[PATCH v2 6/9] net: dhcp: use DHCP options for name and bootfile

[Andre Przywara <andre.przywara@arm.com>]

From: Andrei Borzenkov <arvidjaar@gmail.com>

The BOOTP RFC describes the boot file name and the server name as being
part of the integral BOOTP data structure, with some limits on the size
of them.
DHCP extends this by allowing them to be separate DHCP options, which is
more flexible.

Teach the code dealing with those fields to check for those DHCP options
first and use this information, if provided. We fall back to using the
BOOTP information if those options are not used.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 grub-core/net/bootp.c | 72 +++++++++++++++++++++++++++++++------------
 include/grub/net.h    |  2 ++
 2 files changed, 54 insertions(+), 20 deletions(-)

diff --git a/grub-core/net/bootp.c b/grub-core/net/bootp.c
index 42117b72d..0c6756ea0 100644
--- a/grub-core/net/bootp.c
+++ b/grub-core/net/bootp.c
@@ -169,7 +169,9 @@ grub_net_configure_by_dhcp_ack (const char *name,
   int mask = -1;
   char server_ip[sizeof ("xxx.xxx.xxx.xxx")];
   const grub_uint8_t *opt;
-  grub_uint8_t opt_len;
+  grub_uint8_t opt_len, overload = 0;
+  const char *boot_file = 0, *server_name = 0;
+  grub_size_t boot_file_len, server_name_len;
 
   addr.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
   addr.ipv4 = bp->your_ip;
@@ -188,9 +190,36 @@ grub_net_configure_by_dhcp_ack (const char *name,
   if (!inter)
     return 0;
 
-  if (size > OFFSET_OF (boot_file, bp))
-    grub_env_set_net_property (name, "boot_file", bp->boot_file,
-                               sizeof (bp->boot_file));
+  opt = find_dhcp_option (bp, size, GRUB_NET_DHCP_OVERLOAD, &opt_len);
+  if (opt && opt_len == 1)
+    overload = *opt;
+
+  opt = find_dhcp_option (bp, size, GRUB_NET_DHCP_TFTP_SERVER_NAME, &opt_len);
+  if (opt && opt_len)
+    {
+      server_name = (const char *) opt;
+      server_name_len = opt_len;
+    }
+  else if (size > OFFSET_OF (server_name, bp) && !(overload & GRUB_DHCP_OPT_OVERLOAD_SNAME) &&
+          bp->server_name[0])
+    {
+      server_name = bp->server_name;
+      server_name_len = sizeof (bp->server_name);
+    }
+
+  opt = find_dhcp_option (bp, size, GRUB_NET_DHCP_BOOTFILE_NAME, &opt_len);
+  if (opt && opt_len)
+    {
+      boot_file = (const char *) opt;
+      boot_file_len = opt_len;
+    }
+  else if (size > OFFSET_OF (boot_file, bp) && !(overload && GRUB_DHCP_OPT_OVERLOAD_FILE) &&
+          bp->boot_file[0])
+    {
+      boot_file = bp->boot_file;
+      boot_file_len = sizeof (bp->boot_file);
+    }
+
   if (bp->server_ip)
     {
       grub_snprintf (server_ip, sizeof (server_ip), "%d.%d.%d.%d",
@@ -221,35 +250,38 @@ grub_net_configure_by_dhcp_ack (const char *name,
       *device = grub_xasprintf ("tftp,%s", server_ip);
       grub_print_error ();
     }
-  if (size > OFFSET_OF (server_name, bp)
-      && bp->server_name[0])
+
+  if (server_name)
     {
-      grub_env_set_net_property (name, "dhcp_server_name", bp->server_name,
-                                 sizeof (bp->server_name));
+      grub_env_set_net_property (name, "dhcp_server_name", server_name, server_name_len);
       if (is_def && !grub_net_default_server)
 	{
-	  grub_net_default_server = grub_strdup (bp->server_name);
+	  grub_net_default_server = grub_strdup (server_name);
 	  grub_print_error ();
 	}
       if (device && !*device)
 	{
-	  *device = grub_xasprintf ("tftp,%s", bp->server_name);
+	  *device = grub_xasprintf ("tftp,%s", server_name);
 	  grub_print_error ();
 	}
     }
 
-  if (size > OFFSET_OF (boot_file, bp) && path)
+  if (boot_file)
     {
-      *path = grub_strndup (bp->boot_file, sizeof (bp->boot_file));
-      grub_print_error ();
-      if (*path)
+      grub_env_set_net_property (name, "boot_file", boot_file, boot_file_len);
+      if (path)
 	{
-	  char *slash;
-	  slash = grub_strrchr (*path, '/');
-	  if (slash)
-	    *slash = 0;
-	  else
-	    **path = 0;
+	  *path = grub_strndup (boot_file, boot_file_len);
+	  grub_print_error ();
+	  if (*path)
+	    {
+	      char *slash;
+	      slash = grub_strrchr (*path, '/');
+	      if (slash)
+		*slash = 0;
+	      else
+		**path = 0;
+	    }
 	}
     }
 
diff --git a/include/grub/net.h b/include/grub/net.h
index a1138f5d4..f7b546446 100644
--- a/include/grub/net.h
+++ b/include/grub/net.h
@@ -460,6 +460,8 @@ enum
     GRUB_NET_BOOTP_ROOT_PATH = 0x11,
     GRUB_NET_BOOTP_EXTENSIONS_PATH = 0x12,
     GRUB_NET_DHCP_OVERLOAD = 52,
+    GRUB_NET_DHCP_TFTP_SERVER_NAME = 66,
+    GRUB_NET_DHCP_BOOTFILE_NAME = 67,
     GRUB_NET_BOOTP_END = 0xff
   };
 
-- 
2.17.1