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Date:      Mon, 11 Jan 1999 19:20:06 +0900
From:      Kenjiro Cho <kjc@csl.sony.co.jp>
To:        Mohit Aron <aron@cs.rice.edu>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: TCP bug report for FreeBSD-2.2.6 
Message-ID:  <199901111020.TAA13847@hotaka.csl.sony.co.jp>
In-Reply-To: Your message of "Mon, 11 Jan 1999 00:22:43 CST." <199901110622.AAA00358@cs.rice.edu> 

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Mohit Aron <aron@cs.rice.edu> said:
>>     I'm using FreeBSD-2.2.6. I've discovered that the TCP implementation has a
>> nasty bug that can cause problems in general for any TCP connection with 
>> respect to the end and receive buffer sizes used by a connection. The latter
>> are important for fully utilizing the bandwidth (long fat pipes). I'll outline
>> the problem below.

This is a well-known problem since 2.1.  It was fixed in -current long 
time ago but the fix didn't go into -stable.
I've been using the following patch to enable SO_SNDBUF/SO_RCVBUF.  As 
a side-effect, it disables copying the pipesize in the route.

--Kenjiro

--------------------------------------------------------------------------
diff -urN ../sys/netinet/in_rmx.c ./netinet/in_rmx.c
--- ../sys/netinet/in_rmx.c	Fri Jun 21 00:41:23 1996
+++ ./netinet/in_rmx.c	Tue Dec  8 18:59:00 1998
@@ -130,11 +130,13 @@
 	 * as it sees fit.  This will hopefully allow TCP more
 	 * opportunities to save its ssthresh value.
 	 */
+#if 0  /* commented out for the tcp window problem  --kjc */
 	if (!rt->rt_rmx.rmx_sendpipe && !(rt->rt_rmx.rmx_locks & RTV_SPIPE))
 		rt->rt_rmx.rmx_sendpipe = tcp_sendspace;
 
 	if (!rt->rt_rmx.rmx_recvpipe && !(rt->rt_rmx.rmx_locks & RTV_RPIPE))
 		rt->rt_rmx.rmx_recvpipe = tcp_recvspace;
+#endif
 
 	if (!rt->rt_rmx.rmx_mtu && !(rt->rt_rmx.rmx_locks & RTV_MTU) 
 	    && rt->rt_ifp)
--------------------------------------------------------------------------


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