Added back instructions from old instructions (just for now)

docs/routing/bird/bird.md

@@ -33,3 +33,138 @@ sudo systemctl enable --now bird
 ```
 
 This will ensure that the routing daemon starts on boot.
+
+## Configuration
+
+TODO: Re-do this sections
+
+The configuration template is constructed out of the following files:
+
+1. `filters.conf`
+	* Filter functions and the filter itself
+2. `networks.conf`
+	* Advertisement of ULA
+3. `tables.conf`
+	* The table definitions
+4. `router.conf`
+	* This contains the needed protocol definition for discovering
+	your interface's prefixes and generating routes form them
+	* It also contains the needed protocol definitions to sync bird
+	routes into the Linux kernel's routing table (so you cna forward
+	packets based on the routes from Bird)
+5. `protocols.conf`
+	* Depending on what protocol you want to use this will contains
+	configurations for each
+
+All of these will be included in a file saved at `/etc/bird/bird.conf` like so:
+
+```
+router id <ipv4>;
+
+include "/etc/bird/crxn/tables.conf";
+include "/etc/bird/crxn/filters.conf";
+include "/etc/bird/crxn/router.conf";
+include "/etc/bird/crxn/networks.conf";
+```
+
+Additionally, add the files for the route distribution protocol which we configure in the next steps.
+```
+include "/etc/bird/crxn/babel.conf"; # For babel routing
+include "/etc/bird/crxn/ospfv3.conf"; # For OSPFv3 routing
+```
+
+Remember to set a unique router ID in `<ipv4>`, make it anything - it doesn't have to even be an address you own.
+
+#### `filters.conf`
+
+This file holds all the required functions for subnet matching and also
+filters that match to the specific prefix aggregates (regional subnets)
+that CRXN uses.
+
+```
+filter crxnFilter
+{
+    if (net ~ fd00::/8) then accept;
+    reject;
+}
+```
+
+#### `tables.conf`
+
+This file holds all table definitions. There are only two actually.
+The table `crxn` is the one we actually use, `master` is optional
+and is only present because if one uses `bird-lg-go` (the looking glass
+we use) then it, by default, only shows routes in the `master` table.
+It is meant to have the same routes as the `crxn` table.
+
+```
+# CRXN table
+ipv6 table crxn;
+```
+
+#### `router.conf`
+
+This contains an instance of the `direct` protocol which reads the address
+and prefix assigned to your AF_INET6 interfaces and generates routes from
+those that represent routes to directly atrtached networks those interfaces
+are on. The reason for this is that the `kernel` protocol never learns routes
+in the Linux kernel's routing table that have the `kernel` protocol which
+is what you get when you assign interfaces addresses and prefixes. This
+doesn't even need those, it gets them from the interface.
+
+```
+# The kernel protocol doesn't grab kernel routes that are added by you when you assign an
+# address and prefix. So instead of reading this from all routes with `proto kernel` this just
+# yeets the routes off of the interface structure itself (even if you didn't have a route for your
+# directly attached networks - i.e. nexthop = 0.0.0.0)
+protocol direct crxnDirect
+{
+    ipv6
+    {
+        table crxn;
+        import filter crxnFilter;
+    };
+    # Interfaces to find neighbours on
+    interface "eth*";
+}
+
+protocol device {
+}
+```
+
+The second part is for syncing routes from Bird to the Linux kernel's routing
+table such that you can forward traffic based on the routes in Bird.
+
+TODO: Check, defualt `learn` should learn non `kernel` and non-`bird` routes
+
+```
+# CRXN Kernel protocol
+# We import any routes from the kernel table other than `proto bird` and `proto kernel`,
+# could be `proto static` for example. By default it will learn these.
+# Of course we also then export all routes from our Bird tables into the kernel so you can actually forward packets
+protocol kernel crxnKernel
+{
+    ipv6 {
+        # bird's crxn table -> kernel
+        table crxn;
+        export filter crxnFilter;
+    };
+}
+```
+
+#### `networks.conf`
+
+This is just something we normally add. Usually you would assign a `/64` within your ULA `/48` but you also want to claim the whole `/48` by advertising a blackhole for it. Here our `/48`/ULA is `fd40:ec65:5b4c::/48`.
+
+```
+protocol static crxnStatic
+{
+        # Advertise your /48 with a blackhole
+        route fd40:ec65:5b4c::/48 blackhole;
+
+        ipv6 {
+                import filter crxn6;
+                table crxn;
+        }
+}
+```