clarify osmo_pfcp_msg alloc API

Looking at the osmo_pfcp_msg_alloc API with a bit of distance now, I
found that:

- it is confusing to have a single function for req and resp. A resp
  may pass remote_addr as NULL, and a req may pass in_reply_to as NULL.
  Make this much more obvious with separate req/resp functions.

- the osmo_pfcp_endpoint_tx() implicitly puts the local Node ID into
  sent PFCP messages, so the local_node_id arg for msg alloc is
  redundant. Drop that.

Refactor without backwards compat, because we have not yet officially
released this API. This requires a fixup patch to osmo-upf.git (and
affects unmerged patches to osmo-hnbgw.git).

Related: SYS#5599
Related: I73e6da3b80f05e9408c81f41ac05d6578b8e31cf (osmo-upf)
Change-Id: I0d71134e42932cc72992eba73a15e82bc7cd11bd

3 files changed, 39 insertions, 21 deletions

diff --git a/src/libosmo-pfcp/pfcp_cp_peer.c b/src/libosmo-pfcp/pfcp_cp_peer.c
index c47b440..e1dd9ac 100644
--- a/src/libosmo-pfcp/pfcp_cp_peer.c
+++ b/src/libosmo-pfcp/pfcp_cp_peer.c
@@ -160,7 +160,7 @@ static void pfcp_cp_peer_wait_assoc_setup_resp_onenter(struct osmo_fsm_inst *fi,
 	struct osmo_pfcp_cp_peer *cp_peer = fi->priv;
 	struct osmo_pfcp_msg *m;
 
-	m = osmo_pfcp_cp_peer_new_msg_tx(cp_peer, OSMO_PFCP_MSGT_ASSOC_SETUP_REQ);
+	m = osmo_pfcp_cp_peer_new_req(cp_peer, OSMO_PFCP_MSGT_ASSOC_SETUP_REQ);
 	m->ies.assoc_setup_req.recovery_time_stamp = cp_peer->ep->recovery_time_stamp;
 
 	m->ies.assoc_setup_req.cp_function_features_present = true;
@@ -391,14 +391,25 @@ void osmo_pfcp_cp_peer_set_msg_ctx(struct osmo_pfcp_cp_peer *cp_peer, struct osm
 	osmo_use_count_get_put(m->ctx.peer_use_count, m->ctx.peer_use_token, 1);
 }
 
-struct osmo_pfcp_msg *osmo_pfcp_cp_peer_new_msg_tx(struct osmo_pfcp_cp_peer *cp_peer,
-						   enum osmo_pfcp_message_type msg_type)
+/* Allocate a new PFCP request message to be sent to cp_peer->remote_addr. */
+struct osmo_pfcp_msg *osmo_pfcp_cp_peer_new_req(struct osmo_pfcp_cp_peer *cp_peer,
+						enum osmo_pfcp_message_type msg_type)
 {
 	struct osmo_pfcp_msg *m;
-	m = osmo_pfcp_msg_alloc_tx(cp_peer->ep, &cp_peer->remote_addr, &cp_peer->ep->cfg.local_node_id, NULL,
-				   msg_type);
-	if (!m)
-		return m;
+	m = osmo_pfcp_msg_alloc_tx_req(cp_peer->ep, &cp_peer->remote_addr, msg_type);
+	OSMO_ASSERT(m);
+	osmo_pfcp_cp_peer_set_msg_ctx(cp_peer, m);
+	return m;
+}
+
+/* Allocate a new PFCP response message to be sent to cp_peer->remote_addr. */
+struct osmo_pfcp_msg *osmo_pfcp_cp_peer_new_resp(struct osmo_pfcp_cp_peer *cp_peer,
+						 const struct osmo_pfcp_msg *in_reply_to,
+						 enum osmo_pfcp_message_type msg_type)
+{
+	struct osmo_pfcp_msg *m;
+	m = osmo_pfcp_msg_alloc_tx_resp(cp_peer->ep, in_reply_to, msg_type);
+	OSMO_ASSERT(m);
 	osmo_pfcp_cp_peer_set_msg_ctx(cp_peer, m);
 	return m;
 }
diff --git a/src/libosmo-pfcp/pfcp_endpoint.c b/src/libosmo-pfcp/pfcp_endpoint.c
index f446858..6162086 100644
--- a/src/libosmo-pfcp/pfcp_endpoint.c
+++ b/src/libosmo-pfcp/pfcp_endpoint.c
@@ -242,8 +242,7 @@ int osmo_pfcp_endpoint_tx_data(struct osmo_pfcp_endpoint *ep, struct osmo_pfcp_m
 
 int osmo_pfcp_endpoint_tx_heartbeat_req(struct osmo_pfcp_endpoint *ep, const struct osmo_sockaddr *remote_addr)
 {
-	struct osmo_pfcp_msg *tx = osmo_pfcp_msg_alloc_tx(OTC_SELECT, remote_addr, NULL, NULL,
-							  OSMO_PFCP_MSGT_HEARTBEAT_REQ);
+	struct osmo_pfcp_msg *tx = osmo_pfcp_msg_alloc_tx_req(OTC_SELECT, remote_addr, OSMO_PFCP_MSGT_HEARTBEAT_REQ);
 	tx->ies.heartbeat_req.recovery_time_stamp = ep->recovery_time_stamp;
 	tx->h.sequence_nr = osmo_pfcp_next_seq_nr(&ep->seq_nr_state);
 	return osmo_pfcp_endpoint_tx_data(ep, tx);
@@ -326,7 +325,7 @@ static void osmo_pfcp_endpoint_handle_rx(struct osmo_pfcp_endpoint *ep, struct o
 
 	if (m->h.message_type == OSMO_PFCP_MSGT_HEARTBEAT_REQ) {
 		/* Directly answer with a Heartbeat Response. */
-		struct osmo_pfcp_msg *resp = osmo_pfcp_msg_alloc_tx(OTC_SELECT, NULL, NULL, m, OSMO_PFCP_MSGT_HEARTBEAT_RESP);
+		struct osmo_pfcp_msg *resp = osmo_pfcp_msg_alloc_tx_resp(OTC_SELECT, m, OSMO_PFCP_MSGT_HEARTBEAT_RESP);
 		resp->ies.heartbeat_resp.recovery_time_stamp = ep->recovery_time_stamp;
 		osmo_pfcp_endpoint_tx_data(ep, resp);
 		/* Still also dispatch the Rx event to the peer. */
diff --git a/src/libosmo-pfcp/pfcp_msg.c b/src/libosmo-pfcp/pfcp_msg.c
index 9d65efc..5f55575 100644
--- a/src/libosmo-pfcp/pfcp_msg.c
+++ b/src/libosmo-pfcp/pfcp_msg.c
@@ -418,31 +418,39 @@ struct osmo_pfcp_msg *osmo_pfcp_msg_alloc_rx(void *ctx, const struct osmo_sockad
 	return rx;
 }
 
-struct osmo_pfcp_msg *osmo_pfcp_msg_alloc_tx(void *ctx, const struct osmo_sockaddr *remote_addr,
-					     const struct osmo_pfcp_ie_node_id *node_id,
-					     const struct osmo_pfcp_msg *in_reply_to,
-					     enum osmo_pfcp_message_type msg_type)
+static struct osmo_pfcp_msg *osmo_pfcp_msg_alloc_tx(void *ctx, const struct osmo_sockaddr *remote_addr,
+						    const struct osmo_pfcp_msg *in_reply_to,
+						    enum osmo_pfcp_message_type msg_type)
 {
 	struct osmo_pfcp_msg *tx;
 	if (!remote_addr && in_reply_to)
 		remote_addr = &in_reply_to->remote_addr;
 	OSMO_ASSERT(remote_addr);
 	tx = _osmo_pfcp_msg_alloc(ctx, remote_addr);
+	OSMO_ASSERT(tx);
 	tx->is_response = osmo_pfcp_msgtype_is_response(msg_type);
 	tx->h.message_type = msg_type;
 	if (in_reply_to)
 		tx->h.sequence_nr = in_reply_to->h.sequence_nr;
 	osmo_pfcp_msg_set_memb_ofs(tx);
-
-	/* Write the local node id data to the correct tx->ies.* member. */
-	if (node_id) {
-		struct osmo_pfcp_ie_node_id *tx_node_id = osmo_pfcp_msg_node_id(tx);
-		if (tx_node_id)
-			*tx_node_id = *node_id;
-	}
 	return tx;
 }
 
+/* Allocate a new PFCP Request message to be transmitted to a peer. */
+struct osmo_pfcp_msg *osmo_pfcp_msg_alloc_tx_req(void *ctx, const struct osmo_sockaddr *remote_addr,
+						 enum osmo_pfcp_message_type msg_type)
+{
+	return osmo_pfcp_msg_alloc_tx(ctx, remote_addr, NULL, msg_type);
+}
+
+/* Allocate a new PFCP Response message to be transmitted to a peer, as a response to a received PFCP message.
+ * Pass the received PFCP Request in in_reply_to; take the remote address and sequence nr from in_reply_to. */
+struct osmo_pfcp_msg *osmo_pfcp_msg_alloc_tx_resp(void *ctx, const struct osmo_pfcp_msg *in_reply_to,
+						  enum osmo_pfcp_message_type msg_type)
+{
+	return osmo_pfcp_msg_alloc_tx(ctx, NULL, in_reply_to, msg_type);
+}
+
 static int osmo_pfcp_msg_destructor(struct osmo_pfcp_msg *m)
 {
 	OSMO_LOG_PFCP_MSG(m, LOGL_DEBUG, "discarding\n");