From e033558d7027a40a6996c08b5125e45141192071 Mon Sep 17 00:00:00 2001
From: Eugene Burkov <E.Burkov@AdGuard.COM>
Date: Fri, 14 Jun 2024 14:39:58 +0300
Subject: [PATCH] all: add & use empty fswatcher

---
 CHANGELOG.md                |  5 +++++
 internal/aghos/fswatcher.go | 27 +++++++++++++++++++++++++++
 internal/home/home.go       |  4 +++-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa0f3512c6d..7b34dbb2cf3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -35,6 +35,11 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 - Node 18 support, Node 20 will be required in future releases.
 
+### Fixed
+
+- Tracking `/etc/hosts` file changes causing panics within particular
+  filesystems on start ([#7076]).
+
 <!--
 NOTE: Add new changes ABOVE THIS COMMENT.
 -->
diff --git a/internal/aghos/fswatcher.go b/internal/aghos/fswatcher.go
index 9f3a657046d..5cb1b1c5800 100644
--- a/internal/aghos/fswatcher.go
+++ b/internal/aghos/fswatcher.go
@@ -160,3 +160,30 @@ func (w *osWatcher) handleErrors() {
 		log.Error("%s: %s", osWatcherPref, err)
 	}
 }
+
+// EmptyFSWatcher is a no-op implementation of the [FSWatcher] interface.  It
+// may be used on systems not supporting filesystem events.
+type EmptyFSWatcher struct{}
+
+// type check
+var _ FSWatcher = EmptyFSWatcher{}
+
+// Start implements the [FSWatcher] interface for EmptyFSWatcher.
+func (EmptyFSWatcher) Start() (err error) {
+	return nil
+}
+
+// Close implements the [FSWatcher] interface for EmptyFSWatcher.
+func (EmptyFSWatcher) Close() (err error) {
+	return nil
+}
+
+// Events implements the [FSWatcher] interface for EmptyFSWatcher.
+func (EmptyFSWatcher) Events() (e <-chan event) {
+	return nil
+}
+
+// Add implements the [FSWatcher] interface for EmptyFSWatcher.
+func (EmptyFSWatcher) Add(_ string) (err error) {
+	return nil
+}
diff --git a/internal/home/home.go b/internal/home/home.go
index 93e8e09d123..fc64f3766dd 100644
--- a/internal/home/home.go
+++ b/internal/home/home.go
@@ -232,7 +232,9 @@ func configureOS(conf *configuration) (err error) {
 func setupHostsContainer() (err error) {
 	hostsWatcher, err := aghos.NewOSWritesWatcher()
 	if err != nil {
-		return fmt.Errorf("initing hosts watcher: %w", err)
+		log.Info("WARNING: initializing filesystem watcher: %s; not watching for changes", err)
+
+		hostsWatcher = aghos.EmptyFSWatcher{}
 	}
 
 	paths, err := hostsfile.DefaultHostsPaths()