nixos-module/container/bird: simplify filters

nix/nixos-module/container/bird.nix

@@ -39,20 +39,10 @@ in
             export all;
           ''}
           ${lib.optionalString isUpstream ''
-            export filter {
-              if net = 0.0.0.0/0 then {
-                # Do not set another default route on upstreams
-                reject;
-              }
-              accept;
-            };
-            import filter {
-              if net = 0.0.0.0/0 then {
-                # Learn the upstream default route
-                accept;
-              }
-              reject;
-            };
+            # Do not set another default route on upstreams
+            export where net != 0.0.0.0/0;
+            # Learn the upstream default route
+            import where net = 0.0.0.0/0;
           ''}
         };
       }
@@ -63,20 +53,10 @@ in
             export all;
           ''}
           ${lib.optionalString isUpstream ''
-            export filter {
-              if net = ::/0 then {
-                # Do not set another default route on upstreams
-                reject;
-              }
-              accept;
-            };
+            # Do not set another default route on upstreams
+            export where net != ::/0;
             # Learn the upstream default route
-            import filter {
-              if net = ::/0 then {
-                accept;
-              }
-              reject;
-            };
+            import where net = ::/0;
           ''}
         };
       }
@@ -125,12 +105,7 @@ in
       # OSPFv2 for site-local IPv4
       protocol ospf v2 ZW4 {
         ipv4 {
-          export filter {
-            if net = 0.0.0.0/0 then {
-              reject;
-            }
-            accept;
-          };
+          export where net != 0.0.0.0/0;
         };
         area 0 {
           # Enabled on these networks
@@ -174,12 +149,7 @@ in
         # OSPFv2 to advertise my default route
         protocol ospf v2 ZW4_${hostName} {
           ipv4 {
-            export filter {
-              if net = 0.0.0.0/0 then {
-                accept;
-              }
-              reject;
-            };
+            export where net = 0.0.0.0/0;
           };
           area ${config.site.net.core.hosts4.${hostName}} {
             # Enabled on these networks
@@ -251,12 +221,7 @@ in
       # OSPFv3 for site-local IPv6
       protocol ospf v3 ZW6 {
         ipv6 {
-          export filter {
-            if net = ::/0 then {
-              reject;
-            }
-            accept;
-          };
+          export where net != ::/0;
         };
         area 0 {
           # Enabled on these networks
@@ -302,12 +267,7 @@ in
         # OSPFv3 to advertise my default route
         protocol ospf v3 ZW6_${hostName} {
           ipv6 {
-            export filter {
-              if net = ::/0 then {
-                accept;
-              }
-              reject;
-            };
+            export where net = ::/0;
           };
           area ${config.site.net.core.hosts4.${hostName}} {
             # Enabled on these networks