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Add calculate_multifragmentupdate_len()

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This commit is contained in:
matt335672 2021-12-13 14:43:26 +00:00
parent 5a11b698ef
commit 9140737a6e
1 changed files with 56 additions and 3 deletions
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59
libxrdp/xrdp_caps.c
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@ -23,10 +23,23 @@
#include <config_ac.h>
#endif
#include <limits.h>
#include "libxrdp.h"
#include "ms-rdpbcgr.h"
#include "ms-rdperp.h"
/**
* The largest supported size for a fastpath update
* (TS_MULTIFRAGMENTUPDATE_CAPABILITYSET) we advertise to the client. This
* size is big enough for the tiles required for two 3840x2160 monitors
* without using multiple update PDUS.
*
* Consult calculate_multifragmentupdate_len() below before changing this
* value.
*/
#define MAX_MULTIFRAGMENTUPDATE_SIZE (2U * (3840 * 2160) * 16384 + 16384)
/*****************************************************************************/
static int
xrdp_caps_send_monitorlayout(struct xrdp_rdp *self)
@ -844,6 +857,46 @@ xrdp_caps_process_confirm_active(struct xrdp_rdp *self, struct stream *s)
LOG_DEVEL(LOG_LEVEL_TRACE, "Completed processing received [MS-RDPBCGR] TS_CONFIRM_ACTIVE_PDU");
return 0;
}
/**************************************************************************//**
* Calculate the multifragmentupdate len we advertised to the client
* for fastpath updates
*
* See [MS-RDPBCGR] 2.2.7.2.6
*
* The basic logic is taken from freerdp 2.4. We try to use the highest
* useful request size that will allow us to pack a complete screen
* update into a single fast path PDU using any of the supported codecs.
* For RemoteFX, the client MUST use at least this value
*
* A backstop on the maximum advertised size is implemented to prevent
* extreme memory usage for large screen configurations. RDP supports a
* maximum desktop size of 32768x32768, which would cause overflow for
* 32-bit integers using a simple calculation.
*
* The codecs have to deal with the value returned by the client after
* we advertise our own value, and must not assume a complete update
* will fit in a single PDU
*/
static
unsigned int calculate_multifragmentupdate_len(const struct xrdp_rdp *self)
{
unsigned int result = MAX_MULTIFRAGMENTUPDATE_SIZE;
unsigned int x_tiles = (self->client_info.width + 63) / 64;
unsigned int y_tiles = (self->client_info.height + 63) / 64;
/* Check for overflow on calculation if bad parameters are supplied */
if ((x_tiles * y_tiles + 1) < (UINT_MAX / 16384))
{
result = x_tiles * y_tiles * 16384;
/* and add room for headers, regions, frame markers, etc. */
result += 16384;
}
return result;
}
/*****************************************************************************/
int
xrdp_caps_send_demand_active(struct xrdp_rdp *self)
@ -1137,13 +1190,13 @@ xrdp_caps_send_demand_active(struct xrdp_rdp *self)
if (self->client_info.use_fast_path & FASTPATH_OUTPUT_SUPPORTED) /* fastpath output on */
{
/* multifragment update */
unsigned int max_request_size = calculate_multifragmentupdate_len(self);
caps_count++;
out_uint16_le(s, CAPSSETTYPE_MULTIFRAGMENTUPDATE);
out_uint16_le(s, CAPSSETTYPE_MULTIFRAGMENTUPDATE_LEN);
out_uint32_le(s, 3 * 1024 * 1024); /* 3MB */
out_uint32_le(s, max_request_size);
LOG_DEVEL(LOG_LEVEL_TRACE, "xrdp_caps_send_demand_active: Server Capability "
"CAPSSETTYPE_MULTIFRAGMENTUPDATE = 3MB");
"CAPSSETTYPE_MULTIFRAGMENTUPDATE = %d", max_request_size);
/* frame acks */
caps_count++;