>I need to set up an IPv4 tunnel over an IPv4 connection to connect two
>subnets together.  How do I do this with IPsec?  I have NetBSD 1.5
>(-current) machines at both ends of the connection.

	if you just want tunnelling (not with ipsec) gif(4) should help.

	for ipsec tunnels:
	http://www.netbsd.org/Documentation/network/ipsec/

>Is it possible to configure the NetBSD boxes as firewalls while they
>are doing the tunneling?

	not with 1.5.  http://www.netbsd.org/Documentation/network/ipsec/
	has some caveat documented in it.

itojun