ua,call: prevent double ua_accept

API function ua_accept() can be called by multiple modules which handle
the shortly added UA_EVENT_SIPSESS_CONN. This commit prevents that
multiple call/sipsess/sip_dialog objects are created for a single SIP
INVITE message

include/baresip.h

@@ -236,6 +236,7 @@ bool call_has_video(const struct call *call);
 bool call_early_video_available(const struct call *call);
 bool call_refresh_allowed(const struct call *call);
 bool call_ack_pending(const struct call *call);
+bool call_sess_cmp(const struct call *call, const struct sip_msg *msg);
 int  call_transfer(struct call *call, const char *uri);
 int  call_replace_transfer(struct call *target_call, struct call *source_call);
 int  call_status(struct re_printf *pf, const struct call *call);
@@ -963,6 +964,7 @@ int  ua_call_alloc(struct call **callp, struct ua *ua,
 		   struct call *xcall, const char *local_uri,
 		   bool use_rtp);
 struct call *ua_find_call_state(const struct ua *ua, enum call_state st);
+struct call *ua_find_call_msg(struct ua *ua, const struct sip_msg *msg);
 int ua_raise(struct ua *ua);
 int ua_set_autoanswer_value(struct ua *ua, const char *value);
 void ua_add_extension(struct ua *ua, const char *extension);

src/call.c

@@ -2294,6 +2294,12 @@ int call_accept(struct call *call, struct sipsess_sock *sess_sock,
 }
 
 
+bool call_sess_cmp(const struct call *call, const struct sip_msg *msg)
+{
+	return sipsess_msg_equal(call->sess, msg);
+}
+
+
 static void delayed_answer_handler(void *arg)
 {
 	struct call *call = arg;

src/ua.c

@@ -504,6 +504,22 @@ struct call *ua_find_active_call(struct ua *ua)
 }
 
 
+struct call *ua_find_call_msg(struct ua *ua, const struct sip_msg *msg)
+{
+	if (!ua || !msg)
+		return NULL;
+
+	struct le *le = NULL;
+	for (le = list_tail(&ua->calls); le; le = le->prev) {
+		struct call *call = le->data;
+		if (call_sess_cmp(call, msg))
+			break;
+	}
+
+	return le ? le->data : NULL;
+}
+
+
 static void call_event_handler(struct call *call, enum call_event ev,
 			       const char *str, void *arg)
 {
@@ -786,6 +802,11 @@ int ua_accept(struct ua *ua, const struct sip_msg *msg)
 	if (!ua || !msg)
 		return EINVAL;
 
+	if (ua_find_call_msg(ua, msg)) {
+		warning("ua: call was already accepted\n");
+		return EINVAL;
+	}
+
 	err = pl_strdup(&to_uri, &msg->to.auri);
 	if (err)
 		goto error;