FltSendMessage doesn't get reply

NTFSD
1

I am using FltsendMessage to send some information to user space and the decision made in user space is conveyed back to driver using FilterReplyMessage. Given below is the code I am using. I fail to get any reply from user space and receive STATUS_TIMEOUT error code.
can someone guide me about this?

structure common to user and kernel space:

typedef struct REPLY_BUFFER
{
FILTER_REPLY_HEADER Header;
int Allow;
}REPLY_BUFFER, *PREPLY_BUFFER;

Driver code:

REPLY_BUFFER Reply ;
ULONG ReplyLength = sizeof( REPLY_BUFFER );

timeout.QuadPart = -(LONGLONG) 150000000;

status = FltSendMessage(gFilterHandle,
&gClientPort,
&buffer,
sizeof(buffer),
& Reply,
&ReplyLength,
&timeout) ;

User space code:

REPLY_BUFFER Reply;

//some decision making
Reply.Allow = 1;
else
Reply.Allow = 0;

FilterReplyMessage( hPort,(PFILTER_REPLY_HEADER) &Reply,
sizeof(REPLY_BUFFER) );

2

FSF’s are not my thing, but here a couple of ideas:

Why is this negative: timeout.QuadPart = -(LONGLONG) 150000000;

Unless that encodes some special meaning, that would seem like a problem.

Good luck,

mm

3

Negative values indicate relative time starting from current time. If I specify positive value of time, then it will start counting from 1 Jan 1601 and will return immediately without waiting.
BTW, I checked the return value of FilterReplyMessage and it says ERROR_FLT_NO_WAITER_FOR_REPLY. However the driver is actually waiting for reply. I don’t understand why this is happening.

4

As Daniel pointed you to, get rid of this bull:

timeout.QuadPart = -(LONGLONG) 150000000;

For God sakes, look at the docs and think about it a little…

If need be, go too " http://www.justfuckinggoogleit.com/ "…

That single timeout statement is 100% of your problem.

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of
xxxxx@yahoo.com
Sent: Tuesday, November 17, 2009 6:37 AM
To: Windows File Systems Devs Interest List
Subject: RE:[ntfsd] FltSendMessage doesn’t get reply

Negative values indicate relative time starting from current time. If I
specify positive value of time, then it will start counting from 1 Jan 1601
and will return immediately without waiting.
BTW, I checked the return value of FilterReplyMessage and it says
ERROR_FLT_NO_WAITER_FOR_REPLY. However the driver is actually waiting for
reply. I don’t understand why this is happening.

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5

Please check that you are sending a message on same
port that you are listening on.

6

When you call FilterReplyMessage are you setting the Message ID in the reply header? This tells it how to route the reply:

replyMessage.ReplyHeader.MessageId = ReceivedMessage->MessageHeader.MessageId;

Not doing this is likely the reason for the error you are getting. The mini-filter example code shows how to use the message API’s. They are a better resource that the docs in this case.

7

The relevant thing that is missing from this post is the usermode call to
receive your message (FilterGetMessage). BTW are you sure that negative
values are working ? It’s not mentioned in the doc but it makes sense if
TimeOut is immediately passed to a call to KeWaitForSingleObject. Does it
actually wait for 15 seconds ?

//Daniel

wrote in message news:xxxxx@ntfsd…
> I am using FltsendMessage to send some information to user space and the
> decision made in user space is conveyed back to driver using
> FilterReplyMessage. Given below is the code I am using. I fail to get any
> reply from user space and receive STATUS_TIMEOUT error code.
> can someone guide me about this?
>
> structure common to user and kernel space:
>
> typedef struct REPLY_BUFFER
> {
> FILTER_REPLY_HEADER Header;
> int Allow;
> }REPLY_BUFFER, *PREPLY_BUFFER;
>
>
> Driver code:
>
> REPLY_BUFFER Reply ;
> ULONG ReplyLength = sizeof( REPLY_BUFFER );
>
> timeout.QuadPart = -(LONGLONG) 150000000;
>
> status = FltSendMessage(gFilterHandle,
> &gClientPort,
> &buffer,
> sizeof(buffer),
> & Reply,
> &ReplyLength,
> &timeout) ;
>
> User space code:
>
> REPLY_BUFFER Reply;
>
> //some decision making
> Reply.Allow = 1;
> else
> Reply.Allow = 0;
>
> FilterReplyMessage( hPort,(PFILTER_REPLY_HEADER) &Reply,
> sizeof(REPLY_BUFFER) );
>

8

Negative values should work. I’ll file a doc bug.

Regards,
Alex.
This posting is provided “AS IS” with no warranties, and confers no rights.

9

Thank you one and all.
The problem was, I didn’t specify MessageId in header ( as rightly pointed out by Rick W). After specifying the MessageId, the problem is solved.
Thank you Rick.