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Thomas,

I sent him the latest sctplib. Can you sent him the latest version
of the socketapilib?

Best regards
Michael

On Dec 1, 2004, at 10:41 Uhr, Thomas Dreibholz wrote:

On Tuesday 30 November 2004 16:39, Vanegue julien wrote:

Hi there,

I'm experiencing severe data loss from a tcp socket when using
ext_select() from the latest socketapi. I am afraid this is the
sequel of a former bug that was reported 1 month ago on the list. Thomas
provided me a first sctplib/socketapi patch but some problems still remain.

TCP clients on (1), (2), (3) (... N ...) are sending requests to servers
on (4), (5), (6), (... N ...) using a one-dgram-socket-multiple-streams
sctp tunnel by sendmsg/recvmsg calls, and it works well when I try with
telnet as a client and a web server at the other side for performing a
'simple GET' request.

tcp clients ---> + ---- S C T P T U N N E L ---- + <--- tcp servers


Nevertheless, in case of big traffic with multiple tunneled sockets,
packet loss occurs on both way of the link (on the diagram, + represent
SCTP proxies on both side of the test environment).

I use 1 sctp stream per input TCP client socket. The
stream multiplexing works well.

You use one SCTP association and tunnel each client <-> server association via
a different stream?

However it seems that ext_select() does
not see some data (indeed delivered and received on the network,
verified by sniffing), resulting in a partial web page (in case of www
browser proxying).

Does the data reception just stop or are there data fragments of the
downloaded web page missing?

Is there a more recent snapshot available that could resolve
definitely this issue?

I prepare the lastest snapshot for you and send it via a separate e-mail. If
it does not work, send me your latest source code and information how to
reproduce the problem. Then, I can try to find out the source of the problem.

I tried to use directly the sctplib on both sides of the link without
socketapi, but in this way I dont know how to retreive the real
data sender IP address in the DataArriveNotif() event. I looked
deep inside the sctplib/socketapi source code, and the execution path
that leads to the filling of 'pathindex' (which could help for getting
the peer IP address of the TCP client/server that has sent the data,
if using SCTP_pathStatus() ) seems useless in my case.

The data arrive notification is handled in
SCTPSocketMaster::dataArriveNotif(), it only gets the assoc ID from the
sctplib. Reading and obtaining the source address in handled in
SCTPSocket::internalReceive(). Here, sctp_receivefrom() is used to read the
data and get the path index (pathIndex variable) of the path the data has
been received via. Then, using sctp_getPathStatus() and
sctp_getAssocStatus(), the sender's address and port number can be obtained.


Best regards
--
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Dipl.-Inform. Thomas Dreibholz

University of Essen, Room ES210
Inst. for Experimental Mathematics Ellernstraße 29
Computer Networking Technology Group D-45326 Essen/Germany
-----------------------------------------------------------------------
E-Mail:
dreibh AT exp-math.uni-essen.de
Homepage: http://www.exp-math.uni-essen.de/~dreibh
=======================================================================

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• [SCTP-Discussion] Re: Latest socketapi data loss if using ext_select() on sctp-dgram socket (urgent), Thomas Dreibholz, 12/01/2004
  • [SCTP-Discussion] Re: Latest socketapi data loss if using ext_select() on sctp-dgram socket (urgent), Michael Tuexen, 12/01/2004

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