Move all of NixOS to nixos/ in preparation of the repository merge

nixos/modules/services/networking/tcpcrypt.nix

@@ -0,0 +1,78 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  cfg = config.networking.tcpcrypt;
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    networking.tcpcrypt.enable = mkOption {
+      default = false;
+      description = ''
+        Whether to enable opportunistic TCP encryption. If the other end
+        speaks Tcpcrypt, then your traffic will be encrypted; otherwise
+        it will be sent in clear text. Thus, Tcpcrypt alone provides no
+        guarantees -- it is best effort. If, however, a Tcpcrypt
+        connection is successful and any attackers that exist are
+        passive, then Tcpcrypt guarantees privacy.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+
+    users.extraUsers = singleton {
+      name = "tcpcryptd";
+      uid = config.ids.uids.tcpcryptd;
+      description = "tcpcrypt daemon user";
+    };
+
+    jobs.tcpcrypt = {
+      description = "tcpcrypt";
+
+      wantedBy = ["multi-user.target"];
+      after = ["network-interfaces.target"];
+
+      path = [ pkgs.iptables pkgs.tcpcrypt pkgs.procps ];
+
+      preStart = ''
+        sysctl -n net.ipv4.tcp_ecn >/run/pre-tcpcrypt-ecn-state
+        sysctl -w net.ipv4.tcp_ecn=0
+
+        iptables -t raw -N nixos-tcpcrypt
+        iptables -t raw -A nixos-tcpcrypt -p tcp -m mark --mark 0x0/0x10 -j NFQUEUE --queue-num 666
+        iptables -t raw -I PREROUTING -j nixos-tcpcrypt
+
+        iptables -t mangle -N nixos-tcpcrypt
+        iptables -t mangle -A nixos-tcpcrypt -p tcp -m mark --mark 0x0/0x10 -j NFQUEUE --queue-num 666
+        iptables -t mangle -I POSTROUTING -j nixos-tcpcrypt
+      '';
+
+      exec = "tcpcryptd -x 0x10";
+
+      postStop = ''
+        if [ -f /run/pre-tcpcrypt-ecn-state ]; then
+          sysctl -w net.ipv4.tcp_ecn=$(cat /run/pre-tcpcrypt-ecn-state)
+        fi
+
+        iptables -t mangle -D POSTROUTING -j nixos-tcpcrypt || true
+        iptables -t raw -D PREROUTING -j nixos-tcpcrypt || true
+
+        iptables -t raw -F nixos-tcpcrypt || true
+        iptables -t raw -X nixos-tcpcrypt || true
+
+        iptables -t mangle -F nixos-tcpcrypt || true
+        iptables -t mangle -X nixos-tcpcrypt || true
+      '';
+    };
+  };
+
+}