sys/web: pxe: implement PXE boot server

3 files changed, 182 insertions, 1 deletions

diff --git a/sys/net/interfaces.nix b/sys/net/interfaces.nix
index 3150b02..764973c 100644
--- a/sys/net/interfaces.nix
+++ b/sys/net/interfaces.nix
@@ -103,7 +103,7 @@ in {
     };
 
     systemd.network.networks = mkIf (cfg.dhcpInterface != null) {
-      "40-${cfg.dhcpInterface}" = {
+      ${cfg.dhcpInterface} = {
         matchConfig.Name = cfg.dhcpInterface;
 
         networkConfig = {
diff --git a/sys/web/sites/default.nix b/sys/web/sites/default.nix
index ba2835c..85b6020 100644
--- a/sys/web/sites/default.nix
+++ b/sys/web/sites/default.nix
@@ -3,5 +3,6 @@
     ./home.nix
     ./host.nix
     ./portal.nix
+    ./pxe.nix
   ];
 }
diff --git a/sys/web/sites/pxe.nix b/sys/web/sites/pxe.nix
new file mode 100644
index 0000000..54f3e56
--- /dev/null
+++ b/sys/web/sites/pxe.nix
@@ -0,0 +1,180 @@
+{
+  config,
+  flakes,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.local.web.sites.pxe;
+
+  pxeEnabled = machine: machine.config.local.boot.pxe.enable;
+  machines = listToAttrs (map (name: {
+      inherit name;
+      value = flakes.self.nixosConfigurations.${name};
+    })
+    cfg.machines);
+
+  stage2For = name: machine:
+  # https://purpleidea.com/blog/2025/01/23/working-around-an-ipxe-issue/
+  # "The answer:
+  # They told me that one of their engineers had struggled with the same issue for a while. The solution:
+  # Add the imgfree iPXE command before you boot!
+  # I wish the docs would hint that this is often required, but now I know, and now you know too!
+  # You can see that line here."
+    pkgs.writeText "stage2-${name}.ipxe" ''
+      #!ipxe
+      echo stage2: booting ${name}...
+      imgfree
+      kernel kernel init=${machine.config.system.build.toplevel}/init ${concatStringsSep " " machine.config.boot.kernelParams} || goto fail
+      initrd initrd || goto fail
+      boot ||
+      :fail
+      echo stage2: failed, rebooting in 5 seconds...
+      sleep 5
+      reboot --warm
+    '';
+
+  machineLocations = name: machine: let
+    mac = machine.config.local.boot.pxe.mac;
+    build = machine.config.system.build;
+  in {
+    "= /${mac}/initrd".alias = "${build.initialRamdisk}/initrd";
+    "= /${mac}/kernel".alias = "${build.kernel}/${pkgs.stdenv.hostPlatform.linux-kernel.target}";
+    "= /${mac}/stage2.ipxe".alias = "${stage2For name machine}";
+  };
+in {
+  options.local.web.sites.pxe = {
+    enable = mkEnableOption "PXE netboot image server";
+
+    linkLocal6 = mkOption {
+      type = types.str;
+    };
+
+    network = mkOption {
+      type = types.str;
+    };
+
+    machines = mkOption {
+      type = types.listOf types.str;
+      default = [];
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions =
+      mapAttrsToList (name: machine: {
+        message = "PXE boot is not enabled in config '${name}'";
+        assertion = pxeEnabled machine;
+      })
+      machines;
+
+    local.web.enable = mkDefault true;
+
+    networking = {
+      firewall.extraCommands = ''
+        ip6tables -t filter -A local-input -p udp -i ${cfg.network} --dport 1792 -d ${cfg.linkLocal6} -j ACCEPT
+      '';
+    };
+
+    services = {
+      nginx = {
+        virtualHosts = {
+          "[${cfg.linkLocal6}]" = {
+            listenAddresses = ["[${cfg.linkLocal6}]"];
+
+            addSSL = false;
+            forceSSL = false;
+
+            locations = mergeAttrsList (mapAttrsToList machineLocations (filterAttrs (_: pxeEnabled) machines));
+          };
+        };
+      };
+    };
+
+    systemd = {
+      network = {
+        networks.${cfg.network}.addresses = [
+          {
+            Address = "${cfg.linkLocal6}/128";
+            AddPrefixRoute = "no";
+            PreferredLifetime = "0";
+          }
+        ];
+      };
+
+      services = {
+        pxe-store-upload = {
+          path = [config.nix.package pkgs.sshfs pkgs.squashfsTools];
+
+          script = let
+            host = lib.throw "TODO: pxe host";
+            machine = machines.${host};
+          in ''
+            set -e
+
+            pxe_ip='${machine.config.local.boot.pxe.linkLocal6}'
+            pxe_host='${host}'
+            pxe_system='${machine.config.system.build.toplevel}'
+
+            mountpoint="./pxe-initrd.$pxe_host"
+            store_img="$mountpoint/nix-store.squashfs"
+
+            mkdir -p "$mountpoint"
+
+            export PATH="/run/wrappers/bin:$PATH"
+            sshfs \
+                "root@[$pxe_ip%${cfg.network}]:/nix/.ro-store-img/" \
+                "$mountpoint" \
+                -o idmap=user
+
+            nix-store --query --requisites "$pxe_system" | \
+              xargs -I{} mksquashfs {} - \
+              -stream -comp zstd -one-file-system -no-xattrs \
+              >"$store_img.tmp"
+
+            mksquashfs -fix "$store_img.tmp"
+
+            sync "$store_img.tmp"
+            mv -- "$store_img.tmp" "$store_img"
+            fusermount3 -u "$mountpoint"
+          '';
+
+          serviceConfig = {
+            #AmbientCapabilities = ["CAP_SYS_ADMIN"];
+            #CapabilityBoundingSet = ["CAP_SYS_ADMIN"];
+            #BindPaths = ["/dev/fuse"];
+            #BindReadOnlyPaths = ["/nix/store"];
+            #DeviceAllow = ["/dev/fuse rwm"];
+            #DevicePolicy = "closed";
+            #MountAPIVFS = true;
+            ProtectSystem = "strict";
+            ProtectControlGroups = true;
+            ProtectKernelLogs = true;
+            ProtectKernelModules = true;
+            ProtectKernelTunables = true;
+            #PrivateDevices = true;
+            #PrivateTmp = true;
+            #PrivateUsers = true;
+            #TemporaryFileSystem = ["/"];
+            #DynamicUser = true;
+            RuntimeDirectory = "pxe-store-upload";
+            WorkingDirectory = "/run/pxe-store-upload";
+          };
+        };
+      };
+
+      sockets = {
+        pxe-store-upload = {
+          after = ["network-online.target"];
+          wants = ["network-online.target"];
+          wantedBy = ["sockets.target"];
+
+          socketConfig = {
+            ListenDatagram = "[${cfg.linkLocal6}]:1792%%${cfg.network}";
+          };
+        };
+      };
+    };
+  };
+}