Hello everyone, Recently I designed a specific networking layout to be used on a Xen system, currently running on two dedicated server at a certain hosting company. I'd like to request your comments and ideas on it. It's a bit off topic but not entirely.
While the whole thing works I do have some questions remaining, I'll ask those at the end. The ground work: a 'plain' Xen server with less than 10 VMs; OpenVSwitch; routing; filtering and traffic analysis. Each VM has its own global IP or subnet (like a /30). Dom0 also has an IP. When I request a single new secondary IP my hosting company assigns a 'random' one from one of their subnets. They have many and they route those IPs over the main IP. Via their website I am allowed to route any IP except for the main one to any other server. That allows me to do some "poor man's HA" tasks: each VM has its storage on a DRBD backed LVM2 LV and thus I can move a VM from physical server A to B by shutting down that VM on server A, moving the IP and the DRBD primary to server B, altering routes on A and B and finally booting the VM on server B. The server's physical connection (eth0) is assigned, with PCI passthrough, to a firewall VM. So packets arrive at eth0(fw), are filtered by shorewall, then are sent through eth1(fw) where they reach dom0's OpenVSwitch. dom0's port has proxyarp=1, so all packets flow from VM(fw) eth1(fw), via dom0, to the other VMs. I know that this is not required, but I wanted it this way because OpenVSwitch can do port mirroring. I am using that to duplicate the packets from eth1(fw) to a switch port 'ids0' where a separate VM is running Snort. The other VMs are each on their own VLAN bridge (another function of OpenVSwitch). Doing it in this way allows me to analyse only the filtered packets, i.e. after Shorewall. I couldn't find any other way to do this; packet filtering goes after packet switching. Here's how it works. Say I have one VM "foo", connected to "fake bridge" vbr10 which has VLAN tag 10, and IP address 203.0.113.24. To make it work this is how it looks and what I have to do: .------.(fw).------. <-----. | eth1 |====| eth0 |===| ISP | '------' '------' '-----> || .----------.(mir).------. .-----------. | vSwitch0 |=====| ids0 |---| vm(snort) | '----------' '------' '-----------' || \\ .------. .-------. .-------. | dom0 | | vbr10 |----| VMfoo | '------' '-------' 10 '-------' In the above diagram I did not include the port used by VM(ids) for its own ingress/egress. It actually has eth0 and eth1 where eth1 is the mirrored traffic. Commands: VM(fw): sysctl net.ipv4.conf.eth1.proxy_arp=1 VM(fw): ip route add 203.0.113.24 dev eth1 dom0: sysctl net.ipv4.conf.vm_fw0.proxy_arp=1 dom0: sysctl net.ipv4.conf.vbr10.proxy_arp=1 dom0: ip route add 203.0.113.24 dev vbr10 dom0: ip route add default dev dom0 VM(foo): ip addr add 203.0.113.24/24 brd + dev eth0 VM(foo): ip route add default via 203.0.113.0 dev eth0 The 'via' address is bogus, but it works because the dom0 side has proxyarp=1. Maybe you already figured out the downside: routing has to be setup in two places; on VM(fw) and on dom0. This means that, when I move VM(foo) from server A to B, I have to issue on A: dom0: ip route del 203.0.113.24 dev vbr10 vm(fw): ip route del 203.0.113.0 dev eth1 And the opposite on server B. Also it can become confusing when a VM has been moved. Say VM(foo) runs on server A, then that means that when VM(foo) contacts a VM on server B, VM(fw) on server A sees the address 203.0.113.24 in zone INET and VM(fw) on server B sees that address in zone LCL. Moving them around means the opposite will happen. Luckily I have few VMs and don't move them around often. One remaining query I have is specific to shorewall and has to do with zones. I figured there are various approaches: 1) make one big zone for the hosts that are local to the physical server; i.e. on VM(fw) make a zone LCL with siblings LCL:foo, LCL:bar, define their IPs in /etc/shorewall/hosts, add shared rules under the LCL zone and specific rules under the foo/bar zone; or 2) Only assign a LCL zone to eth1 in /etc/shorewall/interfaces; use params for the internal hosts, e.g. FOO="LCL:203.0.113.24" and use LCL for the shared rules and $FOO for the specific rules. I am looking forward to your comments/suggestions/opinions; if you read this far you probably have some... :) -- Thanks, Mark van Dijk. ,--------------------------------- ----------------------------' Thu Aug 30 07:57 UTC 2012 Today is Boomtime, the 23rd day of Bureaucracy in the YOLD 3178 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Shorewall-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/shorewall-users
