INTERNET-DRAFT Samita Chakrabarti Expires: December, 2003 Erik Nordmark Sun Microsystems, Inc. June, 2003 Extension to Sockets API for Mobile IPv6 Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet Draft expires December, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document describes data structures and API support for Mobile IPv6 as an extension to Advanced Socket API support for IPv6. Mobility Support in IPv6 introduces mobility protocol header for IPv6. It is expected that future Mobile IPv6 applications and implementations may need to access Mobility binding messages and Return Routability messages for diagnostic, packet accounting and local policy setting purposes. In order to provide portability for Mobile IP applications that use sockets under IPv6, standardization is needed for the Mobile IPv6 specific APIs. Chakrabarti, Nordmark Expires December, 2003 [Page 1] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 This document provides mechanism for API access to retrieve and set information for Mobility Header messages, Home address destination option and Type 2 Routing header extension headers. It also discusses the common data structures and defines that might be used by the advanced Mobile IPv6 socket applications. Table of Contents 1. Introduction ........................................... 3 2. Common Structures and Definitions ...................... 4 2.1 The Mobility Header Data Structures ................ 5 2.2 Mobility Header Constants .......................... 8 2.3 IPv6 Home Address Destination Option ................ 10 2.4 Type 2 Routing Header ............................... 10 2.5 ICMP Mobile IPv6 Messages ........................... 11 2.6 IPv6 Neighbor Discovery Changes ..................... 12 3. Access to Home Address Destination Option and Routing Headers ................................ 14 3.1 Routing Header Access Functions ..................... 14 3.2 Home Address Destination Option Access Functions .... 14 4. Mobility Protocol Headers ............................... 15 4.1 Receiving and Sending Mobility Header Messages ..... 15 5. Protocols File ........................................... 17 6. IPv4-Mapped IPv6 Addresses ............................... 17 7. Security Considerations .................................. 17 8. References ............................................... 18 9. Authors' Addresses ....................................... 18 Chakrabarti, Nordmark Expires December, 2003 [Page 2] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 1. Introduction Mobility Support in IPv6 [2] defines a new mobility protocol header, home address destination option and a new routing header type. It is expected that Mobile IPv6 user-level implementations and some applications will need to access and process these IPv6 extension headers. This document is an extension to existing Advanced Sockets API document [1]; it addresses the IPv6 Sockets API for Mobile IPv6 protocol support. The target applications for this socket API is believed to be the debugging and diagnostic applications as well as some policy applications which would like to receive a copy of protocol information at the application layer. This document can be divided into the following parts. 1. Definitions of constants and structures for C programs that capture the Mobile IPv6 packet formats on the wire. A common definition of these is useful at least for packet snooping appplications. This is captured in section 2. 2. Notes on how to use the IPv6 Advanced API to access home address options and type 2 routing headers. This is captured in section 3. 3. Notes on how user-level applications can observe MH (Mobility Header) packets using raw sockets (in section 4). The IPv6 RAW socket interface described in this document, allows applications to receive MH packets whether or not the systems MH processing takes place in the "kernel" or at the "user space". 4. Suggested name for /etc/protocols (in section 5). It is anticipated that Mobile IPv6 will be used widely from mobile devices to Server and Routing platforms. Thus it is useful to have a standard API for portability of Mobile IPv6 applications on a wide variety of platforms and operating systems. Chakrabarti, Nordmark Expires December, 2003 [Page 3] INTERNET-DRAFT Extensions to Sockets API for MIPv6 June, 2003 The packet information along with access to the extension headers (Routing header and Destination options) are specified using the "ancillary data" fields that were added to the 4.3BSD Reno sockets API in 1990. The reason is that these ancillary data fields are part of the Posix.1g standard and should therefore be adopted by most vendors. This is in conformance with Advanced API for IPv6 sockets [1]. This document does not address application access to either the authentication header or the encapsulating security payload header. All examples in this document omit error checking in the favor of brevity. We note that many of the functions and socket options defined in this document may have error returns that are not defined in this document. Many of these possible error returns will be recognized only as implementations proceed. Datatypes in this document follow the Posix.1g format: intN_t means a signed integer of exactly N bits (e.g., int16_t) and uintN_t means an unsigned integer of exactly N bits (e.g., uint32_t). This document provides guidelines on MIPv6 socket applications and believes that some other appropriate standardization body will standardize the APIs along with other IPv6 advanced socket APIs. 2. Common Structures and Definitions This API assumes that the fields in the protocol headers are left in the network byte order, which is big-endian for the Internet protocols. If not, then either these constants or the fields being tested must be converted at run-time, using something like htons() or htonl(). A new header file : Chakrabarti, Nordmark Expires December, 2003 [Page 4] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 2.1. The Mobility Header Data Structures 2.1.1 The ip6_mh Structure The following structure is defined as a result of including . This is fixed part of the mobility header. struct ip6_mh { uint8_t ip6mh_proto; /* NO_NXTHDR by default */ uint8_t ip6mh_hdrlen; /* Header Len in unit of 8 Octets */ uint8_t ip6mh_type; /* Type of Mobility Header */ uint8_t ip6mh_resvd; /* Reserved */ uint16_t ip6mh_cksum; /* Mobility Header Checksum */ /* Followed by type specific messages */ }; 2.1.2 Data structure used by HOTI/COTI messages HoTI/CoTI messages are defined in IPv6 Mobility Support [2] document. These messages are sent by Mobile node in order to initiate Return Routability Procedure in Route Optimization protocol. 2.1.3 Home Address Test Init (HoTI) Message struct ip6mh_home_test_init { struct ip6_mh ip6mhti_hdr; uint16_t ip6mhti_resvd; uint32_t ip6mhti_cookie[2]; /* 64 bit Cookie by MN */ /* Followed by optional Mobility Options */ }; 2.1.4 Care-of Address Test Init (CoTI) Message struct ip6mh_careof_test_init { struct ip6_mh ip6mhci_hdr; uint16_t ip6mhci_resvd; uint32_t ip6mhci_cookie[2]; /* 64 bit Cookie by MN */ /* Followed by optional Mobility Options */ }; Chakrabarti, Nordmark Expires December, 2003 [Page 5] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 2.1.5 Home Address Test (HOT) Message struct ip6mh_home_test { struct ip6_mh ip6mht_hdr; uint16_t ip6mht_nonceId; uint32_t ip6mht_cookie[2]; /* Cookie from HOTI msg */ uint32_t ip6mht_keygen[2]; /* 64 Bit Key by CN */ /* Followed by optional Mobility Options */ }; 2.1.6 Care Of Address Test (COT) Message struct ip6mh_careof_test { struct ip6_mh ip6mhct_hdr; uint16_t ip6mhct_nonceId; uint32_t ip6mhct_cookie[2]; /* Cookie from COTI message */ uint32_t ip6mhct_keygen[2]; /* 64bit key by CN */ /* Followed by optional Mobility Options */ }; 2.1.7 Binding Refresh Request Mobility Message struct ip6mh_binding_request { struct ip6_mh ip6mhbr_hdr; uint16_t ip6mhbr_resvd; /* Followed by optional Mobility Options */ }; 2.1.8 Binding Update Mobility Message struct ip6mh_binding_update { struct ip6_mh ip6mhbu_hdr; uint16_t ip6mhbu_seqno; /* Sequence Number */ uint16_t ip6mhbu_flags; uint16_t ip6mhbu_lifetime; /* Time in unit of 4 sec */ /* Followed by optional Mobility Options */ }; /* Binding Update Flags, in network byte-order */ #define IP6MH_BU_ACK 0x8000 /* Request a binding ack */ #define IP6MH_BU_HOME 0x4000 /* Home Registration */ #define IP6MH_BU_LLOCAL 0x2000 /* Link-local compatibility */ #define IP6MH_BU_KEYM 0x1000 /* Key management mobility */ Chakrabarti, Nordmark Expires December, 2003 [Page 6] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 2.1.9 Binding Acknowledgment Mobility Message struct ip6mh_binding_ack { struct ip6_mh ip6mhba_hdr; uint8_t ip6mhba_status; /* Status code */ uint8_t ip6mhba_flags; uint16_t ip6mhba_seqno; uint16_t ip6mhba_lifetime; /* Followed by optional Mobility Options */ }; /* Binding Acknowledgement Flags */ #define IP6MH_BA_KEYM 0x80 /* Key management mobility */ 2.1.10 Binding Error Mobility Message struct ip6mh_binding_error { struct ip6_mh ip6mhbe_hdr; uint8_t ip6mhbe_status; /* Error Status */ uint8_t ip6mhbe_resvd; struct in6_addr ip6mhbe_homeaddr; /* Followed by optional Mobility Options */ }; 2.1.11 Mobility Option TLV data structure struct ip6mh_opt { uint8_t ip6mhopt_type; /* Option Type */ uint8_t ip6mhopt_len; /* Option Length */ /* Followed by variable length Option Data in bytes */ }; Chakrabarti, Nordmark Expires December, 2003 [Page 7] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 2.1.12 Mobility Option Data Structures 2.1.12.1 Binding Refresh Advice struct ip6mh_opt_refresh_advice { uint8_t ip6morf_type; uint8_t ip6morf_len; uint16_t ip6morf_interval; /* Refresh interval in 4 sec */ } 2.1.12.2 Alternate Care-of Address struct ip6mh_opt_altcoa { uint8_t ip6moa_type; uint8_t ip6moa_len; uint8_t ip6moa_addr[16]; /* Alternate Care-of Address */ } 2.1.12.3 Nonce Indices struct ip6mh_opt_nonce_index { uint8_t ip6moni_type; uint8_t ip6moni_len; uint16_t ip6moni_hm_nonce; uint16_t ip6moni_coa_nonce; } 2.1.12.4 Binding Authorization Data struct ip6mh_opt_auth { uint8_t ip6moau_type; uint8_t ip6moau_len; /* Followed by authentication data */ } 2.2 Mobility Header Constants IPv6 Next Header Value for Mobility: #define IPPROTO_MH 62 /* IPv6 Mobility Header: IANA-TBD */ Chakrabarti, Nordmark Expires December, 2003 [Page 8] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 Mobility Header Message Types: #define IP6MH_TYPE_BRR 0 /* Binding Refresh Request */ #define IP6MH_TYPE_HOTI 1 /* HOTI Message */ #define IP6MH_TYPE_COTI 2 /* COTI Message */ #define IP6MH_TYPE_HOT 3 /* HOT Message */ #define IP6MH_TYPE_COT 4 /* COT Message */ #define IP6MH_TYPE_BU 5 /* Binding Update */ #define IP6MH_TYPE_BACK 6 /* Binding ACK */ #define IP6MH_TYPE_BERROR 7 /* Binding Error */ Mobility Header Message Option Types: #define IP6MHOPT_PAD1 0x00 /* PAD1 */ #define IP6MHOPT_PDAN 0x01 /* PADN */ #define IP6MHOPT_BREFRESH 0x02 /* Binding Refresh */ #define IP6MHOPT_ALTCOA 0x03 /* Alternate COA */ #define IP6MHOPT_NONCEID 0x04 /* Nonce Index */ #define IP6MHOPT_BAUTH 0x05 /* Binding Auth Data */ Status values accompanied with Mobility Binding Acknowledgement: #define IP6MH_BAS_ACCPETED 0 /* BU accepted */ #define IP6MH_BAS_PRFX_DISCOV 1 /* Discovery Required */ #define IP6MH_BAS_UNSPECIFIED 128 /* Reason unspecified */ #define IP6MH_BAS_PROHIBIT 129 /* Administratively prohibited */ #define IP6MH_BAS_INSUFFICIENT 130 /* Insufficient resources */ #define IP6MH_BAS_HA_NOT_SUPPORTED 131 /* HA registration not supported */ #define IP6MH_BAS_NOT_HOME_SUBNET 132 /* Not Home subnet */ #define IP6MH_BAS_NOT_HA 133 /* Not HA for this mobile node */ #define IP6MH_BAS_DAD_FAILED 134 /* DAD failed */ #define IP6MH_BAS_SEQNO_BAD 135 /* Sequence number out of range */ Chakrabarti, Nordmark Expires December, 2003 [Page 9] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 #define IP6MH_BAS_HOME_NI_EXPIRED 136 /* Expired Home nonce index */ #define IP6MH_BAS_COA_NI_EXPIRED 137 /* Expired Care-of nonce index */ #define IP6MH_BAS_NI_EXPIRED 138 /* Expired Nonce Indices */ #define IP6MH_BAS_REG_NOT_ALLOWED 139 /* Registration type change disallowed */ Status values for the Binding Error mobility messages: #define IP6MH_BES_UNKNOWN_HAO 1 /* Unknown binding for HOA */ #define IP6MH_BES_UNKNOWN_MH 2 /* Unknown MH Type */ 2.3. IPv6 Home Address Destination Option /* Home Address Destination Option */ struct ip6_opt_home_address { uint8_t ip6hoa_type; uint8_t ip6hoa_len; uint8_t ip6hoa_addr[16]; /* Home Address */ } Option Type Definition: #define IP6OPT_HOME_ADDRESS 0xc9 /* 11 0 01001 */ 2.4 Type 2 Routing Header /* Type 2 Routing header for Mobile IPv6 */ struct ip6_rthdr2 { uint8_t ip6r2_nxt; /* next header */ uint8_t ip6r2_len; /* length : always 2 */ uint8_t ip6r2_type; /* always 2 */ uint8_t ip6r2_segleft; /* segments left: always 1 */ uint32_t ip6r2_reserved; /* reserved field */ struct in6_addr ip6r2_homeaddr; /* Home Address */ }; Chakrabarti, Nordmark Expires December, 2003 [Page 10] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 2.5 New ICMP Messages for Mobile IPv6 ICMP message types and definitions for Mobile IPv6 are defined in #define ICMP6_MIP_HA_DISCOVERY_REQUEST 150 #define ICMP6_MIP_HA_DISCOVERY_REPLY 151 #define ICMP6_MIP_PREFIX_SOLICIT 152 #define ICMP6_MIP_PREFIX_ADVERT 153 The following data structures can be used for the ICMP message types discussed in section 6.5 through 6.8 in the base Mobile IPv6 [2] specification. struct mip_dhreq { /* Dynamic HA Address Discovery */ struct icmp6_hdr mip_dhreq_hdr; } #define mip_dhreq_type mip_dhreq_hdr.icmp6_type #define mip_dhreq_code mip_dhreq_hdr.icmp6_code #define mip_dhreq_cksum mip_dhreq_hdr.icmp6_cksum #define mip_dhreq_id mip_dhreq_hdr.icmp6_data16[0] #define mip_dhreq_reserved mip_dhreq_hdr.icmp6_data16[1] struct mip_dhrep { /* HA Address Discovery Reply */ struct icmp6_hdr mip_dhrep_hdr; /* Followed by Home Agent IPv6 addresses */ } #define mip_dhrep_type mip_dhrep_hdr.icmp6_type #define mip_dhrep_code mip_dhrep_hdr.icmp6_code #define mip_dhrep_cksum mip_dhrep_hdr.icmp6_cksum #define mip_dhrep_id mip_dhrep_hdr.icmp6_data16[0] #define mip_dhrep_reserved mip_dhrep_hdr.icmp6_data16[1] struct mip_prefix_solicit { /* Mobile Prefix Solicitation */ struct icmp6_hdr mip_ps_hdr; } #define mip_ps_type mip_ps_hdr.icmp6_type #define mip_ps_code mip_ps_hdr.icmp6_code #define mip_ps_cksum mip_ps_hdr.icmp6_cksum #define mip_ps_id mip_ps_hdr.icmp6_data16[0] #define mip_ps_reserved mip_ps_hdr.icmp6_data16[1] Chakrabarti, Nordmark Expires December, 2003 [Page 11] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 struct mip_prefix_advert { /* Mobile Prefix Adverisements */ struct icmp6_hdr mip_pa_hdr; /* Followed by one or more PI options */ } #define mip_pa_type mip_pa_hdr.icmp6_type #define mip_pa_code mip_pa_hdr.icmp6_code #define mip_pa_cksum mip_pa_hdr.icmp6_cksum #define mip_pa_id mip_pa_hdr.icmp6_data16[0] #define mip_pa_flags_reserved mip_pa_hdr.icmp6_data16[1] #define ICMP6_MIP_PA_FLAG_MANAGED 0x8000 #define ICMP6_MIP_PA_FLAG_OTHER 0x4000 Prefix options are defined in IPv6 Advanced Socket API [1]. Mobile IPv6 Base specification [2] describes the modified behavior in 'Modifications to IPv6 Neighbor Discovery' section. Prefix Options for Mobile IP are defined in the following section. 2.6 IPv6 Neighbor Discovery Changes IPv6 Neighbor Discovery changes are also defined in New 'Home Agent' flag in router advertisement: #define ND_RA_FLAG_HOMEAGENT 0x20 /* Home Agent flag in RA */ New Router flag with prefix information of the home agent: #define ND_OPT_PI_FLAG_ROUTER 0x20 /* Router flag in PI */ As per Mobile IPv6 specification [2] a Home Agent MUST include at least one prefix option with the Rouer Address (R) bit set. Advanced Socket API [1] defines data structure for prefix option as follows: struct nd_opt_prefix_info { /* prefix information */ uint8_t nd_opt_pi_type; uint8_t nd_opt_pi_len; uint8_t nd_opt_pi_prefix_len; uint8_t nd_opt_pi_flags_reserved; uint32_t nd_opt_pi_valid_time; uint32_t nd_opt_pi_preferred_time; uint32_t nd_opt_pi_reserved2; struct in6_addr nd_opt_pi_prefix; }; Chakrabarti, Nordmark Expires December, 2003 [Page 12] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 New advertisement interval option and home agent information options are defined in Mobile IPv6 [2] base specification. struct nd_opt_advinterval { /* Advertisement interval option */ uint8_t nd_opt_adv_type; uint8_t nd_opt_adv_len; uint16_t nd_opt_adv_reserved; uint32_t nd_opt_adv_interval; } The option types for the new Mobile IPv6 specific options: #define ND_OPT_ADV_INTERVAL 7 /* Adv Interval Option */ #define ND_OPT_HA_INFORMATION 8 /* HA Information option */ struct nd_opt_homeagent_info { /* Home Agent information */ uint8_t nd_opt_hai_type; uint8_t nd_opt_hai_len; uint16_t nd_opt_hai_reserved; uint16_t nd_opt_hai_preference; uint16_t nd_opt_hai_lifetime; } 3. Access to Home Address Destination Option and Routing Headers Applications that need to be able to access home address destination option and routing header type 2 information should use the same mechanism defined in Advanced Sockets API for IPv6 in section 4. In order to receive Home Address destination option or route header type 2 extension header, application must call setsockopt() to turn on the corresponding flag: int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVRTHDR, &on, sizeof(on)); setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on)); When any of these options are enabled, the corresponding data is returned as control information by recvmsg(), as one or more ancillary data objects. Receiving the above information for TCP applications is not defined in this document (see section 4.1 of Advanced Sockets API for IPv6[1]. Chakrabarti, Nordmark Expires December, 2003 [Page 13] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 For sending home address destination option, ancillary data can be used to specify the option content for a single datagram. This only applies to datagram and raw sockets; not to TCP sockets. For TCP data packets with home-address destination option may be used with "sticky" option for all transmitted packets. However, at this point, it is unknown why an application would want to set home-address option along with its data packets as Mobile IPv6 protocol takes care of it transparently at the protocol stack. Similarly it is not clear that if an application would need to set Router Header Type 2 extension to send data packets as it is taken care by the Mobile IPv6 protocol depending on the binding cache information. Thus this document does not specifically discuss the sending of Route Header Type 2 extension header. However, the following socket option parameters and cmsghdr fields may be used for sending the Home Address destination options. opt level/ optname/ optval/ cmsg_level cmsg_type cmsg_data[] ------------ ------------ ------------------------ IPPROTO_IPV6 IPV6_DSTOPTS ip6_dest structure Some IPv6 implementations may support "sticky" options [1] for IPv6 destination option for datagram sockets. 3.1 Routing Header access functions While accessing Routing header Type 2 extension header, one MUST use type = 2 and segment = 1. The following functions are supported for Mobile IPv6 applications for sending and receiving Routing Header Type 2 headers: size_t inet6_rth_space(int type, int segments); void *inet6_rth_init(void *bp, int bp_len, int type, int segments); int inet6_rth_add(void *bp, const struct in6_addr *addr); int inet6_rth_segments(const void *bp); struct in6_addr *inet6_rth_getaddr(const void *bp, int index); NOTE: Reversing operation is not possible using Route Header Type 2 extension header. Chakrabarti, Nordmark Expires December, 2003 [Page 14] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 Detail description and examples of accessing a IPv6 Routing Header are discussed in Advanced API for IPv6 Sockets [1]. 3.2 Home Address Destination Option access functions The application must enable the IPV6_RECVDSTOPTS socket option in order to receive the home address destination option: int on = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_RECVDSTOPTS, &on, sizeof(on)); Each Destination option header is returned as one ancillary data object described by a cmsghdr structure with cmsg_level set to IPPROTO_IPV6 and cmsg_type set to IPV6_DSTOPTS. These options are then processed by calling the inet6_opt_next(), inet6_opt_find(), and inet6_opt_get_value() functions as defined in Advanced API for IPv6 sockets [1]. This document assumes that Mobile IPv6 applications will not be allowed to send Home Address Destination Option from the application level, as Mobile IPv6 kernel takes care of sending home-address option and routing header type 2. However, the order of extension headers in conjunction with Home Address option sending is specified in Mobility Support in IPv6 [2] in section 6.3. The Destination options are normally constructed using the inet6_opt_init(), inet6_opt_append(), inet6_opt_finish(), and inet6_opt_set_val() functions, described in Section 10 of IPv6 Advanced API sockets [1]. 4. Mobility Protocol Headers Mobile IPv6 [2] defines a new IPv6 protocol header to carry mobility messages between Mobile Nodes, Home Agents and Correspondent Nodes. These protocol headers carry Mobile IPv6 Binding messages as well as Return Routability [2] messages. Currently the specification [2] does not allow transport packets (piggybacking) along with the mobility messages. Thus the mobility protocol header can be accessed through a IPv6 RAW socket. A IPv6 RAW socket that is opened for protocol IPPROTO_MH should always be able to see all the MH (Mobility Header) packets. It is possible that future applications may implement part of Mobile IPv6 signal processing at the Chakrabarti, Nordmark Expires December, 2003 [Page 15] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 application level. Having a RAW socket interface may also enable an application to execute the Return Routability protocol or other future authentication protocol involving mobility header at the user level. 4.1 Receiving and Sending Mobility Header Messages This specification recommends IPv6 RAW sockets mechanism to send and receive Mobility Header (MH) packets. The behavior is similar to ICMPV6 processing, where kernel passes a copy of the mobility header packet to the receiving socket. Depending on the implementation kernel may process the mobility header as well in addition to passing the mobility header to the application. If IPV6_CHECKSUM socket option is set on the RAW socket, kernel will calculate the checksum by default and place it on the mobility header before sending it out. Similarly, if IPV6_CHECKSUM is set, the protocol stack will verify the MH checksum on the inbound path and it will discard any MH packet with invalid checksums. Mobility Header checksum procedure is described in Mobile IPv6 Protocol [2] specification. Thus when IPPROTO_MH is used as the protocol field in the RAW socket() call and IPV6_CHECKSUM option is not set, the application needs to fill the checksum field of the mobility header for outbound data. Similarly the application needs to do checksum validity check for the received packet. However, it is recommended that the application set the IPV6_CHECKSUM socket option along with the RAW sockets for IPPROTO_MH. As an example, a program that wants to send or receive mobility header protocol(MH), could open a socket as following: fd = socket(AF_INET6, SOCK_RAW, IPPROTO_MH); int offset = 4; setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset, sizeof(offset)); For example, if an implementation likes to handle HOTI/HOT and COTI/COT message processing, it can do so by using IPv6 RAW Sockets for IPPROTO_MH at the application layer. The same application may also set IPV6_RECVDSTOPTS socket option for receiving home address option in a binding update [2] from the mobile node. Chakrabarti, Nordmark Expires December, 2003 [Page 16] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 5. Protocols File Many hosts provide the file /etc/protocols that contains the names of the various IP protocols and their protocol numbers. The protocol numbers are obtained through function getprotoXXX() functions. The following addition should be made to the /etc/protocols file, in addition to what is defined in section 2.4 of Advanced Sockets API for IPv6 [1]. The protocol number for Mobility is pending IANA (http://www.iana.orgassignments/protocol-numbers) assignment. ipv6-mh 62 # Mobility Protocol Header 6. IPv4-Mapped IPv6 Addresses The same rule applies as described in section 13 of IPv6 Advanced API for Sockets [1]. Thus processing of IPv4-mapped IPv6 addresses for the MobileIPv6 specific socket options are out of scope of this document. 7. Security Considerations The setting of Home Address Destination option and route header Type 2 IPV6_RTHDR socket option may not be allowed at the application level in order to prevent denial-of-service attacks or man in the middle attacks by hackers. Sending and receiving of mobility header messages are possible by IPv6 RAW sockets. Thus it is assumed that this operation is only possible by priviledged users. However, this API does not prevent the existing security threat from a hacker by sending bogus mobility header or other IPv6 packets using home-address option and Type 2 routing extension header. Chakrabarti, Nordmark Expires December, 2003 [Page 17] INTERNET-DRAFT Extension to Sockets API for MIPv6 June, 2003 8. References [1] Stevens, W. R, Thomas, M., Nordmark, E., Jinmei, T., "Advanced Sockets API for IPv6", RFC 3542, May 2003 April 19, 2002. [2] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in IPv6" draft-ietf-mobileip-ipv6-22.txt, May, 2003. [3] Deering, S., Hinden, R., "Internet Protocol, Version 6 (IPv6), Specification", RFC 2460, Dec. 1998. 9. Authors' Addresses Samita Chakrabarti Sun Microsystems, Inc. 4150 Network Circle Santa Clara, CA 95054, USA Email: samita.chakrabarti@Sun.com Erik Nordmark Sun Microsystems Laboratories 180, avenue de l'Europe 38334 SAINT ISMIER Cedex, France Email: Erik.Nordmark@sun.com Chakrabarti, Nordmark Expires December, 2003 [Page 18]