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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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104
resolv/nss_dns/dns-host.c
View File

@@ -84,6 +84,7 @@
/* Get implementeation for some internal functions. */
#include <resolv/resolv-internal.h>
#include <resolv/resolv_context.h>
#include <resolv/mapv4v6addr.h>
#include <resolv/mapv4v6hostent.h>
@@ -121,13 +122,13 @@ static enum nss_status gaih_getanswer (const querybuf *answer1, int anslen1,
int *errnop, int *h_errnop,
int32_t *ttlp);
extern enum nss_status _nss_dns_gethostbyname3_r (const char *name, int af,
struct hostent *result,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp,
char **canonp);
hidden_proto (_nss_dns_gethostbyname3_r)
static enum nss_status gethostbyname3_context (struct resolv_context *ctx,
const char *name, int af,
struct hostent *result,
char *buffer, size_t buflen,
int *errnop, int *h_errnop,
int32_t *ttlp,
char **canonp);
/* Return the expected RDATA length for an address record type (A or
AAAA). */
@@ -145,10 +146,30 @@ rrtype_to_rdata_length (int type)
}
}
enum nss_status
_nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
char *buffer, size_t buflen, int *errnop,
int *h_errnop, int32_t *ttlp, char **canonp)
{
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*h_errnop = NETDB_INTERNAL;
return NSS_STATUS_UNAVAIL;
}
enum nss_status status = gethostbyname3_context
(ctx, name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
__resolv_context_put (ctx);
return status;
}
static enum nss_status
gethostbyname3_context (struct resolv_context *ctx,
const char *name, int af, struct hostent *result,
char *buffer, size_t buflen, int *errnop,
int *h_errnop, int32_t *ttlp, char **canonp)
{
union
{
@@ -163,13 +184,6 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
int olderr = errno;
enum nss_status status;
if (__res_maybe_init (&_res, 0) == -1)
{
*errnop = errno;
*h_errnop = NETDB_INTERNAL;
return NSS_STATUS_UNAVAIL;
}
switch (af) {
case AF_INET:
size = INADDRSZ;
@@ -194,13 +208,13 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
* function that looks up host names.
*/
if (strchr (name, '.') == NULL
&& (cp = res_hostalias (&_res, name, tmp, sizeof (tmp))) != NULL)
&& (cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp))) != NULL)
name = cp;
host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);
n = __libc_res_nsearch (&_res, name, C_IN, type, host_buffer.buf->buf,
1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
n = __res_context_search (ctx, name, C_IN, type, host_buffer.buf->buf,
1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
if (n < 0)
{
switch (errno)
@@ -232,10 +246,10 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
by having the RES_USE_INET6 bit in _res.options set, we try
another lookup. */
if (af == AF_INET6 && res_use_inet6 ())
n = __libc_res_nsearch (&_res, name, C_IN, T_A, host_buffer.buf->buf,
host_buffer.buf != orig_host_buffer
? MAXPACKET : 1024, &host_buffer.ptr,
NULL, NULL, NULL, NULL);
n = __res_context_search (ctx, name, C_IN, T_A, host_buffer.buf->buf,
host_buffer.buf != orig_host_buffer
? MAXPACKET : 1024, &host_buffer.ptr,
NULL, NULL, NULL, NULL);
if (n < 0)
{
@@ -256,8 +270,6 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
free (host_buffer.buf);
return status;
}
hidden_def (_nss_dns_gethostbyname3_r)
enum nss_status
_nss_dns_gethostbyname2_r (const char *name, int af, struct hostent *result,
@@ -274,15 +286,21 @@ _nss_dns_gethostbyname_r (const char *name, struct hostent *result,
char *buffer, size_t buflen, int *errnop,
int *h_errnop)
{
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*h_errnop = NETDB_INTERNAL;
return NSS_STATUS_UNAVAIL;
}
enum nss_status status = NSS_STATUS_NOTFOUND;
if (res_use_inet6 ())
status = _nss_dns_gethostbyname3_r (name, AF_INET6, result, buffer,
buflen, errnop, h_errnop, NULL, NULL);
status = gethostbyname3_context (ctx, name, AF_INET6, result, buffer,
buflen, errnop, h_errnop, NULL, NULL);
if (status == NSS_STATUS_NOTFOUND)
status = _nss_dns_gethostbyname3_r (name, AF_INET, result, buffer,
buflen, errnop, h_errnop, NULL, NULL);
status = gethostbyname3_context (ctx, name, AF_INET, result, buffer,
buflen, errnop, h_errnop, NULL, NULL);
__resolv_context_put (ctx);
return status;
}
@@ -292,7 +310,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
char *buffer, size_t buflen, int *errnop,
int *herrnop, int32_t *ttlp)
{
if (__res_maybe_init (&_res, 0) == -1)
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*herrnop = NETDB_INTERNAL;
@@ -307,7 +326,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
if (strchr (name, '.') == NULL)
{
char *tmp = alloca (NS_MAXDNAME);
const char *cp = res_hostalias (&_res, name, tmp, NS_MAXDNAME);
const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
if (cp != NULL)
name = cp;
}
@@ -326,9 +345,9 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
int olderr = errno;
enum nss_status status;
int n = __libc_res_nsearch (&_res, name, C_IN, T_QUERY_A_AND_AAAA,
host_buffer.buf->buf, 2048, &host_buffer.ptr,
&ans2p, &nans2p, &resplen2, &ans2p_malloced);
int n = __res_context_search (ctx, name, C_IN, T_QUERY_A_AND_AAAA,
host_buffer.buf->buf, 2048, &host_buffer.ptr,
&ans2p, &nans2p, &resplen2, &ans2p_malloced);
if (n >= 0)
{
status = gaih_getanswer (host_buffer.buf, n, (const querybuf *) ans2p,
@@ -371,6 +390,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
if (host_buffer.buf != orig_host_buffer)
free (host_buffer.buf);
__resolv_context_put (ctx);
return status;
}
@@ -423,7 +443,8 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
host_data = (struct host_data *) buffer;
if (__res_maybe_init (&_res, 0) == -1)
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*h_errnop = NETDB_INTERNAL;
@@ -453,12 +474,14 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
default:
*errnop = EAFNOSUPPORT;
*h_errnop = NETDB_INTERNAL;
__resolv_context_put (ctx);
return NSS_STATUS_UNAVAIL;
}
if (size > len)
{
*errnop = EAFNOSUPPORT;
*h_errnop = NETDB_INTERNAL;
__resolv_context_put (ctx);
return NSS_STATUS_UNAVAIL;
}
@@ -487,14 +510,15 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
break;
}
n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
n = __res_context_query (ctx, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
if (n < 0)
{
*h_errnop = h_errno;
__set_errno (olderr);
if (host_buffer.buf != orig_host_buffer)
free (host_buffer.buf);
__resolv_context_put (ctx);
return errno == ECONNREFUSED ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
}
@@ -503,7 +527,10 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
if (host_buffer.buf != orig_host_buffer)
free (host_buffer.buf);
if (status != NSS_STATUS_SUCCESS)
return status;
{
__resolv_context_put (ctx);
return status;
}
result->h_addrtype = af;
result->h_length = len;
@@ -511,6 +538,7 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
host_data->h_addr_ptrs[0] = (char *) host_data->host_addr;
host_data->h_addr_ptrs[1] = NULL;
*h_errnop = NETDB_SUCCESS;
__resolv_context_put (ctx);
return NSS_STATUS_SUCCESS;
}
hidden_def (_nss_dns_gethostbyaddr2_r)