1 files changed, 88 insertions, 1 deletions
diff --git a/sys/net/options.nix b/sys/net/options.nix
index 2930567..11b913c 100644
--- a/sys/net/options.nix
+++ b/sys/net/options.nix
@@ -1,5 +1,46 @@
 { config, lib, ... }:
-with lib; {
+with lib; let
+  v4PtrHierarchy = address: bits: reverseList (sublist 0 (bits / 8) (splitString "." address));
+
+  v6PtrHierarchy = address: bits:
+    let
+      separator = lists.findFirstIndex (hextet: hextet == "") null colonSplit;
+      colonSplit = splitString ":" address;
+
+      zeroFill = replicate (8 - length colonSplit + 1) "0000";
+      leftSplit = sublist 0 separator colonSplit;
+      rightSplit = sublist (separator + 1) (length colonSplit - separator - 1) colonSplit;
+
+      fullSplit =
+        if separator != null
+        then leftSplit ++ zeroFill ++ rightSplit
+        else colonSplit;
+
+      padded = map (hextet: strings.replicate (4 - stringLength hextet) "0" + hextet) fullSplit;
+    in
+    reverseList (sublist 0 (bits / 4) (flatten (map stringToCharacters padded)));
+
+  matchPtrRecordName = { splitter, netAddress, netBits, targetAddress, targetBits }:
+    let
+      netSplit = splitter netAddress netBits;
+      targetSplit = splitter targetAddress targetBits;
+
+      netLength = length netSplit;
+      lengthDelta = length targetSplit - netLength;
+
+      withinNet = lengthDelta >= 0 && sublist lengthDelta netLength targetSplit == netSplit;
+      throwMessage = "${targetAddress}/${toString targetBits} is not a subset of ${netAddress}/${toString netBits}";
+
+      recordHierarchy = sublist 0 lengthDelta targetSplit;
+
+      recordName =
+        if recordHierarchy != [ ]
+        then concatStringsSep "." recordHierarchy
+        else "@";
+    in
+    throwIfNot withinNet throwMessage recordName;
+in
+{
   options.local.nets = with lib.types; mkOption {
     readOnly = true;
 
@@ -126,14 +167,37 @@ with lib; {
                   type = str;
                   readOnly = true;
                 };
+
+                ptrDomain = mkOption {
+                  type = str;
+                  readOnly = true;
+                };
+
+                ptrRecordName = mkOption {
+                  type = functionTo (functionTo str);
+                  readOnly = true;
+                };
               };
 
               config = {
                 cidr = "${config.subnet}/${toString config.bits}";
+
                 subnet =
                   if config.bits != 0
                   then config.prefix + strings.replicate (4 - config.bits / 8) ".0"
                   else "0.0.0.0";
+
+                ptrDomain = concatStrings (map (x: x + ".") (v4PtrHierarchy config.subnet config.bits)) + "in-addr.arpa";
+
+                ptrRecordName = address: bits: matchPtrRecordName {
+                  splitter = v4PtrHierarchy;
+
+                  netBits = config.bits;
+                  netAddress = config.subnet;
+
+                  targetBits = bits;
+                  targetAddress = address;
+                };
               };
             }));
           };
@@ -162,14 +226,37 @@ with lib; {
                   type = str;
                   readOnly = true;
                 };
+
+                ptrDomain = mkOption {
+                  type = str;
+                  readOnly = true;
+                };
+
+                ptrRecordName = mkOption {
+                  type = functionTo (functionTo str);
+                  readOnly = true;
+                };
               };
 
               config = {
                 cidr = "${config.subnet}/${toString config.bits}";
+
                 subnet =
                   if config.bits == 128 || length (splitString "::" config.prefix) > 1
                   then config.prefix
                   else "${config.prefix}::";
+
+                ptrDomain = concatStrings (map (x: x + ".") (v6PtrHierarchy config.subnet config.bits)) + "ip6.arpa";
+
+                ptrRecordName = address: bits: matchPtrRecordName {
+                  splitter = v6PtrHierarchy;
+
+                  netBits = config.bits;
+                  netAddress = config.subnet;
+
+                  targetBits = bits;
+                  targetAddress = address;
+                };
               };
             }));
           };