accept() doesn't block while running as NT service

accept() doesn't block while running as NT service

[linamat]

I have a problem with accept() on TCP socket. Al things works well when I
start the program under .\\Administrator credentials, but fails in NT
service.

{
 struct sockaddr_in sa;
 int sa_len = sizeof sa;

  for (;;) {

    t = accept(s,(struct sockaddr *)&sa,&sa_len);

    if (t == -1) continue;

// working with client....
    .......
   }
}

It returns -1 and enters in infinite loop.
I've tried such with UNIX socket and it behaved normally.
Can you explain me why?


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Re: accept() doesn't block while running as NT service

[Corinna Vinschen]

On Tue, Aug 19, 2003 at 04:30:47PM +0300, linamat@moldtelecom.md wrote:
> I have a problem with accept() on TCP socket. Al things works well when I
> start the program under .\\Administrator credentials, but fails in NT
> service.
> 
> {
>  struct sockaddr_in sa;
>  int sa_len = sizeof sa;
> 
>   for (;;) {
> 
>     t = accept(s,(struct sockaddr *)&sa,&sa_len);
> 
>     if (t == -1) continue;
> 
> // working with client....
>     .......
>    }
> }
> 
> It returns -1 and enters in infinite loop.
> I've tried such with UNIX socket and it behaved normally.
> Can you explain me why?

No.  No details, no explanation.  Debugging could help.  And reading
http://cygwin.com/problems.html, probably.

Corinna

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Re: accept() doesn't block while running as NT service

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On Tue, Aug 19, 2003 at 04:30:47PM +0300, linamat@moldtelecom.md wrote:
> I have a problem with accept() on TCP socket. Al things works well when I
> start the program under .\\Administrator credentials, but fails in NT
> service.
> 
> {
>  struct sockaddr_in sa;
>  int sa_len = sizeof sa;
> 
>   for (;;) {
> 
>     t = accept(s,(struct sockaddr *)&sa,&sa_len);
> 
>     if (t == -1) continue;
> 
> // working with client....
>     .......
>    }
> }
> 
> It returns -1 and enters in infinite loop.
> I've tried such with UNIX socket and it behaved normally.
> Can you explain me why?

No.  No details, no explanation.  Debugging could help.  And reading
http://cygwin.com/problems.html, probably.

Corinna

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Re: accept() doesn't block while running as NT service

[linamat]

The problem exists under Win2k sp4, cygwin-1.3.22 and cygwin-1.5.2.

Anyhow an explanation would be much appreciated.

I've read cygrunsrv last version and inetd sources, but couldn't find any
error in my code.

Some parameters from CreateService() which I used:
SERVICE_WIN32_OWN_PROCESS
".\\LocalSystem" or NULL served as lpServiceStartName

I also could post all service source.
Does exist any difference for Cygwin call accept() in such case between
executing in a process token level and in user space?

An interesting thing: the TCP port is not even binded, while listen
returns 0.




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Re: accept() doesn't block while running as NT service

[Nedko Arnaudov]

Process that is run under local system credentials cannot use
network. This is why ot is called *local*. Don't know if this WinNT
behaviour can be customized.


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Re: accept() doesn't block while running as NT service

[Corinna Vinschen]

On Wed, Aug 20, 2003 at 11:23:01AM +0300, Nedko Arnaudov wrote:
> Process that is run under local system credentials cannot use
> network. This is why ot is called *local*. Don't know if this WinNT
> behaviour can be customized.

That's wrong.  How should eg. sshd work then?

Corinna

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Re: accept() doesn't block while running as NT service

[Nedko Arnaudov]

Corinna Vinschen <corinna-cygwin@cygwin.com> writes:

> On Wed, Aug 20, 2003 at 11:23:01AM +0300, Nedko Arnaudov wrote:
>> Process that is run under local system credentials cannot use
>> network. This is why ot is called *local*. Don't know if this WinNT
>> behaviour can be customized.
>
> That's wrong.  How should eg. sshd work then?
>

Actually i don't know how sshd is implemented but i guess that it logs
the user into LSA or impersonates him.


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Re: accept() doesn't block while running as NT service

[Corinna Vinschen]

On Wed, Aug 20, 2003 at 06:10:06PM +0300, Nedko Arnaudov wrote:
> Corinna Vinschen <corinna-cygwin@cygwin.com> writes:
> 
> > On Wed, Aug 20, 2003 at 11:23:01AM +0300, Nedko Arnaudov wrote:
> >> Process that is run under local system credentials cannot use
> >> network. This is why ot is called *local*. Don't know if this WinNT
> >> behaviour can be customized.
> >
> > That's wrong.  How should eg. sshd work then?
> 
> Actually i don't know how sshd is implemented but i guess that it logs
> the user into LSA or impersonates him.

And before authentication?  What about the parent process which is
running under SYSTEM account and which is listening for incoming
connections on port 22?

Corinna

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Re: accept() doesn't block while running as NT service

[Nedko Arnaudov]

Corinna Vinschen <corinna-cygwin@cygwin.com> writes:

> On Wed, Aug 20, 2003 at 06:10:06PM +0300, Nedko Arnaudov wrote:
>> Corinna Vinschen <corinna-cygwin@cygwin.com> writes:
>> 
>> > On Wed, Aug 20, 2003 at 11:23:01AM +0300, Nedko Arnaudov wrote:
>> >> Process that is run under local system credentials cannot use
>> >> network. This is why ot is called *local*. Don't know if this WinNT
>> >> behaviour can be customized.
>> >
>> > That's wrong.  How should eg. sshd work then?
>> 
>> Actually i don't know how sshd is implemented but i guess that it logs
>> the user into LSA or impersonates him.
>
> And before authentication?  What about the parent process which is
> running under SYSTEM account and which is listening for incoming
> connections on port 22?
>

Ok, your are right. But using windows redirector functions (netbios
shares) is impossible from local system account or at least it was
some years ago. Of course this is not directly realted to the subject
of this thread. I just wanted to help.


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Re: accept doesn't block while running as NT service

[linamat]

As Corinna said "debugging could help" and she was right.
One of my functions closed file descriptors 0 and 1 after successfull
listen() call. Socket fd is 0 in my case. And so accept()'s errno was EBADF.
Now my service is working.


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Re: accept doesn't block while running as NT service

[linamat]

SYSTEM can use network resources without doubts, because UNIX domain
socket works under NT service, inetd also works as NT service.

Turning to accept() problem errno was set to EBADF.
I parsed fhandler_socket.cc's method accept(); there are 2 places where
EBADF might be set: 1st after sock_event handling if blocking (but I use
FASYNC | O_NONBLOCK), 2nd after ancestor's accept() which checks for
invalid handle.
It seems that socket descriptor is suddenly closed or invalidated under NT
service. I've even tried to run some very simple TCP socket servers
through SCM, but it fail. Don't forget that all OK with it while it runs
from console as application.
Is such behaveour normal?



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