resolv: Introduce struct resolv_context [BZ #21668]

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.

15 files changed, 810 insertions, 291 deletions

diff --git a/resolv/Makefile b/resolv/Makefile
index bab1ac24a6..126da0736a 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -28,7 +28,8 @@ headers	:= resolv.h bits/types/res_state.h \
 	   sys/bitypes.h
 
 routines := herror inet_addr inet_ntop inet_pton nsap_addr res_init \
-	    res_hconf res_libc res-state res_randomid res-close
+	    res_hconf res_libc res-state res_randomid res-close \
+	    resolv_context
 
 tests = tst-aton tst-leaks tst-inet_ntop
 xtests = tst-leaks2
diff --git a/resolv/Versions b/resolv/Versions
index f528ed51e8..b05778d965 100644
--- a/resolv/Versions
+++ b/resolv/Versions
@@ -26,8 +26,12 @@ libc {
 
     __h_errno; __resp;
 
-    __res_maybe_init; __res_iclose;
+    __res_iclose;
     __inet_pton_length;
+    __resolv_context_get;
+    __resolv_context_get_preinit;
+    __resolv_context_get_override;
+    __resolv_context_put;
   }
 }
 
@@ -79,7 +83,9 @@ libresolv {
     # Needed in libnss_dns.
     __ns_name_unpack; __ns_name_ntop;
     __ns_get16; __ns_get32;
-    __libc_res_nquery; __libc_res_nsearch;
+    __res_context_query;
+    __res_context_search;
+    __res_context_hostalias;
   }
 }
 
diff --git a/resolv/compat-gethnamaddr.c b/resolv/compat-gethnamaddr.c
index 813c7d4e85..259378b2be 100644
--- a/resolv/compat-gethnamaddr.c
+++ b/resolv/compat-gethnamaddr.c
@@ -67,6 +67,7 @@
 # include <stdio.h>
 # include <netdb.h>
 # include <resolv/resolv-internal.h>
+# include <resolv/resolv_context.h>
 # include <ctype.h>
 # include <errno.h>
 # include <stdlib.h>
@@ -84,6 +85,9 @@ static u_char host_addr[16];	/* IPv4 or IPv6 */
 static FILE *hostf = NULL;
 static int stayopen = 0;
 
+static struct hostent *res_gethostbyname2_context (struct resolv_context *,
+						   const char *name, int af);
+
 static void map_v4v6_address (const char *src, char *dst) __THROW;
 static void map_v4v6_hostent (struct hostent *hp, char **bp, int *len) __THROW;
 
@@ -428,23 +432,31 @@ libresolv_hidden_proto (res_gethostbyname2)
 struct hostent *
 res_gethostbyname (const char *name)
 {
-	struct hostent *hp;
-
-	if (__res_maybe_init (&_res, 0) == -1) {
-		__set_h_errno (NETDB_INTERNAL);
-		return (NULL);
-	}
-	if (res_use_inet6 ()) {
-		hp = res_gethostbyname2(name, AF_INET6);
-		if (hp)
-			return (hp);
+  struct resolv_context *ctx = __resolv_context_get ();
+  if (ctx == NULL)
+    {
+      __set_h_errno (NETDB_INTERNAL);
+      return NULL;
+    }
+
+  if (res_use_inet6 ())
+    {
+      struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET6);
+      if (hp != NULL)
+	{
+	  __resolv_context_put (ctx);
+	  return hp;
 	}
-	return (res_gethostbyname2(name, AF_INET));
+    }
+  struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET);
+  __resolv_context_put (ctx);
+  return hp;
 }
 compat_symbol (libresolv, res_gethostbyname, res_gethostbyname, GLIBC_2_0);
 
-struct hostent *
-res_gethostbyname2 (const char *name, int af)
+static struct hostent *
+res_gethostbyname2_context (struct resolv_context *ctx,
+			    const char *name, int af)
 {
 	union
 	{
@@ -457,11 +469,6 @@ res_gethostbyname2 (const char *name, int af)
 	int n, size, type, len;
 	struct hostent *ret;
 
-	if (__res_maybe_init (&_res, 0) == -1) {
-		__set_h_errno (NETDB_INTERNAL);
-		return (NULL);
-	}
-
 	switch (af) {
 	case AF_INET:
 		size = INADDRSZ;
@@ -485,8 +492,10 @@ res_gethostbyname2 (const char *name, int af)
 	 * this is also done in res_query() since we are not the only
 	 * function that looks up host names.
 	 */
-	if (!strchr(name, '.') && (cp = __hostalias(name)))
-		name = cp;
+	char abuf[MAXDNAME];
+	if (strchr (name, '.') != NULL
+	    && (cp = __res_context_hostalias (ctx, name, abuf, sizeof (abuf))))
+	  name = cp;
 
 	/*
 	 * disallow names consisting only of digits/dots, unless
@@ -558,8 +567,9 @@ res_gethostbyname2 (const char *name, int af)
 
 	buf.buf = origbuf = (querybuf *) alloca (1024);
 
-	if ((n = __libc_res_nsearch(&_res, name, C_IN, type, buf.buf->buf, 1024,
-				    &buf.ptr, NULL, NULL, NULL, NULL)) < 0) {
+	if ((n = __res_context_search
+	     (ctx, name, C_IN, type, buf.buf->buf, 1024,
+	      &buf.ptr, NULL, NULL, NULL, NULL)) < 0) {
 		if (buf.buf != origbuf)
 			free (buf.buf);
 		Dprintf("res_nsearch failed (%d)\n", n);
@@ -572,11 +582,26 @@ res_gethostbyname2 (const char *name, int af)
 		free (buf.buf);
 	return ret;
 }
+
+struct hostent *
+res_gethostbyname2 (const char *name, int af)
+{
+  struct resolv_context *ctx = __resolv_context_get ();
+  if (ctx == NULL)
+    {
+      __set_h_errno (NETDB_INTERNAL);
+      return NULL;
+    }
+  struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET);
+  __resolv_context_put (ctx);
+  return hp;
+}
 libresolv_hidden_def (res_gethostbyname2)
 compat_symbol (libresolv, res_gethostbyname2, res_gethostbyname2, GLIBC_2_0);
 
-struct hostent *
-res_gethostbyaddr (const void *addr, socklen_t len, int af)
+static struct hostent *
+res_gethostbyaddr_context (struct resolv_context *ctx,
+			   const void *addr, socklen_t len, int af)
 {
 	const u_char *uaddr = (const u_char *)addr;
 	static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
@@ -592,10 +617,6 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
 	struct hostent *hp;
 	char qbuf[MAXDNAME+1], *qp = NULL;
 
-	if (__res_maybe_init (&_res, 0) == -1) {
-		__set_h_errno (NETDB_INTERNAL);
-		return (NULL);
-	}
 	if (af == AF_INET6 && len == IN6ADDRSZ &&
 	    (!memcmp(uaddr, mapped, sizeof mapped) ||
 	     !memcmp(uaddr, tunnelled, sizeof tunnelled))) {
@@ -645,8 +666,8 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
 
 	buf.buf = orig_buf = (querybuf *) alloca (1024);
 
-	n = __libc_res_nquery(&_res, qbuf, C_IN, T_PTR, buf.buf->buf, 1024,
-			      &buf.ptr, NULL, NULL, NULL, NULL);
+	n = __res_context_query (ctx, qbuf, C_IN, T_PTR, buf.buf->buf, 1024,
+				 &buf.ptr, NULL, NULL, NULL, NULL);
 	if (n < 0) {
 		if (buf.buf != orig_buf)
 			free (buf.buf);
@@ -673,6 +694,20 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
 	__set_h_errno (NETDB_SUCCESS);
 	return (hp);
 }
+
+struct hostent *
+res_gethostbyaddr (const void *addr, socklen_t len, int af)
+{
+  struct resolv_context *ctx = __resolv_context_get ();
+  if (ctx == NULL)
+    {
+      __set_h_errno (NETDB_INTERNAL);
+      return NULL;
+    }
+  struct hostent *hp = res_gethostbyaddr_context (ctx, addr, len, af);
+  __resolv_context_put (ctx);
+  return hp;
+}
 compat_symbol (libresolv, res_gethostbyaddr, res_gethostbyaddr, GLIBC_2_0);
 
 void
diff --git a/resolv/nss_dns/dns-canon.c b/resolv/nss_dns/dns-canon.c
index 4276eb6542..7a5c39dc20 100644
--- a/resolv/nss_dns/dns-canon.c
+++ b/resolv/nss_dns/dns-canon.c
@@ -23,7 +23,8 @@
 #include <stdint.h>
 #include <arpa/nameser.h>
 #include <nsswitch.h>
-
+#include <resolv/resolv_context.h>
+#include <resolv/resolv-internal.h>
 
 #if PACKETSZ > 65536
 # define MAXPACKET	PACKETSZ
@@ -58,11 +59,19 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
   } ansp = { .ptr = buf };
   enum nss_status status = NSS_STATUS_UNAVAIL;
 
+  struct resolv_context *ctx = __resolv_context_get ();
+  if (ctx == NULL)
+    {
+      *errnop = errno;
+      *h_errnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
+
   for (int i = 0; i < nqtypes; ++i)
     {
-      int r = __libc_res_nquery (&_res, name, ns_c_in, qtypes[i],
-				 buf, sizeof (buf), &ansp.ptr, NULL, NULL,
-				 NULL, NULL);
+      int r = __res_context_query (ctx, name, ns_c_in, qtypes[i],
+				   buf, sizeof (buf), &ansp.ptr, NULL, NULL,
+				   NULL, NULL);
       if (r > 0)
 	{
 	  /* We need to decode the response.  Just one question record.
@@ -168,6 +177,6 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
 
   if (ansp.ptr != buf)
     free (ansp.ptr);
-
+  __resolv_context_put (ctx);
   return status;
 }
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 206924de86..9d7ceb1691 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -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).  */
@@ -145,11 +146,31 @@ 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
   {
     querybuf *buf;
@@ -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)
diff --git a/resolv/nss_dns/dns-network.c b/resolv/nss_dns/dns-network.c
index dc1599b471..f190eb2225 100644
--- a/resolv/nss_dns/dns-network.c
+++ b/resolv/nss_dns/dns-network.c
@@ -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, N