Dhcp option parsing fixes

dhcp/dhcp_clientv4.ml

@@ -109,13 +109,26 @@ let input t ~src ~dst ~src_port buf =
   let siaddr = Ipaddr.V4.of_int32 (get_dhcp_siaddr buf) in
   let giaddr = Ipaddr.V4.of_int32 (get_dhcp_giaddr buf) in
   let xid = get_dhcp_xid buf in
+  let of_byte x =
+    Printf.sprintf "%02x" (Char.code x) in
+  let chaddr_to_string x =
+    let chaddr_size = (String.length x) in
+    let dst_buffer = (String.make (chaddr_size * 2) '\000') in
+    for i = 0 to (chaddr_size - 1) do 
+      let thischar = of_byte x.[i] in
+        String.set dst_buffer (i*2) (String.get thischar 0);
+        String.set dst_buffer ((i*2)+1) (String.get thischar 1)
+    done;
+    dst_buffer
+  in
+  let chaddr = (chaddr_to_string) (copy_dhcp_chaddr buf) in
   let options = Cstruct.(copy buf sizeof_dhcp (len buf - sizeof_dhcp)) in
   let packet = Dhcpv4_option.Packet.of_bytes options in
   (* For debugging, print out the DHCP response *)
   Console.log_s t.c (sprintf "DHCP: input ciaddr %s yiaddr %s siaddr %s giaddr %s chaddr %s sname %s file %s\n"
     (Ipaddr.V4.to_string ciaddr) (Ipaddr.V4.to_string yiaddr)
     (Ipaddr.V4.to_string siaddr) (Ipaddr.V4.to_string giaddr)
-    (copy_dhcp_chaddr buf) (copy_dhcp_sname buf) (copy_dhcp_file buf))
+    (chaddr) (copy_dhcp_sname buf) (copy_dhcp_file buf)) 
   >>= fun () ->
   (* See what state our Netif is in and if this packet is useful *)
   let open Dhcpv4_option.Packet in
@@ -204,7 +217,6 @@ let input t ~src ~dst ~src_port buf =
     |Shutting_down ->
       Console.log_s t.c "DHCP thread: done"
     |_ -> 
-      (* TODO: This should be looking at the lease time *)
       Time.sleep 3600.0
       >>= fun () ->
       dhcp_thread t

dhcp/dhcpv4_option.ml

@@ -305,7 +305,9 @@ module Unmarshal = struct
     let getint () = (* Get one integer *)
       Char.code (getc ()) in
     let slice len = (* Get a substring *)
-      let r = String.sub buf !pos len in
+      if (!pos + len) > (String.length buf) || !pos > (String.length buf) 
+        then raise (Error (sprintf "Requested too much string at %d %d (%d)" !pos len (String.length buf) ));
+      let r = String.sub buf !pos len in 
       pos := !pos + len;
       r in
     let check c = (* Check that a char is the provided value *)
@@ -314,6 +316,14 @@ module Unmarshal = struct
     let get_addr fn = (* Get one address *)
       check '\004';
       fn (slice 4) in
+    let get_number len = (* Get a number from len bytes *)
+      let bytestring = slice len in
+      let r = ref 0 in 
+      for i = 0 to (len - 1) do
+         let bitshift = ((len - (i + 1)) * 8) in
+         r := ((Char.code bytestring.[i]) lsl bitshift) + !r;
+      done; 
+      !r in
     let get_addrs fn = (* Repeat fn n times and return the list *)
       let len = getint () / 4 in
       let res = ref [] in 
@@ -366,14 +376,16 @@ module Unmarshal = struct
           done;
           cont (`Parameter_request (List.rev !params))
       |`Max_size ->
-          let l1 = getint () lsl 8 in
-          cont (`Max_size (getint () + l1))
-      |`Interface_mtu ->
-          let l1 = getint () lsl 8 in
-          cont (`Interface_mtu (getint () + l1))
+          let len = getint () in
+          cont (`Max_size (get_number len))
+      |`Interface_mtu -> 
+          (* according to some printf/tcpdump testing, this is being set but not
+           * respected by the unikernel *)
+          let len = getint () in
+          cont (`Interface_mtu (get_number len))
       |`Client_id ->
           let len = getint () in 
-          let _ = getint () in 
+          let _ = getint () in (* disregard type information *)
           cont (`Client_id (slice len))
       |`End -> acc
       |`Unknown c -> cont (`Unknown (c, (slice (getint ()))))