Add helper script to install protoc

.gitignore

@@ -64,6 +64,9 @@ network_closure.sh
 /third_party/etcd*
 /default.etcd
 
+# Also ignore protoc installed by hack/install-protoc.sh
+/third_party/protoc*
+
 # User cluster configs
 .kubeconfig
 

hack/install-protoc.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+# Copyright 2023 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This script is convenience to download and install protoc in third_party.
+# Usage: `hack/install-protoc.sh`.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
+source "${KUBE_ROOT}/hack/lib/protoc.sh"
+
+kube::protoc::install

hack/lib/protoc.sh

@@ -94,3 +94,43 @@ function kube::protoc::diff() {
     exit 1
   fi
 }
+
+function kube::protoc::install() {
+  # run in a subshell to isolate caller from directory changes
+  (
+    local os
+    local arch
+    local download_folder
+    local download_file
+
+    os=$(kube::util::host_os)
+    arch=$(kube::util::host_arch)
+    download_folder="protoc-v${PROTOC_VERSION}-${os}-${arch}"
+    download_file="${download_folder}.zip"
+
+    cd "${KUBE_ROOT}/third_party" || return 1
+    if [[ $(readlink protoc) != "${download_folder}" ]]; then
+      local url
+      if [[ ${os} == "darwin" ]]; then
+        # TODO: switch to universal binary when updating to 3.20+
+        url="https://github.com/protocolbuffers/protobuf/releases/download/v${PROTOC_VERSION}/protoc-${PROTOC_VERSION}-osx-x86_64.zip"
+      elif [[ ${os} == "linux" && ${arch} == "amd64" ]]; then
+        url="https://github.com/protocolbuffers/protobuf/releases/download/v${PROTOC_VERSION}/protoc-${PROTOC_VERSION}-linux-x86_64.zip"
+      elif [[ ${os} == "linux" && ${arch} == "arm64" ]]; then
+        url="https://github.com/protocolbuffers/protobuf/releases/download/v${PROTOC_VERSION}/protoc-${PROTOC_VERSION}-linux-aarch_64.zip"
+      else
+        kube::log::info "This install script does not support ${os}/${arch}"
+        return 1
+      fi
+      kube::util::download_file "${url}" "${download_file}"
+      unzip -o "${download_file}" -d "${download_folder}"
+      ln -fns "${download_folder}" protoc
+      mv protoc/bin/protoc protoc/protoc
+      chmod -R +rX protoc/protoc
+      rm -fr protoc/include
+      rm "${download_file}"
+    fi
+    kube::log::info "protoc v${PROTOC_VERSION} installed. To use:"
+    kube::log::info "export PATH=\"$(pwd)/protoc:\${PATH}\""
+  )
+}