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resolv: Allow short error responses to match any query (bug 31890)
Reviewed-by: DJ Delorie <dj@redhat.com>
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@ -106,6 +106,7 @@ tests += \
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tst-resolv-nondecimal \
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tst-resolv-res_init-multi \
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tst-resolv-search \
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tst-resolv-short-response \
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tst-resolv-trailing \
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# This test calls __res_context_send directly, which is not exported
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@ -299,6 +300,8 @@ $(objpfx)tst-resolv-nondecimal: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-search: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-short-response: $(objpfx)libresolv.so \
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$(shared-thread-library)
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$(objpfx)tst-resolv-trailing: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-threads: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-txnid-collision: $(objpfx)libresolv.a \
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@ -1199,19 +1199,30 @@ send_dg(res_state statp,
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}
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/* Check for the correct header layout and a matching
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question. */
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question. Some recursive resolvers send REFUSED
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without copying back the question section
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(producing a response that is only HFIXEDSZ bytes
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long). Skip query matching in this case. */
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bool thisansp_error = (anhp->rcode == SERVFAIL ||
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anhp->rcode == NOTIMP ||
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anhp->rcode == REFUSED);
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bool skip_query_match = (*thisresplenp == HFIXEDSZ
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&& ntohs (anhp->qdcount) == 0
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&& thisansp_error);
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int matching_query = 0; /* Default to no matching query. */
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if (!recvresp1
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&& anhp->id == hp->id
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&& __libc_res_queriesmatch (buf, buf + buflen,
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*thisansp,
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*thisansp + *thisanssizp))
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&& (skip_query_match
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|| __libc_res_queriesmatch (buf, buf + buflen,
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*thisansp,
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*thisansp + *thisanssizp)))
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matching_query = 1;
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if (!recvresp2
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&& anhp->id == hp2->id
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&& __libc_res_queriesmatch (buf2, buf2 + buflen2,
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*thisansp,
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*thisansp + *thisanssizp))
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&& (skip_query_match
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|| __libc_res_queriesmatch (buf2, buf2 + buflen2,
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*thisansp,
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*thisansp + *thisanssizp)))
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matching_query = 2;
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if (matching_query == 0)
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/* Spurious UDP packet. Drop it and continue
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@ -1221,9 +1232,7 @@ send_dg(res_state statp,
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goto wait;
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}
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if (anhp->rcode == SERVFAIL ||
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anhp->rcode == NOTIMP ||
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anhp->rcode == REFUSED) {
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if (thisansp_error) {
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next_ns:
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if (recvresp1 || (buf2 != NULL && recvresp2)) {
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*resplen2 = 0;
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112
resolv/tst-resolv-short-response.c
Normal file
112
resolv/tst-resolv-short-response.c
Normal file
@ -0,0 +1,112 @@
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/* Test for spurious timeouts with short 12-byte responses (bug 31890).
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <resolv.h>
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#include <support/check.h>
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#include <support/resolv_test.h>
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#include <support/check_nss.h>
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/* The rcode in the initial response. */
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static volatile int rcode;
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static void
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response (const struct resolv_response_context *ctx,
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struct resolv_response_builder *b,
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const char *qname, uint16_t qclass, uint16_t qtype)
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{
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switch (ctx->server_index)
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{
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case 0:
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/* First server times out. */
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struct resolv_response_flags flags = {.rcode = rcode};
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resolv_response_init (b, flags);
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break;
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case 1:
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/* Second server sends reply. */
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resolv_response_init (b, (struct resolv_response_flags) {});
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resolv_response_add_question (b, qname, qclass, qtype);
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resolv_response_section (b, ns_s_an);
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resolv_response_open_record (b, qname, qclass, qtype, 0);
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switch (qtype)
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{
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case T_A:
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{
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char ipv4[4] = {192, 0, 2, 17};
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resolv_response_add_data (b, &ipv4, sizeof (ipv4));
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}
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break;
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case T_AAAA:
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{
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char ipv6[16]
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= {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
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resolv_response_add_data (b, &ipv6, sizeof (ipv6));
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}
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break;
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default:
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FAIL_EXIT1 ("unexpected TYPE%d query", qtype);
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}
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resolv_response_close_record (b);
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break;
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default:
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FAIL_EXIT1 ("unexpected query to server %d", ctx->server_index);
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}
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}
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static void
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check_one (void)
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{
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/* The buggy 1-second query timeout results in 30 seconds of delay,
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which triggers a test timeout failure. */
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for (int i = 0; i < 10; ++i)
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{
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check_hostent ("www.example", gethostbyname ("www.example"),
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"name: www.example\n"
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"address: 192.0.2.17\n");
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check_hostent ("www.example", gethostbyname2 ("www.example", AF_INET6),
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"name: www.example\n"
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"address: 2001:db8::1\n");
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}
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}
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static int
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do_test (void)
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{
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struct resolv_test *aux = resolv_test_start
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((struct resolv_redirect_config)
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{
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.response_callback = response,
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});
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_res.options |= RES_SNGLKUP;
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rcode = 2; /* SERVFAIL. */
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check_one ();
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rcode = 4; /* NOTIMP. */
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check_one ();
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rcode = 5; /* REFUSED. */
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check_one ();
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resolv_test_end (aux);
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return 0;
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}
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#include <support/test-driver.c>
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