From efe9b60e371ec4c7420ce2ee65171f8145fe7ee0 Mon Sep 17 00:00:00 2001
From: Ariadne Conill <ariadne@dereferenced.org>
Date: Tue, 8 Sep 2020 19:10:20 -0600
Subject: [PATCH] ifupdown: skip interface config/deconfig based on refcounts

---
 cmd/ifupdown.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/cmd/ifupdown.c b/cmd/ifupdown.c
index bd9a68e..9124320 100644
--- a/cmd/ifupdown.c
+++ b/cmd/ifupdown.c
@@ -93,6 +93,26 @@ acquire_state_lock(const char *state_path, const char *lifname)
 	return fd;
 }
 
+bool
+skip_interface(struct lif_interface *iface, const char *ifname)
+{
+	if (up && iface->refcount > 0)
+	{
+		fprintf(stderr, "%s: skipping %s (already configured), use --force to force configuration\n",
+			argv0, ifname);
+		return true;
+	}
+
+	if (!up && iface->refcount == 0)
+	{
+		fprintf(stderr, "%s: skipping %s (already deconfigured), use --force to force deconfiguration\n",
+			argv0, ifname);
+		return true;
+	}
+
+	return false;
+}
+
 bool
 change_interface(struct lif_interface *iface, struct lif_dict *collection, struct lif_dict *state, const char *ifname)
 {
@@ -104,6 +124,14 @@ change_interface(struct lif_interface *iface, struct lif_dict *collection, struc
 		return false;
 	}
 
+	if (skip_interface(iface, ifname))
+	{
+		if (lockfd != -1)
+			close(lockfd);
+
+		return true;
+	}
+
 	if (exec_opts.verbose)
 	{
 		fprintf(stderr, "%s: changing state of interface %s to '%s'\n",