diff --git a/include/osmocom/msc/call_leg.h b/include/osmocom/msc/call_leg.h
new file mode 100644
index 0000000..b8126e8
--- /dev/null
+++ b/include/osmocom/msc/call_leg.h
@@ -0,0 +1,81 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <osmocom/core/tdef.h>
+
+struct osmo_fsm_inst;
+struct osmo_sockaddr_str;
+struct osmo_mgcpc_ep;
+struct gsm_network;
+struct gsm_trans;
+struct rtp_stream;
+enum rtp_direction;
+
+extern struct osmo_tdef g_mgw_tdefs[];
+
+/* All sides of an MGW endpoint, connecting remote RTP peers via the MGW.
+ *
+ *     BSC                 MGW                PBX
+ *                   CI          CI
+ *                   [MGW-endpoint]
+ *     [--rtp_stream--]          [--rtp_stream--]
+ *     [----------------call_leg----------------]
+ *
+ */
+struct call_leg {
+	struct osmo_fsm_inst *fi;
+
+	struct osmo_mgcpc_ep *mgw_endpoint;
+
+	/* Array indexed by enum rtp_direction. */
+	struct rtp_stream *rtp[2];
+	/* Array indexed by enum rtp_direction. */
+	enum mgcp_connection_mode crcx_conn_mode[2];
+
+	uint32_t parent_event_rtp_addr_available;
+	uint32_t parent_event_rtp_complete;
+	uint32_t parent_event_rtp_released;
+
+	/* For internal MNCC, if RTP addresses for endpoints become assigned by the MGW, implicitly notify the other
+	 * call leg's RTP_TO_CN side rtp_stream with rtp_stream_remote_addr_available(). */
+	struct call_leg *local_bridge;
+
+	/* Prevent events from deallocating for certain release code paths, to prevent use-after-free problems. */
+	bool deallocating;
+};
+
+enum call_leg_event {
+	CALL_LEG_EV_RTP_STREAM_ADDR_AVAILABLE,
+	CALL_LEG_EV_RTP_STREAM_ESTABLISHED,
+	CALL_LEG_EV_RTP_STREAM_GONE,
+	CALL_LEG_EV_MGW_ENDPOINT_GONE,
+};
+
+void call_leg_init(struct gsm_network *net);
+
+struct call_leg *call_leg_alloc(struct osmo_fsm_inst *parent_fi,
+				uint32_t parent_event_term,
+				uint32_t parent_event_rtp_addr_available,
+				uint32_t parent_event_rtp_complete,
+				uint32_t parent_event_rtp_released);
+
+void call_leg_reparent(struct call_leg *cl,
+		       struct osmo_fsm_inst *parent_fi,
+		       uint32_t parent_event_term,
+		       uint32_t parent_event_rtp_addr_available,
+		       uint32_t parent_event_rtp_complete,
+		       uint32_t parent_event_rtp_released);
+
+int call_leg_local_bridge(struct call_leg *cl1, uint32_t call_id1, struct gsm_trans *trans1,
+			  struct call_leg *cl2, uint32_t call_id2, struct gsm_trans *trans2);
+
+int call_leg_ensure_rtp_alloc(struct call_leg *cl, enum rtp_direction dir, uint32_t call_id,
+			      struct gsm_trans *for_trans);
+int call_leg_ensure_ci(struct call_leg *cl, enum rtp_direction dir, uint32_t call_id, struct gsm_trans *for_trans,
+		       const enum mgcp_codecs *codec_if_known, const struct osmo_sockaddr_str *remote_port_if_known);
+struct osmo_sockaddr_str *call_leg_local_ip(struct call_leg *cl, enum rtp_direction dir);
+
+void call_leg_rtp_stream_gone(struct call_leg *cl, struct rtp_stream *rtps);
+void call_leg_release(struct call_leg *cl);