add function to get subnets to schema

This also adds a view to get a list of all containers and their free
space in between.
This is needed for ippool_list to get a nice overview over everything.

schema/01_initial.sql

@@ -196,3 +196,50 @@ create trigger trg_zones before insert or update or delete on zones for each row
 create trigger trg_zoneviews before insert or update or delete on zoneviews for each row execute function record();
 create trigger trg_zoneviews_outputgroups before insert or update or delete on zoneviews_outputgroups for each row execute function record();
 
+create or replace function subnets_between(net_start inet, net_end inet) returns setof cidr as $$
+declare
+        common cidr;
+        mask int;
+begin
+        net_start := host(net_start)::inet;
+        net_end   := host(net_end)::inet;
+        -- check if net_start and net_end are in the same subnet
+        common := inet_merge(host(net_start)::inet, host(net_end)::inet);
+        mask := masklen(common);
+        if set_masklen(net_start, mask) = common and broadcast(common) = set_masklen(net_end, mask) then
+                return next common;
+                return;
+        end if;
+        -- subnet is too big, so make it smaller
+        return query select * from subnets_between(net_start, broadcast(set_masklen(net_start, mask + 1)));
+        return query select * from subnets_between(network(set_masklen(net_end, mask + 1)), net_end);
+end;
+$$ language plpgsql;
+comment on function subnets_between(inet, inet) is 'get a list of subnets between two IPs.';
+
+create or replace view containers_free_list as
+with subnets as (
+        select
+                c.layer3domain_id,
+                c.subnet,
+                ct.subnet child,
+                lag(ct.subnet) over (partition by c.subnet order by ct.subnet) has_before,
+                lead(ct.subnet) over (partition by c.subnet order by ct.subnet) has_after,
+                parents
+        from containers c
+        join containers_tree ct on c.layer3domain_id = ct.layer3domain_id and c.subnet = ct.parents[array_length(ct.parents, 1)]
+                                where host(c.subnet) != host(ct.subnet) and host(broadcast(c.subnet)) != host(broadcast(ct.subnet))
+)
+select * from (
+        select layer3domain_id, parents, 'available' state, ls as subnet
+					from subnets, lateral subnets_between(subnet, child - 1) ls
+				 where has_before is null
+        union all
+        select layer3domain_id, parents, 'available', ls
+					from subnets, lateral subnets_between(broadcast(child) + 1, broadcast(subnet)) ls
+				 where has_after is null
+        union all
+        select layer3domain_id, parents, 'container', subnet
+					from containers_tree
+) freelist order by layer3domain_id, subnet;
+comment on view containers_free_list is 'Creates a list of free space between other containers.';