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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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16
resolv/res_query.c
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@ -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");