support/download: introduce curl backend for FTP transfers

Recent versions of wget, starting with wget 2.0, aka wget2 thereafter,
no longer support FTP (nor FTPS, aka FTP-over-SSL). wget2 is packaged in
Fedora 40, recently released; F40 does not even have the old wget
available in its repository anymore.

Introduce cURL as a download backend, that we use for FTP and FPTS
protocols.

Note that the -q flag does not means being quiet; it means that a curlrc
file should not be parsed. The long option is --disable, which meaning
is not much more obivous than the short -q. It also has to be the first
option on the command line.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Config.in

@@ -103,6 +103,10 @@ menu "Build options"
 
 menu "Commands"
 
+config BR2_CURL
+	string "Curl command"
+	default "curl -q --ftp-pasv --retry 3"
+
 config BR2_WGET
 	string "Wget command"
 	default "wget -nd -t 3"

docs/manual/prerequisite.adoc

@@ -75,6 +75,7 @@ packages using any of these methods, you will need to install the
 corresponding tool on the host system:
 +
 ** +bazaar+
+** +curl+
 ** +cvs+
 ** +git+
 ** +mercurial+

package/pkg-download.mk

@@ -8,6 +8,7 @@
 ################################################################################
 
 # Download method commands
+export CURL := $(call qstrip,$(BR2_CURL))
 export WGET := $(call qstrip,$(BR2_WGET))
 export SVN := $(call qstrip,$(BR2_SVN))
 export CVS := $(call qstrip,$(BR2_CVS))

package/pkg-generic.mk

@@ -1253,6 +1253,8 @@ else ifeq ($$($(2)_SITE_METHOD),hg)
 DL_TOOLS_DEPENDENCIES += hg
 else ifeq ($$($(2)_SITE_METHOD),cvs)
 DL_TOOLS_DEPENDENCIES += cvs
+else ifneq ($(filter ftp ftps,$$($(2)_SITE_METHOD)),)
+DL_TOOLS_DEPENDENCIES += curl
 endif # SITE_METHOD
 
 # cargo/go vendoring (may) need git

support/download/curl

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+
+# We want to catch any unexpected failure, and exit immediately
+set -e
+
+# Download helper for curl, to be called from the download wrapper script
+#
+# Options:
+#   -q          Be quiet.
+#   -o FILE     Save into file FILE.
+#   -f FILENAME The filename of the tarball to get at URL
+#   -u URL      Download file at URL.
+#
+# Environment:
+#   CURL     : the curl command to call
+
+quiet=
+while getopts "${BR_BACKEND_DL_GETOPTS}" OPT; do
+    case "${OPT}" in
+    q)  quiet=-s;;
+    o)  output="${OPTARG}";;
+    f)  filename="${OPTARG}";;
+    u)  url="${OPTARG}";;
+    :)  printf "option '%s' expects a mandatory argument\n" "${OPTARG}"; exit 1;;
+    \?) printf "unknown option '%s'\n" "${OPTARG}" >&2; exit 1;;
+    esac
+done
+
+shift $((OPTIND-1)) # Get rid of our options
+
+# Caller needs to single-quote its arguments to prevent them from
+# being expanded a second time (in case there are spaces in them)
+_curl() {
+    if [ -z "${quiet}" ]; then
+        printf '%s ' "${CURL}" "${@}"; printf '\n'
+    fi
+    _plain_curl "$@"
+}
+# Note: please keep command below aligned with what is printed above
+_plain_curl() {
+    # shellcheck disable=SC2086  # We want splitting
+    eval ${CURL} "${@}"
+}
+
+_curl ${quiet} "${@}" --output "'${output}'" "'${url}/${filename}'"

support/download/dl-wrapper

@@ -91,6 +91,7 @@ main() {
         backend="${backend_urlencode%|*}"
         case "${backend}" in
             git|svn|cvs|bzr|file|scp|hg|sftp) ;;
+            ftp|ftps) backend="curl" ;;
             *) backend="wget" ;;
         esac
         uri=${uri#*+}