip link add "${LINK_VXLAN_LINUX}" \
+        type vxlan \
+        id "${VXLAN_ID_LINUX}" \
+        dstport "${VXLAN_PORT}" \
+        local "${CLIENT_BRIDGE_IP_DOCKER}" \
+        group "${MC_VXLAN_ADDR_LINUX}" \
+        dev "${NET_IF_DOCKER}" \
+        ttl 1
+    ip link set "${LINK_VXLAN_LINUX}" up
+    ip addr add "${CLIENT_VXLAN_IP_LINUX}/${MASK_VXLAN_LINUX}" dev "${LINK_VXLAN_LINUX}"
+
+    # Get MTU of interface. VXLAN must use a smaller value due to overhead.
+    mtu="$(cat /sys/class/net/${NET_IF_DOCKER}/mtu)"
+
+    # Decrease VXLAN MTU. This should already be handled for us by iproute2, but
+    # just being cautious.
+    ip link set dev "${LINK_VXLAN_LINUX}" mtu "$((mtu - 50))"
+
+    # Bring-up VPP and create tap interfaces and VXLAN tunnel.
+    vpp \
+        unix '{' log /tmp/vpp1.log full-coredump cli-listen ${VPP_SOCK} '}' \
+        api-segment '{' prefix vpp1 '}' \
+        api-trace '{' on '}' \
+        dpdk '{' uio-driver uio_pci_generic no-pci '}'
+
+    # Wait for VPP to come up.
+    while ! ${VPPCTL} show log; do
+        sleep 1
+    done
+
+    # Bring up the memif interface and assign an IP to it.
+    ${VPPCTL} create interface memif id 0 slave
+    sleep 1
+    ${VPPCTL} set int state memif0/0 up
+    ${VPPCTL} set int ip address memif0/0 "${CLIENT_VPP_MEMIF_IP}/${VPP_MEMIF_NM}"
+
+    # Create VPP-controlled tap interface bridged to the memif.
+    ${VPPCTL} create tap id 0 host-if-name vpp-tap-0
+    sleep 1
+    ${VPPCTL} set interface state tap0 up
+    ip addr add "${CLIENT_VPP_TAP_IP_MEMIF}/${VPP_TAP_NM}" dev vpp-tap-0
+    ${VPPCTL} set interface l2 bridge tap0          "${VPP_BRIDGE_DOMAIN_TAP}"
+    ${VPPCTL} set interface l2 bridge memif0/0      "${VPP_BRIDGE_DOMAIN_TAP}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Used to shutdown/cleanup the client container.
+function context_destroy()
+{
+    # OS will reclaim interfaces and resources when container is terminated.
+    :
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Client worker loop to keep the container alive. Just idles.
+function context_loop()
+{
+    # Sleep indefinitely (to keep container alive for testing).
+    tail -f /dev/null
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Launches a minimalistic web server via netcat. The Dockerfile
+#           associated with this project is configured to treat the web server
+#           replying with "200 OK" as a sort of simple health probe.
+function health_check_init()
+{
+    while true; do
+        echo -e "HTTP/1.1 200 OK\n\nHOST:$(hostname)\nDATE:$(date)" \
+            | nc -l -p "${DOCKER_HEALTH_PROBE_PORT}" -q 1
+    done
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Main/default entry point.
+function main()
+{
+    # Make sure we always cleanup.
+    trap context_destroy EXIT
+
+    # Bring up interfaces.
+    context_create
+
+    # Enable health check responder.
+    health_check_init &
+
+    # Enter our worker loop.
+    context_loop
+}
+
+#------------------------------------------------------------------------------#
+# Script is generally intended to be sourced and individual functions called.
+# If just run as a standalone script, assume it's being used as the entrypoint
+# for a Docker container.
+if [ "${BASH_SOURCE[0]}" -ef "$0" ]; then
+    # Being run. Launch main.
+    main "${@}"
+else
+    # Being sourced. Do nothing.
+    :
+fi
+
diff --git a/docs/usecases/vpp_testbench/src/entrypoint_server.sh b/docs/usecases/vpp_testbench/src/entrypoint_server.sh
new file mode 100755
index 00000000000..755472a72bf
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/entrypoint_server.sh
@@ -0,0 +1,176 @@
+#!/bin/bash
+################################################################################
+# @brief:       Launcher/entrypoint script plus helper functions for "server
+#               side" container in the VPP testbench.
+# @author:      Matthew Giassa <mgiassa@cisco.com>
+# @copyright:   (C) Cisco 2021.
+################################################################################
+
+################################################################################
+# Dependencies.
+################################################################################
+# Import common settings for server and client. This is supplied via the
+# Dockerfile build.
+# shellcheck disable=SC1091
+. vpp_testbench_helpers.sh
+
+################################################################################
+# Globals.
+################################################################################
+# VPP instance socket.
+export VPP_SOCK=/run/vpp/vpp.testbench-server.sock
+# Alias for vppctl that uses the correct socket name.
+export VPPCTL="vppctl -s ${VPP_SOCK}"
+# Our "Docker bridge network". Don't change this value.
+export NET_IF_DOCKER="eth0"
+# Name of link associated with our VXLAN.
+export LINK_VXLAN_LINUX="vxlan-vid-${VXLAN_ID_LINUX}"
+
+################################################################################
+# Function definitions.
+################################################################################
+#------------------------------------------------------------------------------#
+# @brief:   Alias for vppctl (knowing which API socket to use).
+function vc()
+{
+    vppctl -s "${VPP_SOCK}" "${@}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Used to initialize/configure the server container once it's up and
+#           running.
+function context_create()
+{
+    set -x
+    echo "Running server. Host: $(hostname)"
+    local mtu
+
+    # Setup VXLAN overlay.
+    ip link add "${LINK_VXLAN_LINUX}" \
+        type vxlan \
+        id "${VXLAN_ID_LINUX}" \
+        dstport "${VXLAN_PORT}" \
+        local "${SERVER_BRIDGE_IP_DOCKER}" \
+        group "${MC_VXLAN_ADDR_LINUX}" \
+        dev "${NET_IF_DOCKER}" \
+        ttl 1
+    ip link set "${LINK_VXLAN_LINUX}" up
+    ip addr add "${SERVER_VXLAN_IP_LINUX}/${MASK_VXLAN_LINUX}" dev "${LINK_VXLAN_LINUX}"
+
+    # Get MTU of interface. VXLAN must use a smaller value due to overhead.
+    mtu="$(cat /sys/class/net/${NET_IF_DOCKER}/mtu)"
+
+    # Decrease VXLAN MTU. This should already be handled for us by iproute2, but
+    # just being cautious.
+    ip link set dev "${LINK_VXLAN_LINUX}" mtu "$((mtu - 50))"
+
+    # Bring-up VPP and create tap interfaces and VXLAN tunnel.
+    vpp \
+        unix '{' log /tmp/vpp1.log full-coredump cli-listen ${VPP_SOCK} '}' \
+        api-segment '{' prefix vpp1 '}' \
+        api-trace '{' on '}' \
+        dpdk '{' uio-driver uio_pci_generic no-pci '}'
+
+    # Wait for VPP to come up.
+    while ! ${VPPCTL} show log; do
+        sleep 1
+    done
+
+    # Bring up the memif interface and assign an IP to it.
+    ${VPPCTL} create interface memif id 0 master
+    sleep 1
+    ${VPPCTL} set int state memif0/0 up
+    ${VPPCTL} set int ip address memif0/0 "${SERVER_VPP_MEMIF_IP}/${VPP_MEMIF_NM}"
+
+    # Create VPP-controlled tap interface bridged to the memif.
+    ${VPPCTL} create tap id 0 host-if-name vpp-tap-0
+    sleep 1
+    ${VPPCTL} set interface state tap0 up
+    ip addr add "${SERVER_VPP_TAP_IP_MEMIF}/${VPP_TAP_NM}" dev vpp-tap-0
+    ${VPPCTL} set interface l2 bridge tap0          "${VPP_BRIDGE_DOMAIN_TAP}"
+    ${VPPCTL} set interface l2 bridge memif0/0      "${VPP_BRIDGE_DOMAIN_TAP}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Used to shutdown/cleanup the server container.
+function context_destroy()
+{
+    # OS will reclaim interfaces and resources when container is terminated.
+    :
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Server worker loop to keep the container alive. Just idles.
+function context_loop()
+{
+    # Sleep indefinitely (to keep container alive for testing).
+    tail -f /dev/null
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Launches a minimalistic web server via netcat. The Dockerfile
+#           associated with this project is configured to treat the web server
+#           replying with "200 OK" as a sort of simple health probe.
+function health_check_init()
+{
+    while true; do
+        echo -e "HTTP/1.1 200 OK\n\nHOST:$(hostname)\nDATE:$(date)" \
+            | nc -l -p "${DOCKER_HEALTH_PROBE_PORT}" -q 1
+    done
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Launches a minimalistic web server via netcat. This instance is
+#           meant to bind to the Linux VXLAN tunnel we create.
+function web_server_vxlan_linux()
+{
+    while true; do
+        echo -e "HTTP/1.1 200 OK\n\nHOST:$(hostname)\nDATE:$(date)\nHello from the Linux interface." \
+            | nc -l -s "${SERVER_VXLAN_IP_LINUX}" -p 8000 -q 1
+    done
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Launches a minimalistic web server via netcat. This instance is
+#           meant to bind to the VPP VXLAN tunnel we create.
+function web_server_vpp_tap()
+{
+    while true; do
+        echo -e "HTTP/1.1 200 OK\n\nHOST:$(hostname)\nDATE:$(date)\nHello from the VPP interface." \
+            | nc -l -s "${SERVER_VPP_TAP_IP_MEMIF}" -p 8000 -q 1
+    done
+}
+
+#------------------------------------------------------------------------------#
+# @brief:   Main/default entry point.
+function main()
+{
+    # Make sure we always cleanup.
+    trap context_destroy EXIT
+
+    # Bring up interfaces.
+    context_create
+
+    # Enable health check responder.
+    health_check_init &
+
+    # Bring up test web servers.
+    web_server_vxlan_linux &
+    web_server_vpp_tap &
+
+    # Enter our worker loop.
+    context_loop
+}
+
+#------------------------------------------------------------------------------#
+# Script is generally intended to be sourced and individual functions called.
+# If just run as a standalone script, assume it's being used as the entrypoint
+# for a Docker container.
+if [ "${BASH_SOURCE[0]}" -ef "$0" ]; then
+    # Being run. Launch main.
+    main "${@}"
+else
+    # Being sourced. Do nothing.
+    :
+fi
+
diff --git a/docs/usecases/vpp_testbench/src/vpp_testbench_helpers.sh b/docs/usecases/vpp_testbench/src/vpp_testbench_helpers.sh
new file mode 100755
index 00000000000..7dfb646a1db
--- /dev/null
+++ b/docs/usecases/vpp_testbench/src/vpp_testbench_helpers.sh
@@ -0,0 +1,273 @@
+#!/bin/bash
+################################################################################
+# @brief:       Helper functions for the VPP testbench project.
+#               NOTE: functions prefixed with "host_only" are functions
+#               intended to be executed on the host OS, **outside** of the
+#               Docker containers. These are typically functions for bring-up
+#               (i.e. creating the Docker networks, launching/terminating the
+#               Docker containers, etc.). If a function is not prefixed with
+#               "host_only", assume that the function/value/etc. is intended
+#               for use within the Docker containers. We could maybe re-factor
+#               this in the future so "host_only" functions live in a separate
+#               file.
+# @author:      Matthew Giassa <mgiassa@cisco.com>
+# @copyright:   (C) Cisco 2021.
+################################################################################
+
+# Meant to be sourced, not executed directly.
+if [ "${BASH_SOURCE[0]}" -ef "$0" ]; then
+    echo "This script is intended to be sourced, not run. Aborting."
+    false
+    exit
+fi
+
+#------------------------------------------------------------------------------#
+# For tests using the Linux kernel network stack.
+#------------------------------------------------------------------------------#
+# Health check probe port for all containers.
+export DOCKER_HEALTH_PROBE_PORT="8123"
+# Docker bridge network settings.
+export CLIENT_BRIDGE_IP_DOCKER="169.254.0.1"
+export SERVER_BRIDGE_IP_DOCKER="169.254.0.2"
+export BRIDGE_NET_DOCKER="169.254.0.0/24"
+export BRIDGE_GW_DOCKER="169.254.0.254"
+# Overlay IP addresses.
+export CLIENT_VXLAN_IP_LINUX="169.254.10.1"
+export SERVER_VXLAN_IP_LINUX="169.254.10.2"
+export MASK_VXLAN_LINUX="24"
+export VXLAN_ID_LINUX="42"
+# IANA (rather than Linux legacy port value).
+export VXLAN_PORT="4789"
+
+# Docker network we use to bridge containers.
+export DOCKER_NET="vpp-testbench-net"
+# Docker container names for client and server (runtime aliases).
+export DOCKER_CLIENT_HOST="vpp-testbench-client"
+export DOCKER_SERVER_HOST="vpp-testbench-server"
+# Some related variables have to be computed at the last second, so they
+# are not all defined up-front.
+export CLIENT_VPP_NETNS_DST="/var/run/netns/${DOCKER_CLIENT_HOST}"
+export SERVER_VPP_NETNS_DST="/var/run/netns/${DOCKER_SERVER_HOST}"
+
+# VPP options.
+# These can be arbitrarily named.
+export CLIENT_VPP_HOST_IF="vpp1"
+export SERVER_VPP_HOST_IF="vpp2"
+# Putting VPP interfaces on separate subnet from Linux-stack i/f.
+export CLIENT_VPP_MEMIF_IP="169.254.11.1"
+export SERVER_VPP_MEMIF_IP="169.254.11.2"
+export VPP_MEMIF_NM="24"
+export CLIENT_VPP_TAP_IP_MEMIF="169.254.12.1"
+export SERVER_VPP_TAP_IP_MEMIF="169.254.12.2"
+export VPP_TAP_NM="24"
+# Bridge domain ID (for VPP tap + VXLAN interfaces). Arbitrary.
+export VPP_BRIDGE_DOMAIN_TAP="1000"
+
+# VPP socket path. Make it one level "deeper" than the "/run/vpp" that is used
+# by default, so our containers don't accidentally connect to an instance of
+# VPP running on the host OS (i.e. "/run/vpp/vpp.sock"), and hang the system.
+export VPP_SOCK_PATH="/run/vpp/containers"
+
+#------------------------------------------------------------------------------#
+# @brief:       Converts an integer value representation of a VXLAN ID to a
+#               VXLAN IPv4 multicast address (string represenation). This
+#               effectively sets the first octet to "239" and the remaining 3x
+#               octets to the IP-address equivalent of a 24-bit value.
+#               Assumes that it's never supplied an input greater than what a
+#               24-bit unsigned integer can hold.
+function vxlan_id_to_mc_ip()
+{
+    if [ $# -ne 1 ]; then
+        echo "Sanity failure."
+        false
+        exit
+    fi
+
+    local id="${1}"
+    local a b c d ret
+    a="239"
+    b="$(((id>>16) & 0xff))"
+    c="$(((id>>8)  & 0xff))"
+    d="$(((id)     & 0xff))"
+    ret="${a}.${b}.${c}.${d}"
+
+    echo "${ret}"
+    true
+}
+# Multicast address for VXLAN. Treat the lower three octets as the 24-bit
+# representation of the VXLAN ID for ease-of-use (use-case specific, not
+# necessarily an established rule/protocol).
+MC_VXLAN_ADDR_LINUX="$(vxlan_id_to_mc_ip ${VXLAN_ID_LINUX})"
+export MC_VXLAN_ADDR_LINUX
+
+#------------------------------------------------------------------------------#
+# @brief:       Get'er function (so makefile can re-use common values from this
+#               script, and propagate them down to the Docker build operations
+#               and logic within the Dockerfile; "DRY").
+function host_only_get_docker_health_probe_port()
+{
+    echo "${DOCKER_HEALTH_PROBE_PORT}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Creates the Docker bridge network used to connect the
+#               client and server testbench containers.
+function host_only_create_docker_networks()
+{
+    # Create network (bridge for VXLAN). Don't touch 172.16/12 subnet, as
+    # Docker uses it by default for its own overlay functionality.
+    docker network create \
+        --driver bridge \
+        --subnet=${BRIDGE_NET_DOCKER} \
+        --gateway=${BRIDGE_GW_DOCKER} \
+        "${DOCKER_NET}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Destroys the Docker bridge network for connecting the
+#               containers.
+function host_only_destroy_docker_networks()
+{
+    docker network rm "${DOCKER_NET}" || true
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Bringup/dependency helper for VPP.
+function host_only_create_vpp_deps()
+{
+    # Create area for VPP sockets and mount points, if it doesn't already
+    # exist. Our containers need access to this path so they can see each
+    # others' respective sockets so we can bind them together via memif.
+    sudo mkdir -p "${VPP_SOCK_PATH}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Launches the testbench client container.
+function host_only_run_testbench_client_container()
+{
+    # Sanity check.
+    if [ $# -ne 1 ]; then
+        echo "Sanity failure."
+        false
+        exit
+    fi
+
+    # Launch container. Mount the local PWD into the container too (so we can
+    # backup results).
+    local image_name="${1}"
+    docker run -d --rm \
+        --cap-add=NET_ADMIN \
+        --cap-add=SYS_NICE \
+        --cap-add=SYS_PTRACE \
+        --device=/dev/net/tun:/dev/net/tun \
+        --device=/dev/vfio/vfio:/dev/vfio/vfio \
+        --device=/dev/vhost-net:/dev/vhost-net \
+        --name "${DOCKER_CLIENT_HOST}" \
+        --volume="$(pwd):/work:rw" \
+        --volume="${VPP_SOCK_PATH}:/run/vpp:rw" \
+        --network name="${DOCKER_NET},ip=${CLIENT_BRIDGE_IP_DOCKER}" \
+        --workdir=/work \
+        "${image_name}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Launches the testbench server container.
+function host_only_run_testbench_server_container()
+{
+    # Sanity check.
+    if [ $# -ne 1 ]; then
+        echo "Sanity failure."
+        false
+        exit
+    fi
+
+    # Launch container. Mount the local PWD into the container too (so we can
+    # backup results).
+    local image_name="${1}"
+    docker run -d --rm \
+        --cap-add=NET_ADMIN \
+        --cap-add=SYS_NICE \
+        --cap-add=SYS_PTRACE \
+        --device=/dev/net/tun:/dev/net/tun \
+        --device=/dev/vfio/vfio:/dev/vfio/vfio \
+        --device=/dev/vhost-net:/dev/vhost-net \
+        --name "${DOCKER_SERVER_HOST}" \
+        --volume="${VPP_SOCK_PATH}:/run/vpp:rw" \
+        --network name="${DOCKER_NET},ip=${SERVER_BRIDGE_IP_DOCKER}" \
+        "${image_name}"
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Terminates the testbench client container.
+function host_only_kill_testbench_client_container()
+{
+    docker kill "${DOCKER_CLIENT_HOST}" || true
+    docker rm   "${DOCKER_CLIENT_HOST}" || true
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Terminates the testbench server container.
+function host_only_kill_testbench_server_container()
+{
+    docker kill "${DOCKER_SERVER_HOST}" || true
+    docker rm   "${DOCKER_SERVER_HOST}" || true
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Launches an interactive shell in the client container.
+function host_only_shell_client_container()
+{
+    docker exec -it "${DOCKER_CLIENT_HOST}" bash --init-file /entrypoint.sh
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Launches an interactive shell in the server container.
+function host_only_shell_server_container()
+{
+    docker exec -it "${DOCKER_SERVER_HOST}" bash --init-file /entrypoint.sh
+}
+
+#------------------------------------------------------------------------------#
+# @brief:       Determines the network namespace or "netns" associated with a
+#               running Docker container, and then creates a network interface
+#               in the default/host netns, and moves it into the netns
+#               associated with the container.
+function host_only_move_host_interfaces_into_container()
+{
+    # NOTE: this is only necessary if we want to create Linux network
+    # interfaces while working in the default namespace, and then move them
+    # into container network namespaces.
+    # In earlier versions of this code, we did such an operation, but now we
+    # just create the interfaces inside the containers themselves (requires
+    # CAP_NET_ADMIN, or privileged containers, which we avoid). This is left
+    # here as it's occasionally useful for debug purposes (or might become a
+    # mini-lab itself).
+
+    # Make sure netns path exists.
+    sudo mkdir -p /var/run/netns
+
+    # Mount container network namespaces so that they are accessible via "ip
+    # netns". Ignore "START_OF_SCRIPT": just used to make
+    # linter-compliant text indentation look nicer.
+    DOCKER_CLIENT_PID=$(docker inspect -f '{{.State.Pid}}' ${DOCKER_CLIENT_HOST})
+    DOCKER_SERVER_PID=$(docker inspect -f '{{.State.Pid}}' ${DOCKER_SERVER_HOST})
+    CLIENT_VPP_NETNS_SRC=/proc/${DOCKER_CLIENT_PID}/ns/net
+    SERVER_VPP_NETNS_SRC=/proc/${DOCKER_SERVER_PID}/ns/net
+    sudo ln -sfT "${CLIENT_VPP_NETNS_SRC}" "${CLIENT_VPP_NETNS_DST}"
+    sudo ln -sfT "${SERVER_VPP_NETNS_SRC}" "${SERVER_VPP_NETNS_DST}"
+
+    # Move these interfaces into the namespaces of the containers and assign an
+    # IPv4 address to them.
+    sudo ip link set dev "${CLIENT_VPP_HOST_IF}" netns "${DOCKER_CLIENT_NETNS}"
+    sudo ip link set dev "${SERVER_VPP_HOST_IF}" netns "${DOCKER_SERVER_NETNS}"
+    docker exec ${DOCKER_CLIENT_HOST} ip a
+    docker exec ${DOCKER_SERVER_HOST} ip a
+
+    # Bring up the links and assign IP addresses. This must be done
+    # **after** moving the interfaces to a new netns, as we might have a
+    # hypothetical use case where we assign the same IP to multiple
+    # interfaces, which would be a problem. This collision issue isn't a
+    # problem though if the interfaces are in separate network namespaces
+    # though.
+}
+