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Diffstat (limited to 'support/resolv_test.h')
| -rw-r--r-- | support/resolv_test.h | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/support/resolv_test.h b/support/resolv_test.h new file mode 100644 index 0000000000..6498751569 --- /dev/null +++ b/support/resolv_test.h @@ -0,0 +1,180 @@ +/* DNS test framework and libresolv redirection. + Copyright (C) 2016-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#ifndef SUPPORT_RESOLV_TEST_H +#define SUPPORT_RESOLV_TEST_H + +#include <arpa/nameser.h> +#include <stdbool.h> +#include <sys/cdefs.h> + +__BEGIN_DECLS + +/* Information about EDNS properties of a DNS query. */ +struct resolv_edns_info +{ + bool active; + uint8_t extended_rcode; + uint8_t version; + uint16_t flags; + uint16_t payload_size; +}; + +/* This struct provides context information when the response callback + specified in struct resolv_redirect_config is invoked. */ +struct resolv_response_context +{ + const unsigned char *query_buffer; + size_t query_length; + int server_index; + bool tcp; + struct resolv_edns_info edns; +}; + +/* This opaque struct is used to construct responses from within the + response callback function. */ +struct resolv_response_builder; + +/* This opaque struct collects information about the resolver testing + currently in progress. */ +struct resolv_test; + +enum + { + /* Maximum number of test servers supported by the framework. */ + resolv_max_test_servers = 3, + }; + +/* Configuration settings specific to individual test servers. */ +struct resolv_redirect_server_config +{ + bool disable_tcp; /* If true, no TCP server is listening. */ + bool disable_udp; /* If true, no UDP server is listening. */ +}; + +/* Instructions for setting up the libresolv redirection. */ +struct resolv_redirect_config +{ + /* The response_callback function is called for every incoming DNS + packet, over UDP or TCP. It must be specified, the other + configuration settings are optional. */ + void (*response_callback) (const struct resolv_response_context *, + struct resolv_response_builder *, + const char *qname, + uint16_t qclass, uint16_t qtype); + + /* Per-server configuration. */ + struct resolv_redirect_server_config servers[resolv_max_test_servers]; + + /* Search path entries. The first entry serves as the default + domain name as well. */ + const char *search[7]; + + /* Number of servers to activate in resolv. 0 means the default, + resolv_max_test_servers. */ + int nscount; + + /* If true, use a single thread to process all UDP queries. This + may results in more predictable ordering of queries and + responses. */ + bool single_thread_udp; +}; + +/* Configure NSS to use, nss_dns only for aplicable databases, and try + to put the process into a network namespace for better isolation. + This may have to be called before resolv_test_start, before the + process creates any threads. Otherwise, initialization is + performed by resolv_test_start implicitly. */ +void resolv_test_init (void); + +/* Initiate resolver testing. This updates the _res variable as + needed. As a side effect, NSS is reconfigured to use nss_dns only + for aplicable databases, and the process may enter a network + namespace for better isolation. */ +struct resolv_test *resolv_test_start (struct resolv_redirect_config); + +/* Call this function at the end of resolver testing, to free + resources and report pending errors (if any). */ +void resolv_test_end (struct resolv_test *); + +/* The remaining facilities in this file are used for constructing + response packets from the response_callback function. */ + +/* Special settings for constructing responses from the callback. */ +struct resolv_response_flags +{ + /* 4-bit response code to incorporate into the response. */ + unsigned char rcode; + + /* If true, the TC (truncation) flag will be set. */ + bool tc; + + /* Initial section count values. Can be used to artificially + increase the counts, for malformed packet testing.*/ + unsigned short qdcount; + unsigned short ancount; + unsigned short nscount; + unsigned short adcount; +}; + +/* Begin a new response with the requested flags. Must be called + first. */ +void resolv_response_init (struct resolv_response_builder *, + struct resolv_response_flags); + +/* Switches to the section in the response packet. Only forward + movement is supported. */ +void resolv_response_section (struct resolv_response_builder *, ns_sect); + +/* Add a question record to the question section. */ +void resolv_response_add_question (struct resolv_response_builder *, + const char *name, uint16_t class, + uint16_t type); +/* Starts a new resource record with the specified owner name, class, + type, and TTL. Data is supplied with resolv_response_add_data or + resolv_response_add_name. */ +void resolv_response_open_record (struct resolv_response_builder *, + const char *name, uint16_t class, + uint16_t type, uint32_t ttl); + +/* Add unstructed bytes to the RDATA part of a resource record. */ +void resolv_response_add_data (struct resolv_response_builder *, + const void *, size_t); + +/* Add a compressed domain name to the RDATA part of a resource + record. */ +void resolv_response_add_name (struct resolv_response_builder *, + const char *name); + +/* Mark the end of the constructed record. Must be called last. */ +void resolv_response_close_record (struct resolv_response_builder *); + +/* Drop this query packet (that is, do not send a response, not even + an empty packet). */ +void resolv_response_drop (struct resolv_response_builder *); + +/* In TCP mode, close the connection after this packet (if a response + is sent). */ +void resolv_response_close (struct resolv_response_builder *); + +/* The size of the response packet built so far. */ +size_t resolv_response_length (const struct resolv_response_builder *); + +__END_DECLS + +#endif /* SUPPORT_RESOLV_TEST_H */ |