[User-mode-linux-devel] UML only serves up one packet

[William S. <wst...@po...>]

Good day, Rusty and James,
	Jeff and I have been working on the UML networking code.  
(Translation: "_He's_ been doing all the work, I just break things and
whine loudly." :-)
	If I run apache in UML, it serves up files to the _host_ quite
nicely.  If I try to see those same files from another machine on the real
ethernet segment (my laptop), a bunch of bytes get stuck in the SendQ
according to "netstat -an" in the UML.  Just for reference, the host is
proxyarping the uml.  My laptop can successfully ping the uml, and the uml
can successfully ping my laptop.  For the moment, I'm using the umn-sl0
networking.
	The easiest way to reproduce it is to whip up a script called
/usr/sbin/in.fingerd that is:

#!/bin/bash
cat /home/httpd/html/index.html

	or some other file that's larger than 512 bytes.  When I do

finger @the_uml_ip_address

	i get back on the first part of the file.  

finger @the_uml_ip_address | wc -c

	returns 530 bytes; when I strip out the finger header from the
output ("[the_uml_ip_address]"):

finger @the_uml_ip_address | grep -v '\[the_uml_ip_address\]' | wc -c

	I get exactly 512 bytes.  And nothing more.  Every time,
repeatably.
	I get the impression that when UML has to feed a tcp stream back
to a client application running on some machine other than the uml or the
host, that it simply fails to schedule more than one 512 byte
packet.  Jeff gave me the impression he's really not sure about the
networking code in UML; is there any chance that once of you networking
gods could take a look at the code and see if we can coax a second or
third packet out of it?
	Please let me know if I ran short on details; I'll be glad to try
again or provide more specifics.
	Cheers,
	- Bill

---------------------------------------------------------------------------
	"SCSI is *NOT* magic.  There are *fundamental technical reasons*
why it is necessary to sacrifice a young goat to your SCSI chain now and
then." 
	-- jf...@pr...
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William Stearns (wst...@po...).  Mason, Buildkernel, named2hosts, 
and ipfwadm2ipchains are at:                http://www.pobox.com/~wstearns
LinuxMonth; articles for Linux Enthusiasts! http://www.linuxmonth.com
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