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resolv: Remove EDNS fallback [BZ #21369]

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EDNS is disabled by default (so there is interoperability issue), and
the fallback code is problematic because it prevents an application
from obtaining DNSSEC data after a FORMERR response.
This commit is contained in:
Florian Weimer
2017-04-13 13:22:51 +02:00
parent e14a27723c
commit 44500cbb25
5 changed files with 75 additions and 62 deletions
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84
resolv/tst-resolv-edns.c
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@ -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,
});
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;
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;
}
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;