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37 .Nd Internet protocol version 6 family
44 family is an updated version of
49 implements Internet Protocol version 4,
51 implements Internet Protocol version 6.
54 is a collection of protocols layered atop the
55 .Em Internet Protocol version 6
57 transport layer, and utilizing the IPv6 address format.
60 family provides protocol support for the
61 .Dv SOCK_STREAM , SOCK_DGRAM ,
66 interface provides access to the
70 IPv6 addresses are 16 byte quantities, stored in network standard byteorder.
74 as a discriminated union.
78 family utilize the following addressing structure:
79 .Bd -literal -offset indent
82 sa_family_t sin6_family;
84 uint32_t sin6_flowinfo;
85 struct in6_addr sin6_addr;
86 uint32_t sin6_scope_id;
90 Sockets may be created with the local address
92 (which is equal to IPv6 address
96 matching on incoming messages.
98 The IPv6 specification defines scoped addresses,
99 like link-local or site-local addresses.
100 A scoped address is ambiguous to the kernel,
101 if it is specified without a scope identifier.
102 To manipulate scoped addresses properly from the userland,
103 programs must use the advanced API defined in RFC2292.
104 A compact description of the advanced API is available in
106 If a scoped address is specified without an explicit scope,
107 the kernel may raise an error.
108 Note that scoped addresses are not for daily use at this moment,
109 both from a specification and an implementation point of view.
111 The KAME implementation supports an extended numeric IPv6 address notation
112 for link-local addresses,
122 This notation is supported by
126 Some of normal userland programs, such as
130 are able to use this notation.
131 With special programs
134 you can specify the outgoing interface by an extra command line option
135 to disambiguate scoped addresses.
137 Scoped addresses are handled specially in the kernel.
138 In kernel structures like routing tables or interface structures,
139 a scoped address will have its interface index embedded into the address.
141 the address in some kernel structures is not the same as that on the wire.
142 The embedded index will become visible through a
144 socket, kernel memory accesses via
146 and on some other occasions.
147 HOWEVER, users should never use the embedded form.
148 For details please consult
150 supplied with KAME kit.
154 family is comprised of the
156 network protocol, Internet Control
157 Message Protocol version 6
159 Transmission Control Protocol
161 and User Datagram Protocol
164 is used to support the
168 is used to support the
182 by creating an Internet socket of type
186 message protocol is accessible from a raw socket.
188 A number of variables are implemented in the net.inet6 branch of the
191 In addition to the variables supported by the transport protocols
192 (for which the respective manual pages may be consulted),
193 the following general variables are defined:
194 .Bl -tag -width IPV6CTL_MAXFRAGPACKETS
195 .It Dv IPV6CTL_FORWARDING
197 Boolean: enable/disable forwarding of
200 Also, identify if the node is acting as a router.
202 .It Dv IPV6CTL_SENDREDIRECTS
204 Boolean: enable/disable sending of
206 redirects in response to unforwardable
209 This option is ignored unless the node is routing
212 and should normally be enabled on all systems.
214 .It Dv IPV6CTL_DEFHLIM
216 Integer: default hop limit value to use for outgoing
219 This value applies to all the transport protocols on top of
221 There are APIs to override the value.
222 .It Dv IPV6CTL_MAXFRAGPACKETS
223 .Pq ip6.maxfragpackets
224 Integer: default maximum number of fragmented packets the node will accept.
225 0 means that the node will not accept any fragmented packets.
226 -1 means that the node will accept as many fragmented packets as it receives.
227 The flag is provided basically for avoiding possible DoS attacks.
228 .It Dv IPV6CTL_ACCEPT_RTADV
230 Boolean: the default value of a per-interface flag to
231 enable/disable receiving of
233 router advertisement packets,
234 and autoconfiguration of address prefixes and default routers.
235 The node must be a host
237 for the option to be meaningful.
239 .It Dv IPV6CTL_AUTO_LINKLOCAL
240 .Pq ip6.auto_linklocal
241 Boolean: the default value of a per-interface flag to
242 enable/disable performing automatic link-local address configuration.
244 .It Dv IPV6CTL_LOG_INTERVAL
246 Integer: default interval between
248 packet forwarding engine log output
250 .It Dv IPV6CTL_HDRNESTLIMIT
252 Integer: default number of the maximum
255 permitted on incoming
258 If set to 0, the node will accept as many extension headers as possible.
259 .It Dv IPV6CTL_DAD_COUNT
261 Integer: default number of
264 .Pq duplicated address detection
266 The packets will be generated when
268 interface addresses are configured.
269 .It Dv IPV6CTL_AUTO_FLOWLABEL
270 .Pq ip6.auto_flowlabel
271 Boolean: enable/disable automatic filling of
273 flowlabel field, for outstanding connected transport protocol packets.
274 The field might be used by intermediate routers to identify packet flows.
276 .It Dv IPV6CTL_DEFMCASTHLIM
278 Integer: default hop limit value for an
280 multicast packet sourced by the node.
281 This value applies to all the transport protocols on top of
283 There are APIs to override the value as documented in
285 .It Dv IPV6CTL_GIF_HLIM
287 Integer: default maximum hop limit value for an
292 .It Dv IPV6CTL_KAME_VERSION
294 String: identifies the version of KAME
296 stack implemented in the kernel.
297 .It Dv IPV6CTL_USE_DEPRECATED
298 .Pq ip6.use_deprecated
299 Boolean: enable/disable use of deprecated address,
300 specified in RFC2462 5.5.4.
302 .It Dv IPV6CTL_RR_PRUNE
304 Integer: default interval between
306 router renumbering prefix babysitting, in seconds.
307 .It Dv IPV6CTL_V6ONLY
309 Boolean: enable/disable the prohibited use of
316 .Ss Interaction between IPv4/v6 sockets
319 does not route IPv4 traffic to
322 The default behavior intentionally violates RFC2553 for security reasons.
323 Listen to two sockets if you want to accept both IPv4 and IPv6 traffic.
324 IPv4 traffic may be routed with certain
325 per-socket/per-node configuration, however, it is not recommended to do so.
332 TCP/UDP socket is documented in RFC2553.
333 Basically, it says this:
336 A specific bind on an
340 with an address specified)
341 should accept IPv6 traffic to that address only.
343 If you perform a wildcard bind
350 and there is no wildcard bind
352 socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic
353 should be routed to that
356 IPv4 traffic should be seen as if it came from an IPv6 address like
357 .Li ::ffff:10.1.1.1 .
358 This is called an IPv4 mapped address.
360 If there are both a wildcard bind
362 socket and a wildcard bind
364 socket on one TCP/UDP port, they should behave separately.
365 IPv4 traffic should be routed to the
367 socket and IPv6 should be routed to the
372 However, RFC2553 does not define the ordering constraint between calls to
374 nor how IPv4 TCP/UDP port numbers and IPv6 TCP/UDP port numbers
376 (should they be integrated or separated).
377 Implemented behavior is very different from kernel to kernel.
378 Therefore, it is unwise to rely too much upon the behavior of
380 wildcard bind sockets.
381 It is recommended to listen to two sockets, one for
385 when you would like to accept both IPv4 and IPv6 traffic.
387 It should also be noted that
388 malicious parties can take advantage of the complexity presented above,
389 and are able to bypass access control,
390 if the target node routes IPv4 traffic to
393 Users are advised to take care handling connections
394 from IPv4 mapped address to
410 .%T "An Extension of Format for IPv6 Scoped Addresses"
413 .%N draft-ietf-ipngwg-scopedaddr-format-02.txt
414 .%O work in progress material
419 protocol interfaces are defined in RFC2553 and RFC2292.
420 The implementation described herein appeared in the WIDE/KAME project.
422 The IPv6 support is subject to change as the Internet protocols develop.
423 Users should not depend on details of the current implementation,
424 but rather the services exported.
426 Users are suggested to implement
427 .Dq version independent
428 code as much as possible, as you will need to support both