proposal: Use an additional "default" constructor specific to AEAD algorithms

This allows a caller to create a separated proposal for supported AEAD
algorithms, as required by RFC 5996.

src/libcharon/config/proposal.c

@@ -809,6 +809,29 @@ proposal_t *proposal_create_default(protocol_id_t protocol)
 	return &this->public;
 }
 
+/*
+ * Describtion in header-file
+ */
+proposal_t *proposal_create_default_aead(protocol_id_t protocol)
+{
+	private_proposal_t *this;
+
+	switch (protocol)
+	{
+		case PROTO_IKE:
+			this = (private_proposal_t*)proposal_create(protocol, 0);
+			proposal_add_supported_ike(this, TRUE);
+			return &this->public;
+		case PROTO_ESP:
+			/* we currently don't include any AEAD proposal for ESP, as we
+			 * don't know if our kernel backend actually supports it. */
+			return NULL;
+		case PROTO_AH:
+		default:
+			return NULL;
+	}
+}
+
 /*
  * Describtion in header-file
  */

src/libcharon/config/proposal.h

@@ -195,6 +195,14 @@ proposal_t *proposal_create(protocol_id_t protocol, u_int number);
  */
 proposal_t *proposal_create_default(protocol_id_t protocol);
 
+/**
+ * Create a default proposal for supported AEAD algorithms
+ *
+ * @param protocol			protocol, such as PROTO_ESP
+ * @return					proposal_t object, NULL if none supported
+ */
+proposal_t *proposal_create_default_aead(protocol_id_t protocol);
+
 /**
  * Create a proposal from a string identifying the algorithms.
  *