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Rework the start session method in SCP

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The start session method is reworked to pass a response back to the
client.
If the method was successful, a session list entry is created. This
is different to the provious behaviour, where we created the
session list entry unconditionally.

This new arrangement means that we need a different way to avoid
a race condition where two users may try to create a session at the
same time, and end up with the same display. We do this by keeping
track of newly allocated displays as part of the SCP connections. When
we allocate a display, the SCP connection displays are also taken
into account.
This commit is contained in:
matt335672
2025-06-10 11:06:20 +01:00
parent 7baa27a59f
commit 3e38d9be80
17 changed files with 604 additions and 328 deletions
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sesman/eicp_process.c
+62
View File
@@ -32,12 +32,15 @@
#include "eicp.h"
#include "eicp_process.h"
#include "ercp.h"
#include "os_calls.h"
#include "scp_list.h"
#include "session_list.h"
#include "scp.h"
#include "sesman.h"
#include "sesman_access.h"
#include "sesman_config.h"
#include "guid.h"
/******************************************************************************/
@@ -92,6 +95,61 @@ process_sys_login_response(struct scp_list_item *sli)
return rv;
}
/******************************************************************************/
static int
process_create_session_response(struct scp_list_item *sli)
{
struct session_item *s_item;
int display = -1;
struct guid guid;
enum scp_screate_status status;
int rv = eicp_get_create_session_response(sli->sesexec_trans,
&status, &guid);
if (rv == 0)
{
// Create an entry on the session list for the new session
if (status == E_SCP_SCREATE_OK &&
(s_item = session_list_new()) == NULL)
{
status = E_SCP_SCREATE_NO_MEMORY;
}
if (status == E_SCP_SCREATE_OK)
{
// Further comms from sesexec comes over the ERCP
// protocol
ercp_trans_from_eicp_trans(sli->sesexec_trans,
sesman_ercp_data_in,
(void *)s_item);
// Move the new ERCP transport over to the session list item,
// and initialise enough data so that a connection request
// can be serviced.
s_item->sesexec_trans = sli->sesexec_trans;
s_item->sesexec_pid = sli->sesexec_pid;
s_item->guid = guid;
s_item->uid = sli->uid;
s_item->display = sli->session_display;
display = s_item->display;
// We don't use the sesexec process again
sli->sesexec_trans = NULL;
sli->sesexec_pid = 0;
}
else
{
guid_clear(&guid);
display = -1;
}
rv = scp_send_create_session_response(sli->client_trans, status,
display, &guid);
sli->create_session_in_progress = 0;
sli->session_display = -1;
}
return rv;
}
/******************************************************************************/
int
eicp_process(struct scp_list_item *sli)
@@ -105,6 +163,10 @@ eicp_process(struct scp_list_item *sli)
rv = process_sys_login_response(sli);
break;
case E_EICP_CREATE_SESSION_RESPONSE:
rv = process_create_session_response(sli);
break;
default:
{
char buff[64];