lokinet/llarp/handlers/tun.cpp

#include <llarp/handlers/tun.hpp>
#include "router.hpp"

namespace llarp
{
  namespace handlers
  {
    TunEndpoint::TunEndpoint(const std::string &nickname, llarp_router *r)
        : service::Endpoint(nickname, r)
        , m_UserToNetworkPktQueue(nickname + "_sendq")
        , m_NetworkToUserPktQueue(nickname + "_recvq")
    {
      tunif.user    = this;
      tunif.netmask = DefaultTunNetmask;
      strncpy(tunif.ifaddr, DefaultTunSrcAddr, sizeof(tunif.ifaddr) - 1);
      strncpy(tunif.ifname, DefaultTunIfname, sizeof(tunif.ifname) - 1);
      tunif.tick         = nullptr;
      tunif.before_write = &tunifBeforeWrite;
      tunif.recvpkt      = &tunifRecvPkt;
    }

    bool
    TunEndpoint::SetOption(const std::string &k, const std::string &v)
    {
      if(k == "ifname")
      {
        strncpy(tunif.ifname, v.c_str(), sizeof(tunif.ifname) - 1);
        return true;
      }
      if(k == "ifaddr")
      {
        std::string addr;
        auto pos = v.find("/");
        if(pos != std::string::npos)
        {
          auto num = std::stoi(v.substr(pos + 1));
          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;
        }
        strncpy(tunif.ifaddr, addr.c_str(), sizeof(tunif.ifaddr) - 1);
        return true;
      }
      return Endpoint::SetOption(k, v);
    }

    bool
    TunEndpoint::Start()
    {
      // do network isolation first
      if(!Endpoint::Start())
        return false;

      if(!NetworkIsIsolated())
      {
        // set up networking in currrent thread if we are not isolated
        if(!SetupNetworking())
          return false;
      }
      // wait for result for network setup
      llarp::LogInfo("waiting for tun interface...");
      return m_TunSetupResult.get_future().get();
    }

    constexpr uint32_t
    netmask_ipv4_bits(uint32_t netmask)
    {
      return (32 - netmask)
          ? (1 << (32 - (netmask + 1))) | netmask_ipv4_bits(netmask + 1)
          : 0;
    }

    bool
    TunEndpoint::SetupTun()
    {
      if(!llarp_ev_add_tun(EndpointNetLoop(), &tunif))
      {
        llarp::LogError(Name(), " failed to set up tun interface");
        return false;
      }
      m_OurIP       = inet_addr(tunif.ifaddr);
      m_NextIP      = m_OurIP;
      uint32_t mask = tunif.netmask;

      uint32_t baseaddr = (ntohs(m_OurIP) & netmask_ipv4_bits(mask));
      m_MaxIP           = (ntohs(baseaddr) | ~ntohs(netmask_ipv4_bits(mask)));
      char buf[128]     = {0};
      llarp::LogInfo(Name(), " set ", tunif.ifname, " to have address ",
                     inet_ntop(AF_INET, &m_OurIP, buf, sizeof(buf)));

      llarp::LogInfo(Name(), " allocated up to ",
                     inet_ntop(AF_INET, &m_MaxIP, buf, sizeof(buf)));
      return true;
    }

    bool
    TunEndpoint::SetupNetworking()
    {
      llarp::LogInfo("Set Up networking for ", Name());
      bool result = SetupTun();
      m_TunSetupResult.set_value(result);
      return result;
    }

    void
    TunEndpoint::Tick(llarp_time_t now)
    {
      // call tun code in endpoint logic in case of network isolation
      llarp_logic_queue_job(EndpointLogic(), {this, handleTickTun});
      Endpoint::Tick(now);
    }

    void
    TunEndpoint::HandleDataMessage(service::ProtocolMessage *msg)
    {
      if(msg->proto != service::eProtocolTraffic)
      {
        llarp::LogWarn("dropping unwarrented message, not ip traffic, proto=",
                       msg->proto);
        return;
      }
      uint32_t themIP = ObtainIPForAddr(msg->sender.Addr());
      uint32_t usIP   = m_OurIP;
      auto buf        = llarp::Buffer(msg->payload);
      if(!m_NetworkToUserPktQueue.EmplaceIf(
             [buf, themIP, usIP](net::IPv4Packet *pkt) -> bool {
               // do packet info rewrite here
               // TODO: don't truncate packet here
               memcpy(pkt->buf, buf.base, std::min(buf.sz, sizeof(pkt->buf)));
               pkt->src(themIP);
               pkt->dst(usIP);
               pkt->UpdateChecksum();
               return true;
             }))
      {
        llarp::LogWarn("failed to parse buffer for ip traffic");
        llarp::DumpBuffer(buf);
      }
    }

    uint32_t
    TunEndpoint::ObtainIPForAddr(const service::Address &addr)
    {
      {
        // previously allocated address
        auto itr = m_AddrToIP.find(addr);
        if(itr != m_AddrToIP.end())
          return itr->second;
      }
      llarp_time_t now = llarp_time_now_ms();
      uint32_t nextIP;
      if(m_NextIP < m_MaxIP)
      {
        nextIP = ++m_NextIP;
        m_AddrToIP.insert(std::make_pair(addr, nextIP));
        m_IPToAddr.insert(std::make_pair(nextIP, addr));
      }
      else
      {
        // we are full
        // expire least active ip
        // TODO: prevent DoS
        std::pair< uint32_t, llarp_time_t > oldest = {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] = addr;
        m_AddrToIP[addr]         = oldest.first;
        nextIP                   = oldest.first;
      }

      // mark ip active
      m_IPActivity[nextIP] = now;

      return nextIP;
    }

    bool
    TunEndpoint::HasRemoteForIP(const uint32_t &ip) const
    {
      return m_IPToAddr.find(ip) != m_IPToAddr.end();
    }

    void
    TunEndpoint::MarkIPActive(uint32_t ip)
    {
      m_IPActivity[ip] = llarp_time_now_ms();
    }

    void
    TunEndpoint::handleTickTun(void *u)
    {
      auto now          = llarp_time_now_ms();
      TunEndpoint *self = static_cast< TunEndpoint * >(u);
      self->TickTun(now);
    }

    void
    TunEndpoint::TickTun(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);
      self->m_NetworkToUserPktQueue.Process(
          [tun](const std::unique_ptr< net::IPv4Packet > &pkt) {
            if(!llarp_ev_tun_async_write(tun, pkt->buf, pkt->sz))
              llarp::LogWarn("packet dropped");
          });
    }

    void
    TunEndpoint::tunifRecvPkt(llarp_tun_io *tun, const void *buf, ssize_t sz)
    {
      // called for every packet read from user in isolated network thread
      TunEndpoint *self = static_cast< TunEndpoint * >(tun->user);
      llarp::LogDebug("got pkt ", sz, " bytes");
      if(!self->m_UserToNetworkPktQueue.EmplaceIf(
             [buf, sz](net::IPv4Packet *pkt) -> bool {
               return pkt->Load(llarp::InitBuffer(buf, sz));
             }))
        llarp::LogError("Failed to parse ipv4 packet");
    }

    TunEndpoint::~TunEndpoint()
    {
    }

  }  // namespace handlers
}  // namespace llarp