net/dhcp: Use DHCP options for name and bootfile

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>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/net/bootp.c b/grub-core/net/bootp.c
index 2fb79d1623840d2312aaa741ac3582ef822d4f1f..bfde6ef10c5a62d37759b1c3b27001910e026538 100644 (file)
--- a/grub-core/net/bootp.c
+++ b/grub-core/net/bootp.c
@@ -168,7 +168,9 @@ 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;
@@ -187,9 +189,36 @@ 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",
@@ -220,35 +249,38 @@ 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 a1138f5d44383417ab6c518763cc93fd7ba4edb6..f7b546446b47a267f40a7ef1551a4dbc7cf2c0b6 100644 (file)
--- 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
   };