@@ -220,8 +220,15 @@ Type Stubs
 Auxiliary Functions
 ~~~~~~~~~~~~~~~~~~~
 
+The option helpers are shared with
+:mod:`~pcapkit.protocols.schema.internet.ipv6_opts` and documented in
+:mod:`pcapkit.protocols.schema.internet.ipv6_option`. The functions below bind
+them to this module's error prefix and option schemas;
+:func:`~pcapkit.protocols.schema.internet.ipv6_option.rpl_opt_sub_tlv_len` and
+:func:`~pcapkit.protocols.schema.internet.ipv6_option.pad_opt_data_len` are
+used unchanged.
+
 .. autofunction:: pcapkit.protocols.schema.internet.hopopt.mpl_opt_seed_id_len
-.. autofunction:: pcapkit.protocols.schema.internet.hopopt.pad_opt_data_len
 .. autofunction:: pcapkit.protocols.schema.internet.hopopt.calipso_pad_len
 .. autofunction:: pcapkit.protocols.schema.internet.hopopt.mpl_opt_pad_len
 
 
@@ -20,6 +20,7 @@ internet layer, with detailed implementation and methods.
    ipv6_opts
    ipv6_route
    hopopt
+   ipv6_option
    ipsec
    ah
    esp
 
@@ -0,0 +1,31 @@
+IPv6 Options - Shared Option Helpers
+====================================
+
+.. module:: pcapkit.protocols.schema.internet.ipv6_option
+
+:mod:`pcapkit.protocols.schema.internet.ipv6_option` contains the field helpers
+shared by the option schemas of
+:mod:`~pcapkit.protocols.schema.internet.hopopt` (HOPOPT) and
+:mod:`~pcapkit.protocols.schema.internet.ipv6_opts` (IPv6-Opts), since both
+headers carry the same IPv6 options [*]_. A helper that reports an error takes
+the header's name as ``prefix``, and a selector takes the header's option
+schemas. Each header module binds them in a function of the same name, which
+is what its fields use.
+
+Auxiliary Functions
+-------------------
+
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.rpl_opt_sub_tlv_len
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.mpl_opt_seed_id_len
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.pad_opt_data_len
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.calipso_pad_len
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.mpl_opt_pad_len
+
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.smf_dpd_data_selector
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.smf_i_dpd_tid_selector
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.smf_i_dpd_id_len
+.. autofunction:: pcapkit.protocols.schema.internet.ipv6_option.quick_start_data_selector
+
+.. rubric:: Footnotes
+
+.. [*] https://www.rfc-editor.org/rfc/rfc8200#section-4.2
@@ -220,8 +220,15 @@ Type Stubs
 Auxiliary Functions
 ~~~~~~~~~~~~~~~~~~~
 
+The option helpers are shared with
+:mod:`~pcapkit.protocols.schema.internet.hopopt` and documented in
+:mod:`pcapkit.protocols.schema.internet.ipv6_option`. The functions below bind
+them to this module's error prefix and option schemas;
+:func:`~pcapkit.protocols.schema.internet.ipv6_option.rpl_opt_sub_tlv_len` and
+:func:`~pcapkit.protocols.schema.internet.ipv6_option.pad_opt_data_len` are
+used unchanged.
+
 .. autofunction:: pcapkit.protocols.schema.internet.ipv6_opts.mpl_opt_seed_id_len
-.. autofunction:: pcapkit.protocols.schema.internet.ipv6_opts.pad_opt_data_len
 .. autofunction:: pcapkit.protocols.schema.internet.ipv6_opts.calipso_pad_len
 .. autofunction:: pcapkit.protocols.schema.internet.ipv6_opts.mpl_opt_pad_len
 
 
@@ -10,18 +10,18 @@
 from pcapkit.const.ipv6.router_alert import RouterAlert as Enum_RouterAlert
 from pcapkit.const.ipv6.seed_id import SeedID as Enum_SeedID
 from pcapkit.const.ipv6.smf_dpd_mode import SMFDPDMode as Enum_SMFDPDMode
-from pcapkit.const.ipv6.tagger_id import TaggerID as Enum_TaggerID
 from pcapkit.const.reg.transtype import TransType as Enum_TransType
 from pcapkit.corekit.fields.collections import OptionField
 from pcapkit.corekit.fields.field import NO_VALUE
-from pcapkit.corekit.fields.ipaddress import IPv4AddressField, IPv6AddressField
-from pcapkit.corekit.fields.misc import (ConditionalField, ForwardMatchField, NoValueField,
-                                         PayloadField, SchemaField, SwitchField)
+from pcapkit.corekit.fields.ipaddress import IPv6AddressField
+from pcapkit.corekit.fields.misc import (ConditionalField, ForwardMatchField, PayloadField,
+                                         SwitchField)
 from pcapkit.corekit.fields.numbers import (EnumField, NumberField, UInt8Field, UInt16Field,
                                             UInt32Field)
 from pcapkit.corekit.fields.strings import BitField, BytesField, PaddingField
+from pcapkit.protocols.schema.internet import ipv6_option
+from pcapkit.protocols.schema.internet.ipv6_option import pad_opt_data_len, rpl_opt_sub_tlv_len
 from pcapkit.protocols.schema.schema import EnumSchema, Schema, schema_final
-from pcapkit.utilities.exceptions import FieldValueError
 from pcapkit.utilities.logging import SPHINX_TYPE_CHECKING
 
 __all__ = [
@@ -129,244 +129,83 @@ class QSNonce(TypedDict):
         reserved: int
 
 
-def rpl_opt_sub_tlv_len(pkt: 'dict[str, Any]') -> 'int':
-    """Return RPL option sub-TLV length.
-
-    Args:
-        pkt: RPL option unpacked schema.
-
-    Returns:
-        RPL option sub-TLV length, i.e. ``Opt Data Len`` less the four octets
-        of the fixed fields. An ``Opt Data Len`` below ``4`` gives ``0``, and
-        the reader then rejects the option.
-
-    """
-    return max(pkt['len'] - 4, 0)
+# NOTE: The option helpers are shared with IPv6-Opts and live in
+# :mod:`pcapkit.protocols.schema.internet.ipv6_option`. The functions below bind
+# what differs between the two headers: the ``HOPOPT`` error prefix, and the
+# option schemas of this module.
 
 
 def mpl_opt_seed_id_len(pkt: 'dict[str, Any]') -> 'int':
     """Return MPL Seed-ID length.
 
-    Args:
-        pkt: MPL option unpacked schema.
-
-    Returns:
-        MPL Seed-ID length.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.mpl_opt_seed_id_len`;
+    errors are reported as ``HOPOPT``.
 
     """
-    s_type = pkt['flags']['type']
-    if s_type == 0:
-        return 0
-    if s_type == 1:
-        return 2
-    if s_type == 2:
-        return 8
-    if s_type == 3:
-        return 16
-    raise FieldValueError(f'HOPOPT: invalid MPL Seed-ID type: {s_type}')
+    return ipv6_option.mpl_opt_seed_id_len(pkt, prefix='HOPOPT')
 
 
 def smf_i_dpd_id_len(pkt: 'dict[str, Any]') -> 'int':
     """Return SMF I-DPD identifier length.
 
-    Args:
-        pkt: SMF identification-based DPD option unpacked schema.
-
-    Returns:
-        SMF I-DPD identifier length.
-
-    Raises:
-        FieldValueError: If ``Opt Data Len`` on the wire is too short to hold
-            the TaggerID it declares, which would otherwise underflow the
-            identifier length below zero.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.smf_i_dpd_id_len`;
+    errors are reported as ``HOPOPT``.
 
     """
-    length = pkt['len'] - (1 if pkt['info']['type'] == 0 else (pkt['info']['len'] + 2))
-    if length < 0:
-        raise FieldValueError(f'HOPOPT: invalid SMF I-DPD option length: {pkt["len"]}')
-    return length
+    return ipv6_option.smf_i_dpd_id_len(pkt, prefix='HOPOPT')
 
 
 def smf_dpd_data_selector(pkt: 'dict[str, Any]') -> 'Field':
     """Selector function for :attr:`_SMFDPDOption.data` field.
 
-    Args:
-        pkt: Packet data.
-
-    Returns:
-        * If ``mode`` is ``0``, returns a :class:`~pcapkit.corekit.fields.misc.SchemaField`
-          wrapped :class:`~pcapkit.protocols.schema.internet.hopopt.SMFIdentificationBasedDPDOption`
-          instance.
-        * If ``mode`` is ``1``, returns a :class:`~pcapkit.corekit.fields.misc.SchemaField`
-          wrapped :class:`~pcapkit.protocols.schema.internet.hopopt.SMFHashBasedDPDOption`
-          instance.
-
-    Note:
-        The field is sized ``Opt Data Len + 2`` rather than ``Opt Data Len``.
-        ``Opt Data Len`` counts only what follows the option header
-        [:rfc:`8200#section-4.2`], while both schemas this may return inherit
-        :attr:`Option.type` and :attr:`Option.len` and so parse those two octets
-        themselves. Sizing the field at ``Opt Data Len`` would hand them an area two
-        octets short of the option they read, which
-        :class:`~pcapkit.corekit.fields.collections.OptionField` would then
-        mis-count against the option area.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.smf_dpd_data_selector`,
+    choosing among the schemas registered with :class:`SMFDPDOption`; errors
+    are reported as ``HOPOPT``.
 
     """
-    # NOTE: With ``Opt Data Len`` 0 the option has no data octet, so the mode
-    # bit forward-matched above belongs to whatever follows the option.
-    if pkt['test']['len'] == 0:
-        raise FieldValueError('HOPOPT: invalid SMF DPD option length: 0')
-
-    mode = Enum_SMFDPDMode.get(pkt['test']['mode'])
-    schema = SMFDPDOption.registry[mode]
-    if schema is None:
-        raise FieldValueError(f'HOPOPT: invalid SMF DPD mode: {mode}')
-    return SchemaField(length=pkt['test']['len'] + 2, schema=schema)
+    return ipv6_option.smf_dpd_data_selector(pkt, prefix='HOPOPT', base=SMFDPDOption)
 
 
 def smf_i_dpd_tid_selector(pkt: 'dict[str, Any]') -> 'Field':
     """Selector function for :attr:`SMFIdentificationBasedDPDOption.tid` field.
 
-    Args:
-        pkt: Packet data.
-
-    Returns:
-        * If ``tid_type`` is ``0``, returns a :class:`~pcapkit.corekit.fields.misc.NoValueField`
-          instance.
-        * If ``tid_type`` is ``1``, returns a :class:`~pcapkit.corekit.fields.ipaddress.IPv4AddressField`
-          instance.
-        * If ``tid_type`` is ``2``, returns a :class:`~pcapkit.corekit.fields.ipaddress.IPv6AddressField`
-          instance.
-        * Otherwise, returns a :class:`~pcapkit.corekit.fields.strings.BytesField` instance.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.smf_i_dpd_tid_selector`;
+    errors are reported as ``HOPOPT``.
 
     """
-    tid_type = Enum_TaggerID.get(pkt['info']['type'])
-    tid_len = pkt['info']['len']
-
-    # update type
-    pkt['info']['type'] = tid_type
-
-    if tid_type == Enum_TaggerID.NULL:
-        if tid_len != 0:
-            raise FieldValueError(f'HOPOPT: invalid TaggerID length: {tid_len}')
-        return NoValueField()
-    if tid_type == Enum_TaggerID.IPv4:
-        if tid_len != 3:
-            raise FieldValueError(f'HOPOPT: invalid TaggerID length: {tid_len}')
-        return IPv4AddressField()
-    if tid_type == Enum_TaggerID.IPv6:
-        if tid_len != 15:
-            raise FieldValueError(f'HOPOPT: invalid TaggerID length: {tid_len}')
-        return IPv6AddressField()
-    return BytesField(length=tid_len + 1)
+    return ipv6_option.smf_i_dpd_tid_selector(pkt, prefix='HOPOPT')
 
 
 def quick_start_data_selector(pkt: 'dict[str, Any]') -> 'Field':
     """Selector function for :attr:`_QuickStartOption.data` field.
 
-    Args:
-        pkt: Packet data.
-
-    Returns:
-        * If ``func`` is ``0``, returns a :class:`~pcapkit.corekit.fields.misc.SchemaField`
-          wrapped :class:`~pcapkit.protocols.schema.internet.hopopt.QuickStartRequestOption`
-          instance.
-        * If ``func`` is ``8``, returns a :class:`~pcapkit.corekit.fields.misc.SchemaField`
-          wrapped :class:`~pcapkit.protocols.schema.internet.hopopt.QuickStartReportOption`
-          instance.
-        * Otherwise, returns a :class:`~pcapkit.corekit.fields.misc.SchemaField`
-          wrapped :class:`~pcapkit.protocols.schema.internet.hopopt.UnassignedOption`
-          instance, sized by the option's own ``Opt Data Len``.
-
-    """
-    func = Enum_QSFunction.get(pkt['flags']['func'])
-    pkt['flags']['func'] = func
-
-    schema = QuickStartOption.registry[func]
-    if schema is None:
-        # An unassigned function has no defined layout, so the option is kept
-        # as raw data, sized by its own ``Opt Data Len``.
-        return SchemaField(length=pkt['flags']['len'] + 2, schema=UnassignedOption)
-
-    # NOTE: The suboption schemas carry the option's own ``type`` and ``len``
-    # octets, so this is the width of the whole option: the two header octets
-    # plus the six data octets :rfc:`4782#section-3.2` gives both functions.
-    return SchemaField(length=8, schema=schema)
-
-
-def pad_opt_data_len(pkt: 'dict[str, Any]') -> 'int':
-    """Return the length of the padding data of a padding option.
-
-    Args:
-        pkt: Padding option unpacked schema.
-
-    Returns:
-        Number of padding octets carried after the option header, i.e. the
-        value of the ``Opt Data Len`` field of a ``PadN`` option, and zero for
-        a ``Pad1`` option, which carries no such field.
-
-    Note:
-        A ``Pad1`` option is a single octet with neither an ``Opt Data Len``
-        field nor any option data (c.f. :rfc:`8200#section-4.2`), which is why
-        :attr:`Option.len` is declared as a
-        :class:`~pcapkit.corekit.fields.misc.ConditionalField` and is skipped
-        for it. A skipped conditional field is *recorded* in the packet data as
-        :data:`~pcapkit.corekit.fields.field.NO_VALUE`, rather than being left
-        out of it, so the test below has to be on the **value** and not on the
-        presence of the key: ``pkt.get('len', 0)`` on its own hands that
-        :obj:`~pcapkit.corekit.fields.field.NoValueType` straight to
-        :class:`~pcapkit.corekit.fields.strings.PaddingField`, where it becomes
-        an unusable :mod:`struct` template and surfaces much later as an opaque
-        :exc:`struct.error`, which is how a ``Pad1`` option would fail to parse.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.quick_start_data_selector`,
+    choosing among the schemas registered with :class:`QuickStartOption`, and
+    :class:`UnassignedOption` for an unassigned QS function.
 
     """
-    length = pkt.get('len', 0)
-    if not isinstance(length, int):  # ``NO_VALUE`` (skipped) or :obj:`None` (unset)
-        return 0
-    return length
+    return ipv6_option.quick_start_data_selector(pkt, base=QuickStartOption,
+                                                 unassigned=UnassignedOption)
 
 
 def calipso_pad_len(pkt: 'dict[str, Any]') -> 'int':
     """Return CALIPSO option padding length.
 
-    Args:
-        pkt: CALIPSO option unpacked schema.
-
-    Returns:
-        CALIPSO option padding length.
-
-    Raises:
-        FieldValueError: If ``Opt Data Len`` on the wire is too short to hold
-            the fixed header and the compartment bitmap declared by
-            ``cmpt_len``, which would otherwise underflow the padding length
-            below zero.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.calipso_pad_len`;
+    errors are reported as ``HOPOPT``.
 
     """
-    length = pkt['len'] - 8 - pkt['cmpt_len'] * 4
-    if length < 0:
-        raise FieldValueError(f'HOPOPT: invalid CALIPSO option length: {pkt["len"]}')
-    return length
+    return ipv6_option.calipso_pad_len(pkt, prefix='HOPOPT')
 
 
 def mpl_opt_pad_len(pkt: 'dict[str, Any]') -> 'int':
     """Return MPL option padding length.
 
-    Args:
-        pkt: MPL option unpacked schema.
-
-    Returns:
-        MPL option padding length.
-
-    Raises:
-        FieldValueError: If ``Opt Data Len`` on the wire is too short to hold
-            the fixed header and the Seed-ID declared by ``flags.type``, which
-            would otherwise underflow the padding length below zero.
+    See :func:`pcapkit.protocols.schema.internet.ipv6_option.mpl_opt_pad_len`;
+    errors are reported as ``HOPOPT``.
 
     """
-    length = pkt['len'] - 2 - (0 if pkt['flags']['type'] == 0 else mpl_opt_seed_id_len(pkt))
-    if length < 0:
-        raise FieldValueError(f'HOPOPT: invalid MPL option length: {pkt["len"]}')
-    return length
+    return ipv6_option.mpl_opt_pad_len(pkt, prefix='HOPOPT')
 
 
 class Option(EnumSchema[Enum_Option]):