[DCCP] options: Fix some aspects of mandatory option processing

According to dccp draft (draft-ietf-dccp-spec-13.txt) section 5.8.2
(Mandatory Option) the following patch correct the handling of the
following cases:

1) "... and any Mandatory options received on DCCP-Data packets MUST be
  ignored."

2) "The connection is in error and should be reset with Reset Code 5, ...
  if option O is absent (Mandatory was the last byte of the option list), or
  if option O equals Mandatory."

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/dccp/options.c b/net/dccp/options.c
index 79d228e4d6b2..8867b6f43220 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -109,7 +109,8 @@ int dccp_parse_options(struct sock *sk, struct sk_buff *skb)
                 case DCCPO_MANDATORY:
                         if (mandatory)
                                 goto out_invalid_option;
-                        mandatory = 1;
+                        if (pkt_type != DCCP_PKT_DATA)
+                                mandatory = 1;
                         break;
                 case DCCPO_NDP_COUNT:
                         if (len > 3)
@@ -249,6 +250,10 @@ int dccp_parse_options(struct sock *sk, struct sk_buff *skb)
                         mandatory = 0;
         }
 
+        /* mandatory was the last byte in option list -> reset connection */
+        if (mandatory)
+                goto out_invalid_option;
+
         return 0;
 
 out_invalid_option: