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Network Working Group                                        S. Sugimoto
Internet-Draft                                                  Ericsson
Expires: March 23, 2007                                        F. Dupont
                                                                   CELAR
                                                             M. Nakamura
                                                                 Hitachi
                                                      September 19, 2006


   PF_KEY Extension as an Interface between Mobile IPv6 and IPsec/IKE
                  draft-sugimoto-mip6-pfkey-migrate-03

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on March 23, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document describes the need for an interface between Mobile IPv6
   and IPsec/IKE and show how the two protocols can interwork.  We
   propose a set of extensions to the PF_KEY framework which allows
   smooth and solid operation of IKE in a Mobile IPv6 environment.  The
   first extension is called PF_KEY MIGRATE and is for migrating the



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   endpoint addresses of a IPsec Security Association pair in tunnel
   mode.  The second extension is named SADB_X_EXT_PACKET and allows IKE
   to make the right choice for address selection in bootstrapping
   process.  Both extensions are helpful for assuring smooth
   interworking between Mobile IPv6 and IPsec/IKE and achieving
   performance optimization.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Needs for Interactions between Mobile IPv6 and IPsec/IKE . . .  3
   3.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  PF_KEY Extensions for Mobile IPv6  . . . . . . . . . . . . . .  4
     4.1.  PF_KEY MIGRATE Message . . . . . . . . . . . . . . . . . .  5
       4.1.1.  Overview . . . . . . . . . . . . . . . . . . . . . . .  5
       4.1.2.  Message Sequence . . . . . . . . . . . . . . . . . . .  6
       4.1.3.  Issuing PF_KEY MIGRATE Message . . . . . . . . . . . .  7
       4.1.4.  Processing PF_KEY MIGRATE Message  . . . . . . . . . .  8
       4.1.5.  Applicability of PF_KEY MIGRATE to Other Systems . . .  9
       4.1.6.  Limitation of PF_KEY MIGRATE . . . . . . . . . . . . .  9
     4.2.  PF_KEY Packet Extension  . . . . . . . . . . . . . . . . . 10
       4.2.1.  Inserting Packet Extension to SADB_ACQUIRE Message . . 10
       4.2.2.  Processing SADB_ACQUIRE Message with Packet
               Extension  . . . . . . . . . . . . . . . . . . . . . . 11
       4.2.3.  Relation of Packet Extension to IKEv2  . . . . . . . . 11
   5.  Necessary Modifications to Mobile IPv6 and IPsec/IKE . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Appendix A.  PF_KEY MIGRATE Message Format . . . . . . . . . . . . 14
   Appendix B.  Acknowledgements  . . . . . . . . . . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
   Intellectual Property and Copyright Statements . . . . . . . . . . 18

















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1.  Introduction

   In Mobile IPv6 [RFC3775], the Mobile Node (MN) and the Home Agent
   (HA) use some IPsec Security Associations (SAs) in tunnel mode to
   protect some mobility signaling messages, mobile prefix discovery and
   optionally payload traffic.  Since the MN may change its attachment
   point to the Internet, it is necessary to update its endpoint address
   of the IPsec SAs.  This indicates that corresponding entry in IPsec
   databases (Security Policy (SPD) and SA (SAD) databases) should be
   updated when MN performs movements.  In addition, IKE requires
   treatment to keep its IKE session alive in a Mobile IPv6 environment.

   This document describes the need for an interface between Mobile IPv6
   and IPsec/IKE and shows how the two protocols can interwork.  We
   propose a set of extensions to the PF_KEY framework [RFC2367] which
   allows smooth and solid operation of IKE in an Mobile IPv6
   environment.  The first extension is called PF_KEY MIGRATE and is for
   migrating the endpoint addresses of the IPsec SAs in tunnel mode.
   The second extension is named SADB_X_EXT_PACKET and allows IKE to
   make the right choice in address selection in the bootstrapping
   process.  Both extensions are helpful for assuring smooth
   interworking between Mobile IPv6 and IPsec/IKE and achieving
   performance optimization.

   In this document, the term IKE implicitly stands for both IKEv1
   [RFC2409] and IKEv2 [RFC4306].  In description with regard to any
   functionality that is specific to either of the protocols, specific
   protocol name shall be provided.


2.  Needs for Interactions between Mobile IPv6 and IPsec/IKE

   The section 4.4 of RFC 3776 [RFC3776] specifies the rules which
   applies to IKE for MNs and HAs.  The first requirement is to run IKE
   over the Care-of Address (CoA) because the Home Address (HoA) is
   usable only after the home registration so not yet in the
   bootstrapping phase.

   A tunnel IPsec SA pair protects some signaling messages and
   optionally all the traffic between the MN and HA.  The initial SPD
   entry uses the HoA for the MN endpoint address and updates this
   address to the new CoA at each movement.  A tunnel SA pair is created
   on demand and is updated too.  The RFC 3775 [RFC3775] assumes there
   is an API which performs the update in the SPD and SAD on both the MN
   and HA.  This document is mainly about this API.

   Mobile IPv6 specifies a flag named Key Management Mobility Capability
   bit (K-bit) in Binding Update (BU) and Binding Acknowledgement (BA)



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   messages (section 10.3.1 of [RFC3775]), which indicates the ability
   of IKE sessions to survive movement.  When both the MN and HA agree
   to use this functionality, the IKE daemons dynamically update the IKE
   session when the MN moves.  In order to realize this, IKE daemons
   should be notified by Mobile IPv6, and necessary information to
   migrate the IKE session should be provided.

   Mobile IPv6 may need to make an access to the SPD not only for
   updating an endpoint address but also for the deletion/insertion of a
   specific SPD entry.  When the MN performs Foreign-to-Home movement,
   IPsec SAs established between the MN and HA should be deleted, which
   means that the SPD entry should have no effect any more.  On the
   other hand, when the MN performs Home-to-Foreign movement, the IPsec
   SAs should be restored.  Hence security policy entries that are
   associated with tunnel mode SAs may dynamically be added/removed
   (enabled/disabled) in along with MN's movements.

   It should be noted that NEMO Basic Support [RFC3963] has similar
   requirements for the Mobile Router (MR) and MR's HA (MRHA).  In NEMO,
   the MR works just as same as a MN registering its location
   information to the MRHA and establishes a tunnel (IP-in-IP or IPsec
   tunnel).  When an IPsec tunnel is established between MR and MRHA,
   the MR serves as a Security Gateway for the nodes connected to the
   mobile network.  The MR is responsible for handling its tunnel
   endpoint properly.


3.  Requirements

   Given the need for an interface between Mobile IPv6 and IPsec/IKE,
   there should be a minimum interface between the two protocols.
   Followings are the requirements for the interface from a software
   engineering point of view.

   o  Necessary modifications to the existing software, namely Mobile
      IPv6 and IPsec/IKE, in order to realize proposed mechanisms,
      should be kept minimum.
   o  Proposed mechanism should not be platform dependent.  The
      mechanism should be based on technology which is commonly
      available on various platform.  This seems to be essential for
      achieving high portability of the implementation which supports
      proposed mechanisms.


4.  PF_KEY Extensions for Mobile IPv6

   In order to fulfill the needs and requirements described in Section 2
   and Section 3 we propose to extend the PF_KEY framework so that



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   Mobile IPv6 and IPsec/IKE could interact with each other.

4.1.  PF_KEY MIGRATE Message

   The first extension is primarily for migrating an endpoint address of
   an IPsec SA pair in tunnel mode from one to another, which results in
   updating IPsec databases.  A new PF_KEY message named MIGRATE is
   introduced for the mechanism.

4.1.1.  Overview

   The figure below illustrates how Mobile IPv6 and IPsec/IKE components
   interact with each other using PF_KEY MIGRATE messages in a dynamic
   keying scenario.  On left top, there is a Mobile IPv6 entity.  It may
   be possible that Mobile IPv6 component is completely implemented
   inside the kernel (this is the case for our implementations because
   it makes some facilities and extensions far easier at the cost of
   maintaining a SPD image in daemons).  In any case, Mobile IPv6 should
   be the one which issues the MIGRATE messages.  On right top, there is
   an IKE daemon which is responsible for establishing SAs required for
   Mobile IPv6 operation.  In a manual keying scenario, the difference
   is only that there is no IKE daemon running on the system.

                +-------------+           +------------+
                |             |           |            |
                | Mobile IPv6 |           | IKE Daemon |
                |             |           |            |
                +-------------+           +------------+
                       | 1. PF_KEY               A 4. Update
                       |    MIGRATE              |    SPD & SAD
                       +-----------+ +-----------+
                                   | |
    Userland                       V |
   ==========================[PF_KEY Socket]========================
    Kernel                         | |
                        +----------+ +----------+
                        | 2. Update             | 3. Update
                        V    SPD                V    SAD
                  +-----------+           +------------+
                  |           |           |            |
                  |    SPD    |           |    SAD     |
                  |           |           |            |
                  +-----------+           +------------+

   The primary role of PF_KEY MIGRATE messages is to migrate endpoint
   addresses of tunnel mode SA pairs requesting IPsec to update its
   databases (SPD and SAD).  In addition, the new message can be used by
   IKE to enhance its mobility capability.  When a PF_KEY MIGRATE



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   message is properly processed by the kernel, it is sent to all open
   sockets as normal PF_KEY messages.  The processing of a sequence of
   MIGRATE messages is done in following steps:

   o  Mobile IPv6 issues a PF_KEY MIGRATE message to the PF_KEY socket.
   o  The operating system (kernel) validates the message and checks if
      corresponding security policy entry exists in SPD.
   o  When the message is confirmed to be valid, the target SPD entry is
      updated according to the MIGRATE message.  If there is any target
      SA found that are also target of the update, those should also be
      updated.
   o  After the MIGRATE message is successfully processed inside the
      kernel, it will be sent to all open PF_KEY sockets.
   o  The IKE daemon receives the MIGRATE message from its PF_KEY socket
      and updates its SPD and SAD images.  The IKE daemon may also
      update its state to keep the IKE session alive.

   Note that the way IKE maintains its local copy of SPD (the SPD image)
   is implementation specific issue since there is no standard interface
   to access SPD.  Some IKE implementation may continuously monitor the
   SPD inside the kernel.  Some IKE implementation may expect
   notification from the kernel when the SPD is modified.  In either
   way, the proposed mechanism gives a chance for IKE to keep its SPD
   image up-to-date which is significant in Mobile IPv6 operation.

4.1.2.  Message Sequence

   Next, we will see how migration takes place in along with home
   registration.  The figure below shows sequence of mobility signaling
   and PF_KEY MIGRATE messages while the MN roams around links.  It is
   assumed that in the initial state the tunnel endpoint address for a
   given MN is set as its home address.  In the initial home
   registration, the MN and HA migrate the tunnel endpoint address from
   the HoA to CoA1.  It should be noted that no migration takes place
   when the MN performs re-registration since the care-of address
   remains the same.  Accordingly, the MN performs movement and changes
   its primary care-of address from CoA1 to CoA2.  A PF_KEY MIGRATE
   message is issued on both MN and HA for each direction.  When the MN
   returns to home, migration takes place updating the endpoint address
   with the MN's home address.

   With regard to the timing of issuing a MIGRATE message on the MN
   side, the message can be issued immediately after the home
   registration.  That is, there is no need to wait until the
   acknowledgment from the HA to issue migrate the endpoint addresses
   stored in the IPsec databases.  The Mobile IPv6 specification
   ([RFC3775] Section 11.6.3) actually allows the MN to start using the
   new care-of address immediately after sending a BU message to the HA.



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   This may help the MN to minimize the packet loss of its outbound
   traffic during the handover.

               MN                                        HA
               |                                          |
               ~                                          ~
     Movement->|      BU (Initial home registration)      |
               |----------------------------------------->|
     MIGRATE ->|                   BA                     |<- MIGRATE
   (HoA->CoA1) |<-----------------------------------------| (HoA->CoA1)
               |                                          |
               ~         BU (Home re-registration)        ~
               |----------------------------------------->|
               |                   BA                     |
               |<-----------------------------------------|
               |                                          |
               ~                                          ~
               |                                          |
     Movement->|           BU (Home registration)         |
               |----------------------------------------->|
     MIGRATE ->|                   BA                     |<- MIGRATE
   (CoA1->CoA2)|<-----------------------------------------| (CoA1->CoA2)
               |                                          |
               ~                                          ~
     Movement->|         BU (Home de-registration)        |
               |----------------------------------------->|
     MIGRATE ->|                   BA                     |<- MIGRATE
   (CoA2->HoA) |<-----------------------------------------| (CoA2->HoA)
               |                                          |

4.1.3.  Issuing PF_KEY MIGRATE Message

   The Mobile IPv6 entity (MN or HA code) triggers the migration by
   sending a PF_KEY MIGRATE message to its PF_KEY socket.  Conceptually,
   the PF_KEY MIGRATE message should contain following information:

   o  Selector information:
      *  source address/port
      *  destination address/port
      *  upper layer protocol (i.e., Mobility Header)
      *  direction (inbound/outbound)
   o  Old SA information:
      *  old source endpoint address
      *  old destination endpoint address
      *  IPsec protocol (ESP/AH)
      *  mode (Tunnel)





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   o  New SA information:
      *  new source endpoint address
      *  new destination endpoint address
      *  IPsec protocol (ESP/AH)
      *  mode (Tunnel)

   Selector information is required for specifying the target SPD entry
   to be updated.  Basically the information should contain necessary
   elements which characterize traffic selector as specified in the
   IPsec architecture ([RFC2401], [RFC4301]).  With regard to the upper
   layer protocol, when the Mobile IPv6 stack is not fully aware of
   IPsec configuration, an wild-card value could be given.  In such
   case, an upper layer protocol information should not be taken into
   account for searching SPD entry.  Plus, the direction of the security
   policy (inbound/outbound) should be provided.  The old SA information
   is used to specify target security association to be updated.  The
   source and destination addresses of the target entry should be
   overwritten with the ones included in the new SA information.  Note
   that the IPsec protocol and mode fields should not be updated by a
   PF_KEY MIGRATE message.

   A PF_KEY MIGRATE message should be formed based on security policy
   configuration and binding record.  The selector information and some
   parts of the SA information (IPsec protocol and mode) should be taken
   from the policy configuration.  The rest of the information should be
   taken from the sequential binding information.  For example, in the
   case where the MN updates its inbound security policy and
   corresponding tunnel mode SA pair, the old source address should be
   set as its previous CoA, and the new source address should be set as
   its current CoA.  Hence, the MN should sequentially keep track of its
   CoA record.  Such information shall be stored in binding update list
   entry.  For the same reason, the HA should keep track of previous
   CoAs of MNs.  Such information shall be stored in binding cache
   entry.

   Additionally, a piece of information which indicates a mobility
   capability of IKE (K-bit) should be provided by any means.  This
   makes it possible for IKE to see if there is a need to update its
   state (IKE endpoint addresses) in accordance with PF_KEY MIGRATE
   messages.

   A detailed message format of PF_KEY MIGRATE is provided in
   Appendix A.

4.1.4.  Processing PF_KEY MIGRATE Message

   Since a PF_KEY MIGRATE message is applied to a single SPD entry, the
   kernel should first check validity of the message.  If the message is



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   invalid, an EINVAL error MUST be returned as a return value for the
   write() operation made to the PF_KEY socket.  After the validation,
   the kernel checks if the target SPD entry really exists.  If no entry
   is found, an ENOENT error MUST be returned.  If a SPD entry is found
   and successfully updated, a success (0) MUST be returned regardless
   of subsequent result of SAD lookup/update.  Note that there may be a
   case where a corresponding SAD entry does not exist even if a SPD
   entry is successfully updated.  In any error case, a PF_KEY MIGRATE
   message MUST NOT have any effect on the SPD and SAD.

   With respect to the behavior of a normal process (including the IKE
   daemon) which receives a PF_KEY MIGRATE message from a PF_KEY socket,
   it SHOULD first check if the message does not include erroneous
   information.  When there is any error indicated, the process MUST
   silently discard the PF_KEY MIGRATE message.  Otherwise, the
   processing of the message may continue.

4.1.5.  Applicability of PF_KEY MIGRATE to Other Systems

   It should be noted that the PF_KEY MIGRATE extension is also
   applicable to other systems than Mobile IPv6 and/or IKE.  For
   example, it can be used in a scenario where an IPsec/IKE enabled node
   establishes tunnel mode SAs association with its Security Gateway
   while it roams around the network (aka "road warrior").  The security
   policy is set as such that all traffic should bi-directionally go
   through the tunnel IPsec SAs.  In such case, the migration of a
   tunnel endpoint address can be handled by PF_KEY MIGRATE messages.
   Each time the node changes its attachment point to the Internet,
   PF_KEY MIGRATE messages should be issued to the system.
   Consequently, the IPsec databases (SPD and SAD) shall be properly
   updated.

   It is also essential to keep design of the mechanism protocol
   independent.  More specifically, the PF_KEY MIGRATE extension should
   be able to work on both IPv4 and IPv6.  In order to achieve this, the
   IP addresses to be stored in selector and SA information should be
   handled in a protocol-independent manner.

4.1.6.  Limitation of PF_KEY MIGRATE

   Currently, a Security Parameter Index (SPI) is not included in the
   old SA information to specify target SAD entry.  This helps to lessen
   operational burden of Mobile IPv6.  However, this simplification can
   produce ambiguity in searching for the target security association
   entry.  When the unique SPD level is available, it should be use
   because it avoids this problem both by marking the SAs to update and
   by limiting SA sharing.




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   It should be noted that delivery of PF_KEY MIGRATE messages cannot be
   guaranteed, which is common to other PF_KEY messages.  It may be
   possible that a MIGRATE message is lost.  In such case, there will be
   inconsistency between the binding record managed by Mobile IPv6 and
   IPsec database inside the kernel.  Once a PF_KEY MIGRATE message is
   lost, it would not be possible for the receiver to process some
   subsequent MIGRATE messages properly.  Reinitialization of the Mobile
   IPv6 stack and IPsec databases may be needed for recovery.

4.2.  PF_KEY Packet Extension

   In the initial stage of MIPv6 operation known as the bootstrapping
   process, the MN and HA probably need to establish SAs from scratch in
   order to start the MIPv6 operation.  If IKE is used to maintain the
   SAs, the MN and HA are required to establish a transport mode SA pair
   so that the MN could make the initial protected home registration to
   the HA.  As mentioned in RFC 3776 [RFC3776], the IKE negotiation
   should be done carefully in terms of handling the identity of the MN.
   More specifically, IKE must be run over the MN's primary CoA while
   the SA pair should be based on the MN's HoA.  Note that the HoA
   cannot be used prior to the initial home registration.  This is an
   exceptional case of IKE negotiation in a sense that the peer address
   (the address on which IKE runs) and the IP address to be used as
   selector for the SAs are different.  Since IKE should not be required
   to maintain mobility state, there is a need to guide IKE to make the
   right choice for address/identity.

   A simple solution for this explicit notification can be provided by
   extending PF_KEY framework by including information of the triggering
   packet into SADB_ACQUIRE messages.  This extension allows receiver of
   a SADB_ACQUIRE message to determine which address to use for what
   purpose, i.e., to recognize the exceptional case as all the needed
   informations are already in the home registration binding update.  As
   shown below, a SADB_ACQUIRE message MAY contain an extension which
   contains the triggering packet (the whole packet, information
   extracted from it by the kernel or as we recommend enough of the
   beginning of it).

   <base, address(SD), address(P)*, identity(SD)*,
                           sensitivity*, proposal, packet*>

4.2.1.  Inserting Packet Extension to SADB_ACQUIRE Message

   The IPsec subsystem MAY include a Packet Extension to a SADB_ACQUIRE
   message when it is triggered by an output of data packet.  The Packet
   Extension simply contains the information of the triggering packet.
   Like any other extension headers specified in RFC 2367 [RFC2367], a
   Packet Extension (SADB_X_EXT_PACKET) MUST follow the basic rules and



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   be formulated in the type-length-value format.  A redundant part of
   the original IP packet (i.e., payload/trailer) MAY be eliminated.
   More than one Packet Extension header MUST NOT be appended to the
   message.  A sadb_x_packet extension header is followed by an IP
   packet which has triggered the SADB_ACQUIRE message.  Note that the
   Packet Extension is protocol independent, which means that the
   triggering packet included in the extension header could be either
   IPv4 or IPv6.  The address family of the triggering packet can be
   recognized by the first 4 bits of the IP packet.

   struct sadb_x_packet {
           uint16_t sadb_packet_len;
           uint16_t sadb_packet_exttype;
   };
   /* sizeof(struct sadb_x_packet) == 4 */
   /* followed by an IP packet header which triggered
                                   the SADB_ACQUIRE message */

4.2.2.  Processing SADB_ACQUIRE Message with Packet Extension

   A receiver of a SADB_ACQUIRE message with a Packet Extension MAY
   extract and process the extension header.  A MIPv6-aware IKE daemon
   should be able to process a Packet Extension which includes the IPv6
   packet which carries an initial home registration BU message.  Such
   packet includes a home address destination option which contains the
   primary CoA of the MN and the source address field of the IPv6 header
   contains the HoA of the MN (note the exact layout depends on the
   place of the IPsec acquiring code, we assume here its place follows
   the section 11.3.2 of [RFC3775]).  The destination address field of
   the IPv6 header contains the address of the HA, the mobility header a
   BU (type 5) for home registration (H flag set to one).

   Receipt of SADB_ACQUIRE Message with Packet Extension containing BU
   message implies that IKE is required to establish SAs for the MIPv6
   home registration.  Accordingly, the IKE should be able to make a
   right choice of address selection.  The CoA must be used as a peer
   address in the IKE negotiation and the HoA should be used as selector
   of transport mode SAs and as endpoint address of tunnel mode SAs.

4.2.3.  Relation of Packet Extension to IKEv2

   In IKEv2 [RFC4306], when the initiator has requested to establish SAs
   triggered by a data packet, the first traffic selector of TSi and TSr
   should reflect the triggering packet.  Therefore, IKEv2 could take
   advantage of Packet Extensions when some information from triggering
   packets are needed for a traffic selector negotiation.





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5.  Necessary Modifications to Mobile IPv6 and IPsec/IKE

   In order to realize the proposed mechanism, there are some necessary
   modifications to Mobile IPv6 and IPsec/IKE.  Following are the
   summary of necessary modifications, which could be of interest to
   implementors of Mobile IPv6 and/or IPsec/IKE.

   o  Modifications to Mobile IPv6:
      *  The Mobile IPv6 code can make an access to PF_KEY socket.  In
         particular, the Mobile IPv6 code should have privilege to write
         messages into a PF_KEY socket.
      *  Issuing PF_KEY MIGRATE messages: in order to send MIGRATE
         messages, it is required that the Mobile IPv6 code has some
         knowledge of its IPsec configuration and precise binding
         record.  The Mobile IPv6 code may be aware of exact IPsec
         configuration in form or security policy.  It would also be
         possible that the Mobile IPv6 code is only aware of minimum
         IPsec configuration whether if IPsec is utilized or not.
   o  Modifications to IPsec:
      *  Processing PF_KEY MIGRATE messages: the kernel should be able
         to process PF_KEY MIGRATE messages sent by the Mobile IPv6
         code.  Unless the message is invalid, it should be sent to all
         open PF_KEY sockets.
      *  Enabling Packet Extensions (SADB_X_EXT_PACKET): the kernel
         should be able to append a SADB_X_EXT_PACKET extension to
         SADB_MIGRATE messages when they are triggered by an output of a
         data packet.
   o  Modifications to IKE:
      *  Processing PF_KEY MIGRATE messages: the IKE code may update its
         local copy of IPsec databases (SPD and SAD) in accordance with
         received PF_KEY MIGRATE messages.  In addition, it may update
         its state / IKE session with new endpoint addresses indicated
         by PF_KEY MIGRATE messages.
      *  Processing of Packet Extensions (SADB_X_EXT_PACKET): the IKE
         code may process SADB_X_EXT_PACKET extensions and extract
         necessary information from triggering packets.  In order for
         the IKE code to be MIPv6-aware, it should properly extract the
         home address, care-of address, and HA address from IP packets
         which carry home registration BU messages.


6.  Security Considerations

   There is no specific security considerations for the mechanisms
   introduced by the document but as it should make deployment of
   dynamic keying in Mobile IPv6 environments easier it should improve
   the security of such environments.  Note that dynamic keying is known
   to be more secure (it provides anti-replay for instance) and far more



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   scalable.


7.  Conclusion

   o  There is a need for Mobile IPv6 and IPsec/IKE to interact with
      each other to provide full support of IPsec security functions.
   o  An extension to the PF_KEY framework (PF_KEY MIGRATE message) is
      proposed, which makes it possible for the IPsec/IKE to migrate an
      endpoint address of tunnel IPsec SAs from one to another.
   o  PF_KEY MIGRATE messages also make it possible for IKE to survive
      movements by updating its IKE session.
   o  In order for the IKE to perform key negotiations and rekeying,
      effort should be made to keep its SPD image up-to-date.
   o  The proposed mechanism was implemented on both Linux and BSD
      platforms and confirmed to be working well.
   o  Currently, large portion of the proposed mechanism is
      implementation dependent due to lack of standard interface to
      access the SPD (PF_POLICY?).

8.  References

   [RFC2367]  McDonald, D., Metz, C., and B. Phan, "PF_KEY Key
              Management API, Version 2", RFC 2367, July 1998.

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, November 1998.

   [RFC2409]  Harkins, D. and D. Carrel, "The Internet Key Exchange
              (IKE)", RFC 2409, November 1998.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [RFC3776]  Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
              Protect Mobile IPv6 Signaling Between Mobile Nodes and
              Home Agents", RFC 3776, June 2004.

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, January 2005.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.




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Appendix A.  PF_KEY MIGRATE Message Format

   The figure below shows the message format of PF_KEY MIGRATE.  The
   message consists of 6 parts (boundary of each part is marked with
   ">").  The message starts with PF_KEY base message header followed by
   two address extensions.  A pair of address extensions hold source and
   destination address of the selector.  Rest of the message are
   specific to IPsec implementation on BSD. sadb_x_policy{} structure
   holds additional information of security policy.  The last part of
   the message is a pair of sadb_x_ipsecrequest{} structures that hold
   old and new SA information.

        0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
       +---------------+---------------+---------------+---------------+
       |  ...version   | sadb_msg_type | sadb_msg_errno| ...msg_satype |
       +---------------+---------------+---------------+---------------+
       |          sadb_msg_len         |       sadb_msg_reserved       |
       +---------------+---------------+---------------+---------------+
       |                         sadb_msg_seq                          |
       +---------------+---------------+---------------+---------------+
       |                         sadb_msg_pid                          |
      >+---------------+---------------+---------------+---------------+
       |       sadb_address_len        |     sadb_address_exttype      |
       +---------------+---------------+---------------+---------------+
       | _address_proto| ..._prefixlen |     sadb_address_reserved     |
       +---------------+---------------+---------------+---------------+
       ~         selector source address (64-bit aligned sockaddr)     ~
      >+---------------+---------------+---------------+---------------+
       |       sadb_address_len        |     sadb_address_exttype      |
       +---------------+---------------+---------------+---------------+
       | _address_proto| ..._prefixlen |     sadb_address_reserved     |
       +---------------+---------------+---------------+---------------+
       ~     selector destination address (64-bit aligned sockaddr)    ~
      >+---------------+---------------+---------------+---------------+
       |       sadb_x_policy_len       |     sadb_x_policy_exttype     |
       +---------------+---------------+---------------+---------------+
       |       sadb_x_policy_type      |     ..._dir   |  ..._reserved |
       +---------------+---------------+---------------+---------------+
       |                        sadb_x_policy_id                       |
       +---------------+---------------+---------------+---------------+
       |                     sadb_x_policy_priority                    |
      >+---------------+---------------+---------------+---------------+
       |    sadb_x_ipsecrequest_len    |    sadb_x_ipsecrequest_proto  |
       +---------------+---------------+---------------+---------------+
       |    ..._mode   |   ..._level   | sadb_x_ipsecrequest_reserved1 |
       +---------------+---------------+---------------+---------------+
       |                   sadb_x_ipsecrequest_reqid                   |
       +---------------+---------------+---------------+---------------+



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       |                 sadb_x_ipsecrequest_reserved2                 |
       +---------------+---------------+---------------+---------------+
       ~       old tunnel source address (64-bit aligned sockaddr)     ~
       +---------------+---------------+---------------+---------------+
       ~    old tunnel destination address (64-bit aligned sockaddr)   ~
      >+---------------+---------------+---------------+---------------+
       |    sadb_x_ipsecrequest_len    |    sadb_x_ipsecrequest_proto  |
       +---------------+---------------+---------------+---------------+
       |    ..._mode   |   ..._level   | sadb_x_ipsecrequest_reserved1 |
       +---------------+---------------+---------------+---------------+
       |                   sadb_x_ipsecrequest_reqid                   |
       +---------------+---------------+---------------+---------------+
       |                 sadb_x_ipsecrequest_reserved2                 |
       +---------------+---------------+---------------+---------------+
       ~       new tunnel source address (64-bit aligned sockaddr)     ~
       +---------------+---------------+---------------+---------------+
       ~    new tunnel destination address (64-bit aligned sockaddr)   ~
       +---------------+---------------+---------------+---------------+

   Following is a structure of PF_KEY base message header specified in
   [RFC2367].  A new message type for PF_KEY MIGRATE (i.e.,
   SADB_X_MIGRATE) should be specified in member sadb_msg_type.

           struct sadb_msg {
                   uint8_t         sadb_msg_version;
                   uint8_t         sadb_msg_type;
                   uint8_t         sadb_msg_errno;
                   uint8_t         sadb_msg_satype;
                   uint16_t        sadb_msg_len;
                   uint16_t        sadb_msg_reserved;
                   uint32_t        sadb_msg_seq;
                   uint32_t        sadb_msg_pid;
           };

   Following is a structure of address extension header specified in
   [RFC2367].  Upper layer protocol should be specified in member
   sadb_address_proto.

           struct sadb_address {
                   uint16_t        sadb_address_len;
                   uint16_t        sadb_address_exttype;
                   uint8_t         sadb_address_proto;
                   uint8_t         sadb_address_prefixlen;
                   uint16_t        sadb_address_reserved;
           };

   Following is a structure for holding attributes that are relevant to
   security policy, which is available on BSD IPsec implementation.



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   Direction of the target security policy should be specified in member
   sadb_x_policy_dir.

           struct sadb_x_policy {
                   uint16_t        sadb_x_policy_len;
                   uint16_t        sadb_x_policy_exttype;
                   uint16_t        sadb_x_policy_type;
                   uint8_t         sadb_x_policy_dir;
                   uint8_t         sadb_x_policy_reserved;
                   uint32_t        sadb_x_policy_id;
                   uint32_t        sadb_x_policy_priority;
           };

   Following is a structure for holding attributes that are relevant to
   security association, which is available on BSD IPsec implementation.
   IPsec protocol (ESP or AH) and mode (Tunnel) of the target security
   association should be provided in member sadb_x_ipsecrequest_proto
   and sadb_x_ipsecrequest_mode, respectively.

           struct sadb_x_ipsecrequest {
                   uint16_t        sadb_x_ipsecrequest_len;
                   uint16_t        sadb_x_ipsecrequest_proto;
                   uint8_t         sadb_x_ipsecrequest_mode;
                   uint8_t         sadb_x_ipsecrequest_level;
                   uint16_t        sadb_x_ipsecrequest_reserved1;
                   uint32_t        sadb_x_ipsecrequest_reqid;
                   uint32_t        sadb_x_ipsecrequest_reserved2;
           };


Appendix B.  Acknowledgements

   The authors gratefully acknowledge the contribution of: Kazunori
   Miyazawa, Noriaki Takamiya, Shoichi Sakane, Mitsuru Kanda, Keiichi
   Shima, Tsuyoshi Momose and other members from USAGI Project and KAME
   Project.















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Authors' Addresses

   Shinta Sugimoto
   Nippon Ericsson K.K.
   Koraku Mori Building
   1-4-14, Koraku, Bunkyo-ku
   Tokyo  112-0004
   Japan

   Phone: +81 3 3830 2241
   Email: shinta.sugimoto@ericsson.com


   Francis Dupont
   CELAR

   Email: Francis.Dupont@fdupont.fr


   Masahide Nakamura
   Hitachi Communication Technologies, Ltd.
   216 Totsuka-cho, Totsuka-ku
   Yokohama  244-8567
   Japan

   Phone: +81 45 865 7003
   Email: masahide.nakamura.cz@hitachi.com
























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