iptables blocking local connection to mongodb

Question

I have a VM (Ubuntu 12.04.4 LTS) with mongodb (2.0.4) that I want to restrict with iptables to only accepting SSH (in/out) and nothing else. This is how my setup script looks like to setup the rules: ``` #!/bin/sh # DROP everything iptables -F iptables -X iptables -P FORWARD DROP iptables -P INPUT DROP iptables -P OUTPUT DROP # input iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A INPUT -s 127.0.0.1 -j ACCEPT # accept all ports for local conns # output iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A OUTPUT -p tcp -m tcp --dport 22 -j ACCEPT # ssh ``` But with these rules activated, I can't connect to mongodb locally. ``` ubuntu ~ $ mongo MongoDB shell version: 2.0.4 connecting to: test Fri Mar 28 09:40:40 Error: couldn't connect to server 127.0.0.1 shell/mongo.js:84 exception: connect failed ``` Without them, it works fine. Is there any special firewall case one needs to consider when deploying mongodb? I tried installing mysq…

Accepted Answer

Outbound traffic must be accepted for the loopback (127.0.0.1) as well.

Adding this made it work:

```
iptables -A OUTPUT -o lo -j ACCEPT
```

iptables blocking local connection to mongodb

Solution

Problem