From 66e08077bee03c33b13064b892171bf6e1c320e3 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Mon, 26 Oct 2015 00:40:58 -0400
Subject: tidy

---
 network-online | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

(limited to 'network-online')

diff --git a/network-online b/network-online
index 5bb51d8..484567b 100755
--- a/network-online
+++ b/network-online
@@ -4,10 +4,24 @@
 # terms of the Do What The Fuck You Want To Public License, Version 2,
 # as published by Sam Hocevar. See the COPYING file for more details.
 
+# Usage: network-online [start|stop] NETWORK_NAME
 mode="$1"
 lock=/run/network-online/lock
 fifo=/run/network-online/"$2"
 PS4="$mode: "
+
+# Use a named pipe (fifo) as an inter-process synchronization
+# mechanism; a call to block_{a,b} blocks its counterpart is run.
+block_a() {
+	cat "$fifo" >/dev/null
+}
+block_b() {
+	echo foo >> "$fifo"
+}
+
+# Because of restrictions put in place by systemd, the ExecStart
+# process can't run `systemctl stop network-online.target`, but the
+# ExecStop process can.
 case "$mode" in
 	start)
 		trap 'rm -f -- "$fifo"' EXIT
@@ -16,17 +30,18 @@ case "$mode" in
 		exec 8>"$lock" || exit $?
 		flock -s 8 || exit $?
 		systemctl start network-online.target || exit $?
-
 		mkfifo "$fifo" || exit $?
-		cat "$fifo"
+
+		block_a # wait for 'stop' to be called
 		exec 8>&-
-		echo stopped >> "$fifo"
+		block_a # signal to 'stop' that we've unlocked
 		;;
 	stop)
 		set -x
 		exec 8>"$lock" || exit $?
-		echo stopping >> "$fifo" || exit $?
-		cat "$fifo" || exit $?
+		flock -s 8 || exit $?
+		block_b # signal 'start' to stop
+		block_b # wait for 'start' to unlock
 		if flock -x -n 8; then
 			systemctl stop network-online.target
 			rm -rf /run/network-online
-- 
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