Iptables – (dnat|redirect) with masquerade doesn’t work

dnatiptablesredirect

I have a problem, till a bit ago it was working just fine. but now, it doesn't work, but on another testing server it works just fine

I force all traffic to tor, and this part works just fine.
Problem is on masquerade I think as it not change the dnat/redirect port 9040 to the origin port 80/443 back after receive response

http://ipinfo.io:9040
Software:
- 1.6.1-2ubuntu2
- ubuntu 16.04/18.04 the same result
- tor 0.3.2.9-1build1
Networking
- virbr1 – 192.168.2.0/24 – host only
- eno1 – 192.168.1.0/24 – internet
Iptables:
- /sbin/iptables -t nat -A POSTROUTING -o virbr1 -j MASQUERADE
- /sbin/iptables -t nat -A POSTROUTING -o eno1 -j MASQUERADE # on another server works without that, this was just for testing
- /sbin/iptables -t nat -A PREROUTING -p udp –source 192.168.2.6 ! –destination 192.168.2.1 -j DNAT –to-destination 192.168.2.1:9040 # tested REDIRECT –to-ports 9040, the same

*filter :INPUT ACCEPT [174876:86417485] :FORWARD DROP [0:0] :OUTPUT ACCEPT [170612:89138010] :DOCKER - [0:0] :DOCKER-ISOLATION - [0:0] :DOCKER-USER - [0:0] -A FORWARD -d 192.168.2.8/32 -i virbr1 -o virbr1 -j ACCEPT -A FORWARD -s 192.168.2.8/32 -i virbr1 -o virbr1 -j ACCEPT -A FORWARD -d 192.168.2.0/24 -o virbr1 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 192.168.2.0/24 -i virbr1 -j ACCEPT -A FORWARD -i virbr1 -o virbr1 -j ACCEPT -A OUTPUT -s 192.168.2.8/32 -j DROP COMMIT # Completed on Tue Feb 20 09:32:11 2018 # Generated by iptables-save v1.6.1 on Tue Feb 20 09:32:11 2018 *nat :PREROUTING ACCEPT [193:19723] :INPUT ACCEPT [193:19723] :OUTPUT ACCEPT [129:12889] :POSTROUTING ACCEPT [124:11792] :DOCKER - [0:0] -A PREROUTING -s 192.168.2.8/32 -p tcp -m tcp --dport 53 -j DNAT --to-destination 192.168.2.1:5353 -A PREROUTING -s 192.168.2.8/32 -p udp -m udp --dport 53 -j DNAT --to-destination 192.168.2.1:5353 -A PREROUTING -s 192.168.2.8/32 ! -d 192.168.2.1/32 -p tcp -j DNAT --to-destination 192.168.2.1:9040 -A PREROUTING -s 192.168.2.8/32 ! -d 192.168.2.1/32 -p udp -j DNAT --to-destination 192.168.2.1:9040 -A POSTROUTING -o tun5 -j MASQUERADE -A POSTROUTING -o virbr1 -j MASQUERADE COMMIT # Completed on Tue Feb 20 09:32:11 2018 # Generated by iptables-save v1.6.1 on Tue Feb 20 09:32:11 2018 *mangle :PREROUTING ACCEPT [3538365:1832890486] :INPUT ACCEPT [3538362:1832890258] :FORWARD ACCEPT [3:228] :OUTPUT ACCEPT [3495644:1711746305] :POSTROUTING ACCEPT [3496898:1711973811] -A POSTROUTING -o virbr1 -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill -A POSTROUTING -o virbr0 -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill -A POSTROUTING -o virbr1 -p udp -m udp --dport 68 -j CHECKSUM --checksum-fill COMMIT

/proc/sys/net/ipv4/ip_forward is set to 1
Monitoring with conntrack -L
- tcp 6 431973 ESTABLISHED src=192.168.2.6 dst=172.217.16.4 sport=49215 dport=443 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49215 [ASSURED] mark=0 use=1
- tcp 6 431983 ESTABLISHED src=192.168.2.6 dst=104.81.60.33 sport=49226 dport=80 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49226 [ASSURED] mark=0 use=1
- tcp 6 431972 ESTABLISHED src=192.168.2.6 dst=64.233.184.154 sport=49211 dport=443 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49211 [ASSURED] mark=0 use=1
- tcp 6 431972 ESTABLISHED src=192.168.2.6 dst=54.192.185.106 sport=49216 dport=80 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49216 [ASSURED] mark=0 use=1
- tcp 6 431973 ESTABLISHED src=192.168.2.6 dst=216.58.208.46 sport=49194 dport=80 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49194 [ASSURED] mark=0 use=1
- tcp 6 74 TIME_WAIT src=192.168.2.6 dst=178.255.83.1 sport=49190 dport=80 src=192.168.2.1 dst=192.168.2.6 sport=9040 dport=49190 [ASSURED] mark=0 use=1

PS on another server with the same OS, iptables version, iptables rules it works just fine

Thanks in advance

Best Answer

ok i have solved the problem.

it's related to docker update and change of the kernel network filter, more details here https://forums.fedoraforum.org/showthread.php?312824-Bridge-broken-after-docker-install&p=1785664#post1785664

setting them to 0 looks like solve my problem

net.bridge.bridge-nf-call-ip6tables=0 net.bridge.bridge-nf-call-iptables=0 net.bridge.bridge-nf-call-arptables=0

thanks

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You're sending the traffic to 10.52.208.221. Given the config you posted, your problem is the webserver, not the firewall. Your rules look to be correct. FORWARD and INPUT are redirected to RH-Firewall-1-INPUT where your first rule is to allow all traffic. As somebody else pointed out, you could be allowing all traffic on eth1, while the world is actually coming in eth0. Secondary, you have to NAT the traffic as it goes back out to the world

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In Passive mode, when the client wants to get a file from the server or send a file to the server, the FTP server will pick a random port and send that port to the FTP client.

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