I've read quite a bit and am close, I feel, and I'm pulling my hair out ... please help!
I have an OpenVPN cliend whose server sets local routes and also changes the default gw (I know I can prevent that with --route-nopull). I'd like to have all outgoing http and ssh traffic via the local gw, and everything else via the vpn.
Local IP is 192.168.1.6/24, gw 192.168.1.1.
OpenVPN local IP is 10.102.1.6/32, gw 192.168.1.5
OpenVPN server is at {OPENVPN_SERVER_IP}
Here's the route table after openvpn connection:
# ip route show table main
0.0.0.0/1 via 10.102.1.5 dev tun0
default via 192.168.1.1 dev eth0 proto static
10.102.1.1 via 10.102.1.5 dev tun0
10.102.1.5 dev tun0 proto kernel scope link src 10.102.1.6
{OPENVPN_SERVER_IP} via 192.168.1.1 dev eth0
128.0.0.0/1 via 10.102.1.5 dev tun0
169.254.0.0/16 dev eth0 scope link metric 1000
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.6 metric 1
This makes all packets go via to the VPN tunnel except those destined for 192.168.1.0/24.
Doing wget -qO- http://echoip.org shows the vpn server's address, as expected, the packets have 10.102.1.6 as source address (the vpn local ip), and are routed via tun0 ... as reported by tcpdump -i tun0 (tcpdump -i eth0 sees none of this traffic).
What I tried was:
create a 2nd routing table holding the 192.168.1.6/24 routing info (copied from the main table above)
add an iptables -t mangle -I PREROUTING rule to mark packets destined for port 80
add an ip rule to match on the mangled packet and point it to the 2nd routing table
add an ip rule for to 192.168.1.6 and from 192.168.1.6 to point to the 2nd routing table (though this is superfluous)
changed the ipv4 filter validation to none in net.ipv4.conf.tun0.rp_filter=0 and net.ipv4.conf.eth0.rp_filter=0
I also tried an iptables mangle output rule, iptables nat prerouting rule. It still fails and I'm not sure what I'm missing:
iptables mangle prerouting: packet still goes via vpn
iptables mangle output: packet times out
Is it not the case that to achieve what I want, then when doing wget http://echoip.org I should change the packet's source address to 192.168.1.6 before routing it off? But if I do that, the response from the http server would be routed back to 192.168.1.6 and wget would not see it as it is still bound to tun0 (the vpn interface)?
Can a kind soul please help? What commands would you execute after the openvpn connects to achieve what I want?
Looking forward to hair regrowth ...
