gsupclient: Introduce gsup_client_mux

GSUP supports different message classes (e.g. SMS, USSD, Subscriber management),
within a daemon, the messages are usually handled in different parts of it.
The gsup client mux allow to place callbacks for the different message class.

This code original comes from the osmo-msc code and is here
re-licensed under the GPLv2.

Change-Id: I916c1bb6cfc48f92fc5db2b5c914eb1b4e25fa7f

include/Makefile.am

@@ -3,6 +3,7 @@ SUBDIRS = osmocom
 nobase_include_HEADERS = \
 	osmocom/gsupclient/cni_peer_id.h \
 	osmocom/gsupclient/gsup_client.h \
+	osmocom/gsupclient/gsup_client_mux.h \
 	osmocom/gsupclient/gsup_req.h \
 	osmocom/mslookup/mdns.h \
 	osmocom/mslookup/mdns_sock.h \

include/osmocom/gsupclient/gsup_client_mux.h

@@ -0,0 +1,56 @@
+/*
+ * (C) 2019 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <osmocom/gsm/gsup.h>
+
+struct gsup_client_mux;
+struct ipaccess_unit;
+
+struct gsup_client_mux_rx_cb {
+	int (*func)(struct gsup_client_mux *gcm, void *data, const struct osmo_gsup_message *gsup_msg);
+	void *data;
+};
+
+/* A GSUP client shared between code paths for various GSUP Message Classes.
+ * The main task is to dispatch GSUP messages to code paths corresponding to the respective Message Class, i.e.
+ * subscriber management, SMS, SS/USSD and inter-MSC messaging.
+ * If a GSUP Message Class IE is present in the message, the received message is dispatched directly to the rx_cb entry
+ * for that Message Class. Otherwise, the Message Class is determined by a switch() on the Message Type.*/
+struct gsup_client_mux {
+	struct osmo_gsup_client *gsup_client;
+
+	/* Target clients by enum osmo_gsup_message_class */
+	struct gsup_client_mux_rx_cb rx_cb[OSMO_GSUP_MESSAGE_CLASS_ARRAYSIZE];
+};
+
+struct gsup_client_mux *gsup_client_mux_alloc(void *talloc_ctx);
+int gsup_client_mux_start(struct gsup_client_mux *gcm, const char *gsup_server_addr_str, uint16_t gsup_server_port,
+			  struct ipaccess_unit *ipa_dev);
+
+int gsup_client_mux_tx(struct gsup_client_mux *gcm, const struct osmo_gsup_message *gsup_msg);
+void gsup_client_mux_tx_set_source(const struct gsup_client_mux *gcm, struct osmo_gsup_message *gsup_msg);
+void gsup_client_mux_tx_error_reply(struct gsup_client_mux *gcm, const struct osmo_gsup_message *gsup_orig,
+				    enum gsm48_gmm_cause cause);
+
+int gsup_client_mux_rx(struct osmo_gsup_client *gsup_client, struct msgb *msg);

src/gsupclient/Makefile.am

@@ -11,6 +11,7 @@ lib_LTLIBRARIES = libosmo-gsup-client.la
 libosmo_gsup_client_la_SOURCES = \
 	cni_peer_id.c \
 	gsup_client.c \
+	gsup_client_mux.c \
 	gsup_req.c \
 	$(NULL)
 

src/gsupclient/gsup_client_mux.c

@@ -0,0 +1,194 @@
+/* Directing individual GSUP messages to their respective handlers. */
+/*
+ * (C) 2019 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <errno.h>
+
+#include <osmocom/core/logging.h>
+
+#include <osmocom/gsupclient/gsup_client.h>
+#include <osmocom/gsupclient/gsup_client_mux.h>
+
+static enum osmo_gsup_message_class gsup_client_mux_classify(struct gsup_client_mux *gcm,
+						    const struct osmo_gsup_message *gsup_msg)
+{
+	if (gsup_msg->message_class)
+		return gsup_msg->message_class;
+
+	LOGP(DLGSUP, LOGL_DEBUG, "No explicit GSUP Message Class, trying to guess from message type %s\n",
+	     osmo_gsup_message_type_name(gsup_msg->message_type));
+
+	switch (gsup_msg->message_type) {
+	case OSMO_GSUP_MSGT_PROC_SS_REQUEST:
+	case OSMO_GSUP_MSGT_PROC_SS_RESULT:
+	case OSMO_GSUP_MSGT_PROC_SS_ERROR:
+		return OSMO_GSUP_MESSAGE_CLASS_USSD;
+
+	/* GSM 04.11 code implementing MO SMS */
+	case OSMO_GSUP_MSGT_MO_FORWARD_SM_ERROR:
+	case OSMO_GSUP_MSGT_MO_FORWARD_SM_RESULT:
+	case OSMO_GSUP_MSGT_READY_FOR_SM_ERROR:
+	case OSMO_GSUP_MSGT_READY_FOR_SM_RESULT:
+	case OSMO_GSUP_MSGT_MT_FORWARD_SM_REQUEST:
+		return OSMO_GSUP_MESSAGE_CLASS_SMS;
+
+	default:
+		return OSMO_GSUP_MESSAGE_CLASS_SUBSCRIBER_MANAGEMENT;
+	}
+}
+
+/* Non-static for unit tests */
+int gsup_client_mux_rx(struct osmo_gsup_client *gsup_client, struct msgb *msg)
+{
+	struct gsup_client_mux *gcm = gsup_client->data;
+	struct osmo_gsup_message gsup;
+	enum osmo_gsup_message_class message_class;
+	int rc;
+
+	rc = osmo_gsup_decode(msgb_l2(msg), msgb_l2len(msg), &gsup);
+	if (rc < 0) {
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to decode GSUP message: '%s' (%d) [ %s]\n",
+		     get_value_string(gsm48_gmm_cause_names, -rc), -rc, osmo_hexdump(msg->data, msg->len));
+		goto msgb_free_and_return;
+	}
+
+	if (!gsup.imsi[0]) {
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to decode GSUP message: missing IMSI\n");
+		if (OSMO_GSUP_IS_MSGT_REQUEST(gsup.message_type))
+			gsup_client_mux_tx_error_reply(gcm, &gsup, GMM_CAUSE_INV_MAND_INFO);
+		rc = -GMM_CAUSE_INV_MAND_INFO;
+		goto msgb_free_and_return;
+	}
+
+	message_class = gsup_client_mux_classify(gcm, &gsup);
+
+	if (message_class <= OSMO_GSUP_MESSAGE_CLASS_UNSET || message_class >= ARRAY_SIZE(gcm->rx_cb)) {
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to classify GSUP message target\n");
+		rc = -EINVAL;
+		goto msgb_free_and_return;
+	}
+
+	if (!gcm->rx_cb[message_class].func) {
+		LOGP(DLGSUP, LOGL_ERROR, "No receiver set up for GSUP Message Class %s\n", osmo_gsup_message_class_name(message_class));
+		rc = -ENOTSUP;
+		goto msgb_free_and_return;
+	}
+
+	rc = gcm->rx_cb[message_class].func(gcm, gcm->rx_cb[message_class].data, &gsup);
+
+msgb_free_and_return:
+	msgb_free(msg);
+	return rc;
+}
+
+/* Make it clear that struct gsup_client_mux should be talloc allocated, so that it can be used as talloc parent. */
+struct gsup_client_mux *gsup_client_mux_alloc(void *talloc_ctx)
+{
+	return talloc_zero(talloc_ctx, struct gsup_client_mux);
+}
+
+/* Start a GSUP client to serve this gsup_client_mux. */
+int gsup_client_mux_start(struct gsup_client_mux *gcm, const char *gsup_server_addr_str, uint16_t gsup_server_port,
+			  struct ipaccess_unit *ipa_dev)
+{
+	gcm->gsup_client = osmo_gsup_client_create2(gcm, ipa_dev,
+						    gsup_server_addr_str,
+						    gsup_server_port,
+						    &gsup_client_mux_rx, NULL);
+	if (!gcm->gsup_client)
+		return -ENOMEM;
+	gcm->gsup_client->data = gcm;
+	return 0;
+}
+
+int gsup_client_mux_tx(struct gsup_client_mux *gcm, const struct osmo_gsup_message *gsup_msg)
+{
+	struct msgb *msg;
+	int rc;
+
+	if (!gcm || !gcm->gsup_client) {
+		LOGP(DLGSUP, LOGL_ERROR, "GSUP link is down, cannot send GSUP message\n");
+		return -ENOTSUP;
+	}
+
+	msg = osmo_gsup_client_msgb_alloc();
+	rc = osmo_gsup_encode(msg, gsup_msg);
+	if (rc < 0) {
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to encode GSUP message: '%s'\n", strerror(-rc));
+		return rc;
+	}
+
+	return osmo_gsup_client_send(gcm->gsup_client, msg);
+}
+
+/* Set GSUP source_name to our local IPA name */
+void gsup_client_mux_tx_set_source(const struct gsup_client_mux *gcm,
+				   struct osmo_gsup_message *gsup_msg)
+{
+	const char *local_msc_name;
+
+	if (!gcm)
+		return;
+	if (!gcm->gsup_client)
+		return;
+	if (!gcm->gsup_client->ipa_dev)
+		return;
+	local_msc_name = gcm->gsup_client->ipa_dev->serno;
+	if (!local_msc_name)
+		return;
+	gsup_msg->source_name = (const uint8_t *) local_msc_name;
+	gsup_msg->source_name_len = strlen(local_msc_name) + 1;
+}
+
+/* Transmit GSUP error in response to original message */
+void gsup_client_mux_tx_error_reply(struct gsup_client_mux *gcm, const struct osmo_gsup_message *gsup_orig,
+				    enum gsm48_gmm_cause cause)
+{
+	struct osmo_gsup_message gsup_reply;
+
+	/* No need to answer if we couldn't parse an ERROR message type, only REQUESTs need an error reply. */
+	if (!OSMO_GSUP_IS_MSGT_REQUEST(gsup_orig->message_type))
+		return;
+
+	gsup_reply = (struct osmo_gsup_message){
+		.cause = cause,
+		.message_type = OSMO_GSUP_TO_MSGT_ERROR(gsup_orig->message_type),
+		.message_class = gsup_orig->message_class,
+		.destination_name = gsup_orig->source_name,
+		.destination_name_len = gsup_orig->source_name_len,
+
+		/* RP-Message-Reference is mandatory for SM Service */
+		.sm_rp_mr = gsup_orig->sm_rp_mr,
+	};
+
+	OSMO_STRLCPY_ARRAY(gsup_reply.imsi, gsup_orig->imsi);
+	gsup_client_mux_tx_set_source(gcm, &gsup_reply);
+
+	/* For SS/USSD, it's important to keep both session state and ID IEs */
+	if (gsup_orig->session_state != OSMO_GSUP_SESSION_STATE_NONE) {
+		gsup_reply.session_state = OSMO_GSUP_SESSION_STATE_END;
+		gsup_reply.session_id = gsup_orig->session_id;
+	}
+
+	if (osmo_gsup_client_enc_send(gcm->gsup_client, &gsup_reply))
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to send Error reply (imsi=%s)\n",
+		     osmo_quote_str(gsup_orig->imsi, -1));
+}