nixos/modules/ha/cluster-config.nix

# Cluster-wide HA config shared by both ha-server nodes.
#
# Covers everything that is identical on both nodes and references cluster
# topology (node IPs, hostnames, DRBD resource).  Per-node identity
# (hostname, static IP, stateVersion) lives in hosts/ha-server-{1,2}/host.nix.
#
# Corosync authkey:
#   /etc/corosync/authkey (mode 0400) is managed by sops-nix below.
#   Bootstrap: run scripts/ha/cluster-init.sh on node1 to generate the key,
#   then encrypt it with: sops -e --input-type binary /etc/corosync/authkey > secrets/ha-corosync-authkey
#   Both host keys must be registered via sync-host-keys.sh first so both nodes can decrypt it.
#
# DRBD fencing:
#   Production setting is resource-only: DRBD waits for the STONITH fence
#   agent to confirm the peer is dead before promoting to Primary.  This
#   requires a working fence_pve_ssh STONITH resource in Pacemaker
#   (see scripts/ha/cluster-enable-stonith.sh).  On a fresh cluster with
#   no fence device yet, temporarily change to dont-care and run
#   cluster-enable-stonith.sh once the fence key is deployed.
{ lib, vars, ... }:
{
  # Root SSH access with the admin key — needed for the deploy script to upload
  # and run cluster-init.sh as root on node1, and for node1→node2 SSH during init.
  users.users.root.openssh.authorizedKeys.keys = [ vars.adminSshKey ];

  # Passwordless sudo for wheel — operator SSHes as nixos and uses sudo for
  # cluster management commands (drbdadm, crm*, pcs, etc.)
  security.sudo.wheelNeedsPassword = lib.mkForce false;

  services.drbd = {
    enable = true;
    config = ''
      global {
        usage-count yes;
      }

      common {
        net {
          protocol C;
          ping-int 1;
          verify-alg sha256;
          after-sb-0pri discard-zero-changes;
          after-sb-1pri discard-secondary;
        }
        disk {
          fencing resource-only;
        }
      }

      resource ha-data {
        volume 0 {
          device    /dev/drbd0;
          disk      /dev/sdb;
          meta-disk internal;
        }

        on ${vars.haServer1Host} {
          address ${vars.haServer1StorageIp}:${toString vars.ports.haServerDrbd};
        }

        on ${vars.haServer2Host} {
          address ${vars.haServer2StorageIp}:${toString vars.ports.haServerDrbd};
        }
      }
    '';
  };

  # /etc/corosync/authkey — sops binary secret, identical on both nodes.
  # Decryptable by both ha-server host keys (added by sync-host-keys.sh).
  sops.secrets.corosync_authkey = {
    sopsFile = ../../secrets/ha-corosync-authkey;
    format = "binary";
    path = "/etc/corosync/authkey";
    mode = "0400";
    restartUnits = [ "corosync.service" ];
  };

  # NixOS common config enables NetworkManager by default; HA cluster nodes
  # need stable static IPs with predictable interface names — NM is not suitable.
  networking.networkmanager.enable = lib.mkForce false;

  # services.corosync.enable is set by modules/ha/pacemaker-stack.nix.
  services.corosync = {
    clusterName = "ha-cluster";
    nodelist = [
      { nodeid = 1; name = vars.haServer1Host; ring_addrs = [ vars.haServer1StorageIp ]; }
      { nodeid = 2; name = vars.haServer2Host; ring_addrs = [ vars.haServer2StorageIp ]; }
    ];
  };

  networking.firewall = {
    allowedTCPPorts = [
      vars.ports.haServerIscsi
      vars.ports.haServerPacemakerRemoted
      vars.ports.haServerPcsd
      vars.ports.haServerDrbd
      vars.ports.nfsRpcbind
      vars.ports.nfsd
      vars.ports.nfsMountd
    ];
    allowedUDPPorts = [
      vars.ports.haServerCorosync1
      vars.ports.haServerCorosync2
      vars.ports.haServerCorosyncCrypto
      vars.ports.nfsRpcbind
      vars.ports.nfsd
      vars.ports.nfsMountd
    ];
    extraCommands = ''
      iptables -A INPUT -s ${vars.haServer1Ip}/32 -j ACCEPT
      iptables -A INPUT -s ${vars.haServer2Ip}/32 -j ACCEPT
      iptables -A INPUT -s ${vars.haStorageCidr} -j ACCEPT
    '';
  };
}