2 files changed, 67 insertions, 0 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 031ce350d3c1..2e2a6f229eaf 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -443,6 +443,8 @@ static inline int dccp_ack_pending(const struct sock *sk)
 
 extern int  dccp_feat_finalise_settings(struct dccp_sock *dp);
 extern int  dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq);
+extern int  dccp_feat_insert_opts(struct dccp_sock*, struct dccp_request_sock*,
+                                  struct sk_buff *skb);
 extern void dccp_feat_list_purge(struct list_head *fn_list);
 
 extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 44b10afd3fb6..da686464462d 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -300,6 +300,20 @@ cloning_failed:
         return -ENOMEM;
 }
 
+/**
+ * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
+ * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
+ * incoming options are accepted as long as their values are valid.
+ */
+static u8 dccp_feat_valid_nn_length(u8 feat_num)
+{
+        if (feat_num == DCCPF_ACK_RATIO)        /* RFC 4340, 11.3 and 6.6.8 */
+                return 2;
+        if (feat_num == DCCPF_SEQUENCE_WINDOW)  /* RFC 4340, 7.5.2 and 6.5  */
+                return 6;
+        return 0;
+}
+
 static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
 {
         switch (feat_num) {
@@ -342,6 +356,57 @@ static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
 }
 
 /**
+ * dccp_feat_insert_opts  -  Generate FN options from current list state
+ * @skb: next sk_buff to be sent to the peer
+ * @dp: for client during handshake and general negotiation
+ * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
+ */
+int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
+                          struct sk_buff *skb)
+{
+        struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
+        struct dccp_feat_entry *pos, *next;
+        u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
+        bool rpt;
+
+        /* put entries into @skb in the order they appear in the list */
+        list_for_each_entry_safe_reverse(pos, next, fn, node) {
+                opt  = dccp_feat_genopt(pos);
+                type = dccp_feat_type(pos->feat_num);
+                rpt  = false;
+
+                if (pos->empty_confirm) {
+                        len = 0;
+                        ptr = NULL;
+                } else {
+                        if (type == FEAT_SP) {
+                                len = pos->val.sp.len;
+                                ptr = pos->val.sp.vec;
+                                rpt = pos->needs_confirm;
+                        } else if (type == FEAT_NN) {
+                                len = dccp_feat_valid_nn_length(pos->feat_num);
+                                ptr = nn_in_nbo;
+                                dccp_encode_value_var(pos->val.nn, ptr, len);
+                        } else {
+                                DCCP_BUG("unknown feature %u", pos->feat_num);
+                                return -1;
+                        }
+                }
+
+                if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
+                        return -1;
+                if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
+                        return -1;
+                /*
+                 * Enter CHANGING after transmitting the Change option (6.6.2).
+                 */
+                if (pos->state == FEAT_INITIALISING)
+                        pos->state = FEAT_CHANGING;
+        }
+        return 0;
+}
+
+/**
  * __feat_register_nn  -  Register new NN value on socket
  * @fn: feature-negotiation list to register with
  * @feat: an NN feature from %dccp_feature_numbers