resolv: Add beginnings of a libresolv test suite

1 files changed, 169 insertions, 0 deletions

diff --git a/support/resolv_test.h b/support/resolv_test.h
new file mode 100644
index 0000000000..39dd625a20
--- /dev/null
+++ b/support/resolv_test.h
@@ -0,0 +1,169 @@
+/* DNS test framework and libresolv redirection.
+   Copyright (C) 2016 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
+
+/* 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;
+};
+
+/* 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 */