m3ua: re-factor m3ua_rx_xfer(): Externalize AS for ASP lookup

Let's factor-out the lookup of the AS into the separate function
find_as_for_asp().  This enables us to reuse this code in upcoming
support for SNM messages.

Change-Id: If58ea24efe7d54994a7ca2f0a97944bd297a8cc6

1 files changed, 34 insertions, 21 deletions

diff --git a/src/m3ua.c b/src/m3ua.c
index 08a89b5..542777e 100644
--- a/src/m3ua.c
+++ b/src/m3ua.c
@@ -533,7 +533,7 @@ struct m3ua_data_hdr *data_hdr_from_m3ua(struct xua_msg *xua)
 }
 
 /* if given ASP only has one AS, return that AS */
-static struct osmo_ss7_as *find_single_as_for_asp(struct osmo_ss7_asp *asp)
+static struct osmo_ss7_as *find_single_as_for_asp(const struct osmo_ss7_asp *asp)
 {
 	struct osmo_ss7_as *as, *as_found = NULL;
 
@@ -549,44 +549,33 @@ static struct osmo_ss7_as *find_single_as_for_asp(struct osmo_ss7_asp *asp)
 	return as_found;
 }
 
-static int m3ua_rx_xfer(struct osmo_ss7_asp *asp, struct xua_msg *xua)
+static int find_as_for_asp(struct osmo_ss7_as **as, const struct osmo_ss7_asp *asp,
+			   const struct xua_msg_part *rctx_ie)
 {
-	struct xua_msg_part *rctx_ie = xua_msg_find_tag(xua, M3UA_IEI_ROUTE_CTX);
-	struct m3ua_data_hdr *dh;
-	struct osmo_ss7_as *as;
-
-	LOGPASP(asp, DLM3UA, LOGL_DEBUG, "m3ua_rx_xfer\n");
-
-	if (xua->hdr.msg_type != M3UA_XFER_DATA) {
-		LOGPASP(asp, DLM3UA, LOGL_ERROR,
-			"%s(): unsupported message type: %s\n",
-			__func__,
-			get_value_string(m3ua_xfer_msgt_names, xua->hdr.msg_type));
-		return M3UA_ERR_UNSUPP_MSG_TYPE;
-	}
+	*as = NULL;
 
 	if (rctx_ie) {
 		uint32_t rctx = xua_msg_part_get_u32(rctx_ie);
 		/* Use routing context IE to look up the AS for which the
 		 * message was received. */
-		as = osmo_ss7_as_find_by_rctx(asp->inst, rctx);
-		if (!as) {
+		*as = osmo_ss7_as_find_by_rctx(asp->inst, rctx);
+		if (!*as) {
 			LOGPASP(asp, DLM3UA, LOGL_ERROR, "%s(): invalid routing context: %u\n",
 				__func__, rctx);
 			return M3UA_ERR_INVAL_ROUT_CTX;
 		}
 
 		/* Verify that this ASP is part of the AS. */
-		if (!osmo_ss7_as_has_asp(as, asp)) {
+		if (!osmo_ss7_as_has_asp(*as, asp)) {
 			LOGPASP(asp, DLM3UA, LOGL_ERROR,
 				"%s(): This Application Server Process is not part of the AS %s "
-				"resolved by routing context %u\n", __func__, (as)->cfg.name, rctx);
+				"resolved by routing context %u\n", __func__, (*as)->cfg.name, rctx);
 			return M3UA_ERR_NO_CONFGD_AS_FOR_ASP;
 		}
 	} else {
 		/* no explicit routing context; this only works if there is only one AS in the ASP */
-		as = find_single_as_for_asp(asp);
-		if (!as) {
+		*as = find_single_as_for_asp(asp);
+		if (!*as) {
 			LOGPASP(asp, DLM3UA, LOGL_ERROR,
 				"%s(): ASP sent M3UA without Routing Context IE but unable to uniquely "
 				"identify the AS for this message\n", __func__);
@@ -594,6 +583,30 @@ static int m3ua_rx_xfer(struct osmo_ss7_asp *asp, struct xua_msg *xua)
 		}
 	}
 
+	return 0;
+}
+
+static int m3ua_rx_xfer(struct osmo_ss7_asp *asp, struct xua_msg *xua)
+{
+	struct xua_msg_part *rctx_ie = xua_msg_find_tag(xua, M3UA_IEI_ROUTE_CTX);
+	struct m3ua_data_hdr *dh;
+	struct osmo_ss7_as *as;
+	int rc;
+
+	LOGPASP(asp, DLM3UA, LOGL_DEBUG, "m3ua_rx_xfer\n");
+
+	if (xua->hdr.msg_type != M3UA_XFER_DATA) {
+		LOGPASP(asp, DLM3UA, LOGL_ERROR,
+			"%s(): unsupported message type: %s\n",
+			__func__,
+			get_value_string(m3ua_xfer_msgt_names, xua->hdr.msg_type));
+		return M3UA_ERR_UNSUPP_MSG_TYPE;
+	}
+
+	rc = find_as_for_asp(&as, asp, rctx_ie);
+	if (rc)
+		return rc;
+
 	/* FIXME: check for AS state == ACTIVE */
 
 	/* store the MTP-level information in the xua_msg for use by