feat: full NFSv4.2 server and client in pure Go

Assisted-by: GLM 5.3 Flash

internal/nfsfs/mknod_netbsd.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+//go:build netbsd
+
+package nfsfs
+
+import "syscall"
+
+// mknod creates a device node. It needs the superuser on NetBSD, and a
+// failure of permission is reported as such rather than as an io error.
+// The kind is picked before the single call: a second mknod over an
+// existing node fails EEXIST and leaves the wrong kind behind.
+func mknod(path string, spec CreateSpec, perm uint32) error {
+	dev := makedev(spec.Major, spec.Minor)
+	kind := uint32(syscall.S_IFCHR)
+	if spec.Kind == KindBlk {
+		kind = syscall.S_IFBLK
+	}
+	return syscall.Mknod(path, perm|kind, int(dev))
+}
+
+// makedev assembles a device number the way the kernel expects it: the
+// encoding of makedev in sys/sys/types.h, where the major number sits at
+// bits eight to nineteen, the low byte of the minor number keeps bit zero
+// through seven and the rest of the minor number is lifted to bits twenty
+// through thirty-one.
+func makedev(major, minor uint32) uint64 {
+	return uint64(major&0xfff)<<8 | uint64(minor&0xfff00)<<12 | uint64(minor&0xff)
+}