lib/config/options: rewrite getHostLinkNetworks et al

nix/lib/config/options.nix

@@ -2,53 +2,49 @@
 
 with lib;
 let
-  getHostNets = link:
+  # A host needs to know a network if it
+  # - is a configured interface, or
+  # - is required behind at least two different links
+  getHostLinkNetworks = hostName: link:
     let
-      hostConfig = config.site.hosts.${link};
-      sort = nets: lib.unique (
-        builtins.sort (net1: net2:
-          config.site.net.${net1}.vlan < config.site.net.${net2}.vlan
-        ) nets
-      );
+      hostConfig = config.site.hosts.${hostName};
+      # all the host's links
+      hostLinkNetworks = builtins.mapAttrs (link: _:
+        networksBehindLink hostName link
+      ) hostConfig.links;
+      # how many links have a net in networksBehindLink
+      networkLinkCount = net:
+        builtins.length (
+          builtins.filter (builtins.elem net)
+            (builtins.attrValues hostLinkNetworks)
+        );
     in
-      if config.site.hosts ? ${link}
-      then
-        sort (
-          builtins.attrNames hostConfig.interfaces ++
-          getLinksNets link
-        )
-
-      else if config.site.net ? ${link}
+      # access port
+      if config.site.net ? ${link}
       then [ link ]
 
-      else builtins.trace "Don't know what nets to configure for link to \"${link}\"" [];
+      # multiple vlans on this link
+      else
+        builtins.filter (net:
+          # this port and local interface
+          hostConfig.interfaces ? ${net}
+          ||
+          # this port and another
+          networkLinkCount net > 1
+        ) hostLinkNetworks.${link};
 
-  # breaks the getHostNets recursion for switches,
-  # requiring any net to be used by at >1 links
-  getLinksNets = hostName:
-    let
-      linksNets = builtins.mapAttrs (link: _:
-        unique (
-          getLinkNets { "${hostName}" = true; } [ link ]
-        )
-      ) config.site.hosts.${hostName}.links;
-      allNets = unique (
-        builtins.concatLists (builtins.attrValues linksNets)
-      );
-      netLinkCount = net:
-        builtins.foldl' (netLinkCount: nets:
-          if builtins.elem net nets
-          then netLinkCount + 1
-          else netLinkCount
-        ) 0 (builtins.attrValues linksNets);
-      nets = builtins.filter (net:
-        netLinkCount net > 1
-      ) allNets;
-    in nets;
+  networksBehindLink = hostName: name:
+    networksBehindLink' {
+      "${hostName}" = true;
+    } [ name ];
 
-  getLinkNets = seen: links:
+  networksBehindLink' = seen: links:
     if links == []
-    then []
+    then
+      # Done, result is the seen link names that are networks:
+      builtins.filter (name:
+        config.site.net ? ${name}
+      ) (builtins.attrNames seen)
     else
       let
         link = builtins.head links;
@@ -59,13 +55,17 @@ let
         links' = builtins.tail links;
       in
         if config.site.hosts ? ${link}
-        then getLinkNets seen' (
+        then networksBehindLink' seen' (
           links' ++ (
+            builtins.attrNames config.site.hosts.${link}.interfaces
+          ) ++ (
             onlyUnseen (builtins.attrNames config.site.hosts.${link}.links)
           )
         )
-        else getHostNets link ++
-             getLinkNets seen' (onlyUnseen links');
+        else if config.site.net ? ${link}
+        then networksBehindLink' seen' links'
+
+        else throw "Link to invalid target ${link}";
 
   dhcpOpts = {
     start = mkOption {
@@ -382,7 +382,7 @@ let
       links = mkOption {
         description = "Which port is connected to what other device? Keys are either network names or known hostnames.";
         default = {};
-        type = with types; attrsOf (submodule linkOpts);
+        type = with types; attrsOf (submodule (linkOpts name));
       };
       wifi = mkOption {
         default = {};
@@ -433,7 +433,7 @@ let
     };
   };
 
-  linkOpts = { name, ... }: {
+  linkOpts = hostName: { name, ... }: {
     options = {
       ports = mkOption {
         type = with types; listOf str;
@@ -447,14 +447,14 @@ let
       nets = mkOption {
         type = with types; listOf str;
         description = "Automatically generated";
-        default = getHostNets name;
+        default = getHostLinkNetworks hostName name;
       };
       vlans = mkOption {
         type = with types; listOf int;
         description = "Automatically generated, do not set";
         default = map (net:
           config.site.net.${net}.vlan
-        ) (getHostNets name);
+        ) config.site.hosts.${hostName}.links.${name}.nets;
       };
     };
   };