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From 09ce1e84db1b175195584dd20aa7241f3e95061f Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 14 Jun 2024 08:20:48 +0200
Subject: [PATCH 2/4] resolv: Do not wait for non-existing second DNS response after error (bug 30081)
Message-ID: <09ce1e84db1b175195584dd20aa7241f3e95061f.1718345824.git.fweimer@redhat.com> (raw)
In-Reply-To: <cover.1718345824.git.fweimer@redhat.com>
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.
Conflict:The tst-resolv-short-response test case does not exist. Therefore, the modification of this test case is not incorporated.
Reference:https://inbox.sourceware.org/libc-alpha/09ce1e84db1b175195584dd20aa7241f3e95061f.1718345824.git.fweimer@redhat.com/
---
resolv/Makefile | 3 +
resolv/res_send.c | 2 +-
resolv/tst-resolv-semi-failure.c | 133 +++++++++++++++++++++++++++++++
3 files changed, 137 insertions(+), 1 deletion(-)
create mode 100644 resolv/tst-resolv-semi-failure.c
diff --git a/resolv/Makefile b/resolv/Makefile
index 59e59953..9e12d364 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -96,6 +96,7 @@ tests += \
tst-resolv-nondecimal \
tst-resolv-res_init-multi \
tst-resolv-search \
+ tst-resolv-semi-failure \
tst-resolv-trailing \
# This test calls __res_context_send directly, which is not exported
@@ -260,6 +261,8 @@ $(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-trailing: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-threads: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-txnid-collision: $(objpfx)libresolv.a \
diff --git a/resolv/res_send.c b/resolv/res_send.c
index 9f86f5fe..54226a2e 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -1222,7 +1222,7 @@ 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;
diff --git a/resolv/tst-resolv-semi-failure.c b/resolv/tst-resolv-semi-failure.c
new file mode 100644
index 00000000..aa9798b5
--- /dev/null
+++ b/resolv/tst-resolv-semi-failure.c
@@ -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>
--
2.33.0
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