Blame SOURCES/0452-Issue-separate-DNS-queries-for-ipv4-and-ipv6.patch

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From 590290e07fe45f5fee7cd15e507fe90e54046732 Mon Sep 17 00:00:00 2001
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From: Gustavo Luiz Duarte <gustavold@linux.vnet.ibm.com>
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Date: Fri, 28 Sep 2012 19:42:07 -0400
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Subject: [PATCH 452/482] Issue separate DNS queries for ipv4 and ipv6
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Adding multiple questions on a single DNS query is not supportted by
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most DNS servers. This patch issues two separate DNS queries
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sequentially for ipv4 and then for ipv6.
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There are 4 possible config options:
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 DNS_OPTION_IPV4: issue only one ipv4 query
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 DNS_OPTION_IPV6: issue only one ipv6 query
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 DNS_OPTION_PREFER_IPV4: issue the ipv4 query first and fallback to ipv6
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 DNS_OPTION_PREFER_IPV6: issue the ipv6 query first and fallback to ipv4
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However, there is no code yet to set such config option. The default is
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DNS_OPTION_PREFER_IPV4.
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Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=860829
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---
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 grub-core/net/dns.c | 99 ++++++++++++++++++++++++++++++++++++-----------------
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 include/grub/net.h  |  9 +++++
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 2 files changed, 76 insertions(+), 32 deletions(-)
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diff --git a/grub-core/net/dns.c b/grub-core/net/dns.c
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index 3381ea7..fac97b0 100644
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--- a/grub-core/net/dns.c
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+++ b/grub-core/net/dns.c
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@@ -34,6 +34,14 @@ struct dns_cache_element
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 #define DNS_CACHE_SIZE 1021
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 #define DNS_HASH_BASE 423
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+typedef enum grub_dns_qtype_id
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+  {
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+    GRUB_DNS_QTYPE_A = 1,
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+    GRUB_DNS_QTYPE_AAAA = 28
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+  } grub_dns_qtype_id_t;
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+
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+static grub_dns_option_t dns_type_option = DNS_OPTION_PREFER_IPV4;
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+
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 static struct dns_cache_element dns_cache[DNS_CACHE_SIZE];
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 static struct grub_net_network_level_address *dns_servers;
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 static grub_size_t dns_nservers, dns_servers_alloc;
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@@ -410,13 +418,13 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
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   return GRUB_ERR_NONE;
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 }
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-grub_err_t
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-grub_net_dns_lookup (const char *name,
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+static grub_err_t
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+grub_net_dns_lookup_qtype (const char *name,
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 		     const struct grub_net_network_level_address *servers,
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 		     grub_size_t n_servers,
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 		     grub_size_t *naddresses,
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 		     struct grub_net_network_level_address **addresses,
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-		     int cache)
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+		     int cache, grub_dns_qtype_id_t qtype)
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 {
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   grub_size_t send_servers = 0;
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   grub_size_t i, j;
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@@ -471,8 +479,7 @@ grub_net_dns_lookup (const char *name,
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 			   + GRUB_NET_MAX_LINK_HEADER_SIZE
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 			   + GRUB_NET_UDP_HEADER_SIZE
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 			   + sizeof (struct dns_header)
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-			   + grub_strlen (name) + 2 + 4
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-			   + 2 + 4);
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+			   + grub_strlen (name) + 2 + 4);
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   if (!nb)
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     {
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       grub_free (data.name);
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@@ -482,7 +489,7 @@ grub_net_dns_lookup (const char *name,
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 			+ GRUB_NET_MAX_LINK_HEADER_SIZE
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 			+ GRUB_NET_UDP_HEADER_SIZE);
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   grub_netbuff_put (nb, sizeof (struct dns_header)
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-		    + grub_strlen (name) + 2 + 4 + 2 + 4);
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+		    + grub_strlen (name) + 2 + 4);
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   head = (struct dns_header *) nb->data;
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   optr = (grub_uint8_t *) (head + 1);
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   for (iptr = name; *iptr; )
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@@ -509,18 +516,7 @@ grub_net_dns_lookup (const char *name,
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   /* Type: A.  */
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   *optr++ = 0;
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-  *optr++ = 1;
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-
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-  /* Class.  */
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-  *optr++ = 0;
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-  *optr++ = 1;
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-
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-  /* Compressed name.  */
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-  *optr++ = 0xc0;
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-  *optr++ = 0x0c;
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-  /* Type: AAAA.  */
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-  *optr++ = 0;
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-  *optr++ = 28;
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+  *optr++ = qtype;
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   /* Class.  */
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   *optr++ = 0;
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@@ -529,7 +525,7 @@ grub_net_dns_lookup (const char *name,
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   head->id = data.id;
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   head->flags = FLAGS_RD;
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   head->ra_z_r_code = 0;
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-  head->qdcount = grub_cpu_to_be16_compile_time (2);
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+  head->qdcount = grub_cpu_to_be16_compile_time (1);
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   head->ancount = grub_cpu_to_be16_compile_time (0);
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   head->nscount = grub_cpu_to_be16_compile_time (0);
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   head->arcount = grub_cpu_to_be16_compile_time (0);
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@@ -587,16 +583,47 @@ grub_net_dns_lookup (const char *name,
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   if (*data.naddresses)
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     return GRUB_ERR_NONE;
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   if (data.dns_err)
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-    return grub_error (GRUB_ERR_NET_NO_DOMAIN,
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-		       N_("no DNS record found"));
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-    
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+    {
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+      grub_dprintf ("dns", "%s. QTYPE: %u QNAME: %s\n",
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+                    N_("no DNS record found"), qtype, name);
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+      return GRUB_ERR_NET_NO_DOMAIN;
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+    }
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   if (err)
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     {
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       grub_errno = err;
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       return err;
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     }
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-  return grub_error (GRUB_ERR_TIMEOUT,
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-		     N_("no DNS reply received"));
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+  grub_dprintf ("dns", "%s. QTYPE: %u QNAME: %s\n",
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+                N_("no DNS reply received"), qtype, name);
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+  return GRUB_ERR_TIMEOUT;
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+}
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+
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+grub_err_t
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+grub_net_dns_lookup (const char *name,
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+		     const struct grub_net_network_level_address *servers,
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+		     grub_size_t n_servers,
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+		     grub_size_t *naddresses,
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+		     struct grub_net_network_level_address **addresses,
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+		     int cache)
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+{
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+  if (dns_type_option == DNS_OPTION_IPV6 || dns_type_option == DNS_OPTION_PREFER_IPV6)
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+      grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,
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+                                 addresses, cache, GRUB_DNS_QTYPE_AAAA);
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+  else
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+      grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,
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+                                 addresses, cache, GRUB_DNS_QTYPE_A);
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+  if (!*naddresses)
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+    {
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+      if (dns_type_option == DNS_OPTION_PREFER_IPV4)
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+          grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,
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+                                     addresses, cache, GRUB_DNS_QTYPE_AAAA);
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+      else if (dns_type_option == DNS_OPTION_PREFER_IPV6)
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+          grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,
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+                                     addresses, cache, GRUB_DNS_QTYPE_A);
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+    }
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+  if (!*naddresses)
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+      return GRUB_ERR_NET_NO_DOMAIN;
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+  return GRUB_ERR_NONE;
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 }
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 static grub_err_t
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@@ -604,22 +631,28 @@ grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)),
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 		   int argc, char **args)
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 {
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   grub_err_t err;
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-  grub_size_t naddresses, i;
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+  struct grub_net_network_level_address cmd_server;
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+  struct grub_net_network_level_address *servers;
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+  grub_size_t nservers, i, naddresses = 0;
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   struct grub_net_network_level_address *addresses = 0;
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   if (argc != 2 && argc != 1)
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     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));
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   if (argc == 2)
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     {
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-      struct grub_net_network_level_address server;
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-      err = grub_net_resolve_address (args[1], &server);
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+      err = grub_net_resolve_address (args[1], &cmd_server);
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       if (err)
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 	return err;
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-      err = grub_net_dns_lookup (args[0], &server, 1, &naddresses,
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-				 &addresses, 0);
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+      servers = &cmd_server;
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+      nservers = 1;
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     }
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   else
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-    err = grub_net_dns_lookup (args[0], dns_servers, dns_nservers, &naddresses,
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-			       &addresses, 0);
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+    {
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+      servers = dns_servers;
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+      nservers = dns_nservers;
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+    }
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+
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+  grub_net_dns_lookup (args[0], servers, nservers, &naddresses,
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+                       &addresses, 0);
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   for (i = 0; i < naddresses; i++)
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     {
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@@ -628,7 +661,9 @@ grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)),
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       grub_printf ("%s\n", buf);
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     }
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   grub_free (addresses);
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-  return GRUB_ERR_NONE;
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+  if (naddresses)
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+    return GRUB_ERR_NONE;
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+  return grub_error (GRUB_ERR_NET_NO_DOMAIN, N_("no DNS record found"));
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 }
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 static grub_err_t
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diff --git a/include/grub/net.h b/include/grub/net.h
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index 1bd7af2..e677246 100644
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--- a/include/grub/net.h
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+++ b/include/grub/net.h
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@@ -506,6 +506,15 @@ grub_err_t
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 grub_net_link_layer_resolve (struct grub_net_network_level_interface *inf,
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 			     const grub_net_network_level_address_t *proto_addr,
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 			     grub_net_link_level_address_t *hw_addr);
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+
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+typedef enum
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+  {
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+    DNS_OPTION_IPV4,
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+    DNS_OPTION_IPV6,
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+    DNS_OPTION_PREFER_IPV4,
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+    DNS_OPTION_PREFER_IPV6
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+  } grub_dns_option_t;
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+
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 grub_err_t
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 grub_net_dns_lookup (const char *name,
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 		     const struct grub_net_network_level_address *servers,
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-- 
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1.8.2.1
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