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

Assisted-by: GLM 5.3 Flash

internal/nfs4/fuzz_test.go

@@ -0,0 +1,103 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package nfs4
+
+import (
+	"testing"
+
+	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
+)
+
+// FuzzDecodeCompound feeds arbitrary compound payloads through the
+// argument and result walkers: no input may panic, and every malformed
+// body must arrive as an error, never as a wrong split.
+func FuzzDecodeCompound(f *testing.F) {
+	args := AppendCompoundArgs(nil, "seed", MinorVersion, [][]byte{
+		AppendSequenceArgs(nil, SessionID{1}, 1, 0, 0, true),
+		AppendPutRootfh(nil),
+		AppendLookup(nil, "a"),
+	})
+	f.Add(args)
+	res := AppendCompoundRes(nil, ErrOK, "seed", [][]byte{
+		append(AppendOpHeader(nil, OpSequence, ErrOK), AppendSequenceRes(nil, SessionID{1}, 1, 0, 0, 0)...),
+		AppendOpHeader(nil, OpPutRootfh, ErrOK),
+	})
+	f.Add(res)
+	f.Add([]byte{0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 75, 0, 0, 0, 0})
+	f.Add([]byte{0, 0, 0, 9, 0, 0, 0, 1, 0, 0, 0, 1})
+	f.Fuzz(func(t *testing.T, data []byte) {
+		// The property under test is that none of this panics; a
+		// malformed body is an ordinary error and a well formed one
+		// decodes with bodies that stay inside the payload.
+		_, d, err := DecodeCompoundArgs(data)
+		if err == nil {
+			for {
+				op, oerr := d.Uint32()
+				if oerr != nil || walkArgs(op, d) {
+					break
+				}
+			}
+		}
+		_, _, _ = DecodeCompoundResBodies(data)
+		_, _, _ = DecodeCompoundResBodiesCB(data)
+	})
+}
+
+// walkArgs walks one operation's arguments the way the dispatcher does,
+// so the fuzzed stream exercises the real decoders. The boolean reports
+// that the stream ended or was refused.
+func walkArgs(op uint32, d *xdr.Decoder) bool {
+	switch op {
+	case OpExchangeID:
+		_, err := DecodeExchangeIDArgs(d)
+		return err != nil
+	case OpCreateSession:
+		_, err := DecodeCreateSessionArgs(d)
+		return err != nil
+	case OpSequence:
+		_, err := DecodeSequenceArgs(d)
+		return err != nil
+	case OpSecinfoNoName:
+		_, err := DecodeSecinfoNoNameArgs(d)
+		return err != nil
+	}
+	_, err := d.Uint32()
+	return err != nil
+}
+
+// TestRegistryValues pins the registry numbers this package speaks
+// against the standards: an accidental renumbering of any of these
+// breaks interoperation with every conformant peer, so the values
+// themselves are the contract.
+func TestRegistryValues(t *testing.T) {
+	pins := []struct {
+		name string
+		got  uint32
+		want uint32
+		rfc  string
+	}{
+		{"session id size", uint32(len(SessionID{})), 16, "RFC 7863"},
+		{"FATTR4_TIME_ACCESS_SET", AttrTimeAccessSet, 48, "RFC 7863"},
+		{"FATTR4_TIME_MODIFY_SET", AttrTimeModifySet, 54, "RFC 7863"},
+		{"LAYOUT4_FLEX_FILES", LayoutTypeFlexfiles, 4, "RFC 8435"},
+		{"LAYOUT4_NFSV4_1_FILES", LayoutTypeFiles, 1, "RFC 7863"},
+		{"LAYOUT4_OSD2_OBJECTS", LayoutTypeObjects, 2, "RFC 7863"},
+		{"LAYOUT4_BLOCK_VOLUME", LayoutTypeBlock, 3, "RFC 7863"},
+		{"layoutiomode4 RW", IoModeRW, 2, "RFC 7863"},
+		{"layoutiomode4 ANY", IoModeAny, 3, "RFC 7863"},
+		{"SP4_MACH_CRED", StateProtectMachCred, 1, "RFC 8881"},
+		{"SP4_SSV", StateProtectSSV, 2, "RFC 8881"},
+		{"SECINFO_STYLE4_CURRENT_FH", StyleCurrentFH, 0, "RFC 8881"},
+		{"SECINFO_STYLE4_PARENT", StyleParent, 1, "RFC 8881"},
+		{"NFS4ERR_NXIO", ErrNXIO, 6, "RFC 8881"},
+		{"NFS4ERR_BADOWNER", ErrBadOwner, 10093, "RFC 8881"},
+		{"NFS4ERR_NOXATTR", ErrNoXattr, 10095, "RFC 8276"},
+		{"NFS4ERR_XATTR2BIG", ErrXattr2Big, 10096, "RFC 8276"},
+	}
+	for _, p := range pins {
+		if p.got != p.want {
+			t.Errorf("%s: got %d, want %d per %s", p.name, p.got, p.want, p.rfc)
+		}
+	}
+}