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1 .\" $NetBSD: inet6_rthdr_space.3,v 1.16 2010/03/22 19:30:54 joerg Exp $
2 .\" $KAME: inet6_rthdr_space.3,v 1.8 2000/05/17 14:30:15 itojun Exp $
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31 .Dd December 10, 1999
32 .Dt INET6_RTHDR_SPACE 3
33 .Os
34 .\"
35 .Sh NAME
36 .Nm inet6_rthdr_space ,
37 .Nm inet6_rthdr_init ,
38 .Nm inet6_rthdr_add ,
39 .Nm inet6_rthdr_lasthop ,
40 .Nm inet6_rthdr_reverse ,
41 .Nm inet6_rthdr_segments ,
42 .Nm inet6_rthdr_getaddr ,
43 .Nm inet6_rthdr_getflags
44 .Nd IPv6 Routing Header Options manipulation
45 .\"
46 .Sh SYNOPSIS
47 .In netinet/in.h
48 .Ft size_t
49 .Fn inet6_rthdr_space "int type" "int segments"
50 .Ft "struct cmsghdr *"
51 .Fn inet6_rthdr_init "void *bp" "int type"
52 .Ft int
53 .Fn inet6_rthdr_add "struct cmsghdr *cmsg" "const struct in6_addr *addr" "unsigned int flags"
54 .Ft int
55 .Fn inet6_rthdr_lasthop "struct cmsghdr *cmsg" "unsigned int flags"
56 .Ft int
57 .Fn inet6_rthdr_reverse "const struct cmsghdr *in" "struct cmsghdr *out"
58 .Ft int
59 .Fn inet6_rthdr_segments "const struct cmsghdr *cmsg"
60 .Ft "struct in6_addr *"
61 .Fn inet6_rthdr_getaddr "struct cmsghdr *cmsg" "int index"
62 .Ft int
63 .Fn inet6_rthdr_getflags "const struct cmsghdr *cmsg" "int index"
64 .\"
65 .Sh DESCRIPTION
66 RFC 2292 IPv6 advanced API defines eight
67 functions that the application calls to build and examine a Routing
68 header.
69 Four functions build a Routing header:
70 .Bl -hang
71 .It Fn inet6_rthdr_space
72 return #bytes required for ancillary data
73 .It Fn inet6_rthdr_init
74 initialize ancillary data for Routing header
75 .It Fn inet6_rthdr_add
76 add IPv6 address \*[Am] flags to Routing header
77 .It Fn inet6_rthdr_lasthop
78 specify the flags for the final hop
79 .El
80 .Pp
81 Four functions deal with a returned Routing header:
82 .Bl -hang
83 .It Fn inet6_rthdr_reverse
84 reverse a Routing header
85 .It Fn inet6_rthdr_segments
86 return #segments in a Routing header
87 .It Fn inet6_rthdr_getaddr
88 fetch one address from a Routing header
89 .It Fn inet6_rthdr_getflags
90 fetch one flag from a Routing header
91 .El
92 .Pp
93 The function prototypes for these functions are all in the
94 .In netinet/in.h
95 header.
96 .\"
97 .Ss inet6_rthdr_space
98 This function returns the number of bytes required to hold a Routing
99 header of the specified
100 .Fa type
101 containing the specified number of
102 .Fa segments
103 .Pq addresses .
104 For an IPv6 Type 0 Routing header, the number
105 of segments must be between 1 and 23, inclusive.
106 The return value
107 includes the size of the cmsghdr structure that precedes the Routing
108 header, and any required padding.
109 .Pp
110 If the return value is 0, then either the type of the Routing header
111 is not supported by this implementation or the number of segments is
112 invalid for this type of Routing header.
113 .Pp
114 Note: This function returns the size but does not allocate the space
115 required for the ancillary data.
116 This allows an application to
117 allocate a larger buffer, if other ancillary data objects are
118 desired, since all the ancillary data objects must be specified to
119 .Xr sendmsg 2
120 as a single
121 .Li msg_control
122 buffer.
123 .\"
124 .Ss inet6_rthdr_init
125 This function initializes the buffer pointed to by
126 .Fa bp
127 to contain a
128 .Li cmsghdr
129 structure followed by a Routing header of the specified
130 .Fa type .
131 The
132 .Li cmsg_len
133 member of the
134 .Li cmsghdr
135 structure is initialized to the
136 size of the structure plus the amount of space required by the
137 Routing header.
138 The
139 .Li cmsg_level
140 and
141 .Li cmsg_type
142 members are also initialized as required.
143 .Pp
144 The caller must allocate the buffer and its size can be determined by
145 calling
146 .Fn inet6_rthdr_space .
147 .Pp
148 Upon success the return value is the pointer to the
149 .Li cmsghdr
150 structure, and this is then used as the first argument to the next
151 two functions.
152 Upon an error the return value is
153 .Dv NULL .
154 .\"
155 .Ss inet6_rthdr_add
156 This function adds the address pointed to by
157 .Fa addr
158 to the end of the
159 Routing header being constructed and sets the type of this hop to the
160 value of
161 .Fa flags .
162 For an IPv6 Type 0 Routing header,
163 .Fa flags
164 must be
165 either
166 .Dv IPV6_RTHDR_LOOSE
167 or
168 .Dv IPV6_RTHDR_STRICT .
169 .Pp
170 If successful, the
171 .Li cmsg_len
172 member of the
173 .Li cmsghdr
174 structure is
175 updated to account for the new address in the Routing header and the
176 return value of the function is 0.
177 Upon an error the return value of
178 the function is -1.
179 .\"
180 .Ss inet6_rthdr_lasthop
181 This function specifies the Strict/Loose flag for the final hop of a
182 Routing header.
183 For an IPv6 Type 0 Routing header,
184 .Fa flags
185 must be either
186 .Dv IPV6_RTHDR_LOOSE
187 or
188 .Dv IPV6_RTHDR_STRICT .
189 .Pp
190 The return value of the function is 0 upon success, or -1 upon an error.
191 .Pp
192 Notice that a Routing header specifying
193 .Li N
194 intermediate nodes requires
195 .Li N+1
196 Strict/Loose flags.
197 This requires
198 .Li N
199 calls to
200 .Fn inet6_rthdr_add
201 followed by one call to
202 .Fn inet6_rthdr_lasthop .
203 .\"
204 .Ss inet6_rthdr_reverse
205 This function takes a Routing header that was received as ancillary
206 data
207 .Po
208 pointed to by the first argument,
209 .Fa in
210 .Pc
211 and writes a new Routing
212 header that sends datagrams along the reverse of that route.
213 Both
214 arguments are allowed to point to the same buffer
215 .Pq that is, the reversal can occur in place .
216 .Pp
217 The return value of the function is 0 on success, or -1 upon an
218 error.
219 .\"
220 .Ss inet6_rthdr_segments
221 This function returns the number of segments
222 .Pq addresses
223 contained in
224 the Routing header described by
225 .Fa cmsg .
226 On success the return value is
227 between 1 and 23, inclusive.
228 The return value of the function is -1 upon an error.
229 .\"
230 .Ss inet6_rthdr_getaddr
231 This function returns a pointer to the IPv6 address specified by
232 .Fa index
233 .Po
234 which must have a value between 1 and the value returned by
235 .Fn inet6_rthdr_segments
236 .Pc
237 in the Routing header described by
238 .Fa cmsg .
239 An
240 application should first call
241 .Fn inet6_rthdr_segments
242 to obtain the number of segments in the Routing header.
243 .Pp
244 Upon an error the return value of the function is
245 .Dv NULL .
246 .\"
247 .Ss inet6_rthdr_getflags
248 This function returns the flags value specified by
249 .Fa index
250 .Po
251 which must
252 have a value between 0 and the value returned by
253 .Fn inet6_rthdr_segments
254 .Pc
255 in the Routing header described by
256 .Fa cmsg .
257 For an IPv6 Type 0 Routing header the return value will be either
258 .Dv IPV6_RTHDR_LOOSE
259 or
260 .Dv IPV6_RTHDR_STRICT .
261 .Pp
262 Upon an error the return value of the function is -1.
263 .Pp
264 Note: Addresses are indexed starting at 1, and flags starting at 0,
265 to maintain consistency with the terminology and figures in RFC 2460.
266 .\"
267 .Sh EXAMPLES
268 RFC 2292 gives comprehensive examples in chapter 8.
269 .\"
270 .Sh DIAGNOSTICS
271 .Fn inet6_rthdr_space
272 returns 0 on errors.
273 .Pp
274 .Fn inet6_rthdr_add ,
275 .Fn inet6_rthdr_lasthop
276 and
277 .Fn inet6_rthdr_reverse
278 return 0 on success, and returns -1 on error.
279 .Pp
280 .Fn inet6_rthdr_init
281 and
282 .Fn inet6_rthdr_getaddr
283 return
284 .Dv NULL
285 on error.
286 .Pp
287 .Fn inet6_rthdr_segments
288 and
289 .Fn inet6_rthdr_getflags
290 return -1 on error.
291 .\"
292 .Sh SEE ALSO
293 .Rs
294 .%A W. Stevens
295 .%A M. Thomas
296 .%T "Advanced Sockets API for IPv6"
297 .%N RFC 2292
298 .%D February 1998
299 .Re
300 .Rs
301 .%A S. Deering
302 .%A R. Hinden
303 .%T "Internet Protocol, Version 6 (IPv6) Specification"
304 .%N RFC 2460
305 .%D December 1998
306 .Re
307 .\"
308 .Sh STANDARDS
309 The functions
310 are documented in
311 .Dq Advanced Sockets API for IPv6
312 .Pq RFC 2292 .
313 .\"
314 .Sh HISTORY
315 The implementation first appeared in KAME advanced networking kit.
316 .\"
317 .Sh BUGS
318 The text was shamelessly copied from RFC 2292.
319 .Pp
320 .Fn inet6_rthdr_reverse
321 is not implemented yet.