netdev - Re: Strange connection slowdown on pcnet32

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 16 Feb 2007 09:35:54 -0500
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	netdev@...r.kernel.org
Subject: Re: Strange connection slowdown on pcnet32

On Thu, Feb 15, 2007 at 05:50:30PM -0500, Lennart Sorensen wrote:
> I have encountered a strange behaviour with the pcnet32.
> 
> I am transfering data from a server to a client routing it through my
> router.  The router has 2 ethernet ports, both of which are amd 972
> chips (pcnet32).  The transfer has so far been either http or ftp (both
> see the same problem).  I transfer lots of data, and after a while (I
> have seen anywhere from 200 to 700MB or so) the speed suddenly drops to
> less than 1KB/s.  If I ping from the router to the server, the ping
> requests go out normally (seen by tcpdump on the server) every second,
> but on the router the replies are not seen by the kernel for multiple
> seconds.  Sometimes I will see 3 ping replies together, sometimes 5 or
> even 10.  The turn around times will show 10500, 9500, 8500, ..., 500ms
> for the packets received in a batch.  ifconfig on the router shows the
> packet receive counts showing up in lumps, just as ping does, and
> tcpdump on the interface on the router.
> 
> Doing ifconfig down and up on the port connecting to the server makes
> the problem clear and it can handle another pile of data before the
> problem reappears.
> 
> The CPU on the router is not fast enough to ensure there won't ever be
> dropped packets at 100Mbps.  When I force the port to the server to
> 10Mbps I have no problems at all.
> 
> Replacing the port to the server with an rtl8139 doesn't show any
> problems at 100Mbps, although the transfer rate drops from 6500KBps to
> 4000KBps compared to using the pcnet32.
> 
> Kernel used so far is 2.6.16 and 2.6.18.
> 
> I have a tulip card I intend to try with as well just to see if it
> affects anything other than the pcnet32.
> 
> Does anyone have any hints as to what part of the code to look at for
> changes made by doing ifconfig eth1 down; ifconfig eth1 up?  Any ideas
> as to what could make the reception of packets suddenly get very very
> slow?
> 
> On one pass where I was running tcpdump on the router, I saw a wrap of
> the sequence number right before the problem occoured, but that has not
> been the case every time as far as I can tell, so I am not sure if that
> is related to the problem at all.

I have run some tests using 2.6.8 now, and so far it hasn't failed.

Still investigating...

--
Len Sorensen
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html