Set Default interfaces

lib/tiny-cloud/init

@@ -13,6 +13,7 @@
 INIT_ACTIONS_EARLY="
     expand_root
     install_hotplugs
+    set_interfaces_default
 "
 INIT_ACTIONS_MAIN="
     save_userdata
@@ -80,6 +81,85 @@ init__install_hotplugs() {
     return $rc
 }
 
+# collect ethernet interfaces, sorted by index
+ethernets() {
+    for i in "$ROOT/sys/class/net/"*; do
+        local iface="${i##*/}"
+        case "$iface" in
+            eth*) echo "$(cat "$i/ifindex") $iface";;
+        esac
+    done | sort -n | awk '{print $2}'
+}
+
+# find the interface that is has operstate up
+find_first_interface_up() {
+    local n=0
+    [ $# -eq 0 ] && return
+    while [ $n -le ${TINY_CLOUD_LINK_WAIT_MAX:-10} ]; do
+        for i in "$@"; do
+            if [ "$(cat "$ROOT/sys/class/net/$i/operstate")" = "up" ]; then
+                echo "$i"
+                return
+            fi
+        done
+        sleep 0.1
+        n=$((n+1))
+    done
+}
+
+# auto detect which network interface to auto configure
+# check which is connected or fallback to first
+# This will set link to down to all eth* except the found
+auto_detect_ethernet_interface() {
+    local ifaces="$(ethernets)"
+    [ -z "$ifaces" ] && return
+
+    # find first connected interface
+    for i in $ifaces; do
+        $MOCK ip link set dev $i up >/dev/null
+    done
+    local iface="$(find_first_interface_up $ifaces)"
+
+    # use first if all are disconnected
+    if [ -z "$iface" ]; then
+        set -- $ifaces
+        iface="$1"
+    fi
+
+    # we will use the found interface later so lets keep it up
+    for i in $ifaces; do
+        if [ "$i" != "$iface" ]; then
+            $MOCK ip link set dev $i down >/dev/null
+        fi
+    done
+    echo "$iface"
+}
+
+init__set_interfaces_default() {
+    if [ -f "$ROOT"/etc/network/interfaces ]; then
+        echo "already set up" >&2
+        log info "$phase $ACTION - already set up"
+        return
+    fi
+
+    mkdir -p "$ROOT/etc/network"
+    printf "%s\n%s\n\n" \
+        "auto lo" \
+        "iface lo inet loopback" \
+        > "$ROOT/etc/network/interfaces"
+
+    local iface="$(auto_detect_ethernet_interface)"
+    if [ -z "$iface" ]; then
+        # TODO: message/log?
+        return
+    fi
+    printf "%s\n%s\n\t%s\n\n" \
+        "auto $iface" \
+        "iface $iface" \
+        "use dhcp"  >> "$ROOT/etc/network/interfaces"
+}
+
+
 ### init-main functions
 
 init__set_hostname() {

tests/init-early.test

@@ -9,7 +9,11 @@ lib="$srcdir"/lib/tiny-cloud/init
 init_tests \
 	expand_root \
 	expand_root_partition \
-	install_hotplugs_fail
+	install_hotplugs_fail \
+	ethernets \
+	find_first_interface_up \
+	auto_detect_ethernet_interface \
+	set_interfaces_default
 
 PROVIDERS="aws azure gcp nocloud oci"
 
@@ -46,3 +50,52 @@ install_hotplugs_fail_body() {
 		-e match:"vnic_eth_hotplug\(!\)" \
 		sh -c ". $lib; HOTPLUG_MODULES='vnic_eth_hotplug'; init__install_hotplugs"
 }
+
+ethernets_body() {
+	fake_interfaces lo br0 eth0 eth2 eth11
+
+	# check that they are sorted by ifindex, not name
+	# and that br0 and lo are excluded
+	atf_check \
+		-o match:"eth0 eth2 eth11" \
+		-o not-match:"br0" \
+		-o not-match:"lo" \
+		sh -c ". $lib; ethernets | tr '\n' ' '"
+}
+
+find_first_interface_up_body() {
+	fake_interfaces eth0 eth1
+	echo up > sys/class/net/eth1/operstate
+
+	atf_check \
+		-o match:"eth1" \
+		sh -c ". $lib; find_first_interface_up eth0 eth1"
+}
+
+auto_detect_ethernet_interface_body() {
+	fake_interfaces eth0 eth1
+	echo up > sys/class/net/eth1/operstate
+
+	atf_check \
+		-o match:"^eth1$" \
+		sh -c ". $lib; auto_detect_ethernet_interface"
+
+	# test that we pick first if all are down
+	echo down > sys/class/net/eth1/operstate
+	atf_check \
+		-o match:"^eth0$" \
+		sh -c ". $lib; TINY_CLOUD_LINK_WAIT_MAX=1; auto_detect_ethernet_interface"
+}
+
+set_interfaces_default_body() {
+	fake_interfaces eth0 eth1
+	echo up > sys/class/net/eth1/operstate
+
+	atf_check \
+		sh -c ". $lib; init__set_interfaces_default"
+	atf_check \
+		-o match:"auto lo" \
+		-o match:"iface eth1" \
+		-o match:"use dhcp" \
+		cat etc/network/interfaces
+}

tests/test_env.sh

@@ -67,3 +67,13 @@ fake_metadata_nocloud() {
 	mkdir -p mnt
 	fake_umount
 }
+
+fake_interfaces() {
+	local n=1
+	for i; do
+		mkdir -p sys/class/net/$i
+		echo $n > sys/class/net/$i/ifindex
+		echo down >sys/class/net/$i/operstate
+		n=$((n+1))
+	done
+}