[PATCH v2 3/3] Search for specific config files for netboot

[Javier Martinez Canillas <javierm@redhat.com>]

From: Paulo Flabiano Smorigo <pfsmorigo@br.ibm.com>

This patch implements a search for a specific configuration when the config
file is on a remoteserver. It uses the following order:
   1) DHCP client UUID option.
   2) MAC address (in lower case hexadecimal with dash separators);
   3) IP (in upper case hexadecimal) or IPv6;
   4) The original grub.cfg file.

This procedure is similar to what is used by pxelinux and yaboot:
http://www.syslinux.org/wiki/index.php/PXELINUX#config

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=873406

Signed-off-by: Paulo Flabiano Smorigo <pfsmorigo@br.ibm.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

---

Changes in v2:
- Add Reviewed-by tag from Daniel Kiper.

 grub-core/net/net.c     | 117 ++++++++++++++++++++++++++++++++++++++++
 grub-core/normal/main.c |  17 ++++--
 include/grub/net.h      |   3 ++
 3 files changed, 133 insertions(+), 4 deletions(-)

diff --git a/grub-core/net/net.c b/grub-core/net/net.c
index d5d726a315e..f066b02ebad 100644
--- a/grub-core/net/net.c
+++ b/grub-core/net/net.c
@@ -1735,6 +1735,123 @@ grub_net_restore_hw (void)
   return GRUB_ERR_NONE;
 }
 
+grub_err_t
+grub_net_search_config_file (char *config)
+{
+  grub_size_t config_len;
+  char *suffix;
+
+  auto int search_through (grub_size_t num_tries, grub_size_t slice_size);
+  int search_through (grub_size_t num_tries, grub_size_t slice_size)
+  {
+    while (num_tries-- > 0)
+      {
+        grub_dprintf ("net", "attempt to fetch config %s\n", config);
+
+        grub_file_t file;
+        file = grub_file_open (config, GRUB_FILE_TYPE_CONFIG);
+
+        if (file)
+          {
+            grub_file_close (file);
+            return 0;
+          }
+        else
+          {
+            if (grub_errno == GRUB_ERR_IO)
+              grub_errno = GRUB_ERR_NONE;
+          }
+
+        if (grub_strlen (suffix) < slice_size)
+          break;
+
+        config[grub_strlen (config) - slice_size] = '\0';
+      }
+
+    return 1;
+  }
+
+  config_len = grub_strlen (config);
+  config[config_len] = '-';
+  suffix = config + config_len + 1;
+
+  struct grub_net_network_level_interface *inf;
+  FOR_NET_NETWORK_LEVEL_INTERFACES (inf)
+    {
+      /* By the Client UUID. */
+
+      char client_uuid_var[sizeof ("net_") + grub_strlen (inf->name) +
+                           sizeof ("_clientuuid") + 1];
+      grub_snprintf (client_uuid_var, sizeof (client_uuid_var),
+                     "net_%s_clientuuid", inf->name);
+
+      const char *client_uuid;
+      client_uuid = grub_env_get (client_uuid_var);
+
+      if (client_uuid)
+        {
+          grub_strcpy (suffix, client_uuid);
+          if (search_through (1, 0) == 0) return GRUB_ERR_NONE;
+        }
+
+      /* By the MAC address. */
+
+      /* Add ethernet type */
+      grub_strcpy (suffix, "01-");
+
+      grub_net_hwaddr_to_str (&inf->hwaddress, suffix + 3);
+
+      char *ptr;
+      for (ptr = suffix; *ptr; ptr++)
+        if (*ptr == ':')
+          *ptr = '-';
+
+      if (search_through (1, 0) == 0) return GRUB_ERR_NONE;
+
+      /* By IP address */
+
+      switch ((&inf->address)->type)
+        {
+        case GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4:
+          {
+            grub_uint32_t n = grub_be_to_cpu32 ((&inf->address)->ipv4);
+            grub_snprintf (suffix, GRUB_NET_MAX_STR_ADDR_LEN, "%02X%02X%02X%02X", \
+                           ((n >> 24) & 0xff), ((n >> 16) & 0xff),      \
+                           ((n >> 8) & 0xff), ((n >> 0) & 0xff));
+
+            if (search_through (8, 1) == 0) return GRUB_ERR_NONE;
+            break;
+          }
+        case GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV6:
+          {
+            char buf[GRUB_NET_MAX_STR_ADDR_LEN];
+            struct grub_net_network_level_address base;
+            base.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV6;
+            grub_memcpy (&base.ipv6, ((&inf->address)->ipv6), 16);
+            grub_net_addr_to_str (&base, buf);
+
+            for (ptr = buf; *ptr; ptr++)
+              if (*ptr == ':')
+                *ptr = '-';
+
+            grub_snprintf (suffix, GRUB_NET_MAX_STR_ADDR_LEN, "%s", buf);
+            if (search_through (1, 0) == 0) return GRUB_ERR_NONE;
+            break;
+          }
+        case GRUB_NET_NETWORK_LEVEL_PROTOCOL_DHCP_RECV:
+          return grub_error (GRUB_ERR_BUG, "shouldn't reach here");
+        default:
+          return grub_error (GRUB_ERR_BUG,
+                             "unsupported address type %d", (&inf->address)->type);
+        }
+    }
+
+  /* Remove the remaining minus sign at the end. */
+  config[config_len] = '\0';
+
+  return GRUB_ERR_NONE;
+}
+
 static struct grub_preboot *fini_hnd;
 
 static grub_command_t cmd_addaddr, cmd_deladdr, cmd_addroute, cmd_delroute;
diff --git a/grub-core/normal/main.c b/grub-core/normal/main.c
index 1b03dfd57b9..cdeb58f1a1e 100644
--- a/grub-core/normal/main.c
+++ b/grub-core/normal/main.c
@@ -323,10 +323,19 @@ grub_cmd_normal (struct grub_command *cmd __attribute__ ((unused)),
 
       prefix = grub_env_get ("prefix");
       if (prefix)
-	{
-	  config = grub_xasprintf ("%s/grub.cfg", prefix);
-	  if (! config)
-	    goto quit;
+        {
+          grub_size_t config_len;
+          config_len = grub_strlen (prefix) +
+                      sizeof ("/grub.cfg-XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX");
+          config = grub_malloc (config_len);
+
+          if (! config)
+            goto quit;
+
+          grub_snprintf (config, config_len, "%s/grub.cfg", prefix);
+
+          if (grub_strncmp (prefix + 1, "tftp", sizeof ("tftp") - 1) == 0)
+            grub_net_search_config_file (config);
 
 	  grub_enter_normal_mode (config);
 	  grub_free (config);
diff --git a/include/grub/net.h b/include/grub/net.h
index 556c54e579f..ff6d347f7da 100644
--- a/include/grub/net.h
+++ b/include/grub/net.h
@@ -578,4 +578,7 @@ extern char *grub_net_default_server;
 
 #define VLANTAG_IDENTIFIER 0x8100
 
+grub_err_t
+grub_net_search_configfile (char *config);
+
 #endif /* ! GRUB_NET_HEADER */
-- 
2.21.0