run: replace only owned launcher instance

README.md

@@ -129,9 +129,12 @@ font-file arguments replace these defaults:
 that it starts.  It waits for that daemon's IPC socket and IBus address file
 before reporting success.  With `DISPLAY` set it then starts XIM; without a
 display it keeps the headless daemon in the foreground and does not start
-XIM.  A signal or XIM exit stops and reaps the launcher's daemon.  The
+XIM.  A signal or XIM exit stops and reaps the launcher's daemon.  On repeated
-launcher never replaces an existing daemon: an occupied per-user socket is a
+invocation, it stops a previous live `run.sh` only after confirming that the
-visible startup failure.
+old launcher directly owns the daemon serving the same IPC and IBus
+endpoints and that the daemon carries that launcher's PID and process-start
+identity.  A manually started or orphaned daemon is left untouched and
+reported as a visible startup failure.
 
 The IPC socket is placed at `$XDG_RUNTIME_DIR/strans.sock` when
 `XDG_RUNTIME_DIR` is an absolute path.  Otherwise strans uses the per-user

run.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 cd "$(dirname "$0")" || exit 1
+root=$(pwd -P) || exit 1
+uid=$(id -u) || exit 1
 
 if test "$#" -eq 0; then
 	set --
@@ -46,6 +48,10 @@ fi
 
 strans_pid=
 xim_pid=
+old_daemon_pid=
+old_daemon_start=
+old_launcher_pid=
+old_launcher_start=
 
 cleanup()
 {
@@ -83,12 +89,198 @@ ibusready()
 	return 1
 }
 
+procuid()
+{
+	{
+		while IFS=' 	' read -r key real effective saved filesystem rest; do
+			case $key in
+			Uid:)
+				test "$real" = "$effective" &&
+				    test "$real" = "$saved" &&
+				    test "$real" = "$filesystem" || return 1
+				printf '%s\n' "$real"
+				return 0
+				;;
+			esac
+		done <"/proc/$1/status"
+	} 2>/dev/null
+	return 1
+}
+
+procparent()
+{
+	{
+		while IFS=' 	' read -r key value rest; do
+			case $key in
+			PPid:)	printf '%s\n' "$value"; return 0 ;;
+			esac
+		done <"/proc/$1/status"
+	} 2>/dev/null
+	return 1
+}
+
+procstart()
+{
+	proc_stat=
+	{ IFS= read -r proc_stat <"/proc/$1/stat"; } 2>/dev/null || return 1
+	proc_stat=${proc_stat##*) }
+	set -- $proc_stat
+	test "$#" -ge 20 || return 1
+	test "$1" != Z || return 1
+	printf '%s\n' "${20}"
+}
+
+sameproc()
+{
+	test -n "$2" || return 1
+	proc_now=$(procstart "$1") || return 1
+	test "$proc_now" = "$2"
+}
+
+listeninginode()
+{
+	listener_inode=
+	listener_count=0
+	{
+		while IFS=' 	' read -r num ref proto flags type state inode path; do
+			if test "$flags" = 00010000 && test "$type" = 0001 &&
+			   test "$state" = 01 && test "$path" = "$1"; then
+				listener_inode=$inode
+				listener_count=$((listener_count + 1))
+			fi
+		done </proc/net/unix
+	} 2>/dev/null
+	test "$listener_count" -eq 1 || return 1
+	printf '%s\n' "$listener_inode"
+}
+
+socketowned()
+{
+	socket_inode=$(listeninginode "$2") || return 1
+	for socket_fd in "/proc/$1/fd"/*; do
+		test "$(readlink "$socket_fd" 2>/dev/null)" = \
+		    "socket:[$socket_inode]" && return 0
+	done
+	return 1
+}
+
+validdaemon()
+{
+	test "$(procuid "$1")" = "$uid" || return 1
+	test "$(readlink "/proc/$1/cwd" 2>/dev/null)" = "$root" || return 1
+	daemon_exe=$(readlink "/proc/$1/exe" 2>/dev/null) || return 1
+	case $daemon_exe in
+	"$root/strans"|"$root/strans (deleted)")	;;
+	*)	return 1 ;;
+	esac
+	test -S "$ipc" || return 1
+	socketowned "$1" "$ipc" || return 1
+	socketowned "$1" "@strans-$1"
+}
+
+finddaemon()
+{
+	old_daemon_pid=
+	old_daemon_start=
+	for address in "$busdir"/*; do
+		test -f "$address" || continue
+		address_pid=
+		address_ok=
+		while IFS= read -r line; do
+			case $line in
+			IBUS_DAEMON_PID=*)	address_pid=${line#IBUS_DAEMON_PID=} ;;
+			esac
+		done <"$address"
+		case $address_pid in
+		''|*[!0-9]*)	continue ;;
+		esac
+		while IFS= read -r line; do
+			case $line in
+			IBUS_ADDRESS=unix:abstract=strans-"$address_pid",*)
+				address_ok=1 ;;
+			esac
+		done <"$address"
+		test -n "$address_ok" || continue
+		validdaemon "$address_pid" || continue
+		address_start=$(procstart "$address_pid") || continue
+		validdaemon "$address_pid" || continue
+		old_daemon_pid=$address_pid
+		old_daemon_start=$address_start
+		return 0
+	done
+	return 1
+}
+
+findlauncher()
+{
+	launcher_env=$({ tr '\000' '\n' <"/proc/$old_daemon_pid/environ"; } \
+	    2>/dev/null) || return 1
+	old_launcher_pid=$(printf '%s\n' "$launcher_env" |
+	    sed -n 's/^STRANS_RUN_OWNER_PID=//p')
+	old_launcher_start=$(printf '%s\n' "$launcher_env" |
+	    sed -n 's/^STRANS_RUN_OWNER_START=//p')
+	case $old_launcher_pid in
+	''|*[!0-9]*|0|1|"$$")	return 1 ;;
+	esac
+	case $old_launcher_start in
+	''|*[!0-9]*)	return 1 ;;
+	esac
+	test "$(procuid "$old_launcher_pid")" = "$uid" || return 1
+	test "$(readlink "/proc/$old_launcher_pid/cwd" 2>/dev/null)" = "$root" ||
+		return 1
+	sameproc "$old_launcher_pid" "$old_launcher_start" || return 1
+	sameproc "$old_daemon_pid" "$old_daemon_start" || return 1
+	test "$(procparent "$old_daemon_pid")" = "$old_launcher_pid" || return 1
+	return 0
+}
+
+stoplauncher()
+{
+	sameproc "$old_daemon_pid" "$old_daemon_start" || return 1
+	test "$(procparent "$old_daemon_pid")" = "$old_launcher_pid" || return 1
+	sameproc "$old_launcher_pid" "$old_launcher_start" || return 1
+	kill "$old_launcher_pid" 2>/dev/null || return 1
+	echo "run.sh: stopping previous launcher $old_launcher_pid (daemon $old_daemon_pid)"
+
+	stop_attempt=0
+	while test "$stop_attempt" -lt 10; do
+		if ! sameproc "$old_launcher_pid" "$old_launcher_start" &&
+		   ! sameproc "$old_daemon_pid" "$old_daemon_start"; then
+			return 0
+		fi
+		stop_attempt=$((stop_attempt + 1))
+		if test "$stop_attempt" -lt 10; then
+			sleep 1
+		fi
+	done
+	echo "run.sh: previous launcher did not stop within 10 seconds" >&2
+	return 1
+}
+
 trap cleanup 0
 trap 'exit 129' 1
 trap 'exit 130' 2
 trap 'exit 143' 15
 
-./strans map "$@" &
+launcher_start=$(procstart "$$") || {
+	echo "run.sh: cannot read launcher process identity from /proc" >&2
+	exit 1
+}
+
+if finddaemon; then
+	if ! findlauncher; then
+		echo "run.sh: daemon $old_daemon_pid owns the current endpoints but has no" >&2
+		echo "run.sh: live run.sh owner; leaving it untouched (stop it once, then retry)" >&2
+		exit 1
+	fi
+	if ! stoplauncher; then
+		echo "run.sh: previous launcher did not stop cleanly; refusing to start another daemon" >&2
+		exit 1
+	fi
+fi
+
+STRANS_RUN_OWNER_PID=$$ STRANS_RUN_OWNER_START=$launcher_start \
+	./strans map "$@" &
 strans_pid=$!
 
 attempt=0