From af625987d619388a100b153520d3ee308bda9889 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 24 Jul 2024 12:06:47 +0200 Subject: [PATCH] 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 --- resolv/Makefile | 3 + resolv/res_send.c | 2 +- resolv/tst-resolv-semi-failure.c | 133 +++++++++++++++++++++++++++++ resolv/tst-resolv-short-response.c | 12 +++ 4 files changed, 149 insertions(+), 1 deletion(-) create mode 100644 resolv/tst-resolv-semi-failure.c diff --git a/resolv/Makefile b/resolv/Makefile index d927e337d9..abff7fc007 100644 --- a/resolv/Makefile +++ b/resolv/Makefile @@ -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) diff --git a/resolv/res_send.c b/resolv/res_send.c index 572e72c32f..9c77613f37 100644 --- a/resolv/res_send.c +++ b/resolv/res_send.c @@ -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; diff --git a/resolv/tst-resolv-semi-failure.c b/resolv/tst-resolv-semi-failure.c new file mode 100644 index 0000000000..aa9798b5a7 --- /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 + . */ + +#include +#include +#include +#include + +/* 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 diff --git a/resolv/tst-resolv-short-response.c b/resolv/tst-resolv-short-response.c index cf1e39876f..be354ae1c7 100644 --- a/resolv/tst-resolv-short-response.c +++ b/resolv/tst-resolv-short-response.c @@ -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); } }