Configure ephemeral network if needed

Add ipv4 address from dhcp if datasource is from https and no ipv4
address is configured.

lib/tiny-cloud/cloud/alpine/init

@@ -13,6 +13,36 @@ set_resolv_conf() {
 	done
 }
 
+has_ipv4_address() {
+	$MOCK ip -4 -o addr show | awk '$2 != "lo" {print $4}' \
+		| grep -q -E '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+'
+}
+
+want_ephemeral_network() {
+	if has_ipv4_address; then
+		return 1
+	fi
+	for i in $(cat "$ROOT"/proc/cmdline 2>/dev/null) \
+			$(cat "$ROOT"/sys/class/dmi/id/product_serial 2>/dev/null); do
+		case "$i" in
+			"ds=nocloud;"*)
+				for kv in $(echo "${i#*;}" | tr \; ' '); do
+					k="${kv%%=*}"
+					v="${kv#*=}"
+					case "$k" in
+						s|seedfrom)
+							case "$v" in
+								http://*|https://*) return 0;;
+							esac
+							;;
+					esac
+				done
+				;;
+		esac
+	done
+	return 1
+}
+
 init__set_network_interfaces() {
 	local interfaces="$(imds meta-data/network-interfaces)"
 	mkdir -p "$ROOT"/etc/network

lib/tiny-cloud/init

@@ -14,6 +14,7 @@
 DEFAULT_ACTIONS_BOOT="
 	expand_root
 	install_hotplugs
+	set_ephemeral_network
 	set_default_interfaces
 	enable_sshd
 "
@@ -143,6 +144,22 @@ auto_detect_ethernet_interface() {
 	echo "$iface"
 }
 
+# may be overridded by provider
+want_ephemeral_network() {
+	false
+}
+
+init__set_ephemeral_network() {
+	if ! want_ephemeral_network; then
+		return
+	fi
+	local iface="$(auto_detect_ethernet_interface)"
+	if [ -z "$iface" ]; then
+		return
+	fi
+	$MOCK udhcpc -i "$iface" -f
+}
+
 init__set_default_interfaces() {
 	if [ -f "$ROOT"/etc/network/interfaces ]; then
 		log -i -t "$phase" info "$ACTION: already set up"

tests/tiny-cloud-alpine.test

@@ -10,6 +10,7 @@ export CLOUD=alpine
 lib="$srcdir"/lib/tiny-cloud/cloud/alpine/init
 
 init_tests \
+	set_ephemeral_network_cmdline \
 	set_network_config_network_interfaces \
 	set_network_config_auto \
 	userdata_user_name \
@@ -30,6 +31,16 @@ init_tests \
 	userdata_packages \
 	userdata_runcmd
 
+set_ephemeral_network_cmdline_body() {
+	fake_interfaces eth0 eth1 eth2
+	echo up > sys/class/net/eth1/operstate
+	mkdir -p proc
+	echo "ds=nocloud;h=foo;seedfrom=https://example.tld" > proc/cmdline
+	atf_check \
+		-o match:"udhcpc.*eth1" \
+		-e match:"set_ephemeral_network: done" \
+		tiny-cloud boot
+}
 
 set_network_config_network_interfaces_body() {
 	fake_metadata_nocloud <<-EOF