Implement podman pods option

modules/default.nix

@@ -0,0 +1,5 @@
+{ ... }:
+
+{
+  imports = [ ./virtualisation/pods.nix ];
+}

modules/virtualisation/pods.nix

@@ -0,0 +1,220 @@
+{ lib, config, options, ... }:
+
+with lib;
+
+let
+  cfg = config.virtualisation.pods;
+  list-to-args = arg: list:
+    concatStringsSep " " (map (e: "--${arg}=${escapeShellArg e}") list);
+  possibly-unset-arg = arg: val:
+    (optionalString (val != null) "--${arg}=${escapeShellArg val}");
+
+  mkPod = name: pod: rec {
+    path = [ config.virtualisation.podman.package ];
+
+    wants = [ "network.target" ];
+    after = [ "network-online.target" ];
+    wantedBy = [ "multi-user.target" "default.target" ];
+
+    environment.PODMAN_SYSTEMD_UNIT = "%n";
+
+    preStart = concatStringsSep " " [
+      "mkdir -p /run/podman/pods/ ;"
+      "podman pod create"
+      "--infra-conmon-pidfile=${escapeShellArg "/run/podman/pods/${name}.pid"}"
+      "--name=${escapeShellArg name}"
+      "--replace"
+      (list-to-args "add-host" pod.added-hosts)
+      (possibly-unset-arg "cgroup-parent" pod.cgroup-parent)
+      (list-to-args "dns" pod.dns)
+      (list-to-args "dns-opt" pod.dns-opt)
+      (list-to-args "dns-search" pod.dns-search)
+      (possibly-unset-arg "hostname" pod.hostname)
+      (possibly-unset-arg "infra" pod.infra)
+      (possibly-unset-arg "infra-command" pod.infra-command)
+      (possibly-unset-arg "infra-image" pod.infra-image)
+      (possibly-unset-arg "ip" pod.ip)
+      (possibly-unset-arg "mac-address" pod.mac-address)
+      (possibly-unset-arg "network" pod.network)
+      (possibly-unset-arg "network-alias" pod.network-alias)
+      (possibly-unset-arg "no-hosts" pod.no-hosts)
+      (list-to-args "publish" pod.publish)
+      (list-to-args "share" pod.share)
+    ];
+
+    script = "podman pod start ${escapeShellArg name}";
+    preStop = "podman pod stop ${escapeShellArg name}";
+    # `podman generate systemd` generates a second stop after the
+    # first; not sure why but clearly it's recommended.
+    postStop = preStop;
+
+    serviceConfig = rec {
+      Type = "forking";
+      TimeoutStopSec = 70;
+      Restart = "on-failure";
+      PIDFile = "/run/podman/pods/${name}.pid";
+    };
+  };
+
+in {
+  options.virtualisation.pods = mkOption {
+    type = with types;
+      attrsOf (submodule {
+        options = {
+          added-hosts = mkOption {
+            type = listOf str;
+            default = [ ];
+            description =
+              "Additional hosts to add to /etc/hosts for each container.";
+            example = literalExample ''
+              [ "database:10.0.0.1" ]
+            '';
+          };
+
+          cgroup-parent = mkOption {
+            type = nullOr str;
+            default = null;
+            description =
+              "The cgroups path under which the pod cgroup will be created.";
+          };
+
+          dns = mkOption {
+            type = listOf str;
+            default = [ ];
+            description = "The dns servers to set in /etc/resolv.conf.";
+          };
+
+          dns-opt = mkOption {
+            type = listOf str;
+            default = [ ];
+            description = "dns options to set in /etc/resolv.conf.";
+          };
+
+          dns-search = mkOption {
+            type = listOf str;
+            default = [ ];
+            description = "Search domains to set in /etc/resolv.conf.";
+          };
+
+          hostname = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "The pod hostname.";
+          };
+
+          infra = mkOption {
+            type = nullOr bool;
+            default = null;
+            description = "Whether to create the infra container for the pod.";
+          };
+
+          infra-command = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "The command to run in the infra container.";
+          };
+
+          infra-image = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "The image to use for the infra container.";
+          };
+
+          ip = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "A static IP address for the pod network.";
+          };
+
+          # TODO: set up label file stuff.
+          #
+          # labels = mkOption {};
+
+          mac-address = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "A static mac address for the pod network.";
+          };
+
+          network = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "Network configuration for the pod.";
+          };
+
+          network-alias = mkOption {
+            type = nullOr str;
+            default = null;
+            description = "DNS alias for the pod.";
+          };
+
+          no-hosts = mkOption {
+            type = nullOr bool;
+            default = null;
+            description = "Whether to disable /etc/hosts creation for the pod.";
+          };
+
+          publish = mkOption {
+            type = listOf str;
+            default = [ ];
+            description = "List of ports to publish from the pod.";
+          };
+
+          share = mkOption {
+            type = listOf str;
+            default = [ ];
+            description = "List of kernel namespaces to share.";
+          };
+
+          containers = options.virtualisation.oci-containers.containers;
+        };
+      });
+    default = { };
+    description = "Podman pods to run as systemd services.";
+  };
+
+  config = let
+    # Merge a list of attribute sets together
+    #
+    # TODO: See if there's a generic version for this somewhere in the
+    # pkgs lib?
+    mergeAttrs = attrList: foldr (a: b: a // b) { } attrList;
+
+    # Create services for all defined pods
+    pod-services = mapAttrs' (n: v: nameValuePair "pod-${n}" (mkPod n v)) cfg;
+
+    # Override the systemd-specific settings of containers defined in
+    # pods.
+    #
+    # I.e., make a systemd unit dependency on the pod service.
+    pod-container-services = mergeAttrs (mapAttrsToList (pname: pod:
+      mapAttrs' (cname: container:
+        nameValuePair "podman-${pname}-${cname}" rec {
+          after = [ "pod-${pname}.service" ];
+          requires = after;
+        }) pod.containers) cfg);
+
+    # Override the oci-container settings for containers defined in pods.
+    #
+    # I.e., set the --pod=podname setting, and update the dependsOn so
+    # it points to containers in the same pod.
+    podifyContainer = container: podname:
+      container // {
+        dependsOn =
+          map (dependency: "${podname}-${dependency}") container.dependsOn;
+        extraOptions = container.extraOptions ++ [ "--pod=${podname}" ];
+      };
+
+  in lib.mkIf (cfg != { }) {
+    virtualisation.podman.enable = true;
+    virtualisation.oci-containers.backend = "podman";
+
+    systemd.services = pod-services // pod-container-services;
+
+    virtualisation.oci-containers.containers = mergeAttrs (mapAttrsToList
+      (pname: pod:
+        mapAttrs' (cname: container:
+          nameValuePair "${pname}-${cname}" (podifyContainer container pname))
+        pod.containers) cfg);
+  };
+}