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

Assisted-by: GLM 5.3 Flash

internal/nfs4/xattr.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+// The extended attribute operations of RFC 8276: four narrow operations
+// over named opaque values.
+
+package nfs4
+
+import (
+	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
+)
+
+// SETXATTR modes of the setxattr4mode4 enum.
+const (
+	SetXattrUnchecked = 0
+	SetXattrCreate    = 1
+	SetXattrReplace   = 2
+)
+
+// AppendGetXattrArgs appends the GETXATTR argop: the name alone, the
+// whole argument RFC 8276 defines.
+func AppendGetXattrArgs(b []byte, name string) []byte {
+	b = xdr.AppendUint32(b, OpGetxattr)
+	return xdr.AppendString(b, name)
+}
+
+// AppendGetXattrRes appends a successful GETXATTR result: the value as
+// one opaque.
+func AppendGetXattrRes(b []byte, value []byte) []byte {
+	return xdr.AppendVarOpaque(b, value)
+}
+
+// DecodeGetXattrRes decodes a successful GETXATTR result.
+func DecodeGetXattrRes(body []byte) ([]byte, error) {
+	return xdr.NewDecoder(body).VarOpaque()
+}
+
+// AppendSetXattrArgs appends the SETXATTR argop: the create mode, the
+// name and the value.
+func AppendSetXattrArgs(b []byte, mode uint32, name string, value []byte) []byte {
+	b = xdr.AppendUint32(b, OpSetxattr)
+	b = xdr.AppendUint32(b, mode)
+	b = xdr.AppendString(b, name)
+	return xdr.AppendVarOpaque(b, value)
+}
+
+// AppendListXattrArgs appends the LISTXATTR argop: the cookie the last
+// reply returned and the response size budget.
+func AppendListXattrArgs(b []byte, cookie uint64, maxcount uint32) []byte {
+	b = xdr.AppendUint32(b, OpListxattr)
+	b = xdr.AppendUint64(b, cookie)
+	return xdr.AppendUint32(b, maxcount)
+}
+
+// AppendListXattrRes appends a successful LISTXATTR result: the cookie
+// of the last name, the names and the end of list flag.
+func AppendListXattrRes(b []byte, cookie uint64, names []string, eof bool) []byte {
+	b = xdr.AppendUint64(b, cookie)
+	b = xdr.AppendUint32(b, uint32(len(names)))
+	for _, n := range names {
+		b = xdr.AppendString(b, n)
+	}
+	return xdr.AppendBool(b, eof)
+}
+
+// AppendRemoveXattrArgs appends the REMOVEXATTR argop: the name.
+func AppendRemoveXattrArgs(b []byte, name string) []byte {
+	b = xdr.AppendUint32(b, OpRemovexattr)
+	return xdr.AppendString(b, name)
+}