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(37)

  • 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

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

    • 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

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

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

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

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

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

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

        • 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.

        • @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

            • 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

            • 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

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

            • 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

            • 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

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

            • 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

              • 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.

                • 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.

                  • @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

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

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

                  • Try this: iptables-save | grep -v i_XXXXX_i | iptables-restore – Steven Monday Apr 2 '12 at 19:01

                  • 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.

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

                  • Something along these lines will get all of them in a single line without taking iptables down in any way.

                    for chain in `iptables -L |grep i_XXXXX_i|awk '{ print $2 }'`; do iptables -X $chain; done
                    

                    • You need two steps, but this does it in one command.

                      Create a file, and place this in it.

                      # Empty the entire filter table
                      *filter
                      :INPUT ACCEPT [0:0]
                      :FORWARD ACCEPT [0:0]
                      :OUTPUT ACCEPT [0:0]
                      COMMIT
                      

                      Save the file as "clear-all-rules". Now, do this command:

                      iptables-restore < clear-all-rules
                      

                      Now you can clear it anytime with just one command.

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

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

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

                          • 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

                          • 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

                          • 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

                          • 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