/* Test parallel queries with transaction ID collisions.

   Copyright (C) 2020 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

   <https://www.gnu.org/licenses/>.  */

#include <arpa/nameser.h>

#include <array_length.h>

#include <resolv-internal.h>

#include <resolv_context.h>

#include <stdbool.h>

#include <stdio.h>

#include <string.h>

#include <support/check.h>

#include <support/check_nss.h>

#include <support/resolv_test.h>

#include <support/support.h>

#include <support/test-driver.h>

/* Result of parsing a DNS question name.

   A question name has the form reorder-N-M-rcode-C.example.net, where

   N and M are either 0 and 1, corresponding to the reorder member,

   and C is a number that will be stored in the rcode field.

   Also see parse_qname below.  */

struct parsed_qname

{

  /* The DNS response code requested from the first server.  The

     second server always responds with RCODE zero.  */

  int rcode;

  /* Indicates whether to perform reordering in the responses from the

     respective server.  */

  bool reorder[2];

};

/* Fills *PARSED based on QNAME.  */

static void

parse_qname (struct parsed_qname *parsed, const char *qname)

{

  int reorder0;

  int reorder1;

  int rcode;

  char *suffix;

  if (sscanf (qname, "reorder-%d-%d.rcode-%d.%ms",

              &reorder0, &reorder1, &rcode, &suffix) == 4)

    {

      if (reorder0 != 0)

        TEST_COMPARE (reorder0, 1);

      if (reorder1 != 0)

        TEST_COMPARE (reorder1, 1);

      TEST_VERIFY (rcode >= 0 && rcode <= 15);

      TEST_COMPARE_STRING (suffix, "example.net");

      free (suffix);

      parsed->rcode = rcode;

      parsed->reorder[0] = reorder0;

      parsed->reorder[1] = reorder1;

    }

  else

    FAIL_EXIT1 ("unexpected query: %s", qname);

}

/* Used to construct a response. The first server responds with an

   error, the second server succeeds.  */

static void

build_response (const struct resolv_response_context *ctx,

                struct resolv_response_builder *b,

                const char *qname, uint16_t qclass, uint16_t qtype)

{

  struct parsed_qname parsed;

  parse_qname (&parsed, qname);

  switch (ctx->server_index)

    {

    case 0:

      {

        struct resolv_response_flags flags = { 0 };

        if (parsed.rcode == 0)

          /* Simulate a delegation in case a NODATA (RCODE zero)

             response is requested.  */

          flags.clear_ra = true;

        else

          flags.rcode = parsed.rcode;

        resolv_response_init (b, flags);

        resolv_response_add_question (b, qname, qclass, qtype);

      }

      break;

    case 1:

      {

        struct resolv_response_flags flags = { 0, };

        resolv_response_init (b, flags);

        resolv_response_add_question (b, qname, qclass, qtype);

        resolv_response_section (b, ns_s_an);

        resolv_response_open_record (b, qname, qclass, qtype, 0);

        if (qtype == T_A)

          {

            char ipv4[4] = { 192, 0, 2, 1 };

            resolv_response_add_data (b, &ipv4, sizeof (ipv4));

          }

        else

          {

            char ipv6[16]

              = { 0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 };

            resolv_response_add_data (b, &ipv6, sizeof (ipv6));

          }

        resolv_response_close_record (b);

      }

      break;

    }

}

/* Used to reorder responses.  */

struct resolv_response_context *previous_query;

/* Used to keep track of the queries received.  */

static int previous_server_index = -1;

static uint16_t previous_qtype;

/* For each server, buffer the first query and then send both answers

   to the second query, reordered if requested.  */

static void

response (const struct resolv_response_context *ctx,

          struct resolv_response_builder *b,

          const char *qname, uint16_t qclass, uint16_t qtype)

{

  TEST_VERIFY (qtype == T_A || qtype == T_AAAA);

  if (ctx->server_index != 0)

    TEST_COMPARE (ctx->server_index, 1);

  struct parsed_qname parsed;

  parse_qname (&parsed, qname);

  if (previous_query == NULL)

    {

      /* No buffered query.  Record this query and do not send a

         response.  */

      TEST_COMPARE (previous_qtype, 0);

      previous_query = resolv_response_context_duplicate (ctx);

      previous_qtype = qtype;

      resolv_response_drop (b);

      previous_server_index = ctx->server_index;

      if (test_verbose)

        printf ("info: buffering first query for: %s\n", qname);

    }

  else

    {

      TEST_VERIFY (previous_query != 0);

      TEST_COMPARE (ctx->server_index, previous_server_index);

      TEST_VERIFY (previous_qtype != qtype); /* Not a duplicate.  */

      /* If reordering, send a response for this query explicitly, and

         then skip the implicit send.  */

      if (parsed.reorder[ctx->server_index])

        {

          if (test_verbose)

            printf ("info: sending reordered second response for: %s\n",

                    qname);

          build_response (ctx, b, qname, qclass, qtype);

          resolv_response_send_udp (ctx, b);

          resolv_response_drop (b);

        }

      /* Build a response for the previous query and send it, thus

         reordering the two responses.  */

      {

        if (test_verbose)

          printf ("info: sending first response for: %s\n", qname);

        struct resolv_response_builder *btmp

          = resolv_response_builder_allocate (previous_query->query_buffer,

                                              previous_query->query_length);

        build_response (ctx, btmp, qname, qclass, previous_qtype);

        resolv_response_send_udp (ctx, btmp);

        resolv_response_builder_free (btmp);

      }

      /* If not reordering, send the reply as usual.  */

      if (!parsed.reorder[ctx->server_index])

        {

          if (test_verbose)

            printf ("info: sending non-reordered second response for: %s\n",

                    qname);

          build_response (ctx, b, qname, qclass, qtype);

        }

      /* Unbuffer the response and prepare for the next query.  */

      resolv_response_context_free (previous_query);

      previous_query = NULL;

      previous_qtype = 0;

      previous_server_index = -1;

    }

}

/* Runs a query for QNAME and checks for the expected reply.  See

   struct parsed_qname for the expected format for QNAME.  */

static void

test_qname (const char *qname, int rcode)

{

  struct resolv_context *ctx = __resolv_context_get ();

  TEST_VERIFY_EXIT (ctx != NULL);

  unsigned char q1[512];

  int q1len = res_mkquery (QUERY, qname, C_IN, T_A, NULL, 0, NULL,

                           q1, sizeof (q1));

  TEST_VERIFY_EXIT (q1len > 12);

  unsigned char q2[512];

  int q2len = res_mkquery (QUERY, qname, C_IN, T_AAAA, NULL, 0, NULL,

                           q2, sizeof (q2));

  TEST_VERIFY_EXIT (q2len > 12);

  /* Produce a transaction ID collision.  */

  memcpy (q2, q1, 2);

  unsigned char ans1[512];

  unsigned char *ans1p = ans1;

  unsigned char *ans2p = NULL;

  int nans2p = 0;

  int resplen2 = 0;

  int ans2p_malloced = 0;

  /* Perform a parallel A/AAAA query.  */

  int resplen1 = __res_context_send (ctx, q1, q1len, q2, q2len,

                                     ans1, sizeof (ans1), &ans1p,

                                     &ans2p, &nans2p,

                                     &resplen2, &ans2p_malloced);

  TEST_VERIFY (resplen1 > 12);

  TEST_VERIFY (resplen2 > 12);

  if (resplen1 <= 12 || resplen2 <= 12)

    return;

  if (rcode == 1 || rcode == 3)

    {

      /* Format Error and Name Error responses does not trigger

         switching to the next server.  */

      TEST_COMPARE (ans1p[3] & 0x0f, rcode);

      TEST_COMPARE (ans2p[3] & 0x0f, rcode);

      return;

    }

  /* The response should be successful.  */

  TEST_COMPARE (ans1p[3] & 0x0f, 0);

  TEST_COMPARE (ans2p[3] & 0x0f, 0);

  /* Due to bug 19691, the answer may not be in the slot matching the

     query.  Assume that the AAAA response is the longer one.  */

  unsigned char *a_answer;

  int a_answer_length;

  unsigned char *aaaa_answer;

  int aaaa_answer_length;

  if (resplen2 > resplen1)

    {

      a_answer = ans1p;

      a_answer_length = resplen1;

      aaaa_answer = ans2p;

      aaaa_answer_length = resplen2;

    }

  else

    {

      a_answer = ans2p;

      a_answer_length = resplen2;

      aaaa_answer = ans1p;

      aaaa_answer_length = resplen1;

    }

  {

    char *expected = xasprintf ("name: %s\n"

                                "address: 192.0.2.1\n",

                                qname);

    check_dns_packet (qname, a_answer, a_answer_length, expected);

    free (expected);

  }

  {

    char *expected = xasprintf ("name: %s\n"

                                "address: 2001:db8::1\n",

                                qname);

    check_dns_packet (qname, aaaa_answer, aaaa_answer_length, expected);

    free (expected);

  }

  if (ans2p_malloced)

    free (ans2p);

  __resolv_context_put (ctx);

}

static int

do_test (void)

{

  struct resolv_test *aux = resolv_test_start

    ((struct resolv_redirect_config)

     {

       .response_callback = response,

       /* The response callback use global state (the previous_*

          variables), and query processing must therefore be

          serialized.  */

       .single_thread_udp = true,

     });

  for (int rcode = 0; rcode <= 5; ++rcode)

    for (int do_reorder_0 = 0; do_reorder_0 < 2; ++do_reorder_0)

      for (int do_reorder_1 = 0; do_reorder_1 < 2; ++do_reorder_1)

        {

          char *qname = xasprintf ("reorder-%d-%d.rcode-%d.example.net",

                                   do_reorder_0, do_reorder_1, rcode);

          test_qname (qname, rcode);

          free (qname);

        }

  resolv_test_end (aux);

  return 0;

}

#include <support/test-driver.c>