On 03/09/2009 02:33 PM, Gáspár Lajos wrote:
Dennis Jacobfeuerborn írta:
Hi,
I'm running into a problem on a machine that right now acts as a
simple gateway but is supposed to become a firewall too. When I start
iptables using "/etc/init.d/iptables start" on the Centos 5.2 machine
first everything works fine but after about 30 seconds I'm seeing
packet loss and running a ping outputs "sendmsg: operation not
permitted" sporadically.
The moment I stop iptables again everything returns to normal. What is
consufing to me is that I don't even have any rules defined so far.
This is what my "/etc/sysconfig/iptables" file looks like:
# Generated by iptables-save v1.3.5 on Thu Mar 5 17:40:28 2009
*filter
:INPUT ACCEPT [26715202:4750206096]
:FORWARD ACCEPT [1382646771:1563210213960]
:OUTPUT ACCEPT [22930985:6256734041]
COMMIT
iptables -L says:
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Does anyone have an idea why that would have such a severe impact on
the traffic? The fact that it takes a moment for the problems to show
up makes me suspect some kind of buffer issue so that the packet loss
only begins to occur after some buffer begins to overflow. That just a
guess though and I have no idea what buffer that could be.
Regards,
Dennis
Hi Dennis,
What about the other tables?
iptables -vnL -t raw
iptables -vnL -t mangle
iptables -vnL -t nat
All clear:
[root@gw ~]# iptables -vnL -t raw
Chain PREROUTING (policy ACCEPT 132 packets, 77370 bytes)
pkts bytes target prot opt in out source
destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source
destination
[root@gw ~]# iptables -vnL -t mangle
Chain PREROUTING (policy ACCEPT 2688M packets, 1487G bytes)
pkts bytes target prot opt in out source
destination
Chain INPUT (policy ACCEPT 2048K packets, 368M bytes)
pkts bytes target prot opt in out source
destination
Chain FORWARD (policy ACCEPT 2686M packets, 1486G bytes)
pkts bytes target prot opt in out source
destination
Chain OUTPUT (policy ACCEPT 1961K packets, 997M bytes)
pkts bytes target prot opt in out source
destination
Chain POSTROUTING (policy ACCEPT 2688M packets, 1487G bytes)
pkts bytes target prot opt in out source
destination
[root@gw ~]# iptables -vnL -t nat
Chain PREROUTING (policy ACCEPT 178 packets, 40798 bytes)
pkts bytes target prot opt in out source
destination
Chain POSTROUTING (policy ACCEPT 121 packets, 26962 bytes)
pkts bytes target prot opt in out source
destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source
destination
Regards,
Dennis
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