--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -150,6 +150,135 @@ static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
 	}
 }
 
+/*
+ * List management functions
+ *
+ * Feature negotiation lists rely on and maintain the following invariants:
+ * - each feat_num in the list is known, i.e. we know its type and default value
+ * - each feat_num/is_local combination is unique (old entries are overwritten)
+ * - SP values are always freshly allocated
+ * - list is sorted in increasing order of feature number (faster lookup)
+ */
+static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
+						     u8 feat_num, bool is_local)
+{
+	struct dccp_feat_entry *entry;
+
+	list_for_each_entry(entry, fn_list, node)
+		if (entry->feat_num == feat_num && entry->is_local == is_local)
+			return entry;
+		else if (entry->feat_num > feat_num)
+			break;
+	return NULL;
+}
+
+/**
+ * dccp_feat_entry_new  -  Central list update routine (called by all others)
+ * @head:  list to add to
+ * @feat:  feature number
+ * @local: whether the local (1) or remote feature with number @feat is meant
+ * This is the only constructor and serves to ensure the above invariants.
+ */
+static struct dccp_feat_entry *
+	      dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
+{
+	struct dccp_feat_entry *entry;
+
+	list_for_each_entry(entry, head, node)
+		if (entry->feat_num == feat && entry->is_local == local) {
+			dccp_feat_val_destructor(entry->feat_num, &entry->val);
+			return entry;
+		} else if (entry->feat_num > feat) {
+			head = &entry->node;
+			break;
+		}
+
+	entry = kmalloc(sizeof(*entry), gfp_any());
+	if (entry != NULL) {
+		entry->feat_num = feat;
+		entry->is_local = local;
+		list_add_tail(&entry->node, head);
+	}
+	return entry;
+}
+
+/**
+ * dccp_feat_push_change  -  Add/overwrite a Change option in the list
+ * @fn_list: feature-negotiation list to update
+ * @feat: one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is meant
+ * @needs_mandatory: whether to use Mandatory feature negotiation options
+ * @fval: pointer to NN/SP value to be inserted (will be copied)
+ */
+static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
+				 u8 mandatory, dccp_feat_val *fval)
+{
+	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
+
+	if (new == NULL)
+		return -ENOMEM;
+
+	new->feat_num	     = feat;
+	new->is_local	     = local;
+	new->state	     = FEAT_INITIALISING;
+	new->needs_confirm   = 0;
+	new->empty_confirm   = 0;
+	new->val	     = *fval;
+	new->needs_mandatory = mandatory;
+
+	return 0;
+}
+
+/**
+ * dccp_feat_push_confirm  -  Add a Confirm entry to the FN list
+ * @fn_list: feature-negotiation list to add to
+ * @feat: one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is being confirmed
+ * @fval: pointer to NN/SP value to be inserted or NULL
+ * Returns 0 on success, a Reset code for further processing otherwise.
+ */
+static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
+				  dccp_feat_val *fval)
+{
+	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
+
+	if (new == NULL)
+		return DCCP_RESET_CODE_TOO_BUSY;
+
+	new->feat_num	     = feat;
+	new->is_local	     = local;
+	new->state	     = FEAT_STABLE;	/* transition in 6.6.2 */
+	new->needs_confirm   = 1;
+	new->empty_confirm   = (fval == NULL);
+	new->val.nn	     = 0;		/* zeroes the whole structure */
+	if (!new->empty_confirm)
+		new->val     = *fval;
+	new->needs_mandatory = 0;
+
+	return 0;
+}
+
+static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
+{
+	return dccp_feat_push_confirm(fn_list, feat, local, NULL);
+}
+
+static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
+{
+	list_del(&entry->node);
+	dccp_feat_entry_destructor(entry);
+}
+
+void dccp_feat_list_purge(struct list_head *fn_list)
+{
+	struct dccp_feat_entry *entry, *next;
+
+	list_for_each_entry_safe(entry, next, fn_list, node)
+		dccp_feat_entry_destructor(entry);
+	INIT_LIST_HEAD(fn_list);
+}
+EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
+
 int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
 		     u8 *val, u8 len, gfp_t gfp)
 {