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resolv: Introduce struct resolv_context [BZ #21668]

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struct resolv_context objects provide a temporary resolver context
which does not change during a name lookup operation.  Only when the
outmost context is created, the stub resolver configuration is
verified to be current (at present, only against previous res_init
calls).  Subsequent attempts to obtain the context will reuse the
result of the initial verification operation.

struct resolv_context can also be extended in the future to store
data which needs to be deallocated during thread cancellation.
This commit is contained in:
Florian Weimer
2017-06-30 21:10:23 +02:00
parent 4e45d83c92
commit 352f4ff9a2
24 changed files with 1032 additions and 370 deletions
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21
resolv/nss_dns/dns-network.c
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@ -67,6 +67,8 @@
#include "nsswitch.h"
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv/resolv-internal.h>
#include <resolv/resolv_context.h>
/* Maximum number of aliases we allow. */
#define MAX_NR_ALIASES 48
@ -115,7 +117,8 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
int anslen;
enum nss_status status;
if (__res_maybe_init (&_res, 0) == -1)
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*herrnop = NETDB_INTERNAL;
@ -124,14 +127,16 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
anslen = __libc_res_nsearch (&_res, name, C_IN, T_PTR, net_buffer.buf->buf,
1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
anslen = __res_context_search
(ctx, name, C_IN, T_PTR, net_buffer.buf->buf,
1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
if (anslen < 0)
{
/* Nothing found. */
*errnop = errno;
if (net_buffer.buf != orig_net_buffer)
free (net_buffer.buf);
__resolv_context_put (ctx);
return (errno == ECONNREFUSED
|| errno == EPFNOSUPPORT
|| errno == EAFNOSUPPORT)
@ -142,6 +147,7 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
errnop, herrnop, BYNAME);
if (net_buffer.buf != orig_net_buffer)
free (net_buffer.buf);
__resolv_context_put (ctx);
return status;
}
@ -169,7 +175,8 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
if (type != AF_INET)
return NSS_STATUS_UNAVAIL;
if (__res_maybe_init (&_res, 0) == -1)
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*herrnop = NETDB_INTERNAL;
@ -204,8 +211,8 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
anslen = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
anslen = __res_context_query (ctx, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
if (anslen < 0)
{
/* Nothing found. */
@ -213,6 +220,7 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
__set_errno (olderr);
if (net_buffer.buf != orig_net_buffer)
free (net_buffer.buf);
__resolv_context_put (ctx);
return (err == ECONNREFUSED
|| err == EPFNOSUPPORT
|| err == EAFNOSUPPORT)
@ -233,6 +241,7 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
result->n_net = u_net;
}
__resolv_context_put (ctx);
return status;
}