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sntp_opts.h
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1 /**
2  * @file
3  * SNTP client options list
4  */
5 
6 /*
7  * Copyright (c) 2007-2009 Frédéric Bernon, Simon Goldschmidt
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without modification,
11  * are permitted provided that the following conditions are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright notice,
14  * this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright notice,
16  * this list of conditions and the following disclaimer in the documentation
17  * and/or other materials provided with the distribution.
18  * 3. The name of the author may not be used to endorse or promote products
19  * derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
22  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
24  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
26  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
29  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
30  * OF SUCH DAMAGE.
31  *
32  * This file is part of the lwIP TCP/IP stack.
33  *
34  * Author: Frédéric Bernon, Simon Goldschmidt
35  *
36  */
37 #ifndef LWIP_HDR_APPS_SNTP_OPTS_H
38 #define LWIP_HDR_APPS_SNTP_OPTS_H
39 
40 #include "lwip/opt.h"
41 #include "lwip/prot/iana.h"
42 
43 /**
44  * @defgroup sntp_opts Options
45  * @ingroup sntp
46  * @{
47  */
48 
49 /** SNTP macro to change system time in seconds
50  * Define SNTP_SET_SYSTEM_TIME_US(sec, us) to set the time in microseconds
51  * instead of this one if you need the additional precision. Alternatively,
52  * define SNTP_SET_SYSTEM_TIME_NTP(sec, frac) in order to work with native
53  * NTP timestamps instead.
54  */
55 #if !defined SNTP_SET_SYSTEM_TIME || defined __DOXYGEN__
56 #define SNTP_SET_SYSTEM_TIME(sec) LWIP_UNUSED_ARG(sec)
57 #endif
58 
59 /** The maximum number of SNTP servers that can be set */
60 #if !defined SNTP_MAX_SERVERS || defined __DOXYGEN__
61 #define SNTP_MAX_SERVERS LWIP_DHCP_MAX_NTP_SERVERS
62 #endif
63 
64 /** Set this to 1 to implement the callback function called by dhcp when
65  * NTP servers are received. */
66 #if !defined SNTP_GET_SERVERS_FROM_DHCP || defined __DOXYGEN__
67 #define SNTP_GET_SERVERS_FROM_DHCP LWIP_DHCP_GET_NTP_SRV
68 #endif
69 
70 /** Set this to 1 to support DNS names (or IP address strings) to set sntp servers
71  * One server address/name can be defined as default if SNTP_SERVER_DNS == 1:
72  * \#define SNTP_SERVER_ADDRESS "pool.ntp.org"
73  */
74 #if !defined SNTP_SERVER_DNS || defined __DOXYGEN__
75 #define SNTP_SERVER_DNS 0
76 #endif
77 
78 /**
79  * SNTP_DEBUG: Enable debugging for SNTP.
80  */
81 #if !defined SNTP_DEBUG || defined __DOXYGEN__
82 #define SNTP_DEBUG LWIP_DBG_OFF
83 #endif
84 
85 /** SNTP server port */
86 #if !defined SNTP_PORT || defined __DOXYGEN__
87 #define SNTP_PORT LWIP_IANA_PORT_SNTP
88 #endif
89 
90 /** Sanity check:
91  * Define this to
92  * - 0 to turn off sanity checks (default; smaller code)
93  * - >= 1 to check address and port of the response packet to ensure the
94  * response comes from the server we sent the request to.
95  * - >= 2 to check returned Originate Timestamp against Transmit Timestamp
96  * sent to the server (to ensure response to older request).
97  * - >= 3 @todo: discard reply if any of the VN, Stratum, or Transmit Timestamp
98  * fields is 0 or the Mode field is not 4 (unicast) or 5 (broadcast).
99  * - >= 4 @todo: to check that the Root Delay and Root Dispersion fields are each
100  * greater than or equal to 0 and less than infinity, where infinity is
101  * currently a cozy number like one second. This check avoids using a
102  * server whose synchronization source has expired for a very long time.
103  */
104 #if !defined SNTP_CHECK_RESPONSE || defined __DOXYGEN__
105 #define SNTP_CHECK_RESPONSE 0
106 #endif
107 
108 /** Enable round-trip delay compensation.
109  * Compensate for the round-trip delay by calculating the clock offset from
110  * the originate, receive, transmit and destination timestamps, as per RFC.
111  *
112  * The calculation requires compiler support for 64-bit integers. Also, either
113  * SNTP_SET_SYSTEM_TIME_US or SNTP_SET_SYSTEM_TIME_NTP has to be implemented
114  * for setting the system clock with sub-second precision. Likewise, either
115  * SNTP_GET_SYSTEM_TIME or SNTP_GET_SYSTEM_TIME_NTP needs to be implemented
116  * with sub-second precision.
117  *
118  * Although not strictly required, it makes sense to combine this option with
119  * SNTP_CHECK_RESPONSE >= 2 for sanity-checking of the received timestamps.
120  * Also, in order for the round-trip calculation to work, the difference
121  * between the local clock and the NTP server clock must not be larger than
122  * about 34 years. If that limit is exceeded, the implementation will fall back
123  * to setting the clock without compensation. In order to ensure that the local
124  * clock is always within the permitted range for compensation, even at first
125  * try, it may be necessary to store at least the current year in non-volatile
126  * memory.
127  */
128 #if !defined SNTP_COMP_ROUNDTRIP || defined __DOXYGEN__
129 #define SNTP_COMP_ROUNDTRIP 0
130 #endif
131 
132 /** According to the RFC, this shall be a random delay
133  * between 1 and 5 minutes (in milliseconds) to prevent load peaks.
134  * This can be defined to a random generation function,
135  * which must return the delay in milliseconds as u32_t.
136  * Turned off by default.
137  */
138 #if !defined SNTP_STARTUP_DELAY || defined __DOXYGEN__
139 #ifdef LWIP_RAND
140 #define SNTP_STARTUP_DELAY 1
141 #else
142 #define SNTP_STARTUP_DELAY 0
143 #endif
144 #endif
145 
146 /** If you want the startup delay to be a function, define this
147  * to a function (including the brackets) and define SNTP_STARTUP_DELAY to 1.
148  */
149 #if !defined SNTP_STARTUP_DELAY_FUNC || defined __DOXYGEN__
150 #define SNTP_STARTUP_DELAY_FUNC (LWIP_RAND() % 5000)
151 #endif
152 
153 /** SNTP receive timeout - in milliseconds
154  * Also used as retry timeout - this shouldn't be too low.
155  * Default is 15 seconds. Must not be beolw 15 seconds by specification (i.e. 15000)
156  */
157 #if !defined SNTP_RECV_TIMEOUT || defined __DOXYGEN__
158 #define SNTP_RECV_TIMEOUT 15000
159 #endif
160 
161 /** SNTP update delay - in milliseconds
162  * Default is 1 hour. Must not be beolw 60 seconds by specification (i.e. 60000)
163  */
164 #if !defined SNTP_UPDATE_DELAY || defined __DOXYGEN__
165 #define SNTP_UPDATE_DELAY 3600000
166 #endif
167 
168 /** SNTP macro to get system time, used with SNTP_CHECK_RESPONSE >= 2
169  * to send in request and compare in response. Also used for round-trip
170  * delay compensation if SNTP_COMP_ROUNDTRIP != 0.
171  * Alternatively, define SNTP_GET_SYSTEM_TIME_NTP(sec, frac) in order to
172  * work with native NTP timestamps instead.
173  */
174 #if !defined SNTP_GET_SYSTEM_TIME || defined __DOXYGEN__
175 #define SNTP_GET_SYSTEM_TIME(sec, us) do { (sec) = 0; (us) = 0; } while(0)
176 #endif
177 
178 /** Default retry timeout (in milliseconds) if the response
179  * received is invalid.
180  * This is doubled with each retry until SNTP_RETRY_TIMEOUT_MAX is reached.
181  */
182 #if !defined SNTP_RETRY_TIMEOUT || defined __DOXYGEN__
183 #define SNTP_RETRY_TIMEOUT SNTP_RECV_TIMEOUT
184 #endif
185 
186 /** Maximum retry timeout (in milliseconds). */
187 #if !defined SNTP_RETRY_TIMEOUT_MAX || defined __DOXYGEN__
188 #define SNTP_RETRY_TIMEOUT_MAX (SNTP_RETRY_TIMEOUT * 10)
189 #endif
190 
191 /** Increase retry timeout with every retry sent
192  * Default is on to conform to RFC.
193  */
194 #if !defined SNTP_RETRY_TIMEOUT_EXP || defined __DOXYGEN__
195 #define SNTP_RETRY_TIMEOUT_EXP 1
196 #endif
197 
198 /** Keep a reachability shift register per server
199  * Default is on to conform to RFC.
200  */
201 #if !defined SNTP_MONITOR_SERVER_REACHABILITY || defined __DOXYGEN__
202 #define SNTP_MONITOR_SERVER_REACHABILITY 1
203 #endif
204 
205 /**
206  * @}
207  */
208 
209 #endif /* LWIP_HDR_APPS_SNTP_OPTS_H */
opt.h
lwIP Options Configuration
iana.h
IANA assigned numbers (RFC 1700 and successors)
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