DragonFly BSD
DragonFly bugs List (threaded) for 2004-12
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Re: TCP and natd issues

From: Gary Allan <dragonfly@xxxxxxxxxxxxxxx>
Date: Thu, 23 Dec 2004 21:29:32 +0000

Just completed a buildworld and install of DragonFly head 12/12/04 12:00pm and it shows exactly the same behavior with natd and TCP connections as the current stable.

"tcpdump" is now working correctly and does not cause packet loss or lockups.

Attached is a small tcpdump from vr1 (router) and an ethereal capture from vr0 (desktop) from an attempt to view Google in a webrowser.

Running "Telnet <mailserver> 25" works without problems. Again only TCP traffic with a window size of 65535 seems to have this problem.

[This is the only common thing I can identify from traffic originating from PuTTY, Mozilla, IE, Thunderbird and Outlook.]

I'm tempted to compile snapshots from the past until I can find the commits that break things. Unfortunately my machine takes a while to do full buildworlds, any educated guesses as to when this may have been introduced are appreciated.



hsu@XXXXXXXXXX wrote:
> Hi, can you check if a kernel between Dec 16 and Dec 20 works?  I suspect
> the breakage was before that, but want to rule out the huge commit I
> made on Dec 21.
> The other big networking changes went in on Dec 14, so a Dec 13 kernel
> would also be worth trying.
> Thanks.
> 							Jeffrey


1. Using IPFW2 and natd does not process certain TCP connections correctly.

2. Running "tcpdump -i vr1" causes all traffic to be dropped.

When IPFW2 is configured for NAPT with natd I'm seeing certain TCP traffic blocked. I've used ethereal to capture the traffic from my desktop and the only pattern I can see is that all outgoing TCP traffic with a window size of 65535 never gets a response. (IE, FireFox, Outlook, Thunderbird). TCP connections using lower window sizes proceed normally ("telnet <mymailserver> 25" for example). UDP and ICMP traffic are also unaffected.

                      vr0     vr1
  [desktop]----------[ DragonFly ]----------[   Modem   ]--- NET      50.1        20.4

Here the ipfw logging shows responses from www.google.com and nat taking place. You can see that the packet from google was mapped back to but it was never actually received by my machine!

ipfw: 100 Divert 8668 TCP in via vr1
ipfw: 200 Accept TCP in via vr1
ipfw: 100 Divert 8668 TCP out via vr0
ipfw: 200 Accept TCP out via vr0

Also running tcpdump on the machine causes all network traffic passing through the box to be dropped until the tcpdump process is killed at the console. (as all SSH sessions drop out!)

The setup is identical to a FreeBSD 4.10 box that is working without issues. The machine is running DragonFly stable compiled 22-Dec-04.


I've disabled SACK.
Bridging the interfaces works as expected.
I'm compiling the kernel to remove custom options and try under pf.

I can provide configs and traces to anyone interested, any help in resolving this would be appreciated.



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