glibc/resolv/tst-resolv-txnid-collision.c
Florian Weimer b8b53b338f resolv: Serialize processing in resolv/tst-resolv-txnid-collision
When switching name servers, response processing by two server
threads clobbers the global test state.  (There is still some
risk that this test is negatively impact by packet drops and
packet reordering, but this applies to many of the resolver tests
and is difficult to avoid.)

Fixes commit f1f00c0721 ("resolv:
Handle transaction ID collisions in parallel queries (bug 26600)").
2020-10-15 12:33:13 +02:00

335 lines
10 KiB
C

/* 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>