Setup development environment with libbpf

external/libbpf-bootstrap/libbpf/travis-ci/vmtest/checkout_latest_kernel.sh

@@ -0,0 +1,54 @@
+#!/bin/bash
+
+set -eu
+
+source $(cd $(dirname $0) && pwd)/helpers.sh
+
+CWD=$(pwd)
+LIBBPF_PATH=$(pwd)
+REPO_PATH=$1
+
+KERNEL_ORIGIN=${KERNEL_ORIGIN:-https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git}
+KERNEL_BRANCH=${KERNEL_BRANCH:-CHECKPOINT}
+if [[ "${KERNEL_BRANCH}" = 'CHECKPOINT' ]]; then
+  echo "using CHECKPOINT sha1"
+  LINUX_SHA=$(cat ${LIBBPF_PATH}/CHECKPOINT-COMMIT)
+else
+  echo "using ${KERNEL_BRANCH} sha1"
+  LINUX_SHA=$(git ls-remote ${KERNEL_ORIGIN} ${KERNEL_BRANCH} | awk '{print $1}')
+fi
+SNAPSHOT_URL=${KERNEL_ORIGIN}/snapshot/bpf-next-${LINUX_SHA}.tar.gz
+
+echo REPO_PATH = ${REPO_PATH}
+
+echo KERNEL_ORIGIN = ${KERNEL_ORIGIN}
+echo LINUX_SHA = ${LINUX_SHA}
+echo SNAPSHOT_URL = ${SNAPSHOT_URL}
+
+if [ ! -d "${REPO_PATH}" ]; then
+	echo
+	travis_fold start pull_kernel_srcs "Fetching kernel sources"
+
+	mkdir -p $(dirname "${REPO_PATH}")
+	cd $(dirname "${REPO_PATH}")
+	# attempt to fetch desired bpf-next repo snapshot
+	if wget -nv ${SNAPSHOT_URL} && tar xf bpf-next-${LINUX_SHA}.tar.gz --totals ; then
+		mv bpf-next-${LINUX_SHA} $(basename ${REPO_PATH})
+	else
+		# but fallback to git fetch approach if that fails
+		mkdir -p $(basename ${REPO_PATH})
+		cd $(basename ${REPO_PATH})
+		git init
+		git remote add bpf-next ${KERNEL_ORIGIN}
+		# try shallow clone first
+		git fetch --depth 32 bpf-next
+		# check if desired SHA exists
+		if ! git cat-file -e ${LINUX_SHA}^{commit} ; then
+			# if not, fetch all of bpf-next; slow and painful
+			git fetch bpf-next
+		fi
+		git reset --hard ${LINUX_SHA}
+	fi
+
+	travis_fold end pull_kernel_srcs
+fi