dhcp4:(VPP-1483) linearize chained packets before handling

dhcp packets might (when flooded) arrive in chains of cloned buffers

Change-Id: Ifddecd656b6a5d6ba8cd94184f5c021684e35548
Signed-off-by: Eyal Bari <ebari@cisco.com>
diff --git a/src/vnet/dhcp/dhcp4_packet.h b/src/vnet/dhcp/dhcp4_packet.h
index 9fbeb02..3076dd9 100644
--- a/src/vnet/dhcp/dhcp4_packet.h
+++ b/src/vnet/dhcp/dhcp4_packet.h
@@ -21,6 +21,17 @@
 
 typedef struct
 {
+  u8 option;
+  u8 length;
+  union
+  {
+    u8 data[0];
+    u32 data_as_u32[0];
+  };
+} __attribute__ ((packed)) dhcp_option_t;
+
+typedef struct
+{
   u8 opcode;			/* 1 = request, 2 = reply */
   u8 hardware_type;		/* 1 = ethernet */
   u8 hardware_address_length;
@@ -37,20 +48,9 @@
   u8 server_name[64];
   u8 boot_filename[128];
   ip4_address_t magic_cookie;
-  u8 options[0];
+  dhcp_option_t options[0];
 } dhcp_header_t;
 
-typedef struct
-{
-  u8 option;
-  u8 length;
-  union
-  {
-    u8 data[0];
-    u32 data_as_u32[0];
-  };
-} __attribute__ ((packed)) dhcp_option_t;
-
 typedef enum
 {
   DHCP_PACKET_DISCOVER = 1,
@@ -63,6 +63,7 @@
 typedef enum dhcp_packet_option_t_
 {
   DHCP_PACKET_OPTION_MSG_TYPE = 53,
+  DHCP_PACKET_OPTION_END = 0xff,
 } dhcp_packet_option_t;
 
 /* charming antique: 99.130.83.99 is the dhcp magic cookie */