Initial check-in.

COPYING

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+GNU General Public License, version 2 or any later version.
+See GPL-2 or GPL-3 for the full text of these licenses.

README.md

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+ABSURD: A bewilderingly silly userspace routing daemon
+======================================================
+
+ABSURD is a TCP/IP routing and firewalling tool for performing stateful
+firewalling and routing of IP traffic according to configurable rules.
+
+Right now, no code exists, but the idea is as follows:
+
+- The daemon will consist of a core packet switch which listens on a `tun`
+  interface and exposes some virtual subnets to the host, whilst providing an
+  interface to those subnets via a Unix-domain socket.
+
+- Plug-in applications then connect to the Unix-domain socket and can
+  "register" interest in receiving particular subsets of the traffic routed to
+  the virtual subnet.  They can also bind to virtual addresses on those
+  subnets to be able to initiate communications.
+
+Some possible applications:
+- Stateful NAT64 (RFC-6146) and NAT46 (draft-liu-behave-nat46-02), including
+  cross-protocol port forwarding.
+- DNS64 (RFC-6147)
+- PCP (RFC-6887)
+- SNI-based routing, so your TLS server's logs show an IPv6 address derived
+  from the address of the IPv4 client for auditing purposes, instead of the IP
+  address of your SNI proxy server.
+- Application-level firewalling (e.g. let your Wordpress blog access Wordpress
+  for security updates without having to know every IP they host sites on),
+- Deep-packet inspection.
+
+This is obviously not a replacement for netfilter, pf or any other firewall
+you care to name.  It's a compliment to it.  Passing packets in and out of
+userspace has the distinct downside of performance penalties, thus for high
+performance routing, any kernel solution is going to run rings around this.
+
+That said, on small home/business networks, the Internet link is typically
+100Mbps or less, and even a Raspberry Pi packs a decent amount of computing
+oomph.  Likely, we should be able to keep up with most small Internet
+connections.  The aim will be for something that can keep up with ADSLv2 and
+similar grade links on modest hardware.