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Sean Reifschneider, <jafo@tummy.com>
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Thursday November 27, 2003
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==========================
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These scripts can be used with OpenVPN up and down scripts to set up
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routing on a Linux system such that the VPN traffic is sent via normal
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network connectivity, but other traffic to that network runs over the VPN.
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The idea is to allow encryption of data to the network the remote host is
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on, without interfering with the VPN traffic. You can't simply add a route
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to the remote network, becaues that will cause the VPN traffic to also try
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to run over the VPN, and breaks the VPN.
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These scripts use the Linux "fwmark" iptables rules to specify routing
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based not only on IP address, but also by port and protocol. This allows
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you to effectively say "if the packet is to this IP address on this port
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using this protocol, then use the normal default gateway, otherwise use the
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This is set up on the client VPN system, not the VPN server. These scripts
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also set up all ICMP echo-responses to run across the VPN. You can
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comment the lines in the scripts to disable this, but I find this useful
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at coffee shops which have networks that block ICMP.
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To configure this, you need to set up these scripts as your up and down
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scripts in the config file. You will need to set these values in the
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up /etc/openvpn/fwmarkroute.up
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down /etc/openvpn/fwmarkroute.down
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setenv remote_netmask_bits 24
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Note: For this to work, you can't set the "user" or "group" config options,
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because then the scripts will not run as root.
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The last setting allows you to control the size of the network the remote
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system is on. The remote end has to be set up to route, probably with
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masquerading or NAT. The network this netmask relates to is calculated
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using the value of "remote" in the conf file.
added
removed
contrib/openvpn-fwmarkroute-1.00/README
