Argthtjtr

So I know there is another question on here that I used as a guide as it was super helpful! (Setup routing and iptables for new VPN connection to redirect **only** ports 80 and 443) Only my goal is a bit different. I am running a headless gui-less install of Ubuntu Server 12.04 that is being used for a variety of different purposes... I would like all traffic to travel un-prohibited through my ISP except for my transmission traffic. I have a VPN i subscribe to that allows me access for which I only want to direct a single port's traffic to. I am currently using a modified version of the code from the above link. My current code is below:

#!/bin/sh



sleep 200



DEV1=eth0

IP1=`ifconfig|perl -nE'/dr:(S+)/&&say$1'|grep 192.`

GW1=10.0.1.1

TABLE1=open

TABLE2=vpn

DEV2=tun0

IP2=`ifconfig|perl -nE'/dr:(S+)/&&say$1'|grep 10.`

GW2=`route -n | grep 'UG[ t]' | awk '{print $2}'`



ip route flush table $TABLE1

ip route flush table $TABLE2

ip route show table main | grep -Ev ^default | while read ROUTE ; do

    ip route add table $TABLE1 $ROUTE

    ip route add table $TABLE2 $ROUTE

done

ip route add table $TABLE1 $GW1 dev $DEV1 src $IP1

ip route add table $TABLE2 $GW2 dev $DEV2 src $IP2

ip route add table $TABLE1 default via $GW1

ip route add table $TABLE2 default via $GW2



echo "1" > /proc/sys/net/ipv4/ip_forward

echo "1" > /proc/sys/net/ipv4/ip_dynaddr

echo "2" > /proc/sys/net/ipv4/conf/tun0/rp_filter



ip rule add from $IP1 lookup $TABLE1

ip rule add from $IP2 lookup $TABLE2

ip rule add fwmark 1 lookup $TABLE1

ip rule add fwmark 2 lookup $TABLE2



iptables -t nat -A POSTROUTING -o $DEV1 -j SNAT --to-source $IP1

iptables -t nat -A POSTROUTING -o $DEV2 -j SNAT --to-source $IP2



iptables -t nat -A PREROUTING           -m state --state ESTABLISHED,RELATED          -j CONNMARK --restore-mark

iptables        -A OUTPUT               -m state --state ESTABLISHED,RELATED          -j CONNMARK --restore-mark

iptables -t nat -A PREROUTING -i $DEV1  -m state --state NEW                          -j CONNMARK --set-mark 1

iptables -t nat -A PREROUTING -i $DEV2  -m state --state NEW                          -j CONNMARK --set-mark 2

iptables -t nat -A PREROUTING           -m connmark --mark 1                          -j MARK --set-mark 1

iptables -t nat -A PREROUTING           -m connmark --mark 2                          -j MARK --set-mark 2

iptables -t nat -A PREROUTING           -m state --state NEW -m connmark ! --mark 0   -j CONNMARK --save-mark



iptables -t mangle -A PREROUTING -i $DEV2 -m state --state NEW -p tcp --dport  44447 -j CONNMARK --set-mark 2

iptables -t mangle -A PREROUTING -i $DEV2 -m state --state NEW -p udp --dport 44447 -j CONNMARK --set-mark 2



route del default

ip route del 0.0.0.0/1

ip route del 128.0.0.0/1

route add default gw $GW1 eth0

I took into account the original poster's own comments, modified it to my IP configuration and port needs... extended the sleep to ensure the OpenVPN configuration had occured... And then also deleted two routes that I believe were added by my VPN provider for a fallback incase the default route failed... Now everything seems to be okay except a few things...

1. traceroutes fail... completely...

    $ traceroute yahoo.com

    traceroute to yahoo.com (206.190.36.45), 30 hops max, 60 byte packets

     1  * * *

     2  * * *

     3  * * *

     4  * * *

     5  * * *

2. ping results in 100% packet loss

    $ ping google.com

    PING google.com (173.194.43.46) 56(84) bytes of data.

    ^C

    --- google.com ping statistics ---

    119 packets transmitted, 0 received, 100% packet loss, time 118945ms

I don't know what is causing this???

$ nslookup

> google.com

Server:     10.0.1.1

Address:    10.0.1.1#53



Non-authoritative answer:

Name:   google.com

Address: 173.194.43.46

Name:   google.com

Address: 173.194.43.38

Name:   google.com

Address: 173.194.43.35

Name:   google.com

Address: 173.194.43.41

Name:   google.com

Address: 173.194.43.39

Name:   google.com

Address: 173.194.43.34

Name:   google.com

Address: 173.194.43.36

Name:   google.com

Address: 173.194.43.37

Name:   google.com

Address: 173.194.43.32

Name:   google.com

Address: 173.194.43.40

Name:   google.com

Address: 173.194.43.33

route table below:

$ route

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

default         Rolands-AirPort 0.0.0.0         UG    0      0        0 eth0

default         Rolands-AirPort 0.0.0.0         UG    100    0        0 eth0

10.0.1.0        *               255.255.255.255 UH    0      0        0 eth0

10.0.1.0        *               255.255.255.0   U     0      0        0 eth0

10.4.0.1        10.4.49.21      255.255.255.255 UGH   0      0        0 tun0

10.4.49.21      *               255.255.255.255 UH    0      0        0 tun0

hosted-by.lease Rolands-AirPort 255.255.255.255 UGH   0      0        0 eth0

Any help would be greatly appreciated!

Well I have my work around... I don't know why I wasn't able to get this to work but basically what I found was that even with my routing configured this way, the nature of bittorrent led my ISP provided public IP being announced... which is a major problem for connectivity. To fix my issue I stopped the transmission-daemon and altered the /etc/transmission-daemon/settings.json file to bind on the ipv4 address of the tun0 interface. This is not an ideal solution as it is not dynamic. However, the ip address of my vpn is static enough that this shouldn't be too much of an issue. If anyone has a better answer please let me know!

please note that the issues of 100% packet loss with ping and no traceroute available was fixed by manually removing routes pushed by the VPN provider (within the script).

Forcing the transmission traffic over the VPN was a matter of adjusting a setting within the client to bind on the IP address of the tun0 interface. This is not a proper solution but works none the less. I am continuing to use the script so that the default interface is not the VPN.