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John Smith avatar Server

iptables redirect hardcoded DNS requests

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John Smith

I'm slowly trying to learn iptables and would like to redirect all DNS (port 53) requests not coming from/to a list of IPs (from 192.168.2.1, 192.168.2.29 or to 1.1.1.1). I figured I can use chains. It does not work though. Could you please give me a hint:

iptables -N dnsrewrite
iptables -A dnsrewrite -s 192.168.2.1 -j RETURN
iptables -A dnsrewrite -s 192.168.2.29 -j RETURN
iptables -A dnsrewrite -d 1.1.1.1 -j RETURN
iptables -t nat -A dnsrewrite -j DNAT --to-destination 192.168.2.29
iptables -t nat -A POSTROUTING -p tcp --dport 53 -j MASQUERADE
iptables -t nat -A POSTROUTING -p udp --dport 53 -j MASQUERADE
iptables -A PREROUTING -p tcp --dport 53 -j dnsrewrite
iptables -A PREROUTING -p udp --dport 53 -j dnsrewrite
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Michael Hampton avatar
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Michael Hampton
It said: `Run \`dmesg' for more information.`
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John Smith avatar
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John Smith
There was no more info there really.
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Tom Yan avatar Server
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Tom Yan 
iptables -t nat -N dnsrewrite
iptables -t nat -A dnsrewrite -j DNAT --to-destination 192.168.2.29

iptables -t nat -N whitelist
iptables -t nat -A whitelist -s 192.168.2.1 -j RETURN
iptables -t nat -A whitelist -s 192.168.2.29 -j RETURN
iptables -t nat -A whitelist -d 1.1.1.1 -j RETURN
iptables -t nat -A whitelist -j dnsrewrite

iptables -t nat -A PREROUTING -p tcp --dport 53 -j whitelist
iptables -t nat -A PREROUTING -p udp --dport 53 -j whitelist

Whether these suit you needs depends.

iptables -t nat -A POSTROUTING -p tcp --dport 53 -j MASQUERADE
iptables -t nat -A POSTROUTING -p udp --dport 53 -j MASQUERADE
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