xrdpapi: Add a way to monitor connect/disconnect events

common/Makefile.am

@@ -47,6 +47,7 @@ libcommon_la_SOURCES = \
   arch.h \
   base64.h \
   base64.c \
+  channel_defs.h \
   defines.h \
   fifo.c \
   fifo.h \

common/channel_defs.h

@@ -0,0 +1,69 @@
+/**
+ * Copyright (C) 2024 Matt Burt, all xrdp contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @file    common/channel_defs.h
+ * @brief   Private xrdp channel definitions
+ */
+
+#if !defined(CHANNEL_DEFS_H)
+#define CHANNEL_DEFS_H
+
+#include <stdint.h>
+
+/**
+ * Channel IDs assigned to xrdp private channels. These are chosen to avoid conflicts with
+ * channel IDs returned by other servers.
+ */
+enum
+{
+    CHAN_ID_XRDP_BASE = (('x' << 24) | ('r' << 16) | ('d' << 8) | 'p'),
+    CHAN_ID_XRDP_SESSION_INFO = CHAN_ID_XRDP_BASE,
+    // Add further IDs here
+    CHAN_ID_XRDP_MAX
+};
+
+// Max length of a DVC name. This is taken from the specification of
+// WTSVirtualChannelOpenEx() which limits the length of a virtual channel
+// to Windows MAX_PATH
+#define MAX_DVC_NAME_LEN 260
+
+/**
+ * Information to connect to a channel using xrdpapi
+ */
+#define XRDPAPI_CONNECT_PDU_LEN 384 // Connect PDU is always this length
+#define XRDPAPI_CONNECT_PDU_VERSION 1 // Current connnect PDU version
+
+struct xrdp_chan_connect
+{
+    uint32_t version;
+    uint32_t private_chan; // 0 for a standard channel
+    uint32_t flags;
+    char name[MAX_DVC_NAME_LEN + 1]; // null-terminated
+};
+
+// Events received on the CHAN_ID_XRDP_SESSION_INFO channel
+
+// Update on all the session state data held by chansrv
+//
+// If more information is needed to be exported by xrdpapi, it can be
+// added to this event
+struct xrdp_chan_session_state
+{
+    uint32_t is_connected; // Is the session connected?
+};
+
+#endif /* CHANNEL_DEFS_H */

common/parse.h

@@ -528,6 +528,14 @@ in_utf16_le_terminated_as_utf8_length(struct stream *s);
         (s)->p++; \
     } while (0)
 
+/******************************************************************************/
+// Platform-endian out_uint32
+#if defined(B_ENDIAN)
+#define out_uint32_pe(s, v) out_uint32_be(s, v)
+#else
+#define out_uint32_pe(s, v) out_uint32_le(s, v)
+#endif
+
 /******************************************************************************/
 #define in_uint8p(s, v, n) do \
     { \