$NetBSD: IMPLEMENTATION,v 1.4 2000/01/06 15:48:07 itojun Exp $ # NOTE: this is from original KAME distribution. # Some portion of this document is not applicable to the code merged into # NetBSD-current. Check sys/netinet6/TODO as well. Implementation Note KAME Project http://www.kame.net/ Date: 2000/01/04 17:56:28 1. IPv6 1.1 Conformance The KAME kit conforms, or tries to conform, to the latest set of IPv6 specifications. For future reference we list some of the relevant documents below (NOTE: this is not a complete list - this is too hard to maintain...). For details please refer to specific chapter in the document, RFCs, manpages come with KAME, or comments in the source code. Conformance tests have been performed on the KAME STABLE kit at TAHI project. Results can be viewed at http://www.tahi.org/report/KAME/. We also attended Univ. of New Hampshire IOL tests (http://www.iol.unh.edu/) in the past, with our past snapshots. RFC1639: FTP Operation Over Big Address Records (FOOBAR) * RFC2428 is preferred over RFC1639. ftp clients will first try RFC2428, then RFC1639 if failed. RFC1886: DNS Extensions to support IPv6 RFC1933: Transition Mechanisms for IPv6 Hosts and Routers * IPv4 compatible address is not supported. * automatic tunneling (4.3) is not supported. * "gif" interface implements IPv[46]-over-IPv[46] tunnel in a generic way, and it covers "configured tunnel" described in the spec. See 1.5 in this document for details. RFC1981: Path MTU Discovery for IPv6 RFC2080: RIPng for IPv6 * KAME-supplied route6d, bgpd and hroute6d support this. RFC2283: Multiprotocol Extensions for BGP-4 * so-called "BGP4+". * KAME-supplied bgpd supports this. RFC2292: Advanced Sockets API for IPv6 * For supported library functions/kernel APIs, see sys/netinet6/ADVAPI. RFC2362: Protocol Independent Multicast-Sparse Mode (PIM-SM) * RFC2362 defines packet formats for PIM-SM. draft-ietf-pim-ipv6-01.txt is written based on this. RFC2373: IPv6 Addressing Architecture * KAME supports node required addresses, and conforms to the scope requirement. RFC2374: An IPv6 Aggregatable Global Unicast Address Format * KAME supports 64-bit length of Interface ID. RFC2375: IPv6 Multicast Address Assignments * Userland applications use the well-known addresses assigned in the RFC. RFC2428: FTP Extensions for IPv6 and NATs * RFC2428 is preferred over RFC1639. ftp clients will first try RFC2428, then RFC1639 if failed. RFC2460: IPv6 specification RFC2461: Neighbor discovery for IPv6 * See 1.2 in this document for details. RFC2462: IPv6 Stateless Address Autoconfiguration * See 1.4 in this document for details. RFC2463: ICMPv6 for IPv6 specification * See 1.8 in this document for details. RFC2464: Transmission of IPv6 Packets over Ethernet Networks RFC2465: MIB for IPv6: Textual Conventions and General Group * Necessary statistics are gathered by the kernel. Actual IPv6 MIB support is provided as patchkit for ucd-snmp. RFC2466: MIB for IPv6: ICMPv6 group * Necessary statistics are gathered by the kernel. Actual IPv6 MIB support is provided as patchkit for ucd-snmp. RFC2467: Transmission of IPv6 Packets over FDDI Networks RFC2472: IPv6 over PPP RFC2492: IPv6 over ATM Networks * only PVC is supported. RFC2497: Transmission of IPv6 packet over ARCnet Networks RFC2545: Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing RFC2553: Basic Socket Interface Extensions for IPv6 * IPv4 mapped address (3.7) and special behavior of IPv6 wildcard bind socket (3.8) are, - supported on KAME/FreeBSD3x, - supported on KAME/NetBSD, - supported on KAME/BSDI4, - not supported on KAME/FreeBSD228, KAME/OpenBSD and KAME/BSDI3. see 1.12 in this document for details. RFC2675: IPv6 Jumbograms * See 1.7 in this document for details. RFC2710: Multicast Listener Discovery for IPv6 RFC2711: IPv6 router alert option draft-ietf-ipngwg-router-renum-08: Router renumbering for IPv6 draft-ietf-ipngwg-icmp-namelookups-02: IPv6 Name Lookups Through ICMP draft-ietf-ipngwg-icmp-name-lookups-03: IPv6 Name Lookups Through ICMP draft-ietf-pim-ipv6-01.txt: PIM for IPv6 * pim6dd implements dense mode. pim6sd implements sparse mode. draft-ietf-dhc-dhcpv6-14.txt: DHCPv6 draft-ietf-dhc-v6exts-11.txt: Extensions for DHCPv6 * kame/dhcp6 has test implementation, which will not be compiled in default compilation. draft-itojun-ipv6-tcp-to-anycast-00: Disconnecting TCP connection toward IPv6 anycast address draft-yamamoto-wideipv6-comm-model-00 * See 1.6 in this document for details. draft-ietf-ipngwg-scopedaddr-format-00.txt: An Extension of Format for IPv6 Scoped Addresses 1.2 Neighbor Discovery Neighbor Discovery is fairly stable. Currently Address Resolution, Duplicated Address Detection, and Neighbor Unreachability Detection are supported. In the near future we will be adding Proxy Neighbor Advertisement support in the kernel and Unsolicited Neighbor Advertisement transmission command as admin tool. If DAD fails, the address will be marked "duplicated" and message will be generated to syslog (and usually to console). The "duplicated" mark can be checked with ifconfig. It is administrators' responsibility to check for and recover from DAD failures. The behavior should be improved in the near future. Some of the network driver loops multicast packets back to itself, even if instructed not to do so (especially in promiscuous mode). In such cases DAD may fail, because DAD engine sees inbound NS packet (actually from the node itself) and considers it as a sign of duplicate. You may want to look at #if condition marked "heuristics" in sys/netinet6/nd6_nbr.c:nd6_dad_timer() as workaround (note that the code fragment in "heuristics" section is not spec conformant). Neighbor Discovery specification (RFC2461) does not talk about neighbor cache handling in the following cases: (1) when there was no neighbor cache entry, node received unsolicited RS/NS/NA/redirect packet without link-layer address (2) neighbor cache handling on medium without link-layer address (we need a neighbor cache entry for IsRouter bit) For (1), we implemented workaround based on discussions on IETF ipngwg mailing list. For more details, see the comments in the source code and email thread started from (IPng 7155), dated Feb 6 1999. IPv6 on-link determination rule (RFC2461) is quite different from assumptions in BSD network code. At this moment, KAME does not implement on-link determination rule when default router list is empty (RFC2461, section 5.2, last sentence in 2nd paragraph - note that the spec misuse the word "host" and "node" in several places in the section). To avoid possible DoS attacks and infinite loops, KAME stack will accept only 10 options on ND packet. Therefore, if you have 20 prefix options attached to RA, only the first 10 prefixes will be recognized. If this troubles you, please contact KAME team and/or modify nd6_maxndopt in sys/netinet6/nd6.c. If there are high demands we may provide sysctl knob for the variable. 1.3 Scope Index IPv6 uses scoped addresses. Therefore, it is very important to specify scope index (interface index for link-local address, or site index for site-local address) with an IPv6 address. Without scope index, scoped IPv6 address is ambiguous to the kernel, and kernel will not be able to determine the outbound interface for a packet. Ordinary userland applications should use advanced API (RFC2292) to specify scope index, or interface index. For similar purpose, sin6_scope_id member in sockaddr_in6 structure is defined in RFC2553. However, the semantics for sin6_scope_id is rather vague. If you care about portability of your application, we suggest you to use advanced API rather than sin6_scope_id. In the kernel, an interface index for link-local scoped address is embedded into 2nd 16bit-word (3rd and 4th byte) in IPv6 address. For example, you may see something like: fe80:1::200:f8ff:fe01:6317 in the routing table and interface address structure (struct in6_ifaddr). The address above is a link-local unicast address which belongs to a network interface whose interface identifier is 1. The embedded index enables us to identify IPv6 link local addresses over multiple interfaces effectively and with only a little code change. Routing daemons and configuration programs, like route6d and ifconfig, will need to manipulate the "embedded" scope index. These programs use routing sockets and ioctls (like SIOCGIFADDR_IN6) and the kernel API will return IPv6 addresses with 2nd 16bit-word filled in. The APIs are for manipulating kernel internal structure. Programs that use these APIs have to be prepared about differences in kernels anyway. When you specify scoped address to the command line, NEVER write the embedded form (such as ff02:1::1 or fe80:2::fedc). This is not supposed to work. Always use standard form, like ff02::1 or fe80::fedc, with command line option for specifying interface (like "ping6 -I ne0 ff02::1). In general, if a command does not have command line option to specify outgoing interface, that command is not ready to accept scoped address. This may seem to be opposite from IPv6's premise to support "dentist office" situation. We believe that specifications need some improvements for this. Some of the userland tools support extended numeric IPv6 syntax, as documented in draft-ietf-ipngwg-scopedaddr-format-00.txt. You can specify outgoing link, by using name of the outgoing interface like "fe80::1@ne0". This way you will be able to specify link-local scoped address without much trouble. To use this extension in your program, you'll need to use getaddrinfo(3), and getnameinfo(3) with NI_WITHSCOPEID. The implementation currently assumes 1-to-1 relationship between a link and an interface, which is stronger than what specs say. 1.4 Plug and Play The KAME kit implements most of the IPv6 stateless address autoconfiguration in the kernel. Neighbor Discovery functions are implemented in the kernel as a whole. Router Advertisement (RA) input for hosts is implemented in the kernel. Router Solicitation (RS) output for endhosts, RS input for routers, and RA output for routers are implemented in the userland. 1.4.1 Assignment of link-local, and special addresses IPv6 link-local address is generated from IEEE802 adddress (ethernet MAC address). Each of interface is assigned an IPv6 link-local address automatically, when the interface becomes up (IFF_UP). Also, direct route for the link-local address is added to routing table. Here is an output of netstat command: Internet6: Destination Gateway Flags Netif Expire fe80:1::/64 link#1 UC ed0 fe80:2::/64 link#2 UC ep0 Interfaces that has no IEEE802 address (pseudo interfaces like tunnel interfaces, or ppp interfaces) will borrow IEEE802 address from other interfaces, such as ethernet interfaces, whenever possible. If there is no IEEE802 hardware attached, last-resort pseudorandom value, which is from MD5(hostname), will be used as source of link-local address. If it is not suitable for your usage, you will need to configure the link-local address manually. If an interface is not capable of handling IPv6 (such as lack of multicast support), link-local address will not be assigned to that interface. See section 2 for details. Each interface joins the solicited multicast address and the link-local all-nodes multicast addresses (e.g. fe80::1:ff01:6317 and ff02::1, respectively, on the link the interface is attached). In addition to a link-local address, the loopback address (::1) will be assigned to the loopback interface. Also, ::1/128 and ff01::/32 are automatically added to routing table, and loopback interface joins node-local multicast group ff01::1. 1.4.2 Stateless address autoconfiguration on hosts In IPv6 specification, nodes are separated into two categories: routers and hosts. Routers forward packets addressed to others, hosts does not forward the packets. net.inet6.ip6.forwarding defines whether this node is router or host (router if it is 1, host if it is 0). When a host hears Router Advertisement from the router, a host may autoconfigure itself by stateless address autoconfiguration. This behavior can be controlled by net.inet6.ip6.accept_rtadv (host autoconfigures itself if it is set to 1). By autoconfiguration, network address prefix for the receiving interface (usually global address prefix) is added. Default route is also configured. Routers periodically generate Router Advertisement packets. To request an adjacent router to generate RA packet, a host can transmit Router Solicitation. To generate a RS packet at any time, use the "rtsol" command. "rtsold" daemon is also available. "rtsold" generates Router Solicitation whenever necessary, and it works great for nomadic usage (notebooks/laptops). If one wishes to ignore Router Advertisements, use sysctl to set net.inet6.ip6.accept_rtadv to 0. To generate Router Advertisement from a router, use the "rtadvd" daemon. Note that, IPv6 specification assumes the following items, and nonconforming cases are left unspecified: - Only hosts will listen to router advertisements - Hosts have single network interface (except loopback) Therefore, this is unwise to enable net.inet6.ip6.accept_rtadv on routers, or multi-interface host. A misconfigured node can behave strange (KAME code allows nonconforming configuration, for those who would like to do some experiments). To summarize the sysctl knob: accept_rtadv forwarding role of the node --- --- --- 0 0 host (to be manually configured) 0 1 router 1 0 autoconfigured host (spec assumes that host has single interface only, autoconfigred host with multiple interface is out-of-scope) 1 1 invalid, or experimental (out-of-scope of spec) RFC2462 has validation rule against incoming RA prefix information option, in 5.5.3 (e). This is to protect hosts from malicious (or misconfigured) routers that advertise very short prefix lifetime. There was an update from Jim Bound to ipngwg mailing list (look for "(ipng 6712)" in the archive) and KAME implements Jim's update. See 1.2 in the document for relationship between DAD and autoconfiguration. 1.4.3 DHCPv6 We supply a tiny DHCPv6 server/client in kame/dhcp6. However, the implementation is very premature (for example, this does NOT implement address lease/release), and it is not in default compilation tree. If you want to do some experiment, compile it on your own. DHCPv6 and autoconfiguration also needs more work. "Managed" and "Other" bits in RA have no special effect to stateful autoconfiguration procedure in DHCPv6 client program ("Managed" bit actually prevents stateless autoconfiguration, but no special action will be taken for DHCPv6 client). 1.5 Generic tunnel interface GIF (Generic InterFace) is a pseudo interface for configured tunnel. Details are described in gif(4) manpage. Currently v6 in v6 v6 in v4 v4 in v6 v4 in v4 are available. Use "gifconfig" to assign physical (outer) source and destination address to gif interfaces. Configuration that uses same address family for inner and outer IP header (v4 in v4, or v6 in v6) is dangerous. It is very easy to configure interfaces and routing tables to perform infinite level of tunneling. Please be warned. gif can be configured to be ECN-friendly. See 4.5 for ECN-friendliness of tunnels, and gif(4) manpage for how to configure. If you would like to configure an IPv4-in-IPv6 tunnel with gif interface, read gif(4) carefully. You will need to remove IPv6 link-local address automatically assigned to the gif interface. 1.6 Source Address Selection Source selection of KAME is scope oriented (there are some exceptions - see below). For a given destination, a source IPv6 address is selected by the following rule: 1. If the source address is explicitly specified by the user (e.g. via the advanced API), the specified address is used. 2. If there is an address assigned to the outgoing interface (which is usually determined by looking up the routing table) that has the same scope as the destination address, the address is used. This is the most typical case. 3. If there is no address that satisfies the above condition, choose a global address assigned to one of the interfaces on the sending node. 4. If there is no address that satisfies the above condition and there is no global address on the sending node, choose the address associated with the routing table entry for the destination. This is the last resort, which may cause scope violation. For instance, ::1 is selected for ff01::1, fe80:1::200:f8ff:fe01:6317 for fe80:1::2a0:24ff:feab:839b (note that embedded interface index - described in 1.3 - helps us choose the right source address. Those embedded indices will not be on the wire). If the outgoing interface has multiple address for the scope, a source is selected longest match basis (rule 3). Suppose 3ffe:501:808:1:200:f8ff:fe01:6317 and 3ffe:2001:9:124:200:f8ff:fe01:6317 are given to the outgoing interface. 3ffe:501:808:1:200:f8ff:fe01:6317 is chosen as the source for the destination 3ffe:501:800::1. Note that the above rule is not documented in the IPv6 spec. It is considered "up to implementation" item. There are some cases where we do not use the above rule. One example is connected TCP session, and we use the address kept in tcb as the source. Another example is source address for Neighbor Advertisement. Under the spec (RFC2461 7.2.2) NA's source should be the target address of the corresponding NS's target. In this case we follow the spec rather than the above longest-match rule. For new connections (when rule 1 does not apply), deprecated addresses (addresses with preferred lifetime = 0) will not be chosen as source address if other choises are available. If no other choices are available, deprecated address will be used as a last resort. If there are multiple choice of deprecated addresses, the above scope rule will be used to choose from those deprecated addreses. If you would like to prohibit the use of deprecated address for some reason, configure net.inet6.ip6.use_deprecated to 0. The issue related to deprecated address is described in RFC2462 5.5.4 (NOTE: there is some debate underway in IETF ipngwg on how to use "deprecated" address). 1.7 Jumbo Payload KAME supports the Jumbo Payload hop-by-hop option used to send IPv6 packets with payloads longer than 65,535 octets. But since currently KAME does not support any physical interface whose MTU is more than 65,535, such payloads can be seen only on the loopback interface(i.e. lo0). If you want to try jumbo payloads, you first have to reconfigure the kernel so that the MTU of the loopback interface is more than 65,535 bytes; add the following to the kernel configuration file: options "LARGE_LOMTU" #To test jumbo payload and recompile the new kernel. Then you can test jumbo payloads by the ping6 command with -b and -s options. The -b option must be specified to enlarge the size of the socket buffer and the -s option specifies the length of the packet, which should be more than 65,535. For example, type as follows; % ping6 -b 70000 -s 68000 ::1 The IPv6 specification requires that the Jumbo Payload option must not be used in a packet that carries a fragment header. If this condition is broken, an ICMPv6 Parameter Problem message must be sent to the sender. KAME kernel follows the specification, but you cannot usually see an ICMPv6 error caused by this requirement. If KAME kernel receives an IPv6 packet, it checks the frame length of the packet and compares it to the length specified in the payload length field of the IPv6 header or in the value of the Jumbo Payload option, if any. If the former is shorter than the latter, KAME kernel discards the packet and increments the statistics. You can see the statistics as output of netstat command with `-s -p ip6' option: % netstat -s -p ip6 ip6: (snip) 1 with data size < data length So, KAME kernel does not send an ICMPv6 error unless the erroneous packet is an actual Jumbo Payload, that is, its packet size is more than 65,535 bytes. As described above, KAME kernel currently does not support physical interface with such a huge MTU, so it rarely returns an ICMPv6 error. TCP/UDP over jumbogram is not supported at this moment. This is because we have no medium (other than loopback) to test this. Contact us if you need this. IPsec does not work on jumbograms. This is due to some specification twists in supporting AH with jumbograms (AH header size influences payload length, and this makes it real hard to authenticate inbound packet with jumbo payload option as well as AH). There are fundamental issues in *BSD support for jumbograms. We would like to address those, but we need more time to finalize these. To name a few: - mbuf pkthdr.len field is typed as "int" in 4.4BSD, so it will not hold jumbogram with len > 2G on 32bit architecture CPUs. If we would like to support jumbogram properly, the field must be expanded to hold 4G + IPv6 header + link-layer header. Therefore, it must be expanded to at least int64_t (u_int32_t is NOT enough). - We mistakingly use "int" to hold packet length in many places. We need to convert them into larger integral type. It needs a great care, as we may experience overflow during packet length computation. - We mistakingly check for ip6_plen field of IPv6 header for packet payload length in various places. We should be checking mbuf pkthdr.len instead. ip6_input() will perform sanity check on jumbo payload option on input, and we can safely use mbuf pkthdr.len afterwards. - TCP code needs a careful update in bunch of places, of course. 1.8 Loop prevention in header processing IPv6 specification allows arbitrary number of extension headers to be placed onto packets. If we implement IPv6 packet processing code in the way BSD IPv4 code is implemented, kernel stack may overflow due to long function call chain. KAME sys/netinet6 code is carefully designed to avoid kernel stack overflow. Because of this, KAME sys/netinet6 code defines its own protocol switch structure, as "struct ip6protosw" (see netinet6/ip6protosw.h). IPv4 part (sys/netinet) remains untouched for compatibility. Because of this, if you receive IPsec-over-IPv4 packet with massive number of IPsec headers, kernel stack may blow up. IPsec-over-IPv6 is okay. 1.9 ICMPv6 After RFC2463 was published, IETF ipngwg has decided to disallow ICMPv6 error packet against ICMPv6 redirect, to prevent ICMPv6 storm on a network medium. KAME already implements this into the kernel. 1.10 Applications For userland programming, we support IPv6 socket API as specified in RFC2553, RFC2292 and upcoming internet drafts. TCP/UDP over IPv6 is available and quite stable. You can enjoy "telnet", "ftp", "rlogin", "rsh", "ssh", etc. These applications are protocol independent. That is, they automatically chooses IPv4 or IPv6 according to DNS. 1.11 Kernel Internals (*) TCP/UDP part is handled differently between operating system platforms. See 1.12 for details. The current KAME has escaped from the IPv4 netinet logic. While ip_forward() calls ip_output(), ip6_forward() directly calls if_output() since routers must not divide IPv6 packets into fragments. ICMPv6 should contain the original packet as long as possible up to 1280. UDP6/IP6 port unreach, for instance, should contain all extension headers and the *unchanged* UDP6 and IP6 headers. So, all IP6 functions except TCP6 never convert network byte order into host byte order, to save the original packet. tcp6_input(), udp6_input() and icmp6_input() can't assume that IP6 header is preceding the transport headers due to extension headers. So, in6_cksum() was implemented to handle packets whose IP6 header and transport header is not continuous. TCP/IP6 nor UDP/IP6 header structure don't exist for checksum calculation. To process IP6 header, extension headers and transport headers easily, KAME requires network drivers to store packets in one internal mbuf or one or more external mbufs. A typical old driver prepares two internal mbufs for 100 - 208 bytes data, however, KAME's reference implementation stores it in one external mbuf. "netstat -s -p ip6" tells you whether or not your driver conforms KAME's requirement. In the following example, "cce0" violates the requirement. (For more information, refer to Section 2.) Mbuf statistics: 317 one mbuf two or more mbuf:: lo0 = 8 cce0 = 10 3282 one ext mbuf 0 two or more ext mbuf Each input function calls IP6_EXTHDR_CHECK in the beginning to check if the region between IP6 and its header is continuous. IP6_EXTHDR_CHECK calls m_pullup() only if the mbuf has M_LOOP flag, that is, the packet comes from the loopback interface. m_pullup() is never called for packets coming from physical network interfaces. TCP6 reassembly makes use of IP6 header to store reassemble information. IP6 is not supposed to be just before TCP6, so ip6tcpreass structure has a pointer to TCP6 header. Of course, it has also a pointer back to mbuf to avoid m_pullup(). Like TCP6, both IP and IP6 reassemble functions never call m_pullup(). xxx_ctlinput() calls in_mrejoin() on PRC_IFNEWADDR. We think this is one of 4.4BSD implementation flaws. Since 4.4BSD keeps ia_multiaddrs in in_ifaddr{}, it can't use multicast feature if the interface has no unicast address. So, if an application joins to an interface and then all unicast addresses are removed from the interface, the application can't send/receive any multicast packets. Moreover, if a new unicast address is assigned to the interface, in_mrejoin() must be called. KAME's interfaces, however, have ALWAYS one link-local unicast address. These extensions have thus not been implemented in KAME. 1.12 IPv4 mapped address and IPv6 wildcard socket RFC2553 describes IPv4 mapped address (3.7) and special behavior of IPv6 wildcard bind socket (3.8). The spec allows you to: - Accept IPv4 connections by AF_INET6 wildcard bind socket. - Transmit IPv4 packet over AF_INET6 socket by using special form of the address like ::ffff:10.1.1.1. but the spec itself is very complicated and does not specify how the socket layer should behave. Here we call the former one "listening side" and the latter one "initiating side", for reference purposes. Almost all KAME implementations treat tcp/udp port number space separately between IPv4 and IPv6. You can perform wildcard bind on both of the adderss families, on the same port. There are some OS-platform differences in KAME code, as we use tcp/udp code from different origin. The following table summarizes the behavior. listening side initiating side (AF_INET6 wildcard (connetion to ::ffff:10.1.1.1) socket gets IPv4 conn.) --- --- KAME/BSDI3 not supported not supported KAME/FreeBSD228 not supported not supported KAME/FreeBSD3x configurable supported default: enabled KAME/NetBSD configurable supported default: disabled KAME/BSDI4 enabled supported (*) KAME/OpenBSD not supported not supported (*) on KAME/BSDI4, port number space is not always separated. The following sections will give you more details, and how you can configure the behavior. Comments on listening side: It looks that RFC2553 talks too little on wildcard bind issue, especially on the port space issue, failure mode and relationship between AF_INET/INET6 wildcard bind. There can be several separate interpretation for this RFC which conform to it but behaves differently. So, to implement portable application you should assume nothing about the behavior in the kernel. Using getaddrinfo() is the safest way. Port number space and wildcard bind issues were discussed in detail on ipv6imp mailing list, in mid March 1999 and it looks that there's no concrete consensus (means, up to implementers). You may want to check the mailing list archives. We supply a tool called "bindtest" that explores the behavior of kernel bind(2). The tool will not be compiled by default. If a server application would like to accept IPv4 and IPv6 connections, it should use AF_INET and AF_INET6 socket (you'll need two sockets). Use getaddrinfo() with AI_PASSIVE into ai_flags, and socket(2) and bind(2) to all the addresses returned. By opening multiple sockets, you can accept connections onto the socket with proper address family. IPv4 connections will be accepted by AF_INET socket, and IPv6 connections will be accepted by AF_INET6 socket (NOTE: KAME/BSDI4 kernel sometimes violate this - we will fix it). If you try to support IPv6 traffic only and would like to reject IPv4 traffic, always check the peer address when a connection is made toward AF_INET6 listening socket. If the address is IPv4 mapped address, you may want to reject the connection. You can check the condition by using IN6_IS_ADDR_V4MAPPED() macro. This is one of the reasons the author of the section (itojun) dislikes special behavior of AF_INET6 wildcard bind. Comments on initiating side: Advise to application implementers: to implement a portable IPv6 application (which works on multiple IPv6 kernels), we believe that the following is the key to the success: - NEVER hardcode AF_INET nor AF_INET6. - Use getaddrinfo() and getnameinfo() throughout the system. Never use gethostby*(), getaddrby*(), inet_*() or getipnodeby*(). - If you would like to connect to destination, use getaddrinfo() and try all the destination returned, like telnet does. - Some of the IPv6 stack is shipped with buggy getaddrinfo(). Ship a minimal working version with your application and use that as last resort. If you would like to use AF_INET6 socket for both IPv4 and IPv6 outgoing connection, you will need tweaked implementation in DNS support libraries, as documented in RFC2553 6.1. KAME libinet6 includes the tweak in getipnodebyname(). Note that getipnodebyname() itself is not recommended as it does not handle scoped IPv6 addresses at all. For IPv6 name resolution getaddrinfo() is the preferred API. getaddrinfo() does not implement the tweak. When writing applications that make outgoing connections, story goes much simpler if you treat AF_INET and AF_INET6 as totally seaprate address family. {set,get}sockopt issue goes simpler, DNS issue will be made simpler. We do not recommend you to rely upon IPv4 mapped address. 1.12.1 KAME/BSDI3 and KAME/FreeBSD228 The platforms do not support IPv4 mapped address at all (both listening side and initiating side). AF_INET6 and AF_INET sockets are totally separated. Port number space is totally separate between AF_INET and AF_INET6 sockets. 1.12.2 KAME/FreeBSD3x KAME/FreeBSD3x uses shared tcp4/6 code (from sys/netinet/tcp*) and shared udp4/6 code (from sys/netinet/udp*). It uses unified inpcb/in6pcb structure. 1.12.2.1 KAME/FreeBSD3x, listening side The platform can be configured to support IPv4 mapped address/special AF_INET6 wildcard bind (enabled by default). Kernel configuration is summarized as follows: - By default, MAPPED_ADDR_ENABLED option is defined in the kernel configuration file. In this case, AF_INET6 socket will grab IPv4 connections in certain condition. You can disable it with sysctl, or setsockopt. - If you remove MAPPED_ADDR_ENABLED option, the code to perform special behavior will not be compiled. It behaves as described in 1.12.1. Wildcard AF_INET6 socket grabs IPv4 connection if and only if the following conditions are satisfied: - there's no AF_INET socket that matches the IPv4 connection - the AF_INET6 socket is configured to accept IPv4 traffic, i.e. getsockopt(IPV6_BINDV6ONLY) returns 0. There's no problem with open/close ordering. (XXX need checking) 1.12.2.1 KAME/FreeBSD3x, initiating side KAME/FreeBSD3x supports outgoing connetion to IPv4 mapped address (::ffff:10.1.1.1), if the node is configured to accept IPv4 connections by AF_INET6 socket. (XXX need checking) 1.12.4 KAME/NetBSD KAME/NetBSD uses shared tcp4/6 code (from sys/netinet/tcp*) and shared udp4/6 code (from sys/netinet/udp*). The implementation is made differently from KAME/FreeBSD3x. KAME/NetBSD uses separate inpcb/in6pcb structures, while KAME/FreeBSD3x uses merged inpcb structure. 1.12.4.1 KAME/NetBSD, listening side The platform can be configured to support IPv4 mapped address/special AF_INET6 wildcard bind (disabled by default). Kernel behavior can be summarized as follows: - default: special support code will be compiled in, but is disabled by default. It can be controlled by sysctl (net.inet6.ip6.bindv6only), or setsockopt(IPV6_BINDV6ONLY). - add "INET6_BINDV6ONLY": No special support code for AF_INET6 wildcard socket will be compiled in. AF_INET6 sockets and AF_INET sockets are totally separate. The behavior is similar to what described in 1.12.1. sysctl setting will affect per-socket configuration at in6pcb creation time only. In other words, per-socket configuration will be copied from sysctl configuration at in6pcb creation time. To change per-socket behavior, you must perform setsockopt or reopen the socket. Change in sysctl configuration will not change the behavior or sockets that are already opened. Wildcard AF_INET6 socket grabs IPv4 connection if and only if the following conditions are satisfied: - there's no AF_INET socket that matches the IPv4 connection - the AF_INET6 socket is configured to accept IPv4 traffic, i.e. getsockopt(IPV6_BINDV6ONLY) returns 0. There's no problem with open/close ordering. 1.12.4.1 KAME/NetBSD, initiating side When you initiate a connection, you can always connect to IPv4 destination over AF_INET6 socket, usin IPv4 mapped address destination (::ffff:10.1.1.1). This is enabled independently from the configuration for listening side, and always enabled. 1.12.5 KAME/BSDI4 KAME/BSDI4 uses NRL-based TCP/UDP stack and inpcb source code, which was derived from NRL IPv6/IPsec stack. I guess it supports IPv4 mapped address and speical AF_INET6 wildcard bind. The implementation is, again, different from other KAME/*BSDs. 1.12.5.1 KAME/BSDI4, listening side NRL inpcb layer supports special behavior of AF_INET6 wildcard socket. It grabs IPv4 connection under certain condition. NRL inpcb layer has different behavior than KAME implementation, namely: - If you bind(2) a socket to IPv6 wildcard address (::) then bind(2) another socket to IPv4 wildcard address (0.0.0.0), the latter will fail with EADDRINUSE. - If you bind(2) to IPv4 wildcard address then IPv6 wildcard address, both will success. However, all IPv4 traffic (and IPv6 traffic) will be captured by IPv6 wildcard socket. 1.12.5.2 KAME/BSDI4, initiating side KAME/BSDi4 supports connection initiation to IPv4 mapped address (like ::ffff:10.1.1.1). 1.12.6 KAME/OpenBSD KAME/OpenBSD uses NRL-based TCP/UDP stack and inpcb source code, which was derived from NRL IPv6/IPsec stack. 1.12.6.1 KAME/OpenBSD, listening side KAME/OpenBSD disables special behavior on AF_INET6 wildcard bind for security reasons (if IPv4 traffic toward AF_INET6 wildcard bind is allowed, access control will become much harder). KAME/BSDI4 uses NRL-based TCP/UDP stack as well, however, the behavior is different due to OpenBSD's security policy. As a result the behavior of KAME/OpenBSD is similar to KAME/BSDI3 and KAME/FreeBSD228 (see 1.12.1 for more detail). 1.12.6.2 KAME/OpenBSD, initiating side KAME/OpenBSD does not support connection initiation to IPv4 mapped address (like ::ffff:10.1.1.1). 1.13 sockaddr_storage When RFC2553 was about to be finalized, there was discusson on how struct sockaddr_storage members are named. One proposal is to prepend "__" to the members (like "__ss_len") as they should not be touched. The other proposal was that don't prepend it (like "ss_len") as we need to touch those members directly. There was no clear consensus on it. As a result, RFC2553 defines struct sockaddr_storage as follows: struct sockaddr_storage { u_char __ss_len; /* address length */ u_char __ss_family; /* address family */ /* and bunch of padding */ }; On the contrary, XNET draft defines as follows: struct sockaddr_storage { u_char ss_len; /* address length */ u_char ss_family; /* address family */ /* and bunch of padding */ }; In December 1999, it was agreed that RFC2553bis should pick the latter (XNET) definition. KAME kit prior to December 1999 used RFC2553 definition. KAME kit after December 1999 (including December) will conform to XNET definition, based on RFC2553bis discusson. If you look at multiple IPv6 implementations, you will be able to see both definitions. As an userland programmer, the most portable way of dealing with it is to: (1) ensure ss_family and/or ss_len are available on the platform, by using GNU autoconf, (2) have -Dss_family=__ss_family to unify all occurences (including header file) into __ss_family, or (3) never touch __ss_family. cast to sockaddr * and use sa_family like: struct sockaddr_storage ss; family = ((struct sockaddr *)&ss)->sa_family 2. Network Drivers KAME requires three items to be added into the standard drivers: (1) mbuf clustering requirement. In this stable release, we changed MINCLSIZE into MHLEN+1 for all the operating systems in order to make all the drivers behave as we expect. (2) multicast. If "ifmcstat" yields no multicast group for a interface, that interface has to be patched. To avoid troubles, we suggest you to comment out the device drivers for unsupported/unnecessary cards, from the kernel configuration file. If you accidentally enable unsupported drivers, some of the userland tools may not work correctly (routing daemons are typical example). In the following sections, "official support" means that KAME developers are using that ethernet card/driver frequently. (NOTE: In the past we required all pcmcia drivers to have a call to in6_ifattach(). We have no such requirement any more) 2.1 FreeBSD 2.2.x-RELEASE Here is a list of FreeBSD 2.2.x-RELEASE drivers and its conditions: driver mbuf(1) multicast(2) official support? --- --- --- --- (Ethernet) ar looks ok - - cnw ok ok yes (*) ed ok ok yes ep ok ok yes fe ok ok yes sn looks ok - - (*) vx looks ok - - wlp ok ok - (*) xl ok ok yes zp ok ok - (FDDI) fpa looks ok ? - (ATM) en ok ok yes (Serial) lp ? - not work sl ? - not work sr looks ok ok - (**) You may want to add an invocation of "rtsol" in "/etc/pccard_ether", if you are using notebook computers and PCMCIA ethernet card. (*) These drivers are distributed with PAO (http://www.jp.freebsd.org/PAO/). (**) There was some report says that, if you make sr driver up and down and then up, the kernel may hang up. We have disabled frame-relay support from sr driver and after that this looks to be working fine. If you need frame-relay support to come back, please contact KAME developers. 2.2 BSD/OS 3.x The following lists BSD/OS 3.x device drivers and its conditions: driver mbuf(1) multicast(2) official support? --- --- --- --- (Ethernet) cnw ok ok yes de ok ok - df ok ok - eb ok ok - ef ok ok yes exp ok ok - mz ok ok yes ne ok ok yes we ok ok - (FDDI) fpa ok ok - (ATM) en maybe ok - (Serial) ntwo ok ok yes sl ? - not work appp ? - not work You may want to use "@insert" directive in /etc/pccard.conf to invoke "rtsol" command right after dynamic insertion of PCMCIA ethernet cards. 2.3 NetBSD The following table lists the network drivers we have tried so far. driver mbuf(1) multicast(2) official support? --- --- --- --- (Ethernet) ne pci/i386 ok ok yes ep pcmcia/i386 ok ok - le sbus/sparc ok ok yes bah zbus/amiga NG(*) (ATM) en pci/i386 ok ok - (*) This may need some fix, but I'm not sure what arcnet interfaces assume... 2.4 FreeBSD 3.x-RELEASE Here is a list of FreeBSD 3.x-RELEASE drivers and its conditions: driver mbuf(1) multicast(2) official support? --- --- --- --- (Ethernet) fe ok ok yes fxp ok ok yes wi ok ok yes lnc ? ok - cnw ok ok -(*) ep ok ok - sn ? ? -(*) xl ? ok - ed ? ok - (*) These drivers are distributed with PAO as PAO3 (http://www.jp.freebsd.org/PAO/). More drivers will just simply work on KAME FreeBSD 3.x-RELEASE but have not been checked yet. 2.5 OpenBSD 2.x Here is a list of OpenBSD 2.x drivers and its conditions: driver mbuf(1) multicast(2) official support? --- --- --- --- (Ethernet) ne pci/i386 ok ok yes ne pcmcia/i386 ok ok yes le sbus/sparc ok ok yes 3. Translator We categorize IPv4/IPv6 translator into 4 types. Translator A --- It is used in the early stage of transition to make it possible to establish a connection from an IPv6 host in an IPv6 island to an IPv4 host in the IPv4 ocean. Translator B --- It is used in the early stage of transition to make it possible to establish a connection from an IPv4 host in the IPv4 ocean to an IPv6 host in an IPv6 island. Translator C --- It is used in the late stage of transition to make it possible to establish a connection from an IPv4 host in an IPv4 island to an IPv6 host in the IPv6 ocean. Translator D --- It is used in the late stage of transition to make it possible to establish a connection from an IPv6 host in the IPv6 ocean to an IPv4 host in an IPv4 island. KAME provides an TCP relay translator for category A. This is called "FAITH". We also provide IP header translator for category A. 3.1 FAITH TCP relay translator FAITH system uses TCP relay daemon called "faithd" helped by the KAME kernel. FAITH will reserve an IPv6 address prefix, and relay TCP connection toward that prefix to IPv4 destination. For example, if the reserved IPv6 prefix is 3ffe:0501:0200:ffff::, and the IPv6 destination for TCP connection is 3ffe:0501:0200:ffff::163.221.202.12, the connection will be relayed toward IPv4 destination 163.221.202.12. destination IPv4 node (163.221.202.12) ^ | IPv4 tcp toward 163.221.202.12 FAITH-relay dual stack node ^ | IPv6 TCP toward 3ffe:0501:0200:ffff::163.221.202.12 source IPv6 node faithd must be invoked on FAITH-relay dual stack node. For more details, consult kame/kame/faithd/README. 3.2 IPv6-to-IPv4 header translator (to be written) 4. IPsec IPsec is mainly organized by three components. (1) Policy Management (2) Key Management (3) AH and ESP handling 4.1 Policy Management The policy management code is experimental, but this is almostly conformed to RFC2401. You can manage the SPD by both the command for administrater and the socket operation. By the command "setkey", there are three directive as following: "discard" means to discard the packet. "none" means not to do IPsec. "ipsec" means to do IPsec. "ipsec" is followed by some IPsec requests like "protocol/level". protocol is to be either "ah" or "esp". level is to be either "default", "use" or "require". "use" means that if a security association is available, use it for outbound packet, request SA to the Key management daemon through PF_KEY v2, and accept any inbound packets. "require" means that if a security association does not exist for outbound traffic, acquire one and discard the packet untill SA is found, and require inbound packets to use security. "default" is consulted to system wide default defined "sysctl" MIBs: net.inet.ipsec.esp_trans_deflev net.inet.ipsec.esp_net_deflev net.inet.ipsec.ah_trans_deflev net.inet.ipsec.ah_net_deflev net.inet6.ipsec6.esp_trans_deflev net.inet6.ipsec6.esp_net_deflev net.inet6.ipsec6.ah_trans_deflev net.inet6.ipsec6.ah_net_deflev They are 1:use or 2:require. When you need to setup IPsec tunnel mode, you use the format of "procol/level/peer". "peer" is IP address of the tunnel end-point. By the socket operation, there are three directive as following: "ipsec" means to do IPsec, see above. "entrust" means to consult to SPD defined by the command. "bypass" means not to do IPsec. This is for priveleged socket. If kernel doesn't find out policy entry, then system wide default is applied. You can specify the system wide default as discarding packet or not to do IPsec. net.inet.ipsec.def_policy net.inet6.ipsec6.def_policy They are 0:discard or 1:none. You can see these values in netinet6/ipsec.h. The policy entry is not re-ordered with its indexes, so the order of entry when you add is very significant. But we think it should be fixed in the future. 4.2 Key Management The key management code implemented in this kit (sys/netkey) is a home-brew PFKEY v2 implementation. This conforms to RFC2367. The home-brew IKE daemon, "racoon" is included in the kit (kame/kame/racoon). Basically you'll need to run racoon as daemon, then setup a policy to require keys (like ping -P 'out ipsec esp/transport//use'). The kernel will contact racoon daemon as necessary to exchange keys. 4.3 AH and ESP handling IPsec module is implemented as "hooks" to the standard IPv4/IPv6 processing. When sending a packet, ip{,6}_output() checks if ESP/AH processing is required by checking if a matching SPD (Security Policy Database) is found. If ESP/AH is needed, {esp,ah}{4,6}_output() will be called and mbuf will be updated accordingly. When a packet is received, {esp,ah}4_input() will be called based on protocol number, i.e. (*inetsw[proto])(). {esp,ah}4_input() will decrypt/check authenticity of the packet, and strips off daisy-chained header and padding for ESP/AH. It is safe to strip off the ESP/AH header on packet reception, since we will never use the received packet in "as is" form. By using ESP/AH, TCP4/6 effective data segment size will be affected by extra daisy-chained headers inserted by ESP/AH. Our code takes care of the case. Basic crypto functions can be found in directory "sys/crypto". ESP/AH transform are listed in {esp,ah}_core.c with wrapper functions. If you wish to add some algorithm, add wrapper function in {esp,ah}_core.c, and add your crypto algorithm code into sys/crypto. Tunnel mode is partially supported in this release, with the following restrictions: - IPsec tunnel is not combined with GIF generic tunneling interface. It needs a great care because we may create an infinite loop between ip_output() and tunnelifp->if_output(). Opinion varies if it is better to unify them, or not. - MTU and Don't Fragment bit (IPv4) considerations need more checking, but basically works fine. - Authentication model for AH tunnel must be revisited. We'll need to improve the policy management engine, eventually. 4.4 Conformance to RFCs and IDs The IPsec code in the kernel conforms (or, tries to conform) to the following standards: "old IPsec" specification documented in rfc182[5-9].txt "new IPsec" specification documented in rfc240[1-6].txt, rfc241[01].txt, rfc2451.txt and draft-mcdonald-simple-ipsec-api-01.txt (draft expired, but you can take from ftp://ftp.kame.net/pub/internet-drafts/). (NOTE: IKE specifications, rfc241[7-9].txt are implemented in userland, as "racoon" IKE daemon) Currently supported algorithms are: old IPsec AH null crypto checksum (no document, just for debugging) keyed MD5 with 128bit crypto checksum (rfc1828.txt) keyed SHA1 with 128bit crypto checksum (no document) HMAC MD5 with 128bit crypto checksum (rfc2085.txt) HMAC SHA1 with 128bit crypto checksum (no document) old IPsec ESP null encryption (no document, similar to rfc2410.txt) DES-CBC mode (rfc1829.txt) new IPsec AH null crypto checksum (no document, just for debugging) keyed MD5 with 96bit crypto checksum (no document) keyed SHA1 with 96bit crypto checksum (no document) HMAC MD5 with 96bit crypto checksum (rfc2403.txt HMAC SHA1 with 96bit crypto checksum (rfc2404.txt) new IPsec ESP null encryption (rfc2410.txt) DES-CBC with derived IV (draft-ietf-ipsec-ciph-des-derived-01.txt, draft expired) DES-CBC with explicit IV (rfc2405.txt) 3DES-CBC with explicit IV (rfc2451.txt) BLOWFISH CBC (rfc2451.txt) CAST128 CBC (rfc2451.txt) RC5 CBC (rfc2451.txt) each of the above can be combined with: ESP authentication with HMAC-MD5(96bit) ESP authentication with HMAC-SHA1(96bit) The following algorithms are NOT supported: old IPsec AH HMAC MD5 with 128bit crypto checksum + 64bit replay prevention (rfc2085.txt) keyed SHA1 with 160bit crypto checksum + 32bit padding (rfc1852.txt) IPsec (in kernel) and IKE (in userland as "racoon") has been tested at several interoperability test events, and it is known to interoperate with many other implementations well. Also, KAME IPsec has quite wide coverage for IPsec crypto algorithms documented in RFC (we cover algorithms without intellectual property issues only). 4.5 ECN consideration on IPsec tunnels KAME IPsec implements ECN-friendly IPsec tunnel, described in draft-ipsec-ecn-00.txt. Normal IPsec tunnel is described in RFC2401. On encapsulation, IPv4 TOS field (or, IPv6 traffic class field) will be copied from inner IP header to outer IP header. On decapsulation outer IP header will be simply dropped. The decapsulation rule is not compatible with ECN, since ECN bit on the outer IP TOS/traffic class field will be lost. To make IPsec tunnel ECN-friendly, we should modify encapsulation and decapsulation procedure. This is described in http://www.aciri.org/floyd/papers/draft-ipsec-ecn-00.txt, chapter 3. KAME IPsec tunnel implementation can give you three behaviors, by setting net.inet.ipsec.ecn (or net.inet6.ipsec6.ecn) to some value: - RFC2401: no consideration for ECN (sysctl value -1) - ECN forbidden (sysctl value 0) - ECN allowed (sysctl value 1) Note that the behavior is configurable in per-node manner, not per-SA manner (draft-ipsec-ecn-00 wants per-SA configuration, but it looks too much for me). The behavior is summarized as follows (see source code for more detail): encapsulate decapsulate --- --- RFC2401 copy all TOS bits drop TOS bits on outer from inner to outer. (use inner TOS bits as is) ECN forbidden copy TOS bits except for ECN drop TOS bits on outer (masked with 0xfc) from inner (use inner TOS bits as is) to outer. set ECN bits to 0. ECN allowed copy TOS bits except for ECN use inner TOS bits with some CE (masked with 0xfe) from change. if outer ECN CE bit inner to outer. is 1, enable ECN CE bit on set ECN CE bit to 0. the inner. General strategy for configuration is as follows: - if both IPsec tunnel endpoint are capable of ECN-friendly behavior, you'd better configure both end to "ECN allowed" (sysctl value 1). - if the other end is very strict about TOS bit, use "RFC2401" (sysctl value -1). - in other cases, use "ECN forbidden" (sysctl value 0). The default behavior is "ECN forbidden" (sysctl value 0). For more information, please refer to: http://www.aciri.org/floyd/papers/draft-ipsec-ecn-00.txt RFC2481 (Explicit Congestion Notification) KAME sys/netinet6/{ah,esp}_input.c (Thanks goes to Kenjiro Cho for detailed analysis) 4.6 Interoperability Here are (some of) platforms we have tested IPsec/IKE interoperability in the past. Note that both ends (KAME and others) may have modified their implementation, so use the following list just for reference purposes. Altiga, Ashley-laurent (vpcom.com), Data Fellows (F-Secure), Ericsson ACC, FreeS/WAN, HITACHI, IBM AIX, IIJ, Intel, Microsoft WinNT, NIST (linux IPsec + plutoplus), Netscreen, OpenBSD, RedCreek, Routerware, SSH, Secure Computing, Soliton, Toshiba, VPNet, Yamaha RT100i 5. IPComp IPComp stands for IP payload compression protocol. This is aimed for payload compression, not the header compression like PPP VJ compression. This may be useful when you are using slow serial link (say, cell phone) with powerful CPU (well, recent notebook PCs are really powerful...). The protocol design of IPComp is very similar to IPsec. KAME implements the following specifications: - RFC2393: IP Payload Compression Protocol (IPComp) - RFC2394: IP Payload Compression Using DEFLATE Here are some points to be noted: - IPComp is treated as part of IPsec protocol suite, and SPI and CPI space is unified. Spec says that there's no relationship between two so they are assumed to be separate. - IPComp association (IPCA) is kept in SAD. - It is possible to use well-known CPI (CPI=2 for DEFLATE for example), for outbound/inbound packet, but for indexing purposes one element from SPI/CPI space will be occupied anyway. - pfkey is modified to support IPComp. However, there's no official SA type number assignment yet. Portability with other IPComp stack is questionable (anyway, who else implement IPComp on UN*X?). - Spec says that IPComp output processing must be performed before IPsec output processing, to achieve better compression ratio and "stir" data stream before encryption. However, with manual SPD setting, you are able to violate the ordering requirement (KAME code is too generic, maybe). - Though MTU can be significantly decreased by using IPComp, no special consideration is made about path MTU (spec talks nothing about MTU consideration). IPComp is designed for serial links, not ethernet-like medium, it seems. - You can change compression ratio on outbound packet, by changing deflate_policy in sys/netinet6/ipcomp_core.c. You can also change history buffer size by changing deflate_window in the same source code. (should it be sysctl accessible? or per-SAD configurable?) - Tunnel mode IPComp is not working right. KAME box can generate tunnelled IPComp packet, however, cannot accept tunneled IPComp packet.