resolv: Do not wait for non-existing second DNS response after error (bug 30081)

In single-request mode, there is no second response after an error
because the second query has not been sent yet.  Waiting for it
introduces an unnecessary timeout.

Reviewed-by: DJ Delorie <dj@redhat.com>
This commit is contained in:
Florian Weimer 2024-07-24 12:06:47 +02:00
parent 691a3b2e9b
commit af625987d6
4 changed files with 149 additions and 1 deletions

View File

@ -106,6 +106,7 @@ tests += \
tst-resolv-nondecimal \
tst-resolv-res_init-multi \
tst-resolv-search \
tst-resolv-semi-failure \
tst-resolv-short-response \
tst-resolv-trailing \
@ -300,6 +301,8 @@ $(objpfx)tst-resolv-nondecimal: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-search: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-semi-failure: $(objpfx)libresolv.so \
$(shared-thread-library)
$(objpfx)tst-resolv-short-response: $(objpfx)libresolv.so \
$(shared-thread-library)
$(objpfx)tst-resolv-trailing: $(objpfx)libresolv.so $(shared-thread-library)

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@ -1238,7 +1238,7 @@ send_dg(res_state statp,
*resplen2 = 0;
return resplen;
}
if (buf2 != NULL)
if (buf2 != NULL && !single_request)
{
/* No data from the first reply. */
resplen = 0;

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@ -0,0 +1,133 @@
/* Test parallel failure/success responses (bug 30081).
Copyright (C) 2024 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 <resolv.h>
#include <support/check.h>
#include <support/resolv_test.h>
#include <support/check_nss.h>
/* The rcode in the initial response. */
static volatile int rcode;
/* Whether to fail the initial A query (!fail_aaaa) or the initial
AAAA query (fail_aaaa). */
static volatile bool fail_aaaa;
static void
response (const struct resolv_response_context *ctx,
struct resolv_response_builder *b,
const char *qname, uint16_t qclass, uint16_t qtype)
{
/* Handle the failing query. */
if ((fail_aaaa && qtype == T_AAAA) && ctx->server_index == 0)
{
struct resolv_response_flags flags = {.rcode = rcode};
resolv_response_init (b, flags);
return;
}
/* Otherwise produce a response. */
resolv_response_init (b, (struct resolv_response_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);
switch (qtype)
{
case T_A:
{
char ipv4[4] = {192, 0, 2, 17};
resolv_response_add_data (b, &ipv4, sizeof (ipv4));
}
break;
case T_AAAA:
{
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));
}
break;
default:
FAIL_EXIT1 ("unexpected TYPE%d query", qtype);
}
resolv_response_close_record (b);
}
static void
check_one (void)
{
/* The buggy 1-second query timeout results in 30 seconds of delay,
which triggers are test timeout failure. */
for (int i = 0; i < 30; ++i)
{
static const struct addrinfo hints =
{
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
};
struct addrinfo *ai;
int ret = getaddrinfo ("www.example", "80", &hints, &ai);
const char *expected;
if (ret == 0 && ai->ai_next != NULL)
expected = ("address: STREAM/TCP 192.0.2.17 80\n"
"address: STREAM/TCP 2001:db8::1 80\n");
else
/* Only one response because the AAAA lookup failure is
treated as an ignoreable error. */
expected = "address: STREAM/TCP 192.0.2.17 80\n";
check_addrinfo ("www.example", ai, ret, expected);
if (ret == 0)
freeaddrinfo (ai);
}
}
static int
do_test (void)
{
for (int do_single_lookup = 0; do_single_lookup < 2; ++do_single_lookup)
{
struct resolv_test *aux = resolv_test_start
((struct resolv_redirect_config)
{
.response_callback = response,
});
if (do_single_lookup)
_res.options |= RES_SNGLKUP;
for (int do_fail_aaaa = 0; do_fail_aaaa < 2; ++do_fail_aaaa)
{
fail_aaaa = do_fail_aaaa;
rcode = 2; /* SERVFAIL. */
check_one ();
rcode = 4; /* NOTIMP. */
check_one ();
rcode = 5; /* REFUSED. */
check_one ();
}
resolv_test_end (aux);
}
return 0;
}
#include <support/test-driver.c>

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@ -81,6 +81,18 @@ check_one (void)
check_hostent ("www.example", gethostbyname2 ("www.example", AF_INET6),
"name: www.example\n"
"address: 2001:db8::1\n");
static const struct addrinfo hints =
{
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
};
struct addrinfo *ai;
int ret = getaddrinfo ("www.example", "80", &hints, &ai);
check_addrinfo ("www.example", ai, ret,
"address: STREAM/TCP 192.0.2.17 80\n"
"address: STREAM/TCP 2001:db8::1 80\n");
if (ret == 0)
freeaddrinfo (ai);
}
}