1 /*
2  *  Copyright (c) 2023, The OpenThread Authors.
3  *  All rights reserved.
4  *
5  *  Redistribution and use in source and binary forms, with or without
6  *  modification, are permitted provided that the following conditions are met:
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8  *     notice, this list of conditions and the following disclaimer.
9  *  2. Redistributions in binary form must reproduce the above copyright
10  *     notice, this list of conditions and the following disclaimer in the
11  *     documentation and/or other materials provided with the distribution.
12  *  3. Neither the name of the copyright holder nor the
13  *     names of its contributors may be used to endorse or promote products
14  *     derived from this software without specific prior written permission.
15  *
16  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17  *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
20  *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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25  *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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27  */
28 
29 #ifndef OT_POSIX_PLATFORM_RESOLVER_HPP_
30 #define OT_POSIX_PLATFORM_RESOLVER_HPP_
31 
32 #include <openthread/openthread-system.h>
33 #include <openthread/platform/dns.h>
34 
35 #include <arpa/inet.h>
36 #include <sys/select.h>
37 
38 #include "logger.hpp"
39 
40 #if OPENTHREAD_CONFIG_DNS_UPSTREAM_QUERY_ENABLE
41 
42 namespace ot {
43 namespace Posix {
44 
45 class Resolver : public Logger<Resolver>
46 {
47 public:
48     static const char kLogModuleName[]; ///< Module name used for logging.
49 
50     constexpr static ssize_t kMaxDnsMessageSize           = 512;
51     constexpr static ssize_t kMaxUpstreamTransactionCount = 16;
52     constexpr static ssize_t kMaxUpstreamServerCount      = 3;
53 
54     /**
55      * Initialize the upstream DNS resolver.
56      *
57      */
58     void Init(void);
59 
60     /**
61      * Sends the query to the upstream.
62      *
63      * @param[in] aTxn   A pointer to the OpenThread upstream DNS query transaction.
64      * @param[in] aQuery A pointer to a message for the payload of the DNS query.
65      *
66      */
67     void Query(otPlatDnsUpstreamQuery *aTxn, const otMessage *aQuery);
68 
69     /**
70      * Cancels a upstream DNS query transaction.
71      *
72      * @param[in] aTxn   A pointer to the OpenThread upstream DNS query transaction.
73      *
74      */
75     void Cancel(otPlatDnsUpstreamQuery *aTxn);
76 
77     /**
78      * Updates the file descriptor sets with file descriptors used by the radio driver.
79      *
80      * @param[in,out]  aContext  The mainloop context.
81      *
82      */
83     void UpdateFdSet(otSysMainloopContext &aContext);
84 
85     /**
86      * Handles the result of select.
87      *
88      * @param[in]  aContext  The mainloop context.
89      *
90      */
91     void Process(const otSysMainloopContext &aContext);
92 
93     /**
94      * Sets whether to retrieve upstream DNS servers from "resolv.conf".
95      *
96      * @param[in] aEnabled  TRUE if enable retrieving upstream DNS servers from "resolv.conf", FALSE otherwise.
97      *
98      */
SetResolvConfEnabled(bool aEnabled)99     void SetResolvConfEnabled(bool aEnabled) { mIsResolvConfEnabled = aEnabled; }
100 
101     /**
102      * Sets the upstream DNS servers.
103      *
104      * @param[in] aUpstreamDnsServers  A pointer to the list of upstream DNS server addresses. Each address could be an
105      *                                 IPv6 address or an IPv4-mapped IPv6 address.
106      * @param[in] aNumServers          The number of upstream DNS servers.
107      *
108      */
109     void SetUpstreamDnsServers(const otIp6Address *aUpstreamDnsServers, int aNumServers);
110 
111 private:
112     static constexpr uint64_t kDnsServerListNullCacheTimeoutMs = 1 * 60 * 1000;  // 1 minute
113     static constexpr uint64_t kDnsServerListCacheTimeoutMs     = 10 * 60 * 1000; // 10 minutes
114 
115     struct Transaction
116     {
117         otPlatDnsUpstreamQuery *mThreadTxn;
118         int                     mUdpFd;
119     };
120 
121     Transaction *GetTransaction(int aFd);
122     Transaction *GetTransaction(otPlatDnsUpstreamQuery *aThreadTxn);
123     Transaction *AllocateTransaction(otPlatDnsUpstreamQuery *aThreadTxn);
124 
125     void ForwardResponse(Transaction *aTxn);
126     void CloseTransaction(Transaction *aTxn);
127     void FinishTransaction(int aFd);
128     void TryRefreshDnsServerList(void);
129     void LoadDnsServerListFromConf(void);
130 
131     bool      mIsResolvConfEnabled    = true;
132     int       mUpstreamDnsServerCount = 0;
133     in_addr_t mUpstreamDnsServerList[kMaxUpstreamServerCount];
134     uint64_t  mUpstreamDnsServerListFreshness = 0;
135 
136     Transaction mUpstreamTransaction[kMaxUpstreamTransactionCount];
137 };
138 
139 } // namespace Posix
140 } // namespace ot
141 
142 #endif // OPENTHREAD_CONFIG_DNS_UPSTREAM_QUERY_ENABLE
143 
144 #endif // OT_POSIX_PLATFORM_RESOLVER_HPP_
145