Add SGs Interface

Add an SGs interface (3GPP TS 29.118) to osmo-msc in order to support
SMS tunneling and Circuit Switched Fallback (CSFB)

Change-Id: I73359925fc1ca72b33a1466e6ac41307f2f0b11d
Related: OS#3615

1 files changed, 187 insertions, 0 deletions

diff --git a/src/libmsc/sgs_server.c b/src/libmsc/sgs_server.c
new file mode 100644
index 000000000..56f1548cb
--- /dev/null
+++ b/src/libmsc/sgs_server.c
@@ -0,0 +1,187 @@
+/* (C) 2018-2019 by sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Harald Welte, Philipp Maier
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <osmocom/msc/sgs_iface.h>
+#include <osmocom/msc/debug.h>
+#include <osmocom/msc/sgs_server.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/socket.h>
+#include <osmocom/core/select.h>
+#include <osmocom/netif/stream.h>
+#include <netinet/sctp.h>
+
+#define LOGSGC(sgc, lvl, fmt, args...) \
+	LOGP(DSGS, lvl, "%s: " fmt, (sgc)->sockname, ## args)
+
+/* call-back when data arrives on SGs */
+static int sgs_conn_readable_cb(struct osmo_stream_srv *conn)
+{
+	struct osmo_fd *ofd = osmo_stream_srv_get_ofd(conn);
+	struct sgs_connection *sgc = osmo_stream_srv_get_data(conn);
+	struct msgb *msg = gsm29118_msgb_alloc();
+	struct sctp_sndrcvinfo sinfo;
+	int flags = 0;
+	int rc;
+
+	/* we cannot use osmo_stream_srv_recv() here, as we might get some out-of-band info from
+	 * SCTP. FIXME: add something like osmo_stream_srv_recv_sctp() to libosmo-netif and use
+	 * it here as well as in libosmo-sigtran */
+	rc = sctp_recvmsg(ofd->fd, msgb_data(msg), msgb_tailroom(msg), NULL, NULL, &sinfo, &flags);
+	if (rc < 0) {
+		osmo_stream_srv_destroy(conn);
+		rc = -EBADF;
+		goto out;
+	} else if (rc == 0) {
+		osmo_stream_srv_destroy(conn);
+		rc = -EBADF;
+		goto out;
+	} else {
+		msgb_put(msg, rc);
+	}
+
+	if (flags & MSG_NOTIFICATION) {
+		union sctp_notification *notif = (union sctp_notification *)msgb_data(msg);
+
+		switch (notif->sn_header.sn_type) {
+		case SCTP_SHUTDOWN_EVENT:
+			osmo_stream_srv_destroy(conn);
+			rc = -EBADF;
+			break;
+		case SCTP_ASSOC_CHANGE:
+			/* FIXME: do we have to notify the SGs code about this? */
+			break;
+		default:
+			break;
+		}
+		rc = 0;
+		goto out;
+	}
+
+	/* set l2 header, as that's what we use in SGs code */
+	msg->l2h = msgb_data(msg);
+
+	if (msgb_sctp_ppid(msg) != 0) {
+		LOGSGC(sgc, LOGL_NOTICE, "Ignoring SCTP PPID %ld (spec violation)\n", msgb_sctp_ppid(msg));
+		msgb_free(msg);
+		return 0;
+	}
+
+	/* handle message */
+	sgs_iface_rx(sgc, msg);
+
+	return 0;
+out:
+	msgb_free(msg);
+	return rc;
+}
+
+/* call-back when new connection is closed ed on SGs */
+static int sgs_conn_closed_cb(struct osmo_stream_srv *conn)
+{
+	struct sgs_connection *sgc = osmo_stream_srv_get_data(conn);
+
+	LOGSGC(sgc, LOGL_NOTICE, "Connection lost\n");
+	if (sgc->mme) {
+		/* unlink ourselves from the MME context */
+		if (sgc->mme->conn == sgc)
+			sgc->mme->conn = NULL;
+	}
+	llist_del(&sgc->entry);
+	return 0;
+}
+
+/* call-back when new connection is accept() ed on SGs */
+static int sgs_accept_cb(struct osmo_stream_srv_link *link, int fd)
+{
+	struct sgs_state *sgs = osmo_stream_srv_link_get_data(link);
+	struct sgs_connection *sgc = talloc_zero(link, struct sgs_connection);
+	OSMO_ASSERT(sgc);
+	sgc->sgs = sgs;
+	osmo_sock_get_name_buf(sgc->sockname, sizeof(sgc->sockname), fd);
+	sgc->srv = osmo_stream_srv_create(sgc, link, fd, sgs_conn_readable_cb, sgs_conn_closed_cb, sgc);
+	if (!sgc->srv) {
+		talloc_free(sgc);
+		return -1;
+	}
+	LOGSGC(sgc, LOGL_INFO, "Accepted new SGs connection\n");
+	llist_add_tail(&sgc->entry, &sgs->conn_list);
+
+	return 0;
+}
+
+static struct sgs_state *sgs_state_alloc(void *ctx)
+{
+	struct sgs_state *sgs = talloc_zero(ctx, struct sgs_state);
+
+	INIT_LLIST_HEAD(&sgs->mme_list);
+	INIT_LLIST_HEAD(&sgs->conn_list);
+
+	memcpy(sgs->cfg.timer, sgs_state_timer_defaults, sizeof(sgs->cfg.timer));
+	memcpy(sgs->cfg.counter, sgs_state_counter_defaults, sizeof(sgs->cfg.counter));
+	sgs->cfg.local_port = SGS_PORT_DEFAULT;
+	osmo_strlcpy(sgs->cfg.local_addr, DEFAULT_SGS_SERVER_IP, sizeof(sgs->cfg.local_addr));
+	osmo_strlcpy(sgs->cfg.vlr_name, DEFAULT_SGS_SERVER_VLR_NAME, sizeof(sgs->cfg.vlr_name));
+
+	return sgs;
+}
+
+/*! allocate SGs new sgs state
+ *  \param[in] ctx talloc context
+ *  \returns returns allocated sgs state, NULL in case of error. */
+struct sgs_state *sgs_server_alloc(void *ctx)
+{
+	struct sgs_state *sgs;
+	struct osmo_stream_srv_link *link;
+
+	sgs = sgs_state_alloc(ctx);
+	if (!sgs)
+		return NULL;
+
+	sgs->srv_link = link = osmo_stream_srv_link_create(ctx);
+	if (!sgs->srv_link)
+		return NULL;
+
+	osmo_stream_srv_link_set_nodelay(link, true);
+	osmo_stream_srv_link_set_addr(link, sgs->cfg.local_addr);
+	osmo_stream_srv_link_set_port(link, sgs->cfg.local_port);
+	osmo_stream_srv_link_set_proto(link, IPPROTO_SCTP);
+	osmo_stream_srv_link_set_data(link, sgs);
+	osmo_stream_srv_link_set_accept_cb(link, sgs_accept_cb);
+
+	return sgs;
+}
+
+/*! (re)open SGs interface (SCTP)
+ *  \param[in] sgs associated sgs state
+ *  \returns 0 in case of success, -EINVAL in case of error. */
+int sgs_server_open(struct sgs_state *sgs)
+{
+	int rc;
+	struct osmo_fd *ofd = osmo_stream_srv_link_get_ofd(sgs->srv_link);
+
+	rc = osmo_stream_srv_link_open(sgs->srv_link);
+	if (rc < 0) {
+		LOGP(DSGS, LOGL_ERROR, "SGs socket cannot be opened: %s\n", strerror(errno));
+		return -EINVAL;
+	}
+
+	LOGP(DSGS, LOGL_NOTICE, "SGs socket bound to %s\n", osmo_sock_get_name2(ofd->fd));
+	return 0;
+}