this is the dhcp6c service we want

modules/dhcp6c/acquire-delegated-prefix.fnl

@@ -0,0 +1,31 @@
+(local { : system } (require :anoia))
+(local svc (require :anoia.svc))
+
+(fn changes [old-addresses new-addresses]
+  (let [added {}
+        deleted {}]
+    (each [n address (pairs new-addresses)]
+      (if (not (. old-addresses n))
+          (table.insert added address)))
+    (each [n address (pairs old-addresses)]
+      (if (not (. new-addresses n))
+          (table.insert deleted address)))
+    (values added deleted)))
+
+(fn update-prefixes [device prefixes new-prefixes]
+  (let [(added deleted) (changes prefixes new-prefixes)]
+    (each [_ p (ipairs added)]
+      (system
+       (.. "ip address add " p.address "1/" p.len " dev " device)))
+    (each [_ p (ipairs deleted)]
+      (system
+       (.. "ip address del " p.address "1/" p.len " dev " device)))))
+
+(fn run []
+  (let [[state-directory lan-device] arg
+        dir (svc.open state-directory)]
+    (accumulate [addresses []
+                 v (dir:events)]
+      (update-prefixes lan-device addresses (v:output "prefix")))))
+
+{ : changes : run }

modules/dhcp6c/acquire-delegated-prefix.nix

@@ -0,0 +1,10 @@
+{
+  writeFennel
+, linotify
+, anoia
+, lua
+}:
+writeFennel "acquire-delegated-prefix" {
+  packages = [ linotify anoia lua.pkgs.luafilesystem ];
+  mainFunction = "run";
+} ./acquire-delegated-prefix.fnl

modules/dhcp6c/acquire-wan-address-test.fnl

@@ -0,0 +1,68 @@
+(local subject (require :acquire-wan-address))
+(local { : view } (require :fennel))
+(local { : merge : dup } (require :anoia))
+
+
+(local a1
+       {
+        "2001-ab-cd-ef_hjgKHGhKJH" {
+                                    :address "2001:ab:cd:ef"
+                                    :len "64"
+                                    :preferred "200"
+                                    :valid "200"
+                                    }
+        }
+       )
+
+(local a2
+       {
+        "2001-0-1-2-3_aNteBnb" {
+                                :address "2001:0:1:2:3"
+                                :len "64"
+                                :preferred "200"
+                                :valid "200"
+                                }
+        }
+       )
+
+(macro expect [assertion]
+  (let [msg (.. "expectation failed: " (view assertion))]
+    `(when (not ,assertion)
+       (assert false ,msg))))
+
+(fn first-address []
+  (let [(add del)
+        (subject.changes
+         { }
+         a1
+         )]
+    (expect (= (# del) 0))
+    (expect (= (# add) 1))
+    (let [[first] add]
+      (expect (= first.address "2001:ab:cd:ef")))))
+
+(fn second-address []
+  (let [(add del)
+        (subject.changes
+         a1
+         (merge (dup a1) a2)
+         )]
+    (expect (= (# del) 0))
+    (expect (= (# add) 1))
+    (let [[first] add] (expect (= first.address  "2001:0:1:2:3")))))
+
+(fn less-address []1
+  (let [(add del)
+        (subject.changes
+         (merge (dup a1) a2)
+         a1
+         )]
+    (expect (= (# add) 0))
+    (expect (= (# del) 1))
+
+    (let [[first] del] (expect (= first.address  "2001:0:1:2:3")))))
+
+
+(first-address)
+(second-address)
+(less-address)

modules/dhcp6c/acquire-wan-address.fnl

@@ -0,0 +1,35 @@
+(local { : system } (require :anoia))
+(local svc (require :anoia.svc))
+
+;; acquire-delegated-prefix has very similar code: we'd like to move
+;; this to anoia.svc when we see what the general form would look like
+
+(fn changes [old-addresses new-addresses]
+  (let [added {}
+        deleted {}]
+    (each [n address (pairs new-addresses)]
+      (if (not (. old-addresses n))
+          (table.insert added address)))
+    (each [n address (pairs old-addresses)]
+      (if (not (. new-addresses n))
+          (table.insert deleted address)))
+    (values added deleted)))
+
+(fn update-addresses [wan-device addresses new-addresses]
+  (let [(added deleted) (changes addresses new-addresses)]
+    (each [_ p (ipairs added)]
+      (system
+       (.. "ip address add " p.address "/" p.len " dev " wan-device)))
+    (each [_ p (ipairs deleted)]
+      (system
+       (.. "ip address del " p.address "/" p.len " dev " wan-device)))
+    new-addresses))
+
+(fn run []
+  (let [[state-directory wan-device] arg
+        dir (svc.open state-directory)]
+    (accumulate [addresses []
+                 v (dir:events)]
+      (update-addresses wan-device addresses (v:output "address")))))
+
+{ : update-addresses : changes : run }

modules/dhcp6c/acquire-wan-address.nix

@@ -0,0 +1,10 @@
+{
+  writeFennel
+, linotify
+, anoia
+, lua
+}:
+writeFennel "acquire-wan-address" {
+  packages = [ linotify anoia lua.pkgs.luafilesystem ];
+  mainFunction = "run";
+} ./acquire-wan-address.fnl

modules/dhcp6c/address.nix

@@ -0,0 +1,16 @@
+{
+  liminix
+, lib
+, callPackage
+}:
+{ client, interface } :
+let
+  inherit (liminix.services) longrun;
+  inherit (lib) mkOption types;
+  name = "dhcp6c.addr.${client.name}.${interface.name}";
+  script = callPackage ./acquire-wan-address.nix {  };
+in longrun {
+  inherit name;
+  run = "${script} /run/service-state/${client.name} $(output ${interface} ifname)";
+  dependencies = [ client interface ];
+}

modules/dhcp6c/client.nix

@@ -0,0 +1,21 @@
+{
+  liminix
+, lib
+, odhcp6c
+, odhcp-script
+}:
+{ interface } :
+let
+  inherit (liminix.services) longrun;
+  inherit (lib) mkOption types;
+  name = "dhcp6c.${interface.name}";
+in longrun {
+  inherit name;
+  notification-fd = 10;
+  run = ''
+    export SERVICE_STATE=/run/service-state/${name}
+    ${odhcp6c}/bin/odhcp6c -s ${odhcp-script} -e -v -p /run/${name}.pid -P0 $(output ${interface} ifname)
+    )
+  '';
+  dependencies = [ interface ];
+}

modules/dhcp6c/default.nix

@@ -0,0 +1,52 @@
+## DHCP6 client module
+## ===================
+##
+##  This is for use if you have an IPv6-capable upstream that provides
+##  address information and/or prefix delegation using DHCP6. It
+##  provides a service to request address information in the form of a
+##  DHCP lease, and two dependent services that listen for updates
+##  to the DHCP address information and can be used to update
+##  addresses of network interfaces that you want to assign those
+##  prefixes to
+
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs.liminix.services) oneshot;
+  inherit (pkgs) liminix;
+in
+{
+  options = {
+    system.service.dhcp6c = {
+      client = mkOption { type = liminix.lib.types.serviceDefn; };
+      prefix = mkOption { type = liminix.lib.types.serviceDefn; };
+      address = mkOption { type = liminix.lib.types.serviceDefn; };
+    };
+  };
+  config.system.service.dhcp6c = {
+    client = liminix.callService ./client.nix {
+      interface = mkOption {
+        type = liminix.lib.types.interface;
+        description = "interface (usually WAN) to query for DHCP6";
+      };
+    };
+    address = liminix.callService ./address.nix {
+      client = mkOption {
+        type = types.anything; # liminix.lib.types.service;
+      };
+      interface = mkOption {
+        type = liminix.lib.types.interface;
+        description = "interface to assign the address to";
+      };
+    };
+    prefix = liminix.callService ./prefix.nix {
+      client = mkOption {
+        type = types.anything; # liminix.lib.types.service;
+      };
+      interface = mkOption {
+        type = liminix.lib.types.interface;
+        description = "interface to assign <prefix>::1 to";
+      };
+    };
+  };
+}

modules/dhcp6c/prefix.nix

@@ -0,0 +1,16 @@
+{
+  liminix
+, lib
+, callPackage
+}:
+{ client, interface } :
+let
+  inherit (liminix.services) longrun;
+  inherit (lib) mkOption types;
+  name = "dhcp6c.prefix.${client.name}.${interface.name}";
+  script = callPackage ./acquire-delegated-prefix.nix {  };
+in longrun {
+  inherit name;
+  run = "${script} /run/service-state/${client.name} $(output ${interface} ifname)";
+  dependencies = [ client interface ];
+}