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Hi list, |
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I'm kind of despair. |
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The history: We recently brought up a new firewall with Gentoo. |
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There are (for my finding) some big nets behind this firewall (1x public |
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/24, 2x public /27, 1x public /26, at least 2 private /24). |
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Filtering is done via iptables and snort should jump as IPS on |
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software-bridge br0. If it helps: There is also ip rule involved for |
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source-based routing. |
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The new firewall replaces an older Gentoo-system which did not show this |
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behavior. We therefore copied several configfiles from the old to the new |
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one. |
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After getting it live, it runs well for a few hours and then becomes |
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unreachable (also for hosts behind the bridge). |
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Dmesg / kern.log stated at this time a neighbor table overflow and indeed, |
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arp -n | wc -l showed a lot of entry's. |
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As Google suggested, We then adjusted /proc/sys/net/ipv4/neigh/default/ to: |
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gc_thershold1 -> 8192 |
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gc_thershold2 -> 16384 |
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gc_thershold3 -> 32768 |
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Fireing an "arp -d $bogus-ip-adress" is failing with "SIOCDARP(dontpub): |
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Network is unreachable", adding -i br0 doesn't fail, but does not remove the |
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line in the arp-table (it only says "incomplete" after greping arp -n |
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again).. |
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Therefore we are currently killing the arp-cache with "ip link set arp off |
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dev br0 && ip link set arp on dev br0" by a cronjob. |
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The combination of these workarounds are keeping the firewall reachable and |
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"alive". |
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After stabilizing, we looked at the output of arp -n and noticed, that about |
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99(.999)% of the roundabout 11.000 (and rising) arp-cache-entry's contained |
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public addresses for which the bridge of the firewall should not feel |
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responsible (e.g. the public Google-dns-resolver and a load of more). |
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The MAC-entry for these public addresses is always the one of our router, |
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which is for sure the correct next hop. |
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But from my understanding, it should arp-cache only "our" net's directly at |
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the cable and not those public ones. |
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It looks like a configuration-issue, but I don't know, where to start |
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looking. I've already checked the default-gateway, netmasks, |
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broadcast-addresses and to me, they are looking fine, so any poke where to |
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start looking is greatly appreciated. |
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In case it will help, I attached the /etc/conf.d/net, ifconfig -a and route |
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-n. |
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If something else is needed, feel free to ask. |
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Hope, anyone can help. |
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Thanks in advance, |
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Ralf |
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