Initial revisin of healthchecker, inspired by HAProxy

internal/prober/netns.go

@@ -0,0 +1,40 @@
+package prober
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/vishvananda/netns"
+)
+
+// inNetns runs fn while the current OS thread is switched into the named
+// network namespace. The thread is locked for the duration so the switch is safe.
+// The original netns is restored before returning.
+// If nsName is empty, fn is run in the current namespace without any switching.
+func inNetns(nsName string, fn func() error) error {
+	if nsName == "" {
+		return fn()
+	}
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	origNs, err := netns.Get()
+	if err != nil {
+		return fmt.Errorf("get current netns: %w", err)
+	}
+	defer origNs.Close()
+	defer netns.Set(origNs) //nolint:errcheck
+
+	targetNs, err := netns.GetFromName(nsName)
+	if err != nil {
+		return fmt.Errorf("get netns %q: %w", nsName, err)
+	}
+	defer targetNs.Close()
+
+	if err := netns.Set(targetNs); err != nil {
+		return fmt.Errorf("enter netns %q: %w", nsName, err)
+	}
+
+	return fn()
+}