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#!/usr/bin/env bash
# This script is a wrapper to the other download backends.
# Its role is to ensure atomicity when saving downloaded files
# back to BR2_DL_DIR, and not clutter BR2_DL_DIR with partial,
# failed downloads.
# To avoid cluttering BR2_DL_DIR, we download to a trashable
# location, namely in $(BUILD_DIR).
# Then, we move the downloaded file to a temporary file in the
# same directory as the final output file.
# This allows us to finally atomically rename it to its final
# name.
# If anything goes wrong, we just remove all the temporaries
# created so far.
# We want to catch any unexpected failure, and exit immediately.
set -e
export BR_BACKEND_DL_GETOPTS=":hc:d:o:n:N:H:ru:qf:e"
main() {
local OPT OPTARG
local backend output hfile recurse quiet rc
local -a uris
# Parse our options; anything after '--' is for the backend
while getopts ":c:d:D:o:n:N:H:rf:u:q" OPT; do
case "${OPT}" in
c) cset="${OPTARG}";;
d) dl_dir="${OPTARG}";;
D) old_dl_dir="${OPTARG}";;
o) output="${OPTARG}";;
n) raw_base_name="${OPTARG}";;
N) base_name="${OPTARG}";;
H) hfile="${OPTARG}";;
r) recurse="-r";;
f) filename="${OPTARG}";;
u) uris+=( "${OPTARG}" );;
q) quiet="-q";;
:) error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
\?) error "unknown option '%s'\n" "${OPTARG}";;
esac
done
# Forget our options, and keep only those for the backend
shift $((OPTIND-1))
if [ -z "${output}" ]; then
error "no output specified, use -o\n"
fi
# Legacy handling: check if the file already exists in the global
# download directory. If it does, hard-link it. If it turns out it
# was an incorrect download, we'd still check it below anyway.
# If we can neither link nor copy, fallback to doing a download.
# NOTE! This is not atomic, is subject to TOCTTOU, but the whole
# dl-wrapper runs under an flock, so we're safe.
if [ ! -e "${output}" -a -e "${old_dl_dir}/${filename}" ]; then
ln "${old_dl_dir}/${filename}" "${output}" || \
cp "${old_dl_dir}/${filename}" "${output}" || \
true
fi
# If the output file already exists and:
# - there's no .hash file: do not download it again and exit promptly
# - matches all its hashes: do not download it again and exit promptly
# - fails at least one of its hashes: force a re-download
# - there's no hash (but a .hash file): consider it a hard error
if [ -e "${output}" ]; then
if support/download/check-hash ${quiet} "${hfile}" "${output}" "${output##*/}"; then
exit 0
elif [ ${?} -ne 2 ]; then
# Do not remove the file, otherwise it might get re-downloaded
# from a later location (i.e. primary -> upstream -> mirror).
# Do not print a message, check-hash already did.
exit 1
fi
rm -f "${output}"
warn "Re-downloading '%s'...\n" "${output##*/}"
fi
# Look through all the uris that we were given to download the package
# source
download_and_check=0
rc=1
for uri in "${uris[@]}"; do
backend_urlencode="${uri%%+*}"
backend="${backend_urlencode%|*}"
case "${backend}" in
git|svn|cvs|bzr|file|scp|hg) ;;
*) backend="wget" ;;
esac
uri=${uri#*+}
urlencode=${backend#*|}
# urlencode must be "urlencode"
[ "${urlencode}" != "urlencode" ] && urlencode=""
# tmpd is a temporary directory in which backends may store
# intermediate by-products of the download.
# tmpf is the file in which the backends should put the downloaded
# content.
# tmpd is located in $(BUILD_DIR), so as not to clutter the (precious)
# $(BR2_DL_DIR)
# We let the backends create tmpf, so they are able to set whatever
# permission bits they want (although we're only really interested in
# the executable bit.)
tmpd="$(mktemp -d "${BUILD_DIR}/.${output##*/}.XXXXXX")"
tmpf="${tmpd}/output"
# Helpers expect to run in a directory that is *really* trashable, so
# they are free to create whatever files and/or sub-dirs they might need.
# Doing the 'cd' here rather than in all backends is easier.
cd "${tmpd}"
# If the backend fails, we can just remove the content of the temporary
# directory to remove all the cruft it may have left behind, and try
# the next URI until it succeeds. Once out of URI to try, we need to
# cleanup and exit.
if ! "${OLDPWD}/support/download/${backend}" \
$([ -n "${urlencode}" ] && printf %s '-e') \
-c "${cset}" \
-d "${dl_dir}" \
-n "${raw_base_name}" \
-N "${base_name}" \
-f "${filename}" \
-u "${uri}" \
-o "${tmpf}" \
${quiet} ${recurse} -- "${@}"
then
# cd back to keep path coherence
cd "${OLDPWD}"
rm -rf "${tmpd}"
continue
fi
# cd back to free the temp-dir, so we can remove it later
cd "${OLDPWD}"
# Check if the downloaded file is sane, and matches the stored hashes
# for that file
if support/download/check-hash ${quiet} "${hfile}" "${tmpf}" "${output##*/}"; then
rc=0
else
if [ ${?} -ne 3 ]; then
rm -rf "${tmpd}"
continue
fi
# the hash file exists and there was no hash to check the file
# against
rc=1
fi
download_and_check=1
break
done
# We tried every URI possible, none seems to work or to check against the
# available hash. *ABORT MISSION*
if [ "${download_and_check}" -eq 0 ]; then
rm -rf "${tmpd}"
exit 1
fi
# tmp_output is in the same directory as the final output, so we can
# later move it atomically.
tmp_output="$(mktemp "${output}.XXXXXX")"
# 'mktemp' creates files with 'go=-rwx', so the files are not accessible
# to users other than the one doing the download (and root, of course).
# This can be problematic when a shared BR2_DL_DIR is used by different
# users (e.g. on a build server), where all users may write to the shared
# location, since other users would not be allowed to read the files
# another user downloaded.
# So, we restore the 'go' access rights to a more sensible value, while
# still abiding by the current user's umask. We must do that before the
# final 'mv', so just do it now.
# Some backends (cp and scp) may create executable files, so we need to
# carry the executable bit if needed.
[ -x "${tmpf}" ] && new_mode=755 || new_mode=644
new_mode=$(printf "%04o" $((0${new_mode} & ~0$(umask))))
chmod ${new_mode} "${tmp_output}"
# We must *not* unlink tmp_output, otherwise there is a small window
# during which another download process may create the same tmp_output
# name (very, very unlikely; but not impossible.)
# Using 'cp' is not reliable, since 'cp' may unlink the destination file
# if it is unable to open it with O_WRONLY|O_TRUNC; see:
# http://pubs.opengroup.org/onlinepubs/9699919799/utilities/cp.html
# Since the destination filesystem can be anything, it might not support
# O_TRUNC, so 'cp' would unlink it first.
# Use 'cat' and append-redirection '>>' to save to the final location,
# since that is the only way we can be 100% sure of the behaviour.
if ! cat "${tmpf}" >>"${tmp_output}"; then
rm -rf "${tmpd}" "${tmp_output}"
exit 1
fi
rm -rf "${tmpd}"
# tmp_output and output are on the same filesystem, so POSIX guarantees
# that 'mv' is atomic, because it then uses rename() that POSIX mandates
# to be atomic, see:
# http://pubs.opengroup.org/onlinepubs/9699919799/functions/rename.html
if ! mv -f "${tmp_output}" "${output}"; then
rm -f "${tmp_output}"
exit 1
fi
return ${rc}
}
trace() { local msg="${1}"; shift; printf "%s: ${msg}" "${my_name}" "${@}"; }
warn() { trace "${@}" >&2; }
errorN() { local ret="${1}"; shift; warn "${@}"; exit ${ret}; }
error() { errorN 1 "${@}"; }
my_name="${0##*/}"
main "${@}"
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