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5840c75c | 1 | /* DNS test framework and libresolv redirection. |
d614a753 | 2 | Copyright (C) 2016-2020 Free Software Foundation, Inc. |
5840c75c FW |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
5840c75c FW |
18 | |
19 | #ifndef SUPPORT_RESOLV_TEST_H | |
20 | #define SUPPORT_RESOLV_TEST_H | |
21 | ||
22 | #include <arpa/nameser.h> | |
23 | #include <stdbool.h> | |
24 | #include <sys/cdefs.h> | |
25 | ||
26 | __BEGIN_DECLS | |
27 | ||
e14a2772 FW |
28 | /* Information about EDNS properties of a DNS query. */ |
29 | struct resolv_edns_info | |
30 | { | |
31 | bool active; | |
32 | uint8_t extended_rcode; | |
33 | uint8_t version; | |
34 | uint16_t flags; | |
35 | uint16_t payload_size; | |
36 | }; | |
37 | ||
5840c75c FW |
38 | /* This struct provides context information when the response callback |
39 | specified in struct resolv_redirect_config is invoked. */ | |
40 | struct resolv_response_context | |
41 | { | |
42 | const unsigned char *query_buffer; | |
43 | size_t query_length; | |
44 | int server_index; | |
45 | bool tcp; | |
e14a2772 | 46 | struct resolv_edns_info edns; |
5840c75c FW |
47 | }; |
48 | ||
49 | /* This opaque struct is used to construct responses from within the | |
50 | response callback function. */ | |
51 | struct resolv_response_builder; | |
52 | ||
53 | /* This opaque struct collects information about the resolver testing | |
54 | currently in progress. */ | |
55 | struct resolv_test; | |
56 | ||
57 | enum | |
58 | { | |
59 | /* Maximum number of test servers supported by the framework. */ | |
60 | resolv_max_test_servers = 3, | |
61 | }; | |
62 | ||
63 | /* Configuration settings specific to individual test servers. */ | |
64 | struct resolv_redirect_server_config | |
65 | { | |
66 | bool disable_tcp; /* If true, no TCP server is listening. */ | |
67 | bool disable_udp; /* If true, no UDP server is listening. */ | |
68 | }; | |
69 | ||
70 | /* Instructions for setting up the libresolv redirection. */ | |
71 | struct resolv_redirect_config | |
72 | { | |
73 | /* The response_callback function is called for every incoming DNS | |
74 | packet, over UDP or TCP. It must be specified, the other | |
75 | configuration settings are optional. */ | |
76 | void (*response_callback) (const struct resolv_response_context *, | |
77 | struct resolv_response_builder *, | |
78 | const char *qname, | |
79 | uint16_t qclass, uint16_t qtype); | |
80 | ||
81 | /* Per-server configuration. */ | |
82 | struct resolv_redirect_server_config servers[resolv_max_test_servers]; | |
83 | ||
84 | /* Search path entries. The first entry serves as the default | |
85 | domain name as well. */ | |
86 | const char *search[7]; | |
87 | ||
88 | /* Number of servers to activate in resolv. 0 means the default, | |
89 | resolv_max_test_servers. */ | |
90 | int nscount; | |
91 | ||
92 | /* If true, use a single thread to process all UDP queries. This | |
93 | may results in more predictable ordering of queries and | |
94 | responses. */ | |
95 | bool single_thread_udp; | |
cb3c27e8 FW |
96 | |
97 | /* Do not rewrite the _res variable or change NSS defaults. Use | |
98 | server_address_overrides below to tell the testing framework on | |
99 | which addresses to create the servers. */ | |
100 | bool disable_redirect; | |
101 | ||
102 | /* Use these addresses for creating the DNS servers. The array must | |
103 | have ns_count (or resolv_max_test_servers) sockaddr * elements if | |
104 | not NULL. */ | |
105 | const struct sockaddr *const *server_address_overrides; | |
5840c75c FW |
106 | }; |
107 | ||
108 | /* Configure NSS to use, nss_dns only for aplicable databases, and try | |
109 | to put the process into a network namespace for better isolation. | |
110 | This may have to be called before resolv_test_start, before the | |
111 | process creates any threads. Otherwise, initialization is | |
112 | performed by resolv_test_start implicitly. */ | |
113 | void resolv_test_init (void); | |
114 | ||
115 | /* Initiate resolver testing. This updates the _res variable as | |
116 | needed. As a side effect, NSS is reconfigured to use nss_dns only | |
117 | for aplicable databases, and the process may enter a network | |
118 | namespace for better isolation. */ | |
119 | struct resolv_test *resolv_test_start (struct resolv_redirect_config); | |
120 | ||
121 | /* Call this function at the end of resolver testing, to free | |
122 | resources and report pending errors (if any). */ | |
123 | void resolv_test_end (struct resolv_test *); | |
124 | ||
125 | /* The remaining facilities in this file are used for constructing | |
126 | response packets from the response_callback function. */ | |
127 | ||
128 | /* Special settings for constructing responses from the callback. */ | |
129 | struct resolv_response_flags | |
130 | { | |
131 | /* 4-bit response code to incorporate into the response. */ | |
132 | unsigned char rcode; | |
133 | ||
134 | /* If true, the TC (truncation) flag will be set. */ | |
135 | bool tc; | |
136 | ||
446997ff FW |
137 | /* If true, the AD (authenticated data) flag will be set. */ |
138 | bool ad; | |
139 | ||
5840c75c FW |
140 | /* Initial section count values. Can be used to artificially |
141 | increase the counts, for malformed packet testing.*/ | |
142 | unsigned short qdcount; | |
143 | unsigned short ancount; | |
144 | unsigned short nscount; | |
145 | unsigned short adcount; | |
146 | }; | |
147 | ||
148 | /* Begin a new response with the requested flags. Must be called | |
149 | first. */ | |
150 | void resolv_response_init (struct resolv_response_builder *, | |
151 | struct resolv_response_flags); | |
152 | ||
153 | /* Switches to the section in the response packet. Only forward | |
154 | movement is supported. */ | |
155 | void resolv_response_section (struct resolv_response_builder *, ns_sect); | |
156 | ||
157 | /* Add a question record to the question section. */ | |
158 | void resolv_response_add_question (struct resolv_response_builder *, | |
159 | const char *name, uint16_t class, | |
160 | uint16_t type); | |
161 | /* Starts a new resource record with the specified owner name, class, | |
162 | type, and TTL. Data is supplied with resolv_response_add_data or | |
163 | resolv_response_add_name. */ | |
164 | void resolv_response_open_record (struct resolv_response_builder *, | |
165 | const char *name, uint16_t class, | |
166 | uint16_t type, uint32_t ttl); | |
167 | ||
168 | /* Add unstructed bytes to the RDATA part of a resource record. */ | |
169 | void resolv_response_add_data (struct resolv_response_builder *, | |
170 | const void *, size_t); | |
171 | ||
172 | /* Add a compressed domain name to the RDATA part of a resource | |
173 | record. */ | |
174 | void resolv_response_add_name (struct resolv_response_builder *, | |
175 | const char *name); | |
176 | ||
177 | /* Mark the end of the constructed record. Must be called last. */ | |
178 | void resolv_response_close_record (struct resolv_response_builder *); | |
179 | ||
180 | /* Drop this query packet (that is, do not send a response, not even | |
181 | an empty packet). */ | |
182 | void resolv_response_drop (struct resolv_response_builder *); | |
183 | ||
184 | /* In TCP mode, close the connection after this packet (if a response | |
185 | is sent). */ | |
186 | void resolv_response_close (struct resolv_response_builder *); | |
187 | ||
188 | /* The size of the response packet built so far. */ | |
189 | size_t resolv_response_length (const struct resolv_response_builder *); | |
190 | ||
191 | __END_DECLS | |
192 | ||
193 | #endif /* SUPPORT_RESOLV_TEST_H */ |