{ ... }: {
  # TCP Hardening
  boot.kernel.sysctl = {
    # 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 on 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;
  };
}
