225 lines
8.1 KiB
C
225 lines
8.1 KiB
C
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/* DNS test framework and libresolv redirection.
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Copyright (C) 2016-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef SUPPORT_RESOLV_TEST_H
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#define SUPPORT_RESOLV_TEST_H
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#include <arpa/nameser.h>
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#include <stdbool.h>
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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/* Information about EDNS properties of a DNS query. */
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struct resolv_edns_info
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{
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bool active;
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uint8_t extended_rcode;
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uint8_t version;
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uint16_t flags;
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uint16_t payload_size;
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};
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/* This opaque struct collects information about the resolver testing
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currently in progress. */
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struct resolv_test;
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/* This struct provides context information when the response callback
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specified in struct resolv_redirect_config is invoked. */
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struct resolv_response_context
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{
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struct resolv_test *test;
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void *client_address;
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size_t client_address_length;
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unsigned char *query_buffer;
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size_t query_length;
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int server_index;
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bool tcp;
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struct resolv_edns_info edns;
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};
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/* Produces a deep copy of the context. */
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struct resolv_response_context *
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resolv_response_context_duplicate (const struct resolv_response_context *);
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/* Frees the copy. For the context passed to the response function,
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this happens implicitly. */
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void resolv_response_context_free (struct resolv_response_context *);
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/* This opaque struct is used to construct responses from within the
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response callback function. */
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struct resolv_response_builder;
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enum
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{
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/* Maximum number of test servers supported by the framework. */
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resolv_max_test_servers = 3,
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};
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/* Configuration settings specific to individual test servers. */
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struct resolv_redirect_server_config
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{
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bool disable_tcp; /* If true, no TCP server is listening. */
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bool disable_udp; /* If true, no UDP server is listening. */
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};
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/* Instructions for setting up the libresolv redirection. */
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struct resolv_redirect_config
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{
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/* The response_callback function is called for every incoming DNS
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packet, over UDP or TCP. It must be specified, the other
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configuration settings are optional. */
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void (*response_callback) (const struct resolv_response_context *,
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struct resolv_response_builder *,
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const char *qname,
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uint16_t qclass, uint16_t qtype);
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/* Per-server configuration. */
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struct resolv_redirect_server_config servers[resolv_max_test_servers];
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/* Search path entries. The first entry serves as the default
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domain name as well. */
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const char *search[7];
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/* Number of servers to activate in resolv. 0 means the default,
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resolv_max_test_servers. */
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int nscount;
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/* If true, use a single thread to process all UDP queries. This
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may results in more predictable ordering of queries and
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responses. */
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bool single_thread_udp;
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/* Do not rewrite the _res variable or change NSS defaults. Use
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server_address_overrides below to tell the testing framework on
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which addresses to create the servers. */
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bool disable_redirect;
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/* Use these addresses for creating the DNS servers. The array must
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have ns_count (or resolv_max_test_servers) sockaddr * elements if
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not NULL. */
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const struct sockaddr *const *server_address_overrides;
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};
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/* Configure NSS to use, nss_dns only for aplicable databases, and try
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to put the process into a network namespace for better isolation.
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This may have to be called before resolv_test_start, before the
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process creates any threads. Otherwise, initialization is
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performed by resolv_test_start implicitly. */
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void resolv_test_init (void);
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/* Initiate resolver testing. This updates the _res variable as
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needed. As a side effect, NSS is reconfigured to use nss_dns only
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for aplicable databases, and the process may enter a network
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namespace for better isolation. */
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struct resolv_test *resolv_test_start (struct resolv_redirect_config);
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/* Call this function at the end of resolver testing, to free
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resources and report pending errors (if any). */
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void resolv_test_end (struct resolv_test *);
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/* The remaining facilities in this file are used for constructing
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response packets from the response_callback function. */
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/* Special settings for constructing responses from the callback. */
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struct resolv_response_flags
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{
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/* 4-bit response code to incorporate into the response. */
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unsigned char rcode;
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/* If true, the TC (truncation) flag will be set. */
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bool tc;
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/* If true, the AD (authenticated data) flag will be set. */
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bool ad;
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/* If true, do not set the RA (recursion available) flag in the
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response. */
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bool clear_ra;
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/* Initial section count values. Can be used to artificially
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increase the counts, for malformed packet testing.*/
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unsigned short qdcount;
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unsigned short ancount;
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unsigned short nscount;
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unsigned short adcount;
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};
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/* Begin a new response with the requested flags. Must be called
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first. */
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void resolv_response_init (struct resolv_response_builder *,
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struct resolv_response_flags);
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/* Switches to the section in the response packet. Only forward
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movement is supported. */
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void resolv_response_section (struct resolv_response_builder *, ns_sect);
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/* Add a question record to the question section. */
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void resolv_response_add_question (struct resolv_response_builder *,
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const char *name, uint16_t class,
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uint16_t type);
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/* Starts a new resource record with the specified owner name, class,
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type, and TTL. Data is supplied with resolv_response_add_data or
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resolv_response_add_name. */
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void resolv_response_open_record (struct resolv_response_builder *,
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const char *name, uint16_t class,
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uint16_t type, uint32_t ttl);
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/* Add unstructed bytes to the RDATA part of a resource record. */
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void resolv_response_add_data (struct resolv_response_builder *,
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const void *, size_t);
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/* Add a compressed domain name to the RDATA part of a resource
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record. */
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void resolv_response_add_name (struct resolv_response_builder *,
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const char *name);
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/* Mark the end of the constructed record. Must be called last. */
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void resolv_response_close_record (struct resolv_response_builder *);
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/* Drop this query packet (that is, do not send a response, not even
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an empty packet). */
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void resolv_response_drop (struct resolv_response_builder *);
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/* In TCP mode, close the connection after this packet (if a response
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is sent). */
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void resolv_response_close (struct resolv_response_builder *);
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/* The size of the response packet built so far. */
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size_t resolv_response_length (const struct resolv_response_builder *);
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/* Allocates a response builder tied to a specific query packet,
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starting at QUERY_BUFFER, containing QUERY_LENGTH bytes. */
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struct resolv_response_builder *
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resolv_response_builder_allocate (const unsigned char *query_buffer,
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size_t query_length);
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/* Deallocates a response buffer. */
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void resolv_response_builder_free (struct resolv_response_builder *);
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/* Sends a UDP response using a specific context. This can be used to
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reorder or duplicate responses, along with
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resolv_response_context_duplicate and
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response_builder_allocate. */
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void resolv_response_send_udp (const struct resolv_response_context *,
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struct resolv_response_builder *);
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__END_DECLS
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#endif /* SUPPORT_RESOLV_TEST_H */
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