//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#pragma once

#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>
#include <net/if.h>
#include <linux/if_tun.h>

#include <openvpn/common/exception.hpp>
#include <openvpn/common/file.hpp>
#include <openvpn/common/split.hpp>
#include <openvpn/common/splitlines.hpp>
#include <openvpn/common/hexstr.hpp>
#include <openvpn/common/to_string.hpp>
#include <openvpn/common/process.hpp>
#include <openvpn/common/action.hpp>
#include <openvpn/addr/route.hpp>
#include <openvpn/tun/builder/capture.hpp>
#include <openvpn/tun/builder/setup.hpp>
#include <openvpn/tun/client/tunbase.hpp>
#include <openvpn/tun/client/tunprop.hpp>
#include <openvpn/tun/client/tunprop.hpp>
#include <openvpn/tun/linux/client/tunsetup.hpp>
#include <openvpn/netconf/linux/gw.hpp>

namespace openvpn {
  namespace TunIPRoute {

    using namespace openvpn::TunLinuxSetup;

    enum { // add_del_route flags
      R_IPv6=(1<<0),
      R_ADD_SYS=(1<<1),
      R_ADD_DCO=(1<<2),
      R_ADD_ALL=R_ADD_SYS|R_ADD_DCO,
    };

    inline IP::Addr cvt_pnr_ip_v4(const std::string& hexaddr)
    {
      BufferAllocated v(4, BufferAllocated::CONSTRUCT_ZERO);
      parse_hex(v, hexaddr);
      if (v.size() != 4)
	throw tun_linux_error("bad hex address");
      IPv4::Addr ret = IPv4::Addr::from_bytes(v.data());
      return IP::Addr::from_ipv4(ret);
    }

    inline void add_del_route(const std::string& addr_str,
			      const int prefix_len,
			      const std::string& gateway_str,
			      const std::string& dev,
			      const unsigned int flags,
			      std::vector<IP::Route>* rtvec,
			      Action::Ptr& create,
			      Action::Ptr& destroy)
    {
      if (flags & R_IPv6)
	{
	  const IPv6::Addr addr = IPv6::Addr::from_string(addr_str);
	  const IPv6::Addr netmask = IPv6::Addr::netmask_from_prefix_len(prefix_len);
	  const IPv6::Addr net = addr & netmask;

	  if (flags & R_ADD_SYS)
	    {
	      // ip route add 2001:db8:1::/48 via 2001:db8:1::1
	      Command::Ptr add(new Command);
	      add->argv.push_back("/sbin/ip");
	      add->argv.push_back("-6");
	      add->argv.push_back("route");
	      add->argv.push_back("prepend");
	      add->argv.push_back(net.to_string() + '/' + openvpn::to_string(prefix_len));
	      add->argv.push_back("via");
	      add->argv.push_back(gateway_str);
	      if (!dev.empty())
		{
		  add->argv.push_back("dev");
		  add->argv.push_back(dev);
		}
	      create = add;

	      // for the destroy command, copy the add command but replace "add" with "delete"
	      Command::Ptr del(add->copy());
	      del->argv[3] = "del";
	      destroy = del;
	    }

	if (rtvec && (flags & R_ADD_DCO))
	  rtvec->emplace_back(IP::Addr::from_ipv6(net), prefix_len);
      }
      else
      {
	const IPv4::Addr addr = IPv4::Addr::from_string(addr_str);
	const IPv4::Addr netmask = IPv4::Addr::netmask_from_prefix_len(prefix_len);
	const IPv4::Addr net = addr & netmask;

	if (flags & R_ADD_SYS)
	  {
	    // ip route add 192.0.2.128/25 via 192.0.2.1
	    Command::Ptr add(new Command);
	    add->argv.push_back("/sbin/ip");
	    add->argv.push_back("-4");
	    add->argv.push_back("route");
	    add->argv.push_back("prepend");
	    add->argv.push_back(net.to_string() + '/' + openvpn::to_string(prefix_len));
	    add->argv.push_back("via");
	    add->argv.push_back(gateway_str);
	    if (!dev.empty())
	    {
	      add->argv.push_back("dev");
	      add->argv.push_back(dev);
	    }
	    create = add;

	    // for the destroy command, copy the add command but replace "add" with "delete"
	    Command::Ptr del(add->copy());
	    del->argv[3] = "del";
	    destroy = del;
	  }

	if (rtvec && (flags & R_ADD_DCO))
	  rtvec->emplace_back(IP::Addr::from_ipv4(net), prefix_len);
      }
    }

    inline void add_del_route(const std::string& addr_str,
			      const int prefix_len,
			      const std::string& gateway_str,
			      const std::string& dev,
			      const unsigned int flags,// add interface route to rtvec if defined
			      std::vector<IP::Route>* rtvec,
			      ActionList& create,
			      ActionList& destroy)
    {
      Action::Ptr c, d;
      add_del_route(addr_str, prefix_len, gateway_str, dev, flags, rtvec, c, d);
      create.add(c);
      destroy.add(d);
    }

    inline void iface_up(const std::string& iface_name,
			 const int mtu,
			 ActionList& create,
			 ActionList& destroy)
    {
      {
	Command::Ptr add(new Command);
	add->argv.push_back("/sbin/ip");
	add->argv.push_back("link");
	add->argv.push_back("set");
	add->argv.push_back(iface_name);
	add->argv.push_back("up");
	if (mtu > 0)
	  {
	    add->argv.push_back("mtu");
	    add->argv.push_back(openvpn::to_string(mtu));
	  }
	create.add(add);

	// for the destroy command, copy the add command but replace "up" with "down"
	Command::Ptr del(add->copy());
	del->argv[4] = "down";
	destroy.add(del);
      }
    }

    inline void iface_config(const std::string& iface_name,
			     int unit,
			     const TunBuilderCapture& pull,
			     std::vector<IP::Route>* rtvec,
			     ActionList& create,
			     ActionList& destroy)
    {
      // set local4 and local6 to point to IPv4/6 route configurations
      const TunBuilderCapture::RouteAddress* local4 = pull.vpn_ipv4();
      const TunBuilderCapture::RouteAddress* local6 = pull.vpn_ipv6();

      // Set IPv4 Interface
      if (local4)
	{
	  Command::Ptr add(new Command);
	  add->argv.push_back("/sbin/ip");
	  add->argv.push_back("-4");
	  add->argv.push_back("addr");
	  add->argv.push_back("add");
	  add->argv.push_back(local4->address + '/' + openvpn::to_string(local4->prefix_length));
	  add->argv.push_back("broadcast");
	  add->argv.push_back((IPv4::Addr::from_string(local4->address) | ~IPv4::Addr::netmask_from_prefix_len(local4->prefix_length)).to_string());
	  add->argv.push_back("dev");
	  add->argv.push_back(iface_name);
	  if (unit >= 0)
	    {
	      add->argv.push_back("label");
	      add->argv.push_back(iface_name + ':' + openvpn::to_string(unit));
	    }
	  create.add(add);

	  // for the destroy command, copy the add command but replace "add" with "delete"
	  Command::Ptr del(add->copy());
	  del->argv[3] = "del";
	  destroy.add(del);

	  // add interface route to rtvec if defined
	  add_del_route(local4->address, local4->prefix_length, local4->address, iface_name, R_ADD_DCO, rtvec, create, destroy);
	}

      // Set IPv6 Interface
      if (local6 && !pull.block_ipv6)
      {
	Command::Ptr add(new Command);
	add->argv.push_back("/sbin/ip");
	add->argv.push_back("-6");
	add->argv.push_back("addr");
	add->argv.push_back("add");
	add->argv.push_back(local6->address + '/' + openvpn::to_string(local6->prefix_length));
	add->argv.push_back("dev");
	add->argv.push_back(iface_name);
	create.add(add);

	// for the destroy command, copy the add command but replace "add" with "delete"
	Command::Ptr del(add->copy());
	del->argv[3] = "del";
	destroy.add(del);

	// add interface route to rtvec if defined
	add_del_route(local6->address, local6->prefix_length, local6->address, iface_name, R_ADD_DCO|R_IPv6, rtvec, create, destroy);
      }
    }

    struct TunMethods
    {
      static inline void tun_config(const std::string& iface_name,
			     const TunBuilderCapture& pull,
			     std::vector<IP::Route>* rtvec,
			     ActionList& create,
			     ActionList& destroy,
			     bool add_bypass_routes = true)
      {
	const LinuxGW46 gw(true);

	// set local4 and local6 to point to IPv4/6 route configurations
	const TunBuilderCapture::RouteAddress* local4 = pull.vpn_ipv4();
	const TunBuilderCapture::RouteAddress* local6 = pull.vpn_ipv6();

	// configure interface
	iface_up(iface_name, pull.mtu, create, destroy);
	iface_config(iface_name, -1, pull, rtvec, create, destroy);

	// Process Routes
	{
	  for (const auto &route : pull.add_routes)
	    {
	      if (route.ipv6)
		{
		  if (local6 && !pull.block_ipv6)
		    add_del_route(route.address, route.prefix_length, local6->gateway, iface_name, R_ADD_ALL|R_IPv6, rtvec, create, destroy);
		}
	      else
		{
		  if (local4 && !local4->gateway.empty())
		    add_del_route(route.address, route.prefix_length, local4->gateway, iface_name, R_ADD_ALL, rtvec, create, destroy);
		  else
		    OPENVPN_LOG("ERROR: IPv4 route pushed without IPv4 ifconfig and/or route-gateway");
		}
	    }
	}

	// Process exclude routes
	{
	  for (const auto &route : pull.exclude_routes)
	    {
	      if (route.ipv6)
		{
		  OPENVPN_LOG("NOTE: exclude IPv6 routes not supported yet"); // fixme
		}
	      else
		{
		  if (gw.v4.defined())
		    add_del_route(route.address, route.prefix_length, gw.v4.addr().to_string(), gw.v4.dev(), R_ADD_SYS, rtvec, create, destroy);
		  else
		    OPENVPN_LOG("NOTE: cannot determine gateway for exclude IPv4 routes");
		}
	    }
	}

	// Process IPv4 redirect-gateway
	if (pull.reroute_gw.ipv4)
	  {
	    // add bypass route
	    if (add_bypass_routes && !pull.remote_address.ipv6 && !(pull.reroute_gw.flags & RedirectGatewayFlags::RG_LOCAL) && gw.v4.defined())
	      add_del_route(pull.remote_address.address, 32, gw.v4.addr().to_string(), gw.v4.dev(), R_ADD_SYS, rtvec, create, destroy);

	    add_del_route("0.0.0.0", 1, local4->gateway, iface_name, R_ADD_ALL, rtvec, create, destroy);
	    add_del_route("128.0.0.0", 1, local4->gateway, iface_name, R_ADD_ALL, rtvec, create, destroy);
	  }

	// Process IPv6 redirect-gateway
	if (pull.reroute_gw.ipv6 && !pull.block_ipv6)
	  {
	    // add bypass route
	    if (add_bypass_routes && pull.remote_address.ipv6 && !(pull.reroute_gw.flags & RedirectGatewayFlags::RG_LOCAL) && gw.v4.defined())
	      add_del_route(pull.remote_address.address, 128, gw.v6.addr().to_string(), gw.v6.dev(), R_ADD_SYS|R_IPv6, rtvec, create, destroy);

	    add_del_route("0000::", 1, local6->gateway, iface_name, R_ADD_ALL|R_IPv6, rtvec, create, destroy);
	    add_del_route("8000::", 1, local6->gateway, iface_name, R_ADD_ALL|R_IPv6, rtvec, create, destroy);
	  }

	// fixme -- Process block-ipv6

	// fixme -- Handle pushed DNS servers
      }

      static inline void add_bypass_route(const std::string& tun_iface_name,
					  const std::string& address,
					  bool ipv6,
					  std::vector<IP::Route>* rtvec,
					  ActionList& create,
					  ActionList& destroy)
      {
	LinuxGW46 gw(true);

	if (!ipv6 && gw.v4.defined())
	  add_del_route(address, 32, gw.v4.addr().to_string(), gw.dev(), R_ADD_SYS, rtvec, create, destroy);

	if (ipv6 && gw.v6.defined())
	  add_del_route(address, 128, gw.v6.addr().to_string(), gw.dev(), R_ADD_SYS, rtvec, create, destroy);
      }
    };
  }
} // namespace openvpn