lokinet/llarp/handlers/tun.cpp

#include <algorithm>
// harmless on other platforms
#define __USE_MINGW_ANSI_STDIO 1
#include <handlers/tun.hpp>
#include <sys/types.h>
#ifndef _WIN32
#include <sys/socket.h>
#include <netdb.h>
#endif

#include <ev.hpp>
#include <router.hpp>
#include <dns/dns.hpp>

namespace llarp
{
  namespace handlers
  {
    static llarp_fd_promise *
    get_tun_fd_promise(llarp_tun_io *tun)
    {
      return static_cast< TunEndpoint * >(tun->user)->Promise.get();
    }

    static void
    tunifTick(llarp_tun_io *tun)
    {
      TunEndpoint *self = static_cast< TunEndpoint * >(tun->user);
      self->Flush();
    }

    TunEndpoint::TunEndpoint(const std::string &nickname, llarp::Router *r)
        : service::Endpoint(nickname, r)
        , m_UserToNetworkPktQueue(nickname + "_sendq", r->netloop, r->netloop)
        , m_NetworkToUserPktQueue(nickname + "_recvq", r->netloop, r->netloop)
        , m_Resolver(r->netloop, this)
    {
#ifdef ANDROID
      tunif.get_fd_promise = &get_tun_fd_promise;
      Promise.reset(new llarp_fd_promise(&m_VPNPromise));
#else
      tunif.get_fd_promise = nullptr;
#endif
      tunif.user    = this;
      tunif.netmask = DefaultTunNetmask;

      // eh this shouldn't do anything on windows anyway
      strncpy(tunif.ifaddr, DefaultTunSrcAddr, sizeof(tunif.ifaddr) - 1);
      strncpy(tunif.ifname, DefaultTunIfname, sizeof(tunif.ifname) - 1);
      tunif.tick         = &tunifTick;
      tunif.before_write = &tunifBeforeWrite;
      tunif.recvpkt      = &tunifRecvPkt;
    }

    bool
    TunEndpoint::SetOption(const std::string &k, const std::string &v)
    {
      if(k == "exit-node")
      {
        llarp::RouterID exitRouter;
        if(!(exitRouter.FromString(v)
             || HexDecode(v.c_str(), exitRouter.begin(), exitRouter.size())))
        {
          llarp::LogError(Name(), " bad exit router key: ", v);
          return false;
        }
        m_Exit.reset(new llarp::exit::ExitSession(
            exitRouter,
            std::bind(&TunEndpoint::QueueInboundPacketForExit, this,
                      std::placeholders::_1),
            router, m_NumPaths, numHops));
        llarp::LogInfo(Name(), " using exit at ", exitRouter);
      }
      if(k == "local-dns")
      {
        std::string resolverAddr = v;
        uint16_t dnsport         = 53;
        auto pos                 = v.find(":");
        if(pos != std::string::npos)
        {
          resolverAddr = v.substr(0, pos);
          dnsport      = std::atoi(v.substr(pos + 1).c_str());
        }
        m_LocalResolverAddr = llarp::Addr(resolverAddr, dnsport);
        llarp::LogInfo(Name(), " local dns set to ", m_LocalResolverAddr);
      }
      if(k == "upstream-dns")
      {
        std::string resolverAddr = v;
        uint16_t dnsport         = 53;
        auto pos                 = v.find(":");
        if(pos != std::string::npos)
        {
          resolverAddr = v.substr(0, pos);
          dnsport      = std::atoi(v.substr(pos + 1).c_str());
        }
        m_UpstreamResolvers.emplace_back(resolverAddr, dnsport);
        llarp::LogInfo(Name(), " adding upstream dns set to ", resolverAddr,
                       ":", dnsport);
      }
      if(k == "mapaddr")
      {
        auto pos = v.find(":");
        if(pos == std::string::npos)
        {
          llarp::LogError("Cannot map address ", v,
                          " invalid format, missing colon (:), expects "
                          "address.loki:ip.address.goes.here");
          return false;
        }
        service::Address addr;
        auto addr_str = v.substr(0, pos);
        if(!addr.FromString(addr_str))
        {
          llarp::LogError(Name() + " cannot map invalid address ", addr_str);
          return false;
        }
        auto ip_str = v.substr(pos + 1);
        in_addr ip;
        if(inet_pton(AF_INET, ip_str.c_str(), &ip) != 1)
        {
          llarp::LogError("cannot map to invalid ip ", ip_str);
          return false;
        }
        return MapAddress(addr, huint32_t{ntohl(ip.s_addr)}, false);
      }
      if(k == "ifname")
      {
        if(v.length() >= sizeof(tunif.ifname))
        {
          llarp::LogError(Name() + " ifname '", v, "' is too long");
          return false;
        }
        strncpy(tunif.ifname, v.c_str(), sizeof(tunif.ifname) - 1);
        llarp::LogInfo(Name() + " setting ifname to ", tunif.ifname);
        return true;
      }
      if(k == "ifaddr")
      {
        std::string addr;
        auto pos = v.find("/");
        if(pos != std::string::npos)
        {
          int num;
          std::string part = v.substr(pos + 1);
#if defined(ANDROID) || defined(RPI)
          num = atoi(part.c_str());
#else
          num = std::stoi(part);
#endif
          if(num > 0)
          {
            tunif.netmask = num;
            addr          = v.substr(0, pos);
          }
          else
          {
            llarp::LogError("bad ifaddr value: ", v);
            return false;
          }
        }
        else
        {
          tunif.netmask = 32;
          addr          = v;
        }
        llarp::LogInfo(Name() + " set ifaddr to ", addr, " with netmask ",
                       tunif.netmask);
        strncpy(tunif.ifaddr, addr.c_str(), sizeof(tunif.ifaddr) - 1);
        return true;
      }
      return Endpoint::SetOption(k, v);
    }

    bool
    TunEndpoint::HasLocalIP(const huint32_t &ip) const
    {
      return m_IPToAddr.find(ip) != m_IPToAddr.end();
    }

    bool
    TunEndpoint::QueueOutboundTraffic(llarp::net::IPv4Packet &&pkt)
    {
      return m_NetworkToUserPktQueue.EmplaceIf(
          [](llarp::net::IPv4Packet &) -> bool { return true; },
          std::move(pkt));
    }

    void
    TunEndpoint::Flush()
    {
      FlushSend();
    }

    bool
    TunEndpoint::HandleHookedDNSMessage(
        dns::Message &&msg, std::function< void(dns::Message) > reply)
    {
      if(msg.questions.size() != 1)
      {
        llarp::LogWarn("bad number of dns questions: ", msg.questions.size());
        return false;
      }
      std::string qname = msg.questions[0].qname;
      if(msg.questions[0].qtype == 15)
      {
        // mx record
        llarp::service::Address addr;
        if(addr.FromString(qname, ".loki"))
          msg.AddMXReply(qname, 1);
        else
          msg.AddNXReply();
        reply(msg);
      }
      else if(msg.questions[0].qtype == 1)
      {
        // forward dns
        llarp::service::Address addr;
        if(qname == "random.snode" || qname == "random.snode.")
        {
          RouterID random;
          if(Router()->GetRandomGoodRouter(random))
            msg.AddCNAMEReply(random.ToString(), 1);
          else
            msg.AddNXReply();
        }
        else if(addr.FromString(qname, ".loki"))
        {
          if(HasAddress(addr))
          {
            huint32_t ip = ObtainIPForAddr(addr, false);
            msg.AddINReply(ip);
          }
          else
          {
            service::Endpoint::PathEnsureHook hook = [&](service::Address addr,
                                                         OutboundContext *ctx) {
              this->SendDNSReply(addr, ctx, std::move(msg), reply);
            };
            return EnsurePathToService(addr, hook, 2000);
          }
        }
        else if(addr.FromString(qname, ".snode"))
        {
          // TODO: add hook to EnsurePathToSNode
          EnsurePathToSNode(addr.as_array());
          huint32_t ip = ObtainIPForAddr(addr, true);
          msg.AddINReply(ip);
        }
        else
          msg.AddNXReply();

        reply(msg);
      }
      else if(msg.questions[0].qtype == 12)
      {
        // reverse dns
        huint32_t ip = {0};
        if(!dns::DecodePTR(msg.questions[0].qname, ip))
        {
          msg.AddNXReply();
          reply(msg);
          return true;
        }
        llarp::service::Address addr(
            ObtainAddrForIP< llarp::service::Address >(ip, true));
        if(!addr.IsZero())
        {
          msg.AddAReply(addr.ToString(".snode"));
          reply(msg);
          return true;
        }
        addr = ObtainAddrForIP< llarp::service::Address >(ip, false);
        if(!addr.IsZero())
        {
          msg.AddAReply(addr.ToString(".loki"));
          reply(msg);
          return true;
        }
        msg.AddNXReply();
        reply(msg);
        return true;
      }
      else
      {
        msg.AddNXReply();
        reply(msg);
      }
      return true;
    }

    bool
    TunEndpoint::ShouldHookDNSMessage(const dns::Message &msg) const
    {
      llarp::service::Address addr;
      if(msg.questions.size() == 1)
      {
        // always hook mx records
        if(msg.questions[0].qtype == llarp::dns::qTypeMX)
          return true;
        if(msg.questions[0].qname == "random.snode"
           || msg.questions[0].qname == "random.snode.")
          return true;
        // always hook .loki
        if(addr.FromString(msg.questions[0].qname, ".loki"))
          return true;
        // always hook .snode
        if(addr.FromString(msg.questions[0].qname, ".snode"))
          return true;
        if(msg.questions[0].qtype == llarp::dns::qTypePTR)
        {
          huint32_t ip = {0};
          if(!dns::DecodePTR(msg.questions[0].qname, ip))
            return false;
          return m_OurRange.Contains(ip);
        }
      }
      return false;
    }

    void
    TunEndpoint::SendDNSReply(service::Address addr,
                              service::Endpoint::OutboundContext *ctx,
                              dns::Message &&request,
                              std::function< void(dns::Message) > reply)
    {
      if(ctx)
      {
        huint32_t ip = ObtainIPForAddr(addr, false);
        request.AddINReply(ip);
      }
      else
        request.AddNXReply();

      reply(request);
    }

    bool
    TunEndpoint::MapAddress(const service::Address &addr, huint32_t ip,
                            bool SNode)
    {
      auto itr = m_IPToAddr.find(ip);
      if(itr != m_IPToAddr.end())
      {
        // XXX is calling inet_ntoa safe in this context? it's MP-unsafe
        llarp::LogWarn(ip, " already mapped to ",
                       service::Address(itr->second.as_array()).ToString());
        return false;
      }
      llarp::LogInfo(Name() + " map ", addr.ToString(), " to ", ip);

      m_IPToAddr[ip]   = addr;
      m_AddrToIP[addr] = ip;
      m_SNodes[addr]   = SNode;
      MarkIPActiveForever(ip);
      return true;
    }

    bool
    TunEndpoint::Start()
    {
      if(!Endpoint::Start())
        return false;
      return SetupNetworking();
    }

    bool
    TunEndpoint::IsSNode() const
    {
      // TODO : implement me
      return false;
    }

    bool
    TunEndpoint::SetupTun()
    {
      if(!llarp_ev_add_tun(EndpointNetLoop(), &tunif))
      {
        llarp::LogError(Name(), " failed to set up tun interface");
        return false;
      }

      struct addrinfo hint, *res = NULL;
      int ret;

      memset(&hint, 0, sizeof hint);

      hint.ai_family = PF_UNSPEC;
      hint.ai_flags  = AI_NUMERICHOST;

      ret = getaddrinfo(tunif.ifaddr, NULL, &hint, &res);
      if(ret)
      {
        llarp::LogError(Name(),
                        " failed to set up tun interface, cant determine "
                        "family from ",
                        tunif.ifaddr);
        return false;
      }

      /*
      // output is in network byte order
      unsigned char buf[sizeof(struct in6_addr)];
      int s = inet_pton(res->ai_family, tunif.ifaddr, buf);
      if (s <= 0)
      {
        llarp::LogError(Name(), " failed to set up tun interface, cant parse
      ", tunif.ifaddr); return false;
      }
      */
      if(res->ai_family == AF_INET6)
      {
        llarp::LogError(Name(),
                        " failed to set up tun interface, we don't support "
                        "IPv6 format");
        return false;
      }
      freeaddrinfo(res);

      struct in_addr addr;  // network byte order
      if(inet_aton(tunif.ifaddr, &addr) == 0)
      {
        llarp::LogError(Name(), " failed to set up tun interface, cant parse ",
                        tunif.ifaddr);
        return false;
      }

      llarp::Addr lAddr(tunif.ifaddr);

      m_OurIP                 = lAddr.xtohl();
      m_NextIP                = m_OurIP;
      m_OurRange.netmask_bits = netmask_ipv4_bits(tunif.netmask);
      m_OurRange.addr         = m_OurIP;
      m_MaxIP                 = m_OurIP | (~m_OurRange.netmask_bits);
      llarp::LogInfo(Name(), " set ", tunif.ifname, " to have address ", lAddr);
      llarp::LogInfo(Name(), " allocated up to ", m_MaxIP, " on range ",
                     m_OurRange);
      MapAddress(m_Identity.pub.Addr(), m_OurIP, IsSNode());
      return true;
    }

    bool
    TunEndpoint::SetupNetworking()
    {
      llarp::LogInfo("Set Up networking for ", Name());
      if(!SetupTun())
      {
        llarp::LogError(Name(), " failed to set up network interface");
        return false;
      }
      if(!m_Resolver.Start(m_LocalResolverAddr, m_UpstreamResolvers))
      {
        llarp::LogError(Name(), " failed to start dns server");
        return false;
      }
      return true;
    }

    void
    TunEndpoint::Tick(llarp_time_t now)
    {
      // call tun code in endpoint logic in case of network isolation
      // EndpointLogic()->queue_job({this, handleTickTun});
      if(m_Exit)
        EnsureRouterIsKnown(m_Exit->Endpoint());
      Endpoint::Tick(now);
    }

    bool
    TunEndpoint::Stop()
    {
      if(m_Exit)
        m_Exit->Stop();
      return llarp::service::Endpoint::Stop();
    }

    void
    TunEndpoint::FlushSend()
    {
      m_UserToNetworkPktQueue.Process([&](net::IPv4Packet &pkt) {
        std::function< bool(llarp_buffer_t) > sendFunc;
        auto itr = m_IPToAddr.find(pkt.dst());
        if(itr == m_IPToAddr.end())
        {
          if(m_Exit && !llarp::IsIPv4Bogon(pkt.dst()))
          {
            pkt.UpdateIPv4PacketOnDst({0}, pkt.dst());
            m_Exit->QueueUpstreamTraffic(std::move(pkt),
                                         llarp::routing::ExitPadSize);
          }
          else
            llarp::LogWarn(Name(), " has no endpoint for ", pkt.dst());
          return true;
        }

        if(m_SNodes.at(itr->second))
        {
          sendFunc = std::bind(&TunEndpoint::SendToSNodeOrQueue, this,
                               itr->second.as_array(), std::placeholders::_1);
        }
        else
        {
          sendFunc = std::bind(&TunEndpoint::SendToServiceOrQueue, this,
                               itr->second.as_array(), std::placeholders::_1,
                               service::eProtocolTraffic);
        }
        // prepare packet for insertion into network
        // this includes clearing IP addresses, recalculating checksums, etc
        pkt.UpdateIPv4PacketOnSrc();

        if(sendFunc && sendFunc(pkt.Buffer()))
          return true;
        llarp::LogWarn(Name(), " did not flush packets");
        return true;
      });
    }

    bool
    TunEndpoint::HandleWriteIPPacket(llarp_buffer_t buf,
                                     std::function< huint32_t(void) > getFromIP)
    {
      // llarp::LogInfo("got packet from ", msg->sender.Addr());
      auto themIP = getFromIP();
      // llarp::LogInfo("themIP ", themIP);
      auto usIP = m_OurIP;
      return m_NetworkToUserPktQueue.EmplaceIf(
          [buf, themIP, usIP](net::IPv4Packet &pkt) -> bool {
            // load
            if(!pkt.Load(buf))
              return false;
            // filter out:
            // - packets smaller than minimal IPv4 header
            // - non-IPv4 packets
            // - packets with weird src/dst addresses
            //   (0.0.0.0/8 but not 0.0.0.0)
            // - packets with 0 src but non-0 dst and oposite
            auto hdr = pkt.Header();
            if(pkt.sz < sizeof(*hdr) || hdr->version != 4
               || (hdr->saddr != 0 && *(byte_t *)&(hdr->saddr) == 0)
               || (hdr->daddr != 0 && *(byte_t *)&(hdr->daddr) == 0)
               || ((hdr->saddr == 0) != (hdr->daddr == 0)))
            {
              return false;
            }

            // update packet to use proper addresses, recalc checksums
            pkt.UpdateIPv4PacketOnDst(themIP, usIP);
            return true;
          });
    }

    huint32_t
    TunEndpoint::GetIfAddr() const
    {
      return m_OurIP;
    }

    huint32_t
    TunEndpoint::ObtainIPForAddr(const AlignedBuffer< 32 > &addr, bool snode)
    {
      llarp_time_t now = Now();
      huint32_t nextIP = {0};
      AlignedBuffer< 32 > ident(addr);
      {
        // previously allocated address
        auto itr = m_AddrToIP.find(ident);
        if(itr != m_AddrToIP.end())
        {
          // mark ip active
          MarkIPActive(itr->second);
          return itr->second;
        }
      }
      // allocate new address
      if(m_NextIP < m_MaxIP)
      {
        do
        {
          nextIP = ++m_NextIP;
        } while(m_IPToAddr.find(nextIP) != m_IPToAddr.end()
                && m_NextIP < m_MaxIP);
        if(nextIP < m_MaxIP)
        {
          m_AddrToIP[ident]  = nextIP;
          m_IPToAddr[nextIP] = ident;
          m_SNodes[ident]    = snode;
          llarp::LogInfo(Name(), " mapped ", ident, " to ", nextIP);
          MarkIPActive(nextIP);
          return nextIP;
        }
      }

      // we are full
      // expire least active ip
      // TODO: prevent DoS
      std::pair< huint32_t, llarp_time_t > oldest = {huint32_t{0}, 0};

      // find oldest entry
      auto itr = m_IPActivity.begin();
      while(itr != m_IPActivity.end())
      {
        if(itr->second <= now)
        {
          if((now - itr->second) > oldest.second)
          {
            oldest.first  = itr->first;
            oldest.second = itr->second;
          }
        }
        ++itr;
      }
      // remap address
      m_IPToAddr[oldest.first] = ident;
      m_AddrToIP[ident]        = oldest.first;
      m_SNodes[ident]          = snode;
      nextIP                   = oldest.first;

      // mark ip active
      m_IPActivity[nextIP] = std::max(m_IPActivity[nextIP], now);

      return nextIP;
    }

    bool
    TunEndpoint::HasRemoteForIP(huint32_t ip) const
    {
      return m_IPToAddr.find(ip) != m_IPToAddr.end();
    }

    void
    TunEndpoint::MarkIPActive(huint32_t ip)
    {
      m_IPActivity[ip] = std::max(Now(), m_IPActivity[ip]);
    }

    void
    TunEndpoint::MarkIPActiveForever(huint32_t ip)
    {
      m_IPActivity[ip] = std::numeric_limits< uint64_t >::max();
    }

    void
    TunEndpoint::TickTun(__attribute__((unused)) llarp_time_t now)
    {
      // called in the isolated thread
    }

    void
    TunEndpoint::tunifBeforeWrite(llarp_tun_io *tun)
    {
      // called in the isolated network thread
      TunEndpoint *self = static_cast< TunEndpoint * >(tun->user);
      // flush user to network
      self->FlushSend();
      // flush exit traffic queues if it's there
      if(self->m_Exit)
        self->m_Exit->Flush();
      // flush snode traffic
      self->FlushSNodeTraffic();
      // flush network to user
      self->m_NetworkToUserPktQueue.Process([tun](net::IPv4Packet &pkt) {
        if(!llarp_ev_tun_async_write(tun, pkt.Buffer()))
          llarp::LogWarn("packet dropped");
      });
    }

    void
    TunEndpoint::tunifRecvPkt(llarp_tun_io *tun, llarp_buffer_t buf)
    {
      // called for every packet read from user in isolated network thread
      TunEndpoint *self = static_cast< TunEndpoint * >(tun->user);
      if(!self->m_UserToNetworkPktQueue.EmplaceIf(
             [buf](net::IPv4Packet &pkt) -> bool {
               return pkt.Load(buf) && pkt.Header()->version == 4;
             }))
      {
        llarp::LogInfo("invalid pkt");
        llarp::DumpBuffer(buf);
      }
    }

    TunEndpoint::~TunEndpoint()
    {
    }

  }  // namespace handlers
}  // namespace llarp