# security tweaks borrowed from @hlissner
{
  boot.kernel.sysctl = {
    # The Magic SysRq key is a key combo that allows users connected to the
    # system console of a Linux kernel to perform some low-level commands.

    ## TCP hardening
    # Prevent bogus ICMP errors from filling up logs.
    "net.ipv4.icmp_ignore_bogus_error_responses" = 1;
    # Reverse path filtering causes the kernel to do source validation of
    # packets received from all interfaces. This can mitigate IP spoofing.
    "net.ipv4.conf.default.rp_filter" = 1;
    "net.ipv4.conf.all.rp_filter" = 1;
    # Do not accept IP source route packets (we're not a router)
    "net.ipv4.conf.all.accept_source_route" = 0;
    "net.ipv6.conf.all.accept_source_route" = 0;
    # Don't send ICMP redirects (again, we're not a router)
    "net.ipv4.conf.all.send_redirects" = 0;
    "net.ipv4.conf.default.send_redirects" = 0;
    # Refuse ICMP redirects (MITM mitigations)
    "net.ipv4.conf.all.accept_redirects" = 0;
    "net.ipv4.conf.default.accept_redirects" = 0;
    "net.ipv4.conf.all.secure_redirects" = 0;
    "net.ipv4.conf.default.secure_redirects" = 0;
    "net.ipv6.conf.all.accept_redirects" = 0;
    "net.ipv6.conf.default.accept_redirects" = 0;
    # Protects against SYN flood attacks
    "net.ipv4.tcp_syncookies" = 1;
    # Incomplete protection again TIME-WAIT assassination
    "net.ipv4.tcp_rfc1337" = 1;

    ## TCP optimization
    # TCP Fast Open is a TCP extension that reduces network latency by packing
    # data in the sender’s initial TCP SYN. Setting 3 = enable TCP Fast Open for
    # both incoming and outgoing connections:
    "net.ipv4.tcp_fastopen" = 3;

    # Enable IPv4 forwarding for VPN/container routing
    "net.ipv4.ip_forward" = 1;
    # Bufferbloat mitigations + slight improvement in throughput & latency
    "net.ipv4.tcp_congestion_control" = "bbr";
    "net.core.default_qdisc" = "cake";

    ## Network performance optimizations
    # Increase network buffer sizes
    "net.core.rmem_default" = 262144;
    "net.core.rmem_max" = 134217728;
    "net.core.wmem_default" = 262144;
    "net.core.wmem_max" = 134217728;

    # TCP buffer sizes
    "net.ipv4.tcp_rmem" = "4096 131072 134217728";
    "net.ipv4.tcp_wmem" = "4096 65536 134217728";

    # TCP performance
    "net.ipv4.tcp_window_scaling" = 1;
    "net.ipv4.tcp_timestamps" = 1;
    "net.ipv4.tcp_sack" = 1;
    "net.ipv4.tcp_fack" = 1;
    "net.ipv4.tcp_low_latency" = 1;
    "net.ipv4.tcp_adv_win_scale" = 1;

    # Reduce TIME_WAIT sockets
    "net.ipv4.tcp_fin_timeout" = 15;
    "net.ipv4.tcp_tw_reuse" = 1;
  };

  boot.kernelModules = ["tcp_bbr"];

  security = {
    # allow wayland lockers to unlock the screen
    # userland niceness
    rtkit.enable = true;
    polkit.enable = true;

    sudo-rs = {
      enable = true;
      execWheelOnly = true;
      wheelNeedsPassword = false;
    };

    # don't ask for password for wheel group
    sudo = {
      wheelNeedsPassword = false;
    };
  };
}
