lokinet/llarp/handlers/tun.hpp

#pragma once

#include <llarp/dns/server.hpp>
#include <llarp/ev/ev.hpp>
#include <llarp/net/ip.hpp>
#include <llarp/net/ip_packet.hpp>
#include <llarp/net/net.hpp>
#include <llarp/service/endpoint.hpp>
#include <llarp/service/protocol_type.hpp>
#include <llarp/util/priority_queue.hpp>
#include <llarp/util/thread/threading.hpp>
#include <llarp/vpn/packet_router.hpp>
#include <llarp/vpn/platform.hpp>

#include <future>
#include <type_traits>
#include <variant>

namespace llarp
{
  namespace handlers
  {
    struct TunEndpoint : public service::Endpoint,
                         public dns::Resolver_Base,
                         public std::enable_shared_from_this<TunEndpoint>
    {
      TunEndpoint(AbstractRouter* r, llarp::service::Context* parent);
      ~TunEndpoint() override;

      vpn::NetworkInterface*
      GetVPNInterface() override
      {
        return m_NetIf.get();
      }

      int
      Rank() const override
      {
        return 0;
      }

      std::string_view
      ResolverName() const override
      {
        return "lokinet";
      }

      bool
      MaybeHookDNS(
          std::shared_ptr<dns::PacketSource_Base> source,
          const dns::Message& query,
          const SockAddr& to,
          const SockAddr& from) override;

      path::PathSet_ptr
      GetSelf() override
      {
        return shared_from_this();
      }

      std::weak_ptr<path::PathSet>
      GetWeak() override
      {
        return weak_from_this();
      }

      void
      Thaw() override;

      // Reconfigures DNS servers and restarts libunbound with the new servers.  Returns the old set
      // of configured dns servers.
      std::vector<SockAddr>
      ReconfigureDNS(std::vector<SockAddr> servers);

      bool
      Configure(const NetworkConfig& conf, const DnsConfig& dnsConf) override;

      void
      SendPacketToRemote(const llarp_buffer_t&, service::ProtocolType) override{};

      std::string
      GetIfName() const override;

      void
      Tick(llarp_time_t now) override;

      util::StatusObject
      ExtractStatus() const override;

      std::unordered_map<std::string, std::string>
      NotifyParams() const override;

      bool
      SupportsV6() const override;

      bool
      ShouldHookDNSMessage(const dns::Message& msg) const;

      bool
      HandleHookedDNSMessage(dns::Message query, std::function<void(dns::Message)> sendreply);

      void
      TickTun(llarp_time_t now);

      bool
      MapAddress(const service::Address& remote, huint128_t ip, bool SNode);

      bool
      Start() override;

      bool
      Stop() override;

      bool
      IsSNode() const;

      /// set up tun interface, blocking
      bool
      SetupTun();

      void
      SetupDNS();

      /// overrides Endpoint
      std::shared_ptr<dns::Server>
      DNS() const override
      {
        return m_DNS;
      };

      /// overrides Endpoint
      bool
      SetupNetworking() override;

      /// overrides Endpoint
      bool
      HandleInboundPacket(
          const service::ConvoTag tag,
          const llarp_buffer_t& pkt,
          service::ProtocolType t,
          uint64_t seqno) override;

      /// handle inbound traffic
      bool
      HandleWriteIPPacket(
          const llarp_buffer_t& buf, huint128_t src, huint128_t dst, uint64_t seqno);

      /// we got a packet from the user
      void
      HandleGotUserPacket(llarp::net::IPPacket pkt);

      /// get the local interface's address
      huint128_t
      GetIfAddr() const override;

      /// we have an interface addr
      bool
      HasIfAddr() const override
      {
        return true;
      }

      bool
      HasLocalIP(const huint128_t& ip) const;

      std::optional<net::TrafficPolicy>
      GetExitPolicy() const override
      {
        return m_TrafficPolicy;
      }

      std::set<IPRange>
      GetOwnedRanges() const override
      {
        return m_OwnedRanges;
      }

      llarp_time_t
      PathAlignmentTimeout() const override
      {
        return m_PathAlignmentTimeout;
      }

      /// ip packet against any exit policies we have
      /// returns false if this traffic is disallowed by any of those policies
      /// returns true otherwise
      bool
      ShouldAllowTraffic(const net::IPPacket& pkt) const;

      /// get a key for ip address
      std::optional<std::variant<service::Address, RouterID>>
      ObtainAddrForIP(huint128_t ip) const override;

      bool
      HasAddress(const AlignedBuffer<32>& addr) const
      {
        return m_AddrToIP.find(addr) != m_AddrToIP.end();
      }

      /// get ip address for key unconditionally
      huint128_t
      ObtainIPForAddr(std::variant<service::Address, RouterID> addr) override;

      void
      ResetInternalState() override;

     protected:
      struct WritePacket
      {
        uint64_t seqno;
        net::IPPacket pkt;

        bool
        operator>(const WritePacket& other) const
        {
          return seqno > other.seqno;
        }
      };

      /// queue for sending packets to user from network
      util::ascending_priority_queue<WritePacket> m_NetworkToUserPktQueue;

      void
      Pump(llarp_time_t now) override;

      /// return true if we have a remote loki address for this ip address
      bool
      HasRemoteForIP(huint128_t ipv4) const;

      /// mark this address as active
      void
      MarkIPActive(huint128_t ip);

      /// mark this address as active forever
      void
      MarkIPActiveForever(huint128_t ip);

      /// flush writing ip packets to interface
      void
      FlushWrite();

      /// maps ip to key (host byte order)
      std::unordered_map<huint128_t, AlignedBuffer<32>> m_IPToAddr;
      /// maps key to ip (host byte order)
      std::unordered_map<AlignedBuffer<32>, huint128_t> m_AddrToIP;

      /// maps key to true if key is a service node, maps key to false if key is
      /// a hidden service
      std::unordered_map<AlignedBuffer<32>, bool> m_SNodes;

      /// maps ip address to an exit endpoint, useful when we have multiple exits on a range
      std::unordered_map<huint128_t, service::Address> m_ExitIPToExitAddress;

     private:
      /// given an ip address that is not mapped locally find the address it shall be forwarded to
      /// optionally provide a custom selection strategy, if none is provided it will choose a
      /// random entry from the available choices
      /// return std::nullopt if we cannot route this address to an exit
      std::optional<service::Address>
      ObtainExitAddressFor(
          huint128_t ip,
          std::function<service::Address(std::unordered_set<service::Address>)> exitSelectionStrat =
              nullptr);

      template <typename Addr_t, typename Endpoint_t>
      void
      SendDNSReply(
          Addr_t addr,
          Endpoint_t ctx,
          std::shared_ptr<dns::Message> query,
          std::function<void(dns::Message)> reply,
          bool sendIPv6)
      {
        if (ctx)
        {
          huint128_t ip = ObtainIPForAddr(addr);
          query->answers.clear();
          query->AddINReply(ip, sendIPv6);
        }
        else
          query->AddNXReply();
        reply(*query);
      }

      /// dns subsystem for this endpoint
      std::shared_ptr<dns::Server> m_DNS;

      DnsConfig m_DnsConfig;

      /// maps ip address to timestamp last active
      std::unordered_map<huint128_t, llarp_time_t> m_IPActivity;
      /// our ip address (host byte order)
      huint128_t m_OurIP;
      /// our network interface's ipv6 address
      huint128_t m_OurIPv6;

      /// next ip address to allocate (host byte order)
      huint128_t m_NextIP;
      /// highest ip address to allocate (host byte order)
      huint128_t m_MaxIP;
      /// our ip range we are using
      llarp::IPRange m_OurRange;
      /// list of strict connect addresses for hooks
      std::vector<IpAddress> m_StrictConnectAddrs;
      /// use v6?
      bool m_UseV6;
      std::string m_IfName;

      std::optional<huint128_t> m_BaseV6Address;

      std::shared_ptr<vpn::NetworkInterface> m_NetIf;

      std::shared_ptr<vpn::PacketRouter> m_PacketRouter;

      std::optional<net::TrafficPolicy> m_TrafficPolicy;
      /// ranges we advetise as reachable
      std::set<IPRange> m_OwnedRanges;
      /// how long to wait for path alignment
      llarp_time_t m_PathAlignmentTimeout;

      /// a file to load / store the ephemeral address map to
      std::optional<fs::path> m_PersistAddrMapFile;

      /// for raw packet dns
      std::shared_ptr<vpn::I_Packet_IO> m_RawDNS;
    };

  }  // namespace handlers
}  // namespace llarp