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::handlers
{
  struct TunEndpoint : public service::Endpoint,
                       public dns::Resolver_Base,
                       public std::enable_shared_from_this<TunEndpoint>
  {
    TunEndpoint(Router* 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.
    void
    ReconfigureDNS(std::vector<SockAddr> servers);

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

    void send_packet_to_remote(std::string) 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;
      }
    };

    /// 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 llarp::handlers