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Bug 48284 - Port forwarding (+masq?) can freeze kernel
Port forwarding (+masq?) can freeze kernel
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
i686 Linux
medium Severity high
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Assigned To: David Miller
Brock Organ
Depends On:
  Show dependency treegraph
Reported: 2001-07-09 22:31 EDT by stone
Modified: 2007-04-18 12:34 EDT (History)
0 users

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2003-07-30 19:45:27 EDT
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description stone 2001-07-09 22:31:54 EDT
Description of Problem:
Set up Masq + port forwarding in rc.local:
echo "NAT..."
/sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE


iptables -A PREROUTING -t nat -p tcp -d $EXT --dport $DPORT -j DNAT --to $INT:$DPORT
iptables -A OUTPUT -t nat -p tcp -d $EXT --dport $DPORT -j DNAT --to $INT:$DPORT

echo 1 > /proc/sys/net/ipv4/ip_forward

use the port forwarding for a while, watch it work fine (LimeWire on a win2k box)
kernel will hang, no oops, nothing in logs, nothing on screen. no response to pings

How Reproducible:
when running gnutella on a box behind the machine, It stays up maybe 5-20minutes.
when not running gnutella (but lots of other network traffic) it stays up indefinitely

Steps to Reproduce:

Actual Results:

Expected Results:

Additional Information:
Standard RH7.1 installation, all updates installed. Kernel "2.4.3-12 #1 Fri Jun 8 15:05:56 EDT 2001 i686 unknown"	
50 ip aliases were present on eth1 (200-250), the box forwarded to, was on the subnet with eth1:201 as gateway
Comment 1 stone 2001-07-23 22:25:15 EDT
seems to be related to having 2 realtek network cards installed, switching to hp100 cards seems to have resolved problem.
The realteks also caused problems (same total hang as above) when routing between two alias interfaces (eth1:100 and eth1:200).
Comment 2 David Miller 2003-07-30 00:34:43 EDT
Can you retry with current errata kernels? :-)
Comment 3 stone 2003-07-30 13:54:28 EDT
sorry, I don't have that old box anymore...
but I'm doing similar stuff now on a newer kernel with no problems.

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