Tayga configuration can be generated.

This facilitates more configuration being authoritatively
in `rc.conf`.

defaults/rc.conf

@@ -56,4 +56,44 @@ allow_hosts_rules="${rc_router_gen_dir}/pf.rules.conf"
 
 rtsold_flags="-F"
 
+###################
+## Tayga options ##
+###################
+tayga_enable="NO"
+tayga_config="${rc_router_gen_dir}/tayga.conf"
+tayga_device="nat64"
+
+# The Tayga defaults for 6to4 make a few weird
+# assumptions -- you're okay with using 6to4 space
+# and you do not explicitly enable Class E on FreeBSD
+# Otherwise `240.0.0.0/8` makes a heck of a lot more sense.
+
+# For Tayga, we use the old 6to4 space.
+# It's mostly unused these days, and it's a similar purpose
+tayga_ipv4_addr="192.88.99.1"
+tayga_ipv4_endpoint="192.88.99.129"
+
+# For Tayga, we use the lower half of the 6to4 space for the
+# 6to4 space as the pool.
+tayga_ipv4_net="192.88.99.0/25"
+
+# This variable can be set to a list of prefixes that get directed to
+# Tayga for routing.  This is exceptionally useful to redirect v4
+# addresses to v6-only hosts, thus simplifying the v4 compat story
+# for v6-only hosts.  Instead of dual stack throughout, just route
+# v4 addresses and ranges for "pseudo-dual-stack" hosts here.
+# This is especially useful to conserve and publish personal v4 public
+# allocations.  The first and last of any range can be used, thus
+# reclaiming much of your limited v4 space utility.
+tayga_v4_prefixes=""
+
+tayga_group="internal group tayga"
+
+# We claim the address right after the end of the 32-bit slice.
+# A different addrss could be taken, but this seemed somewhat safe.
+tayga_ipv6_endpoint="64:ff9b::1:0:0"
+tayga_ipv6_net="64:ff9b::/96" # The default NAT64 prefix
+
+tayga_data_dir="/var/db/tayga"
+
 # vim: ft=bash