How to define iptables rule to add all transport to a given interface to nfqueue

  • Running on Ubuntu. I have machine 1 < - > machine 2 < - > machine 3. I dont know machine 1 or machine 3 ip. It can be any ip. machine 1 send packet to machine 3 and machine 3 send packet to machine 1.

    Machine 2 is used as a bridge:

    ifconfig eth0 0.0.0.0
    ifconfig eth2 0.0.0.0
    brctl addbr br0
    brctl addif br0 eth0 eth2
    ifconfig br0 up
    

    i want to have an iptable rule in machine 2 that will add all traffic that come to eth0 to nfqueue1 and all traffic that come to eth2 to nefqueue2.

      Now i have the following rule:

      iptables -A FORWARD -p tcp -j NFQUEUE --queue-num 0
      

        which is not good to me because i want to distinguish between traffic that come from machine 3 to traffic that come from machine 1, so i want to have 2 rule.

          Add -i eth0 to the rule doesn’t help.

        Answers(35)

          • since you're operating a bridge, you need to use -m physdev

            for usage, run iptables -m physdev -h - if you compile your own kernel, you may need to add this module.

          • because the incoming interface is considered to be the bridge interface ( br0 ), not the bridge port. – Olipro Aug 12 '12 at 20:18

          • Here's an alternate plan. It involves three commands, not one, but with luck, it should work.

            Dump your iptables ruleset to a file:

            iptables-save > /tmp/iptables.txt
            

            Remove ALL uses of (and references to) the offending chain:

            sed -i '/i_XXXXX_i/d' /tmp/iptables.txt
            

            Then reload the ruleset:

            iptables-restore < /tmp/iptables.txt && rm /tmp/iptables.txt
            
          • Try this: iptables-save | grep -v i_XXXXX_i | iptables-restore – Steven Monday Apr 2 '12 at 19:01

            • 2 many is many :) if I try to delete the rules first, it will like typing many times: iptables -D OUTPUT -d XXX/32 -j i_XXXXX_i – timy Apr 2 '12 at 17:23

            • Can you just add a -s specifier? – larsks Aug 12 '12 at 12:20

            • I've not seen iptables barf like that before when trying to flush. – Tom O'Connor ♦ Apr 2 '12 at 17:18

            • You're missing a line with --set --name SSH2 somewhere before the one that's listed in the error message.

                The --rttl option requres there to be a --set option for the same list. You have one for the

                SSH list but not for the
                SSH2 list.

                The error message could be a little clearer about this.

              • since you're operating a bridge, you need to use -m physdev

                for usage, run iptables -m physdev -h - if you compile your own kernel, you may need to add this module.

                • Right, and I'm suggesting that you use the source ip address to distinguish machine 1 from machine 3 (I'm not suggesting blocking traffic). You would need two rules in your FORWARD chain instead of 1... – larsks Aug 12 '12 at 12:54

                • Ah, that wasn't clear. – larsks Aug 12 '12 at 13:06

                • But iptables-restore /etc/sysconfig/iptables fails after replacing anti-bruteforce rules in /etc/sysconfig/iptables with second fragment of code (see question body) . It contains -A SSH_CHECK -m recent --set --name SSH2 line before -A SSH_CHECK -m recent --update --seconds 86400 --hitcount 100 --rttl --name SSH2 -j SSH_ATTACKED . – technocrat May 5 '12 at 8:13

                • iptables -A FORWARD -m physdev --physdev-in eth0 .... work!!!! great!!! – Avihai Marchiano Aug 13 '12 at 7:15

                • How can you know that? You don't know enough to solve the problem yourself, and yet you're absolutely , 100% certain that the error message could not possibly be of any help to anyone else who might have an interest in helping you solve your problem? – womble May 5 '12 at 7:19

                • 10x i will test it tommorow. Why -i interfacename dosnt work ? – Avihai Marchiano Aug 12 '12 at 16:44

                • I was only looking at your current /etc/sysconfig/iptables file and the command you ran at the end. I see the --set --name SSH2 in the earlier section now. The command at the bottom has -I SSH_CHECK 3 which may be its problem depending on what rules are already in place. What I would recommend is finding the smallest/simplest set of rules that still cause the error and update your question with that set of rules if still required. – Ladadadada May 5 '12 at 13:27

                  • @timy StevenMonday's comment will single-pass remove any references to the chain. Perhaps not ideal, but darned close. – Jeff Ferland Apr 3 '12 at 13:20

                  • You can't delete chains when rules with '-j CHAINTODELETE' are referencing them. Figure out what is referencing your chain (the link), and remove that. Also, flush then kill.

                    -F, --flush [chain]

                    Flush the selected chain (all the chains in the table if none is given). This is equivalent to deleting all the rules one by one.

                    -X, --delete-chain [chain]

                    Delete the optional user-defined chain specified. There must be no references to the chain. If there are, you must delete or replace the referring rules before the chain can be deleted. The chain must be empty, i.e. not contain any rules. If no argument is given, it will attempt to delete every non-builtin chain in the table.

                  • It just doesn't say anything that could help. iptables-restore /etc/sysconfig/iptables says "iptables-restore: line ## failed" where ## is number of last line in /etc/sysconfig/iptables iptables -I SSH_CHECK 3 -m recent --update --seconds 86400 --hitcount 100 --rttl --name SSH2 -j SSH_ATTACKED says iptables: Invalid argument. Run `dmesg' for more information. – technocrat May 5 '12 at 7:17

                    • Ah, that wasn't clear. – larsks Aug 12 '12 at 13:06

                      • Can you just add a -s specifier? – larsks Aug 12 '12 at 12:20

                      • No . All trafic allowed but i need to distinguish between traffic from machine 1 to machine 3 – Avihai Marchiano Aug 12 '12 at 12:32

                      • The ip of the machines is not known its group of machines. – Avihai Marchiano Aug 12 '12 at 13:05

                        • Yes. You are right. I often overestimate my abilities. I added info about error messagees to question body. – technocrat May 5 '12 at 7:26

                          • @StevenMonday why not write as answer, this is the most useful one (alternative do this via file and edit file). Only thing it does not remove is complete tables ("raw" anyway) – nhed Mar 7 at 0:56

                          • iptables -A FORWARD -m physdev --physdev-in eth0 .... work!!!! great!!! – Avihai Marchiano Aug 13 '12 at 7:15

                          • This is potentially off-topic, but it's what I did after I found this post! For some use cases the iptables -D option might be useful. Since it allows you to clear out referring rules added programmatically with -A (if you know precisely how you added them).

                              E.g

                                  iptables -N MYCHAIN
                                  iptables -A INPUT -i interface -j MYCHAIN
                                  iptables -A MYCHAIN -j ACCEPT
                              

                              can be reversed with

                                 iptables -D INPUT -i interface -j MYCHAIN
                                 iptables --flush MYCHAIN
                                 iptables -X MYCHAIN
                              
                            • Right, and I'm suggesting that you use the source ip address to distinguish machine 1 from machine 3 (I'm not suggesting blocking traffic). You would need two rules in your FORWARD chain instead of 1... – larsks Aug 12 '12 at 12:54

                              • I just want to find a way to delete the chain(has many '-j CHAINTODELETE' ref rules) directly, but from your answer, it seems impossible :( – timy Apr 3 '12 at 10:11

                              • because the incoming interface is considered to be the bridge interface ( br0 ), not the bridge port. – Olipro Aug 12 '12 at 20:18

                              • Just curious... how many rules is "many" ? – Ladadadada Apr 2 '12 at 17:21

                              • 10x i will test it tommorow. Why -i interfacename dosnt work ? – Avihai Marchiano Aug 12 '12 at 16:44

                              • No . All trafic allowed but i need to distinguish between traffic from machine 1 to machine 3 – Avihai Marchiano Aug 12 '12 at 12:32

                              • Gah! What error does it generate? How can you not think that is important information to convey? – womble May 5 '12 at 6:37

                                  • The ip of the machines is not known its group of machines. – Avihai Marchiano Aug 12 '12 at 13:05