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Dear Florence,

I didn't saw the questions at the end of your mail when I first
answered it. See my comments below.

Best regards and a happy new year
Michael
On Friday, December 21, 2001, at 08:03 PM, Florence M Fowler wrote:

I am trying to change the receiver's rwnd. The sequence of events is:
initialize the callback procedures table
getArgs(arvc, argv)
checkArgs()
SCTP_initLibrary()
sctpInstance=SCTP_registerInstance(....)
SCTP_getAssocDefaults(....) (this said myRwnd was set at 32767)
SCTP_setAssocDefaults(....) I attempted to set myRwnd to
65534--OK
98301--it started ok but then
partway thru core dumped
giving the following when looked
at with gdb:
This GDB was configured as "i386-redhat-linux"...
Core was generated by `scttcp -r -w 128000 -s 160.91.192.149'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /usr/lib/libgmodule-1.2.so.0...done.
Loaded symbols for /usr/lib/libgmodule-1.2.so.0
Reading symbols from /usr/lib/libglib-1.2.so.0...done.
Loaded symbols for /usr/lib/libglib-1.2.so.0
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /lib/i686/libc.so.6...done.
Loaded symbols for /lib/i686/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
#0 0x400ced89 in __libc_free (mem=0x40177f10) at malloc.c:3055
3055 malloc.c: No such file or directory.
in malloc.c

Normally there is a relationship between socket buffer size the receiver
window size...is there here? Can someone help me understand what is
happening beyond just the guess that it is attempting to get more memory
and can't? Is there something else I need to set that I am not setting?

I do not understand this. Yes, normally (this means in a kernel implementation)
there is a relationship. But with this prototype you have to set the receive
space for raw sockets in the way your OS wants it. On BSD like systems, for example,
you use a sysctl command. The rwnd stuff handled by the prototype deals not with
that stuff, but only with reporting the receiver space. This could be the problem:
If you set the receiver space for the raw socket to 32K but SCTP announces 64k than
your peer may send 64k, but the receiver can only handle 32 k which results in
packet loss! But beside that there should be no problem.

I can't reproduce the problem on a BSD system with our pre15 code I'm testing.
Andreas will test it on Linux. But if the problem remains (after the release of
pre15) please contact us again.

Thanks.

Florence Fowler

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Michael.Tuexen AT micmac.franken.de

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• [SCTP-Discussion] setting rwnd, Florence M Fowler, 12/21/2001
  • Re: [SCTP-Discussion] setting rwnd, Michael Tuexen, 12/21/2001
  • Re: [SCTP-Discussion] setting rwnd, Michael Tuexen, 12/29/2001

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