From 90e713969110306cd979f0edcbbd86a46d97518a Mon Sep 17 00:00:00 2001
From: Holger Hans Peter Freyther <holger@moiji-mobile.com>
Date: Tue, 22 Mar 2016 19:17:17 +0100
Subject: mncc: Handle the hello message from NITB

Make a simple version comparison and close the socket in case of a
version mismatch. Begin to dispatch messages coming from the NITB
and log (all) unhandled messages.
---
 src/mncc.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 src/mncc.h |  7 +++++++
 2 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/src/mncc.c b/src/mncc.c
index 7539334..500d1e9 100644
--- a/src/mncc.c
+++ b/src/mncc.c
@@ -19,6 +19,7 @@
  */
 
 #include "mncc.h"
+#include "mncc_protocol.h"
 #include "app.h"
 #include "logging.h"
 
@@ -30,6 +31,38 @@
 #include <errno.h>
 #include <unistd.h>
 
+static void close_connection(struct mncc_connection *conn)
+{
+	osmo_fd_unregister(&conn->fd);
+	close(conn->fd.fd);
+	osmo_timer_schedule(&conn->reconnect, 5, 0);
+	conn->state = MNCC_DISCONNECTED;
+	if (conn->on_disconnect)
+		conn->on_disconnect(conn);
+}
+
+static void check_hello(struct mncc_connection *conn, char *buf, int rc)
+{
+	struct gsm_mncc_hello *hello;
+
+	if (rc != sizeof(*hello)) {
+		LOGP(DMNCC, LOGL_ERROR, "Hello shorter than expected %d vs. %d\n",
+			rc, sizeof(*hello));
+		return close_connection(conn);
+	}
+
+	hello = (struct gsm_mncc_hello *) buf;
+	LOGP(DMNCC, LOGL_NOTICE, "Got hello message version %d\n", hello->version);
+
+	if (hello->version != MNCC_SOCK_VERSION) {
+		LOGP(DMNCC, LOGL_NOTICE, "Incompatible version(%d) expected %d\n",
+			hello->version, MNCC_SOCK_VERSION);
+		return close_connection(conn);
+	}
+
+	conn->state = MNCC_READY;
+}
+
 static void mncc_reconnect(void *data)
 {
 	int rc;
@@ -40,16 +73,19 @@ static void mncc_reconnect(void *data)
 	if (rc < 0) {
 		LOGP(DMNCC, LOGL_ERROR, "Failed to connect(%s). Retrying\n",
 			conn->app->mncc.path);
+		conn->state = MNCC_DISCONNECTED;
 		osmo_timer_schedule(&conn->reconnect, 5, 0);
 		return;
 	}
 
 	LOGP(DMNCC, LOGL_NOTICE, "Reconnected to %s\n", conn->app->mncc.path);
+	conn->state = MNCC_WAIT_VERSION;
 }
 
 static int mncc_data(struct osmo_fd *fd, unsigned int what)
 {
 	char buf[4096];
+	uint32_t msg_type;
 	int rc;
 	struct mncc_connection *conn = fd->data;
 
@@ -57,14 +93,27 @@ static int mncc_data(struct osmo_fd *fd, unsigned int what)
 	if (rc <= 0) {
 		LOGP(DMNCC, LOGL_ERROR, "Failed to read %d/%s. Re-connecting.\n",
 			rc, strerror(errno));
-		osmo_fd_unregister(fd);
-		close(fd->fd);
-		osmo_timer_schedule(&conn->reconnect, 5, 0);
-		if (conn->on_disconnect)
-			conn->on_disconnect(conn);
-		return 0;
+		goto bad_data;
 	}
+	if (rc <= 4) {
+		LOGP(DMNCC, LOGL_ERROR, "Data too short with: %d\n", rc);
+		goto bad_data;
+	}
+
+	memcpy(&msg_type, buf, 4);
+	switch (msg_type) {
+	case MNCC_SOCKET_HELLO:
+		check_hello(conn, buf, rc);
+		break;
+	default:
+		LOGP(DMNCC, LOGL_ERROR, "Unhandled message type %d/0x%x\n",
+			msg_type, msg_type);
+		break;
+	}
+	return 0;
 
+bad_data:
+	close_connection(conn);
 	return 0;
 }
 
@@ -75,6 +124,7 @@ void mncc_connection_init(struct mncc_connection *conn, struct app_config *cfg)
 	conn->fd.cb = mncc_data;
 	conn->fd.data = conn;
 	conn->app = cfg;
+	conn->state = MNCC_DISCONNECTED;
 }
 
 void mncc_connection_start(struct mncc_connection *conn)
diff --git a/src/mncc.h b/src/mncc.h
index d6afadc..5cbee4d 100644
--- a/src/mncc.h
+++ b/src/mncc.h
@@ -5,7 +5,14 @@
 
 struct app_config;
 
+enum {
+	MNCC_DISCONNECTED,
+	MNCC_WAIT_VERSION,
+	MNCC_READY,
+};
+
 struct mncc_connection {
+	int state;
 	struct app_config *app;
 	struct osmo_fd fd;
 
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