convert network link/address to module-based-service

... and make bridge use it.

We also had to convert bridge back into a pair of services.
Downstreams want to depend on the bridge it self being configured
even if not necessarily all the members are up. e.g. don't want
to break ssh on lan if there's a misconfigured wlan device

modules/network/address.nix

@@ -0,0 +1,29 @@
+{
+  liminix
+, ifwait
+, serviceFns
+, lib
+}:
+{interface, family, address, prefixLength} :
+let
+  inherit (liminix.services) oneshot;
+  # rather depending on the assumption that nobody will
+  # ever add two addresses which are the same but with different
+  # prefixes, or the same but different protocols
+  name = "${interface.name}.a.${address}";
+  up = ''
+    . ${serviceFns}
+    dev=$(output ${interface} ifname)
+    ip address add ${address}/${toString prefixLength} dev $dev
+    (in_outputs ${name}
+     echo ${address} > address
+     echo ${toString prefixLength} > prefix-length
+     echo ${family} > family
+     echo $dev > ifname
+    )
+  '';
+in oneshot {
+  inherit name up;
+  down = "true";                # this has been broken for ~ ages
+  dependencies = [ interface ];
+}

modules/network/default.nix

@@ -0,0 +1,54 @@
+## Network
+## =======
+##
+## Basic network services for creating hardware ethernet devices
+## and adding addresses
+
+
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs) liminix;
+in {
+  options = {
+    system.service.network = {
+      link = mkOption {
+        description = "hardware network interface";
+        type = liminix.lib.types.serviceDefn;
+      };
+      address = mkOption {
+        description = "network interface address";
+        type = liminix.lib.types.serviceDefn;
+      };
+    };
+  };
+  config = {
+    system.service.network = {
+      link = liminix.callService ./link.nix {
+        ifname = mkOption {
+          type = types.str;
+          example = "eth0";
+        };
+        # other "ip link add" options could go here as well
+        mtu = mkOption {
+          type = types.nullOr types.int;
+          example = 1480;
+        };
+      };
+      address = liminix.callService ./address.nix {
+        interface = mkOption {
+          type = liminix.lib.types.service;
+        };
+        family = mkOption {
+          type = types.enum [ "inet" "inet6" ];
+        };
+        address = mkOption {
+          type = types.str;
+        };
+        prefixLength = mkOption {
+          type = types.ints.between 0 128;
+        };
+      };
+    };
+  };
+}

modules/network/link.nix

@@ -0,0 +1,16 @@
+{
+  liminix
+, ifwait
+, serviceFns
+, lib
+}:
+{ifname, mtu} :
+let
+  inherit (liminix.services) longrun oneshot;
+  inherit (lib) concatStringsSep;
+  name = "${ifname}.link";
+  up = liminix.networking.ifup name ifname;
+in oneshot {
+  inherit name up;
+  down = "ip link set down dev ${ifname}";
+}