1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- This manual is last updated 4 March 2015 for version
3.5.4 of GnuTLS.
Copyright (C) 2001-2015 Free Software Foundation, Inc.\\
Copyright (C) 2001-2015 Nikos Mavrogiannopoulos
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled "GNU Free
Documentation License". -->
<!-- Created by GNU Texinfo 6.1, http://www.gnu.org/software/texinfo/ -->
<head>
<title>GnuTLS 3.5.4: Datagram TLS API</title>
<meta name="description" content="GnuTLS 3.5.4: Datagram TLS API">
<meta name="keywords" content="GnuTLS 3.5.4: Datagram TLS API">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Function-and-Data-Index.html#Function-and-Data-Index" rel="index" title="Function and Data Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="API-reference.html#API-reference" rel="up" title="API reference">
<link href="X509-certificate-API.html#X509-certificate-API" rel="next" title="X509 certificate API">
<link href="Core-TLS-API.html#Core-TLS-API" rel="prev" title="Core TLS API">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
body {
margin: 2%;
padding: 0 5%;
background: #ffffff;
}
h1,h2,h3,h4,h5 {
font-weight: bold;
padding: 5px 5px 5px 5px;
background-color: #c2e0ff;
color: #336699;
}
h1 {
padding: 2em 2em 2em 5%;
color: white;
background: #336699;
text-align: center;
letter-spacing: 3px;
}
h2 { text-decoration: underline; }
pre {
margin: 0 5%;
padding: 0.5em;
}
pre.example,pre.verbatim {
padding-bottom: 1em;
border: solid #c2e0ff;
background: #f0faff;
border-width: 1px 1px 1px 5px;
margin: 1em auto;
width: 90%;
}
div.node {
margin: 0 -5% 0 -2%;
padding: 0.5em 0.5em;
margin-top: 0.5em;
margin-bottom: 0.5em;
font-weight: bold;
}
dd, li {
padding-top: 0.1em;
padding-bottom: 0.1em;
}
div.float {
margin-bottom: 0.5em;
text-align: center;
}
table {
text-align: left;
margin-left:auto;
margin-right:auto;
border-spacing: 7px;
width: 50%;
}
th {
padding: 0;
color: #336699;
background-color: #c2e0ff;
border: solid #000000;
border-width: 0px;
margin: 1em auto;
text-align: center;
margin-left:auto;
margin-right:auto;
}
td {
padding: 0;
border: solid #000000;
background-color: #f0faff;
border-width: 0px;
margin: 1em auto;
text-align: left;
margin-left:auto;
margin-right:auto;
padding-left: 1em;
}
dl {
text-align: left;
margin-left:auto;
margin-right:auto;
width: 50%;
padding-left: 1em;
border: solid #c2e0ff;
background: #f0faff;
border-width: 5px 1px 1px 1px;
margin: 1em auto;
}
-->
</style>
</head>
<body lang="en">
<a name="Datagram-TLS-API"></a>
<div class="header">
<p>
Next: <a href="X509-certificate-API.html#X509-certificate-API" accesskey="n" rel="next">X509 certificate API</a>, Previous: <a href="Core-TLS-API.html#Core-TLS-API" accesskey="p" rel="prev">Core TLS API</a>, Up: <a href="API-reference.html#API-reference" accesskey="u" rel="up">API reference</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Datagram-TLS-API-1"></a>
<h3 class="section">E.2 Datagram TLS API</h3>
<p>The prototypes for the following functions lie in
<samp>gnutls/dtls.h</samp>.
</p>
<a name="gnutls_005fdtls_005fcookie_005fsend-1"></a>
<h4 class="subheading">gnutls_dtls_cookie_send</h4>
<a name="gnutls_005fdtls_005fcookie_005fsend"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fcookie_005fsend"></a>Function: <em>int</em> <strong>gnutls_dtls_cookie_send</strong> <em>(gnutls_datum_t * <var>key</var>, void * <var>client_data</var>, size_t <var>client_data_size</var>, gnutls_dtls_prestate_st * <var>prestate</var>, gnutls_transport_ptr_t <var>ptr</var>, gnutls_push_func <var>push_func</var>)</em></dt>
<dd><p><var>key</var>: is a random key to be used at cookie generation
</p>
<p><var>client_data</var>: contains data identifying the client (i.e. address)
</p>
<p><var>client_data_size</var>: The size of client’s data
</p>
<p><var>prestate</var>: The previous cookie returned by <code>gnutls_dtls_cookie_verify()</code>
</p>
<p><var>ptr</var>: A transport pointer to be used by <code>push_func</code>
</p>
<p><var>push_func</var>: A function that will be used to reply
</p>
<p>This function can be used to prevent denial of service
attacks to a DTLS server by requiring the client to
reply using a cookie sent by this function. That way
it can be ensured that a client we allocated resources
for (i.e. <code>gnutls_session_t</code> ) is the one that the
original incoming packet was originated from.
</p>
<p>This function must be called at the first incoming packet,
prior to allocating any resources and must be succeeded
by <code>gnutls_dtls_cookie_verify()</code> .
</p>
<p><strong>Returns:</strong> the number of bytes sent, or a negative error code.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fcookie_005fverify-1"></a>
<h4 class="subheading">gnutls_dtls_cookie_verify</h4>
<a name="gnutls_005fdtls_005fcookie_005fverify"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fcookie_005fverify"></a>Function: <em>int</em> <strong>gnutls_dtls_cookie_verify</strong> <em>(gnutls_datum_t * <var>key</var>, void * <var>client_data</var>, size_t <var>client_data_size</var>, void * <var>_msg</var>, size_t <var>msg_size</var>, gnutls_dtls_prestate_st * <var>prestate</var>)</em></dt>
<dd><p><var>key</var>: is a random key to be used at cookie generation
</p>
<p><var>client_data</var>: contains data identifying the client (i.e. address)
</p>
<p><var>client_data_size</var>: The size of client’s data
</p>
<p><var>_msg</var>: An incoming message that initiates a connection.
</p>
<p><var>msg_size</var>: The size of the message.
</p>
<p><var>prestate</var>: The cookie of this client.
</p>
<p>This function will verify the received message for
a valid cookie. If a valid cookie is returned then
it should be associated with the session using
<code>gnutls_dtls_prestate_set()</code> ;
</p>
<p>This function must be called after <code>gnutls_dtls_cookie_send()</code> .
</p>
<p><strong>Returns:</strong> <code>GNUTLS_E_SUCCESS</code> (0) on success, or a negative error code.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fget_005fdata_005fmtu-1"></a>
<h4 class="subheading">gnutls_dtls_get_data_mtu</h4>
<a name="gnutls_005fdtls_005fget_005fdata_005fmtu"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fget_005fdata_005fmtu"></a>Function: <em>unsigned int</em> <strong>gnutls_dtls_get_data_mtu</strong> <em>(gnutls_session_t <var>session</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p>This function will return the actual maximum transfer unit for
application data. I.e. DTLS headers are subtracted from the
actual MTU which is set using <code>gnutls_dtls_set_mtu()</code> .
</p>
<p><strong>Returns:</strong> the maximum allowed transfer unit.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fget_005fmtu-1"></a>
<h4 class="subheading">gnutls_dtls_get_mtu</h4>
<a name="gnutls_005fdtls_005fget_005fmtu"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fget_005fmtu"></a>Function: <em>unsigned int</em> <strong>gnutls_dtls_get_mtu</strong> <em>(gnutls_session_t <var>session</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p>This function will return the MTU size as set with
<code>gnutls_dtls_set_mtu()</code> . This is not the actual MTU
of data you can transmit. Use <code>gnutls_dtls_get_data_mtu()</code>
for that reason.
</p>
<p><strong>Returns:</strong> the set maximum transfer unit.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fget_005ftimeout-1"></a>
<h4 class="subheading">gnutls_dtls_get_timeout</h4>
<a name="gnutls_005fdtls_005fget_005ftimeout"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fget_005ftimeout-1"></a>Function: <em>unsigned int</em> <strong>gnutls_dtls_get_timeout</strong> <em>(gnutls_session_t <var>session</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p>This function will return the milliseconds remaining
for a retransmission of the previously sent handshake
message. This function is useful when DTLS is used in
non-blocking mode, to estimate when to call <code>gnutls_handshake()</code>
if no packets have been received.
</p>
<p><strong>Returns:</strong> the remaining time in milliseconds.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fprestate_005fset-1"></a>
<h4 class="subheading">gnutls_dtls_prestate_set</h4>
<a name="gnutls_005fdtls_005fprestate_005fset"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fprestate_005fset"></a>Function: <em>void</em> <strong>gnutls_dtls_prestate_set</strong> <em>(gnutls_session_t <var>session</var>, gnutls_dtls_prestate_st * <var>prestate</var>)</em></dt>
<dd><p><var>session</var>: a new session
</p>
<p><var>prestate</var>: contains the client’s prestate
</p>
<p>This function will associate the prestate acquired by
the cookie authentication with the client, with the newly
established session.
</p>
<p>This functions must be called after a successful <code>gnutls_dtls_cookie_verify()</code>
and should be succeeded by the actual DTLS handshake using <code>gnutls_handshake()</code> .
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fset_005fdata_005fmtu-1"></a>
<h4 class="subheading">gnutls_dtls_set_data_mtu</h4>
<a name="gnutls_005fdtls_005fset_005fdata_005fmtu"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fset_005fdata_005fmtu"></a>Function: <em>int</em> <strong>gnutls_dtls_set_data_mtu</strong> <em>(gnutls_session_t <var>session</var>, unsigned int <var>mtu</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p><var>mtu</var>: The maximum unencrypted transfer unit of the session
</p>
<p>This function will set the maximum size of the *unencrypted* records
which will be sent over a DTLS session. It is equivalent to calculating
the DTLS packet overhead with the current encryption parameters, and
calling <code>gnutls_dtls_set_mtu()</code> with that value. In particular, this means
that you may need to call this function again after any negotiation or
renegotiation, in order to ensure that the MTU is still sufficient to
account for the new protocol overhead.
</p>
<p>In most cases you only need to call <code>gnutls_dtls_set_mtu()</code> with
the maximum MTU of your transport layer.
</p>
<p><strong>Returns:</strong> <code>GNUTLS_E_SUCCESS</code> (0) on success, or a negative error code.
</p>
<p><strong>Since:</strong> 3.1
</p></dd></dl>
<a name="gnutls_005fdtls_005fset_005fmtu-1"></a>
<h4 class="subheading">gnutls_dtls_set_mtu</h4>
<a name="gnutls_005fdtls_005fset_005fmtu"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fset_005fmtu"></a>Function: <em>void</em> <strong>gnutls_dtls_set_mtu</strong> <em>(gnutls_session_t <var>session</var>, unsigned int <var>mtu</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p><var>mtu</var>: The maximum transfer unit of the transport
</p>
<p>This function will set the maximum transfer unit of the transport
that DTLS packets are sent over. Note that this should exclude
the IP (or IPv6) and UDP headers. So for DTLS over IPv6 on an
Ethernet device with MTU 1500, the DTLS MTU set with this function
would be 1500 - 40 (IPV6 header) - 8 (UDP header) = 1452.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005fdtls_005fset_005ftimeouts-1"></a>
<h4 class="subheading">gnutls_dtls_set_timeouts</h4>
<a name="gnutls_005fdtls_005fset_005ftimeouts"></a><dl>
<dt><a name="index-gnutls_005fdtls_005fset_005ftimeouts"></a>Function: <em>void</em> <strong>gnutls_dtls_set_timeouts</strong> <em>(gnutls_session_t <var>session</var>, unsigned int <var>retrans_timeout</var>, unsigned int <var>total_timeout</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p><var>retrans_timeout</var>: The time at which a retransmission will occur in milliseconds
</p>
<p><var>total_timeout</var>: The time at which the connection will be aborted, in milliseconds.
</p>
<p>This function will set the timeouts required for the DTLS handshake
protocol. The retransmission timeout is the time after which a
message from the peer is not received, the previous messages will
be retransmitted. The total timeout is the time after which the
handshake will be aborted with <code>GNUTLS_E_TIMEDOUT</code> .
</p>
<p>The DTLS protocol recommends the values of 1 sec and 60 seconds
respectively, and these are the default values.
</p>
<p>To disable retransmissions set a <code>retrans_timeout</code> larger than the <code>total_timeout</code> .
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<a name="gnutls_005frecord_005fget_005fdiscarded-1"></a>
<h4 class="subheading">gnutls_record_get_discarded</h4>
<a name="gnutls_005frecord_005fget_005fdiscarded"></a><dl>
<dt><a name="index-gnutls_005frecord_005fget_005fdiscarded"></a>Function: <em>unsigned int</em> <strong>gnutls_record_get_discarded</strong> <em>(gnutls_session_t <var>session</var>)</em></dt>
<dd><p><var>session</var>: is a <code>gnutls_session_t</code> type.
</p>
<p>Returns the number of discarded packets in a
DTLS connection.
</p>
<p><strong>Returns:</strong> The number of discarded packets.
</p>
<p><strong>Since:</strong> 3.0
</p></dd></dl>
<hr>
<div class="header">
<p>
Next: <a href="X509-certificate-API.html#X509-certificate-API" accesskey="n" rel="next">X509 certificate API</a>, Previous: <a href="Core-TLS-API.html#Core-TLS-API" accesskey="p" rel="prev">Core TLS API</a>, Up: <a href="API-reference.html#API-reference" accesskey="u" rel="up">API reference</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
