1/* DNS test framework and libresolv redirection.
2 Copyright (C) 2016-2017 Free Software Foundation, Inc.
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
17 <http://www.gnu.org/licenses/>. */
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
28/* Information about EDNS properties of a DNS query. */
29struct 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
38/* This struct provides context information when the response callback
39 specified in struct resolv_redirect_config is invoked. */
40struct resolv_response_context
41{
42 const unsigned char *query_buffer;
43 size_t query_length;
44 int server_index;
45 bool tcp;
46 struct resolv_edns_info edns;
47};
48
49/* This opaque struct is used to construct responses from within the
50 response callback function. */
51struct resolv_response_builder;
52
53/* This opaque struct collects information about the resolver testing
54 currently in progress. */
55struct resolv_test;
56
57enum
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. */
64struct 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. */
71struct 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;
96};
97
98/* Configure NSS to use, nss_dns only for aplicable databases, and try
99 to put the process into a network namespace for better isolation.
100 This may have to be called before resolv_test_start, before the
101 process creates any threads. Otherwise, initialization is
102 performed by resolv_test_start implicitly. */
103void resolv_test_init (void);
104
105/* Initiate resolver testing. This updates the _res variable as
106 needed. As a side effect, NSS is reconfigured to use nss_dns only
107 for aplicable databases, and the process may enter a network
108 namespace for better isolation. */
109struct resolv_test *resolv_test_start (struct resolv_redirect_config);
110
111/* Call this function at the end of resolver testing, to free
112 resources and report pending errors (if any). */
113void resolv_test_end (struct resolv_test *);
114
115/* The remaining facilities in this file are used for constructing
116 response packets from the response_callback function. */
117
118/* Special settings for constructing responses from the callback. */
119struct resolv_response_flags
120{
121 /* 4-bit response code to incorporate into the response. */
122 unsigned char rcode;
123
124 /* If true, the TC (truncation) flag will be set. */
125 bool tc;
126
127 /* Initial section count values. Can be used to artificially
128 increase the counts, for malformed packet testing.*/
129 unsigned short qdcount;
130 unsigned short ancount;
131 unsigned short nscount;
132 unsigned short adcount;
133};
134
135/* Begin a new response with the requested flags. Must be called
136 first. */
137void resolv_response_init (struct resolv_response_builder *,
138 struct resolv_response_flags);
139
140/* Switches to the section in the response packet. Only forward
141 movement is supported. */
142void resolv_response_section (struct resolv_response_builder *, ns_sect);
143
144/* Add a question record to the question section. */
145void resolv_response_add_question (struct resolv_response_builder *,
146 const char *name, uint16_t class,
147 uint16_t type);
148/* Starts a new resource record with the specified owner name, class,
149 type, and TTL. Data is supplied with resolv_response_add_data or
150 resolv_response_add_name. */
151void resolv_response_open_record (struct resolv_response_builder *,
152 const char *name, uint16_t class,
153 uint16_t type, uint32_t ttl);
154
155/* Add unstructed bytes to the RDATA part of a resource record. */
156void resolv_response_add_data (struct resolv_response_builder *,
157 const void *, size_t);
158
159/* Add a compressed domain name to the RDATA part of a resource
160 record. */
161void resolv_response_add_name (struct resolv_response_builder *,
162 const char *name);
163
164/* Mark the end of the constructed record. Must be called last. */
165void resolv_response_close_record (struct resolv_response_builder *);
166
167/* Drop this query packet (that is, do not send a response, not even
168 an empty packet). */
169void resolv_response_drop (struct resolv_response_builder *);
170
171/* In TCP mode, close the connection after this packet (if a response
172 is sent). */
173void resolv_response_close (struct resolv_response_builder *);
174
175/* The size of the response packet built so far. */
176size_t resolv_response_length (const struct resolv_response_builder *);
177
178__END_DECLS
179
180#endif /* SUPPORT_RESOLV_TEST_H */
181