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[solved] stop network on TAP device
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toralf
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Joined: 01 Feb 2004
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Location: Hamburg

PostPosted: Sun Aug 04, 2013 9:34 pm    Post subject: [solved] stop network on TAP device Reply with quote

I'm playing here with running 2 user mode linux images a the same time. Each UML gets its DHCP address from the host. Now I'd like to suddenly break the network from /to 1 of both images. I'd thinking to do that with iptables. Anybody knows a working solution ? I'm already running an iptables script located in /etc/init.d and b/c rules are just added at the end of I'd like to avoid cleaning the tables it by restarting the init.d script. Instead I just like to revert the particular rule which can be used to stop the network traffic.

Last edited by toralf on Mon Aug 05, 2013 5:45 pm; edited 1 time in total
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BradN
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PostPosted: Mon Aug 05, 2013 6:35 am    Post subject: Reply with quote

iptables -t tablename -D (rest of command would match the rest of the -A command that created it)

This is in general how you remove a rule from iptables manually.

Like, let's say my iptables-save looks like:
Code:
# Generated by iptables-save v1.4.13 on Mon Aug  5 01:33:47 2013
*filter
:INPUT ACCEPT [8191684:9297331274]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [6192315:606443488]
-A FORWARD -s 192.168.0.0/16 -i eth0 -j ACCEPT
-A FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
-A FORWARD -d 192.168.0.0/16 -i ppp0 -j ACCEPT
-A FORWARD -s 192.168.0.0/16 -i eth2 -j ACCEPT
-A FORWARD -d 192.168.0.0/16 -i eth2 -j ACCEPT
COMMIT
# Completed on Mon Aug  5 01:33:47 2013
# Generated by iptables-save v1.4.13 on Mon Aug  5 01:33:47 2013
*nat
:PREROUTING ACCEPT [2690134:845364370]
:INPUT ACCEPT [164830:39214556]
:OUTPUT ACCEPT [203937:13325685]
:POSTROUTING ACCEPT [203784:13316196]
-A POSTROUTING -o ppp0 -j MASQUERADE
-A POSTROUTING -o eth2 -j MASQUERADE
COMMIT
# Completed on Mon Aug  5 01:33:47 2013


and I want to get rid of "-A FORWARD -d 192.168.0.0/16 -i ppp0 -j ACCEPT"

This takes...

iptables -t filter -D FORWARD -d 192.168.0.0/16 -i ppp0 -j ACCEPT
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toralf
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PostPosted: Mon Aug 05, 2013 1:56 pm    Post subject: Reply with quote

BradN wrote:
iptables -t tablename -D (rest of command would match the rest of the -A command that created it)

This is in general how you remove a rule from iptables manually.
Ah - this helps me.
Thanks for your examples.

UpdateBut now I'm realizing that one of my first iptables rules is to allow all on 192.168.x.x - pff ...
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