From 3e00d82827f80461f9fe6da37acd84235c08e5a5 Mon Sep 17 00:00:00 2001

From: Gustavo Luiz Duarte <gustavold@linux.vnet.ibm.com>

Date: Fri, 28 Sep 2012 19:42:07 -0400

Subject: [PATCH] Issue separate DNS queries for ipv4 and ipv6

Adding multiple questions on a single DNS query is not supportted by

most DNS servers. This patch issues two separate DNS queries

sequentially for ipv4 and then for ipv6.

There are 4 possible config options:

 DNS_OPTION_IPV4: issue only one ipv4 query

 DNS_OPTION_IPV6: issue only one ipv6 query

 DNS_OPTION_PREFER_IPV4: issue the ipv4 query first and fallback to ipv6

 DNS_OPTION_PREFER_IPV6: issue the ipv6 query first and fallback to ipv4

However, there is no code yet to set such config option. The default is

DNS_OPTION_PREFER_IPV4.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=860829

---

 grub-core/net/dns.c | 99 ++++++++++++++++++++++++++++++++++++-----------------

 include/grub/net.h  |  9 +++++

 2 files changed, 76 insertions(+), 32 deletions(-)

diff --git a/grub-core/net/dns.c b/grub-core/net/dns.c

index 3381ea7..725725c 100644

--- a/grub-core/net/dns.c

+++ b/grub-core/net/dns.c

@@ -34,6 +34,14 @@ struct dns_cache_element

 #define DNS_CACHE_SIZE 1021

 #define DNS_HASH_BASE 423

+typedef enum grub_dns_qtype_id

+  {

+    GRUB_DNS_QTYPE_A = 1,

+    GRUB_DNS_QTYPE_AAAA = 28

+  } grub_dns_qtype_id_t;

+

+static grub_dns_option_t dns_type_option = DNS_OPTION_PREFER_IPV4;

+

 static struct dns_cache_element dns_cache[DNS_CACHE_SIZE];

 static struct grub_net_network_level_address *dns_servers;

 static grub_size_t dns_nservers, dns_servers_alloc;

@@ -410,13 +418,13 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),

   return GRUB_ERR_NONE;

 }

-grub_err_t

-grub_net_dns_lookup (const char *name,

+static grub_err_t

+grub_net_dns_lookup_qtype (const char *name,

 		     const struct grub_net_network_level_address *servers,

 		     grub_size_t n_servers,

 		     grub_size_t *naddresses,

 		     struct grub_net_network_level_address **addresses,

-		     int cache)

+		     int cache, grub_dns_qtype_id_t qtype)

 {

   grub_size_t send_servers = 0;

   grub_size_t i, j;

@@ -471,8 +479,7 @@ grub_net_dns_lookup (const char *name,

 			   + GRUB_NET_MAX_LINK_HEADER_SIZE

 			   + GRUB_NET_UDP_HEADER_SIZE

 			   + sizeof (struct dns_header)

-			   + grub_strlen (name) + 2 + 4

-			   + 2 + 4);

+			   + grub_strlen (name) + 2 + 4);

   if (!nb)

     {

       grub_free (data.name);

@@ -482,7 +489,7 @@ grub_net_dns_lookup (const char *name,

 			+ GRUB_NET_MAX_LINK_HEADER_SIZE

 			+ GRUB_NET_UDP_HEADER_SIZE);

   grub_netbuff_put (nb, sizeof (struct dns_header)

-		    + grub_strlen (name) + 2 + 4 + 2 + 4);

+		    + grub_strlen (name) + 2 + 4);

   head = (struct dns_header *) nb->data;

   optr = (grub_uint8_t *) (head + 1);

   for (iptr = name; *iptr; )

@@ -509,18 +516,7 @@ grub_net_dns_lookup (const char *name,

   /* Type: A.  */

   *optr++ = 0;

-  *optr++ = 1;

-

-  /* Class.  */

-  *optr++ = 0;

-  *optr++ = 1;

-

-  /* Compressed name.  */

-  *optr++ = 0xc0;

-  *optr++ = 0x0c;

-  /* Type: AAAA.  */

-  *optr++ = 0;

-  *optr++ = 28;

+  *optr++ = qtype;

   /* Class.  */

   *optr++ = 0;

@@ -529,7 +525,7 @@ grub_net_dns_lookup (const char *name,

   head->id = data.id;

   head->flags = FLAGS_RD;

   head->ra_z_r_code = 0;

-  head->qdcount = grub_cpu_to_be16_compile_time (2);

+  head->qdcount = grub_cpu_to_be16_compile_time (1);

   head->ancount = grub_cpu_to_be16_compile_time (0);

   head->nscount = grub_cpu_to_be16_compile_time (0);

   head->arcount = grub_cpu_to_be16_compile_time (0);

@@ -587,16 +583,47 @@ grub_net_dns_lookup (const char *name,

   if (*data.naddresses)

     return GRUB_ERR_NONE;

   if (data.dns_err)

-    return grub_error (GRUB_ERR_NET_NO_DOMAIN,

-		       N_("no DNS record found"));

-    

+    {

+      grub_dprintf ("dns", "%s. QTYPE: %u QNAME: %s\n",

+                    N_("no DNS record found"), qtype, name);

+      return GRUB_ERR_NET_NO_DOMAIN;

+    }

   if (err)

     {

       grub_errno = err;

       return err;

     }

-  return grub_error (GRUB_ERR_TIMEOUT,

-		     N_("no DNS reply received"));

+  grub_dprintf ("dns", "%s. QTYPE: %u QNAME: %s\n",

+                N_("no DNS reply received"), qtype, name);

+  return GRUB_ERR_TIMEOUT;

+}

+

+grub_err_t

+grub_net_dns_lookup (const char *name,

+		     const struct grub_net_network_level_address *servers,

+		     grub_size_t n_servers,

+		     grub_size_t *naddresses,

+		     struct grub_net_network_level_address **addresses,

+		     int cache)

+{

+  if (dns_type_option == DNS_OPTION_IPV6 || dns_type_option == DNS_OPTION_PREFER_IPV6)

+      grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,

+                                 addresses, cache, GRUB_DNS_QTYPE_AAAA);

+  else

+      grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,

+                                 addresses, cache, GRUB_DNS_QTYPE_A);

+  if (!*naddresses)

+    {

+      if (dns_type_option == DNS_OPTION_PREFER_IPV4)

+          grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,

+                                     addresses, cache, GRUB_DNS_QTYPE_AAAA);

+      else if (dns_type_option == DNS_OPTION_PREFER_IPV6)

+          grub_net_dns_lookup_qtype (name, servers, n_servers, naddresses,

+                                     addresses, cache, GRUB_DNS_QTYPE_A);

+    }

+  if (!*naddresses)

+      return GRUB_ERR_NET_NO_DOMAIN;

+  return GRUB_ERR_NONE;

 }

 static grub_err_t

@@ -604,22 +631,28 @@ grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)),

 		   int argc, char **args)

 {

   grub_err_t err;

-  grub_size_t naddresses, i;

+  struct grub_net_network_level_address cmd_server;

+  struct grub_net_network_level_address *servers;

+  grub_size_t nservers, i, naddresses = 0;

   struct grub_net_network_level_address *addresses = 0;

   if (argc != 2 && argc != 1)

     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));

   if (argc == 2)

     {

-      struct grub_net_network_level_address server;

-      err = grub_net_resolve_address (args[1], &server);

+      err = grub_net_resolve_address (args[1], &cmd_server);

       if (err)

 	return err;

-      err = grub_net_dns_lookup (args[0], &server, 1, &naddresses,

-				 &addresses, 0);

+      servers = &cmd_server;

+      nservers = 1;

     }

   else

-    err = grub_net_dns_lookup (args[0], dns_servers, dns_nservers, &naddresses,

-			       &addresses, 0);

+    {

+      servers = dns_servers;

+      nservers = dns_nservers;

+    }

+

+  grub_net_dns_lookup (args[0], servers, nservers, &naddresses,

+                       &addresses, 0);

   for (i = 0; i < naddresses; i++)

     {

@@ -628,7 +661,9 @@ grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)),

       grub_printf ("%s\n", buf);

     }

   grub_free (addresses);

-  return GRUB_ERR_NONE;

+  if (naddresses)

+    return GRUB_ERR_NONE;

+  return grub_error (GRUB_ERR_NET_NO_DOMAIN, N_("no DNS record found"));

 }

 static grub_err_t

diff --git a/include/grub/net.h b/include/grub/net.h

index 3877451..a7e5b2c 100644

--- a/include/grub/net.h

+++ b/include/grub/net.h

@@ -505,6 +505,15 @@ grub_err_t

 grub_net_link_layer_resolve (struct grub_net_network_level_interface *inf,

 			     const grub_net_network_level_address_t *proto_addr,

 			     grub_net_link_level_address_t *hw_addr);

+

+typedef enum

+  {

+    DNS_OPTION_IPV4,

+    DNS_OPTION_IPV6,

+    DNS_OPTION_PREFER_IPV4,

+    DNS_OPTION_PREFER_IPV6

+  } grub_dns_option_t;

+

 grub_err_t

 grub_net_dns_lookup (const char *name,

 		     const struct grub_net_network_level_address *servers,

-- 

1.7.11.4