I'm setting up a VPN site-to-site link from a m0n0wall firewall to a debian server:
http://doc.m0n0.ch/handbook/examplevpn-freeswan.html
http://www.freeswan.org/freeswan_trees/freeswan-1.99/doc/manpage.d/ipsec.conf.5.html
Its not working... though one the freeswan side I'm getting this error:
FATAL: Error inserting xfrm4_tunnel (/lib/modules/2.6.16-xen/kernel/net/ipv4/xfrm4_tunnel.ko): Resource temporarily unavailable
Time to buy another netgate m1n1wall!
you need to disable Opportunistic Encryption when using netkey. on modern openswan's this is done by adding the following line at the end of your ipsec.conf:
include /etc/ipsec.d/examples/no_oe.conf