diff options
| -rw-r--r-- | ChangeLog | 12 | ||||
| -rw-r--r-- | NEWS | 5 | ||||
| -rw-r--r-- | resolv/res_query.c | 16 | ||||
| -rw-r--r-- | resolv/res_send.c | 20 | ||||
| -rw-r--r-- | resolv/tst-resolv-edns.c | 88 |
5 files changed, 77 insertions, 64 deletions
@@ -1,5 +1,17 @@ 2017-04-13 Florian Weimer <fweimer@redhat.com> + [BZ #21369] + Remove EDNS fallback. + * resolv/res_query.c (__libc_res_nquery): Remove RES_F_EDNS0ERR + handling. + * resolv/res_send.c (send_dg): Likewise. + * resolv/tst-resolv-edns.c (response): Handle "formerr." and + "tcp." prefixes. + (do_test): Send a "formerr."-prefixed query in an attempt to + trigger EDNS fallback. + +2017-04-13 Florian Weimer <fweimer@redhat.com> + [BZ #21361] Limit EDNS buffer size to 1200 bytes. * include/resolv.h (__res_nopt): Remove declaration. @@ -41,6 +41,11 @@ Version 2.26 "The Rules of Hungarian Orthography, 12th edition" and the work of Egmont Koblinger (Bug 18934). +* The DNS stub resolver no longer performs EDNS fallback. If EDNS or DNSSEC + support is enabled, the configured recursive resolver must support EDNS. + (Responding to EDNS-enabled queries with responses which are not + EDNS-enabled is fine, but FORMERR responses are not.) + * res_mkquery and res_nmkquery no longer support the IQUERY opcode. DNS servers have not supported this opcode for a long time. diff --git a/resolv/res_query.c b/resolv/res_query.c index c3ebcbf6b5..ec65bab041 100644 --- a/resolv/res_query.c +++ b/resolv/res_query.c @@ -122,7 +122,6 @@ __libc_res_nquery(res_state statp, HEADER *hp = (HEADER *) answer; HEADER *hp2; int n, use_malloc = 0; - u_int oflags = statp->_flags; size_t bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * QUERYSIZE; u_char *buf = alloca (bufsize); @@ -145,8 +144,7 @@ __libc_res_nquery(res_state statp, query1, bufsize); if (n > 0) { - if ((oflags & RES_F_EDNS0ERR) == 0 - && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) + if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) { /* Use RESOLV_EDNS_BUFFER_SIZE because the receive buffer can be reallocated. */ @@ -170,7 +168,6 @@ __libc_res_nquery(res_state statp, n = res_nmkquery(statp, QUERY, name, class, T_AAAA, NULL, 0, NULL, query2, bufsize - nused); if (n > 0 - && (oflags & RES_F_EDNS0ERR) == 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) /* Use RESOLV_EDNS_BUFFER_SIZE because the receive buffer can be reallocated. */ @@ -187,7 +184,6 @@ __libc_res_nquery(res_state statp, query1, bufsize); if (n > 0 - && (oflags & RES_F_EDNS0ERR) == 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) { /* Use RESOLV_EDNS_BUFFER_SIZE if the receive buffer @@ -215,16 +211,6 @@ __libc_res_nquery(res_state statp, } } if (__glibc_unlikely (n <= 0)) { - /* If the query choked with EDNS0, retry without EDNS0. */ - if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0 - && ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) { - statp->_flags |= RES_F_EDNS0ERR; -#ifdef DEBUG - if (statp->options & RES_DEBUG) - printf(";; res_nquery: retry without EDNS0\n"); -#endif - goto again; - } #ifdef DEBUG if (statp->options & RES_DEBUG) printf(";; res_query: mkquery failed\n"); diff --git a/resolv/res_send.c b/resolv/res_send.c index 995e1be730..ffb9a6af7b 100644 --- a/resolv/res_send.c +++ b/resolv/res_send.c @@ -1321,26 +1321,6 @@ send_dg(res_state statp, ? *thisanssizp : *thisresplenp); goto wait; } -#ifdef RES_USE_EDNS0 - if (anhp->rcode == FORMERR - && (statp->options & RES_USE_EDNS0) != 0U) { - /* - * Do not retry if the server does not understand - * EDNS0. The case has to be captured here, as - * FORMERR packet do not carry query section, hence - * res_queriesmatch() returns 0. - */ - DprintQ(statp->options & RES_DEBUG, - (stdout, - "server rejected query with EDNS0:\n"), - *thisansp, - (*thisresplenp > *thisanssizp) - ? *thisanssizp : *thisresplenp); - /* record the error */ - statp->_flags |= RES_F_EDNS0ERR; - return close_and_return_error (statp, resplen2); - } -#endif if (!(statp->options & RES_INSECURE2) && (recvresp1 || !res_queriesmatch(buf, buf + buflen, *thisansp, diff --git a/resolv/tst-resolv-edns.c b/resolv/tst-resolv-edns.c index f17dbc3450..093a4f5f22 100644 --- a/resolv/tst-resolv-edns.c +++ b/resolv/tst-resolv-edns.c @@ -115,8 +115,23 @@ response (const struct resolv_response_context *ctx, { TEST_VERIFY_EXIT (qname != NULL); - /* The "tcp." prefix can be used to request TCP fallback. */ const char *qname_compare = qname; + + /* The "formerr." prefix can be used to request a FORMERR response on the + first server. */ + bool send_formerr; + if (strncmp ("formerr.", qname, strlen ("formerr.")) == 0) + { + send_formerr = true; + qname_compare = qname + strlen ("formerr."); + } + else + { + send_formerr = false; + qname_compare = qname; + } + + /* The "tcp." prefix can be used to request TCP fallback. */ bool force_tcp; if (strncmp ("tcp.", qname_compare, strlen ("tcp.")) == 0) { @@ -132,14 +147,20 @@ response (const struct resolv_response_context *ctx, else { support_record_failure (); - printf ("error: unexpected QNAME: %s\n", qname); + printf ("error: unexpected QNAME: %s (reduced: %s)\n", + qname, qname_compare); return; } TEST_VERIFY_EXIT (qclass == C_IN); - struct resolv_response_flags flags = {.tc = force_tcp && !ctx->tcp}; + struct resolv_response_flags flags = { }; + flags.tc = force_tcp && !ctx->tcp; + if (!flags.tc && send_formerr && ctx->server_index == 0) + /* Send a FORMERR for the first full response from the first + server. */ + flags.rcode = 1; /* FORMERR */ resolv_response_init (b, flags); resolv_response_add_question (b, qname, qclass, qtype); - if (flags.tc) + if (flags.tc || flags.rcode != 0) return; if (test_verbose) @@ -466,33 +487,42 @@ do_test (void) for (int do_edns = 0; do_edns < 2; ++do_edns) for (int do_dnssec = 0; do_dnssec < 2; ++do_dnssec) for (int do_tcp = 0; do_tcp < 2; ++do_tcp) - { - struct resolv_test *aux = resolv_test_start - ((struct resolv_redirect_config) - { - .response_callback = response, - }); - - use_edns = do_edns; - if (do_edns) - _res.options |= RES_USE_EDNS0; - use_dnssec = do_dnssec; - if (do_dnssec) - _res.options |= RES_USE_DNSSEC; - - char *probe_name = xstrdup (EDNS_PROBE_EXAMPLE); - if (do_tcp) - { - char *n = xasprintf ("tcp.%s", probe_name); - free (probe_name); - probe_name = n; - } + for (int do_formerr = 0; do_formerr < 2; ++do_formerr) + { + struct resolv_test *aux = resolv_test_start + ((struct resolv_redirect_config) + { + .response_callback = response, + }); + + use_edns = do_edns; + if (do_edns) + _res.options |= RES_USE_EDNS0; + use_dnssec = do_dnssec; + if (do_dnssec) + _res.options |= RES_USE_DNSSEC; + + char *probe_name = xstrdup (EDNS_PROBE_EXAMPLE); + if (do_tcp) + { + char *n = xasprintf ("tcp.%s", probe_name); + free (probe_name); + probe_name = n; + } + if (do_formerr) + { + /* Send a garbage query in an attempt to trigger EDNS + fallback. */ + char *n = xasprintf ("formerr.%s", probe_name); + gethostbyname (n); + free (n); + } - run_test (probe_name); + run_test (probe_name); - free (probe_name); - resolv_test_end (aux); - } + free (probe_name); + resolv_test_end (aux); + } free_response_data (); return 0; |