add FSM update

FSM to handle firmware update process in a synchronized all-or-nothing
manner. See doc/overview.org for details.

1 files changed, 72 insertions, 0 deletions

diff --git a/files/common/etc/fsm/update/watch/default b/files/common/etc/fsm/update/watch/default
new file mode 100755
index 0000000..a6858af
--- /dev/null
+++ b/files/common/etc/fsm/update/watch/default
@@ -0,0 +1,72 @@
+#!/bin/sh -e
+set -x
+
+. ../common.sh
+
+# announce a transition and terminate
+trans () {
+    echo $1
+    exit
+}
+
+# is the firmware file available?
+checkFw () {
+    [ -n "$TargetFw" -a -f "$FwDst" ] || trans idle
+}
+
+checkFwHash () {
+    [ "$(sha256sum <$FwDst 2>/dev/null | cut -f1 -d' ')" == "$TargetFw" ] || trans idle
+}
+
+# is target time passed but not set
+checkTime () {
+    [ $CurTime -lt "$TargetTime" -o "$AckTime" -eq "$TargetTime" ] 2>/dev/null \
+	|| trans ready
+}
+
+# check all-or-nothing-invariant for whole update state table
+checkPeerState() {
+    p2ptbl show $Tbl \
+	| (
+	IFS=$'\t'
+	while read OId OCurFw OTargetFw OTargetTime OAckTime; do
+	    [ -z "$OTargetFw" -a -z "$OTargetTime" -a -z "$OAckTime" ] && continue
+	    [ -n "$OTargetFw" -a "$OTargetTime" -eq "$OAckTime" ] && continue
+	    exit 1
+	done ) || trans ready
+}
+
+
+case $CurState in
+    idle)
+	checkFw
+	checkFwHash
+	# ^^ check hash of firmware file once if the hash is correct;
+	# do not optimize for the rare case of a wrong hash or
+	# continuously failing updates
+	trans ready
+	;;
+    ready)
+	checkFw
+	checkTime
+	[ "$TargetTime" -gt $CurTime ] 2>/dev/null || trans ready
+	trans scheduled
+	;;
+    scheduled)
+	checkFw
+	checkTime
+	[ $CurTime -gt "$TargetTime" ] || trans scheduled
+	checkPeerState
+	trans applying
+	;;
+    *)
+	# anything else is illegal; especially the state "applying"
+	# must not be reached: during transition toward it the
+	# firmware is flashed and the router rebooted
+	echo "illegal state $CurState" >&2
+	exit 1
+	;;
+esac
+
+# default and if any case falls through
+trans idle
\ No newline at end of file