#18: implement SMTP Submission (587/465), SASL PLAIN/LOGIN auth and preflight diagnostics

services/protocols/cmd/lambdamail-protocols/disk_unix.go

@@ -0,0 +1,22 @@
+//go:build unix
+
+package main
+
+import "syscall"
+
+// freeDiskPercent reports the free space on the filesystem holding path.
+// PLAN.md section 15 treats a nearly full spool as a medium-severity finding:
+// once it fills, accepted mail cannot be written and has to be refused.
+func freeDiskPercent(path string) (float64, error) {
+	var stat syscall.Statfs_t
+	if err := syscall.Statfs(path, &stat); err != nil {
+		return 0, err
+	}
+	total := stat.Blocks
+	if total == 0 {
+		return 0, nil
+	}
+	// Bavail rather than Bfree: the blocks reserved for root are not usable
+	// by this process.
+	return float64(stat.Bavail) / float64(total) * 100, nil
+}