No response traffic on application after port forward Topic is solved

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S10
Posts: 23
Joined: Wed Oct 31, 2018 7:06 pm

Re: No response traffic on application after port forward

Post by S10 »

I did a reboot without removing lsof and i'm back at square 1 :-(

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root@DietPi:~# tcpdump -n -i eth0 port 443
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
17:52:12.001598 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,nop,wscale 7,nop,nop,TS val 458575080 ecr 0,sackOK,eol], length 0
17:52:12.360788 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,nop,wscale 7,nop,nop,TS val 458575447 ecr 0,sackOK,eol], length 0
17:52:12.508828 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,nop,wscale 7,nop,nop,TS val 458575583 ecr 0,sackOK,eol], length 0
17:52:12.648418 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,nop,wscale 7,nop,nop,TS val 458575719 ecr 0,sackOK,eol], length 0
17:52:13.480744 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,nop,wscale 7,nop,nop,TS val 458576557 ecr 0,sackOK,eol], length 0
17:52:24.672036 IP 109.36.143.39.1344 > 192.168.1.20.443: Flags [S], seq 1941187099, win 65535, options [mss 1300,sackOK,eol], length 0
Something changed in between the reboot. i didnt change anything but installed lsof. Maybe the iptables?

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root@DietPi:~# iptables --list
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
S10
Posts: 23
Joined: Wed Oct 31, 2018 7:06 pm

Re: No response traffic on application after port forward

Post by S10 »

Solved it!

I totally forgot that on the background i was running a vpn connection which conflicts with my portforward rules. Becasuse the traffic is rerouted through the vpn tunnel and so the reply traffic is tunneled through a totally different public ip than it came in.

Disabling the vpn, and the port forward works.
User avatar
Joulinar
Posts: 2277
Joined: Sat Nov 16, 2019 12:49 am

Re: No response traffic on application after port forward

Post by Joulinar »

uh yeah that's a good reason. Good that you found it. 8)
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team
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