Couple questions:
1) Why are there 2 routes for
10.10.90.0/24 going to 2 different interfaces?
2) What interface is the tunnel bound to on the linux side?
3) Is this openswan box alse the default gateway for the 10.10.90/24 network? and the Cisco?
It's been a while since I used a Cisco device to setup a vpn as I've been using Junipers ScreenOS (awesome device BTW, much much better than a pix), so I can't quite recall how to do it off the top of my head.
Personally, I like to create a tunnel network to make routing and policy creation (acls, iptables) easier. So in this case, I would create a subinterface and give it an ip of say
10.10.91.1/30 and on the cisco device, the ip would be
10.10.91.2/30.
If the answer to 3) is yes, then just add a route for
192.168.1.0/24 going to eth0:1 (or
10.10.91.1). Conversely on the Cisco, you add a route for 10.10.90/24 to point to
10.10.91.2. This will then route the appropriate traffic through the tunnel to the other network.
If anything, I hope this helps you get on the right track! =)
-Mike