bugmldonkey, a multi-networks file-sharing client - Bugs: bug #11384, Source of Orphaned File Descriptor...

 
 

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bug #11384: Source of Orphaned File Descriptor Bug

Submitted by:  Shunga <shunga>
Submitted on:  Thu 23 Dec 2004 03:46:35 PM UTC  
 
Category:  Core Severity:  3 - Normal
Item Group:  Program malfunction Status:  Fixed
Assigned to:  None Open/Closed:  Closed
Release:  2.5-22 Release:  None
Operating System:  Mac OS X 10.3 Binaries Origin:  CVS / Self compiled
CPU type:  PowerPC

( Jump to the original submission)

Thu 13 Jan 2005 07:02:56 PM UTC, comment #19: 

It looks like the fix was applied to the tag named "release308" which I assume will eventually become the 3.08.3 release.  I think you will have to use the CVS -r option with the CVS checkout command to download that tagged version.

cvs co -r release308 ocaml

Shunga <shunga>
Thu 13 Jan 2005 12:48:18 AM UTC, comment #18: 

Patch #3637 is online...

spiralvoice <spiralvoice>
Project Administrator
Thu 13 Jan 2005 12:25:07 AM UTC, comment #17: 

Saw that as well, but I don't know how to download OCaml CVS version. Some months ago I used these commands:

cvs -d:pserver:anoncvs@camlcvs.inria.fr:/caml login
cvs -z3 -d:pserver:anoncvs@camlcvs.inria.fr:/caml co -P ocaml

as described on this page: http://camlcvs.inria.fr/cvsserver-eng.html

But now I get Ocaml 3.08+2 instead of Ocaml 3.09 CVS:-(

spiralvoice <spiralvoice>
Project Administrator
Wed 12 Jan 2005 09:56:27 PM UTC, comment #16: 

I've received an email from caml that the OCAML issue with the open file descriptors (id = 3423)  has been fixed in the CVS version of OCAML.

Shunga <shunga>
Mon 10 Jan 2005 09:20:01 PM UTC, comment #15: 

FYI: There are bug reports at Inria so this problem will be fixed sometime.
http://caml.inria.fr/bin/caml-bugs/incoming?id=3422
http://caml.inria.fr/bin/caml-bugs/incoming?id=3423

spiralvoice <spiralvoice>
Project Administrator
Fri 07 Jan 2005 04:06:19 AM UTC, comment #14: 

I think I've verified that the problem is in the OCAML unix library, not in mldonkey.  I modified OCAML's unix library and moved the unix_error call that was in alloc_sockaddr to the routines that called alloc_sockaddr and returned a value of -1 from within alloc_sockaddr.  That allowed me in unix_accept to close(retcode) before calling unix_error.  I rebuilt 2.5.29ab with the begin/end added to tcp_handler, but removed the "close t" because that is incorrect.  The log file indicates that I've gotten a number of tcp_handler errors but now I have only one orphaned file descriptor (the one due to send_paquet_to_mlchat and I've verified that I still have a high ID (since the close t was removed).

It is probably a good idea to continue to trap the error in the tcp_handler routine so mine now looks like:

let tcp_handler t sock event =
  match event with
  | CAN_READ
  | CAN_WRITE ->
     begin
     try
       let s,id = Unix.accept (fd sock) in
       if !verbose_bandwidth > 1 then lprintf "[BW2 %6d] accept on %s\n" (last_time ()) t.name;
       (match t.accept_control with
          None -> () | Some cc ->
             cc.nconnections_last_second <- cc.nconnections_last_second + 1);
       incr nconnections_last_second;
       t.event_handler t (CONNECTION (s,id))
 with e ->
    lprintf "Exception tcp_handler: %s\n" (Printexc2.to_string e);
    raise e
    end
  | _ -> t.event_handler t (BASIC_EVENT event)

although this doesn't fix the problem, it does keep other lines of code from executing when an error occurs.

The final orphaned file descriptor can be fixed by changing send_paquet_to_mlchat in src/daemon/common/commonChat.ml to close chan_out on a connect error.  My routine looks like:

let send_paquet_to_mlchat (p : C.packet) =
  let domain = Unix.PF_INET in
  let sock = Unix.socket domain Unix.SOCK_STREAM 0 in
  let inet_addr =
    let host = !!O.chat_app_host in
    try Unix.inet_addr_of_string host
    with _ ->
        let h = Unix.gethostbyname host in
        h.Unix.h_addr_list.(0)
  in
  let sockaddr = Unix.ADDR_INET (inet_addr, !!O.chat_app_port) in
  let chanout = Unix.out_channel_of_descr sock in
  try
    Unix.connect sock sockaddr;
    Chat_proto.write_packet_channel chanout p;
    flush chanout;
    close_out chanout
  with
  | Unix.Unix_error (e,s1,s2) ->
      let s = (Unix.error_message e)^" : "^s1^" "^s2 in
      lprintf "%s\nchat_app_host=%s chat_app_port=%d\n" s
        !!O.chat_app_host !!O.chat_app_port;
      close_out chanout
  | e ->
      lprintf "%s\nchat_app_host=%s chat_app_port=%d\n"
        (Printexc2.to_string e)
      !!O.chat_app_host !!O.chat_app_port;
      close_out chanout

With the change to the OCAML unix library and these changes to mldonkey, I no longer have any orphaned file descriptors and continue to have a high ID.

So if someone that knows the OCAML developers, maybe you could get them to change the OCAML unix library.

The other question is on Mac OS X, why is sa_family sometimes not defined in alloc_sockaddr?  I have not looked at what the value is, but it may be that the value is AF_INET6 and HAS_IPV6 is not defined in the makefile for making OCAML on Mac OS X.  It could be that if HAS_IPV6 was defined for Mac OS X when OCAML was made, that the error would not have occurred.

Shunga

Shunga <shunga>
Fri 07 Jan 2005 02:26:53 AM UTC, comment #13: 

Although I don't understand the source of the problem, I think I now know the reason for the orphaned socket on Mac OS X.  I believe the source of the problem is the OCAML Unix.accept routine.  This routine I think calls the OCAML unix_accept routine defined in ocaml-3.08.0/otherlibs/unix/accept.c and the code looks like this:

CAMLprim value unix_accept(value sock)
{
  int retcode;
  value res;
  value a;
  union sock_addr_union addr;
  socklen_param_type addr_len;

 

  addr_len = sizeof(addr);
  enter_blocking_section();
  retcode = accept(Int_val(sock), &addr.s_gen, &addr_len);
  leave_blocking_section();
  if (retcode == -1) uerror("accept", Nothing);
  a = alloc_sockaddr(&addr, addr_len);
  Begin_root (a);
    res = alloc_small(2, 0);
    Field(res, 0) = Val_int(retcode);
    Field(res, 1) = a;
  End_roots();
  return res;
}

Notice that the unix accept routine is called which creates a file descriptor in retcode (assuming no error).    Then this routine calls alloc_sockaddr which is defined in ocaml-3.08.0/otherlibs/unix/socketaddr.c and this routine looks like this:

value alloc_sockaddr(union sock_addr_union * adr /*in*/,
                     socklen_param_type adr_len)
{
  value res;
  switch(adr->s_gen.sa_family) {
#ifndef _WIN32
  case AF_UNIX:
    { value n = copy_string(adr->s_unix.sun_path);
      Begin_root (n);
        res = alloc_small(1, 0);
        Field(res,0) = n;
      End_roots();
      break;
    }
#endif
  case AF_INET:
    { value a = alloc_inet_addr(&adr->s_inet.sin_addr);
      Begin_root (a);
        res = alloc_small(2, 1);
        Field(res,0) = a;
        Field(res,1) = Val_int(ntohs(adr->s_inet.sin_port));
      End_roots();
      break;
    }
#ifdef HAS_IPV6
  case AF_INET6:
    { value a = alloc_inet6_addr(&adr->s_inet6.sin6_addr);
      Begin_root (a);
        res = alloc_small(2, 1);
        Field(res,0) = a;
        Field(res,1) = Val_int(ntohs(adr->s_inet6.sin6_port));
      End_roots();
      break;
    }
#endif
  default:
    unix_error(EAFNOSUPPORT, "", Nothing);
  }
  return res;
}

Note that if the sa_family doesn't match any case, the default is to set the unix error to "EAFNOSUPPORT" which is exactly the error that is seen in mldonkey.   Now I'm not sure exactly what happens when unix_error is called, but if alloc_socketaddr doesn't return in unix_accept that would keep retcode from being put into the result of unix_accept which would mean that there would be no way in mldonkey to access the file descriptor to close it when this error occurs.   If this is true, the problem has to be corrected in the OCAML library by closing retcode if alloc_sockaddr gets an error.

On the other hand if alloc_sockaddr does return after calling unix_error and unix_accept does fill in the return value with the file descriptor (retcode), then the mldonkey code would have to "close s" in the error part of the routine and I don't know OCAML well enough to figure out how to get to s to close it.

So, bottom line is that it may be that the OCAML library needs to be modified to close the file descriptor in retcode if alloc_sockaddr gets an error.

Shunga

Anonymous
Thu 06 Jan 2005 04:55:26 PM UTC, comment #12: 

Just my observation: with 2-5-28i and this patch I always got LowID´s, without it HighID´s.

spiralvoice <spiralvoice>
Project Administrator
Thu 06 Jan 2005 02:47:12 PM UTC, comment #11: 

Adding the begin/end around the "try" in tcp_handler fixed the compilation warning bug didn't change anything.  It still appears that when "close t" is performed that the socket for port 4662 is closed and from that point on because that port is now closed future server connections get a low ID.   The error in the log "Exception tcp_handler:  failed: Address family not supported by protocol family" appears to be an error due to a Unix connect call and not due to the accept call, although when I added a Unix.Unix_error match to the try, Unix.Unix_error was never matched, only "e".  What I would like to try but don't know how to do is when the error occurs, close the socket "s" that was created by the Unix.accept call instead of closing t (which appears to be the socket for port 4662).  I expect that whaterver the problem is, it is not actually in tcp_handler, but somewhere else and perhaps related to a connect call.

Shunga

Shunga <shunga>
Thu 06 Jan 2005 02:06:30 PM UTC, comment #10: 

I compiled the tag-2-5-29ab source that you pointed to that schlumpf provided with no changes.  After I posted the bug and the "try" suggestion to illustrate the error, I did notice the compilation warning and added the begin/end combination just as you did in the patch.  As I recall, it didn't change anything, but I'll try it once more to make sure using the tag-2-5-29ab source..

Shunga

Anonymous
Thu 06 Jan 2005 01:40:02 PM UTC, comment #9: 

I compiled the tag-2-5-29ab source that you pointed to that schlumpf provided with no changes.  After I posted the bug and the "try" suggestion to illustrate the error, I did notice the compilation warning and added the begin/end combination just as you did in the patch.  As I recall, it didn't change anything, but I'll try it once more to make sure using the tag-2-5-29ab source..

Shunga

Anonymous
Thu 06 Jan 2005 04:55:25 AM UTC, comment #8: 

did you try that with or without the patch i posted in the forum linked in my last comment to this bug? if without please try with it applied. (oh and no need to message me through savannah i get notified on changes of bugs i posted to)

Amorphous <amorphous>
Thu 06 Jan 2005 03:33:04 AM UTC, comment #7: 

When I suggested the try, I noticed the same thing that I'm noticing with 2.5.29ab.  When I originally suggested the "try" in tcp_handler to illustrate the error, I noticed the following issue which also occurs with the patch.  When the error occurs and the "close t" is issued, that close apparently closes the socket on port 4662.  After that occurs, it is true that there are no more orphaned file descriptors, however, it appears that any additional connections to servers results in a lowid.  For example in my console log, after the error occurs, I start seeing the following when attaching to new servers:

+-- From server  [193.41.142.148:10000] ------
| WARNING : You have a lowid. Please review your network config and/or your settings.

+-- From server DonkeyServer No6  [62.241.53.4:4242] ------
| WARNING : You have a lowid. Please review your network config and/or your settings.

+-- From server http://www.MESSENGER7.NET [205.209.178.170:12933] ------
| WARNING : Your 4662 port is not reachable. Please review your network config.
| server version 17.1 (lugdunum)

Before the error occured, servers did not report lowid.

Shunga.

Shunga <shunga>
Wed 05 Jan 2005 06:53:56 PM UTC, comment #6: 

it's in the svn repository mentioned in another thread in that forum-group. i added a link to an archive of the source, schlumpf provided.

Amorphous <amorphous>
Wed 05 Jan 2005 09:34:49 AM UTC, comment #5: 

I would like to try this but with what? I read the post at http://mldonkey.berlios.de/modules.php?name=Forums&file=viewtopic&t=3201&sid=6c52a2530f6046d72fdfbbb94c0c1d72 and I have looked at the CVS-page but I don't know where the/which source to download - where is the 29ab-version?

d-b
Wed 05 Jan 2005 09:30:54 AM UTC, comment #4: 

I would like to try this but with what? I read the post at http://mldonkey.berlios.de/modules.php?name=Forums&file=viewtopic&t=3201&sid=6c52a2530f6046d72fdfbbb94c0c1d72 and I have looked at the CVS-page but I don't know where the/which source to download - where is the 29ab-version?

d-b
Wed 05 Jan 2005 08:23:28 AM UTC, comment #3: 
Amorphous <amorphous>
Thu 23 Dec 2004 08:51:27 PM UTC, comment #2: 

Programmer asleep at the switch :-).  I was wrong about some other software change.  Turns out tcp_handler does fail if changed as follows:

let tcp_handler t sock event =
  match event with
  | CAN_READ
  | CAN_WRITE ->
      try
        let s,id = Unix.accept (fd sock) in
        if !verbose_bandwidth > 1 then lprintf "[BW2 %6d] accept on %s\n" (last_time ()) t.name;
        (match t.accept_control with
            None -> () | Some cc ->
              cc.nconnections_last_second <- cc.nconnections_last_second + 1);
        incr nconnections_last_second;
        t.event_handler t (CONNECTION (s,id))
      with  e ->
        lprintf "Exception tcp_handler: %s\n" (Printexc2.to_string e);
        close t (Closed_for_error (Printexc2.to_string e));
        raise e
  | _ -> t.event_handler t (BASIC_EVENT event)

and it leaves one socket orphaned which I assume is "s".  I don't know how to get "s" down into the "with -> e" so that it can be closed and I don't know if I need to "close t" as is indicated in the code which at the moment is closing one of the server sockets that is being listened to., however, with this change "mlnet" has run for hours with only one orphaned socket.  This plus the commonChat change should get rid of the orphaned sockets.  I'll leave it up to the experts to figure out what is really going on and how to best fix it.

Shunga <shunga>
Thu 23 Dec 2004 08:03:07 PM UTC, comment #1: 

Well it would appear that the failure in tcp_handler was due to some other change that I must have made while attempting to debug this.  When I start over with a fresh copy of the source the handler doesn't fail and the file descriptors start building up.

Guess I have to go back and see if I can figure out what else it was that I changed.  :-(

Shunga <shunga>
Thu 23 Dec 2004 03:46:35 PM UTC, original submission:  

On Mac OS X and I assume other systems there are two bugs in mlnet which together generate hundreds of orphaned file descriptors causing mlnet to eventually hang.  I worked with mlnet 2.5-22 source and ocaml 3.07-p12 to debug the source of the problem:

I don't know the source code or OCAML well enough to suggest exactly why it is happening or the best way to fix it, but I have done enough debugging to figure out the cause of the probem. There are two issues:

1. The first is in src/daemon/common/commonChat.ml in the routine send_paquet_to_mlchat. The Unix.connect fails with "Connection refused : connect" but the error is not trapped and the socket is not closed. Trapping the error and closing the socket fixes this one.

2. The rest of the orphaned file descriptors is in src/utils/net/tcpServerSocket.ml in the routine tcp_handler. The Unix.accept fails with Exception tcp_handler: failed: Address family not supported by protocol family" but apparently has created a new socket which is never closed. If I trap the exception and issue the following "close t (Closed_for_error (Printexc2.to_string e));" I find that lsof only shows one orphaned socket after hours of running. I assume that issuing "close t" closes the original socket that is being listened to and this stop this Unix.accept from being called again. I don't know why it is getting this error unless perhaps the previous bind failed and that wasn't trapped, but maybe there is some other reason.

So if a developer who knows the code and OCAML can fix these two problems and get the patches in the current release then that should solve the orhpaned file descriptor problem which causes mlnet to hang after running for some hours

Shunga <shunga>

 

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Follow 4 latest changes.

Date Changed by Updated Field Previous Value => Replaced by
2005-01-30 spiralvoice StatusNone => Fixed
    Open/ClosedOpen => Closed
2005-01-03 hgd Carbon-Copy- => Added hgd
2005-01-02 d-b Carbon-Copy- => Added i97_bed --AT-- i --DOT-- kth --DOT-- se

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