From b004b9e2a18bf6425d25e41257fd38954d82bf6e Mon Sep 17 00:00:00 2001
From: Jeff Becker <jeff@i2p.rocks>
Date: Wed, 28 Nov 2018 07:32:38 -0500
Subject: [PATCH] fix up exit logic

---
 include/llarp/aligned.hpp       |  2 +-
 include/llarp/exit/endpoint.hpp |  5 +++++
 include/llarp/handlers/exit.hpp |  3 +++
 llarp/exit/endpoint.cpp         | 11 +++++++++++
 llarp/handlers/exit.cpp         | 26 ++++++++++++++++++--------
 5 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/include/llarp/aligned.hpp b/include/llarp/aligned.hpp
index dc63e5635..f5ee817d7 100644
--- a/include/llarp/aligned.hpp
+++ b/include/llarp/aligned.hpp
@@ -19,7 +19,7 @@ extern "C"
 }
 namespace llarp
 {
-  /// aligned buffer, aligns to the nears Long_t
+  /// aligned buffer that is sz bytes long and aligns to the nears Long_t
   template < size_t sz, bool randomize = false, typename Long_t = uint64_t >
   struct AlignedBuffer
   {
diff --git a/include/llarp/exit/endpoint.hpp b/include/llarp/exit/endpoint.hpp
index fd101cfab..251dd5851 100644
--- a/include/llarp/exit/endpoint.hpp
+++ b/include/llarp/exit/endpoint.hpp
@@ -35,6 +35,10 @@ namespace llarp
       bool
       ExpiresSoon(llarp_time_t now, llarp_time_t dlt = 5000) const;
 
+      /// return true if this endpoint looks dead right now
+      bool 
+      LooksDead(llarp_time_t now, llarp_time_t timeout = 10000) const;
+
       /// tick ourself, reset tx/rx rates
       void
       Tick(llarp_time_t now);
@@ -92,6 +96,7 @@ namespace llarp
       llarp::PathID_t m_CurrentPath;
       llarp::huint32_t m_IP;
       uint64_t m_TxRate, m_RxRate;
+      llarp_time_t m_LastActive;
       bool m_RewriteSource;
     };
   }  // namespace exit
diff --git a/include/llarp/handlers/exit.hpp b/include/llarp/handlers/exit.hpp
index 14f78f381..94613956c 100644
--- a/include/llarp/handlers/exit.hpp
+++ b/include/llarp/handlers/exit.hpp
@@ -44,6 +44,9 @@ namespace llarp
       llarp_router*
       Router();
 
+      llarp_time_t
+      Now() const;
+
       llarp_crypto*
       Crypto();
 
diff --git a/llarp/exit/endpoint.cpp b/llarp/exit/endpoint.cpp
index c50b81bf7..c990964cd 100644
--- a/llarp/exit/endpoint.cpp
+++ b/llarp/exit/endpoint.cpp
@@ -14,6 +14,7 @@ namespace llarp
         , m_IP(ip)
         , m_RewriteSource(rewriteIP)
     {
+      m_LastActive = parent->Now();
     }
 
     Endpoint::~Endpoint()
@@ -65,6 +66,15 @@ namespace llarp
       return true;
     }
 
+    bool Endpoint::LooksDead(llarp_time_t now, llarp_time_t timeout) const 
+    {
+      if(ExpiresSoon(now, timeout))
+        return true;
+      if (now > m_LastActive)
+        return now - m_LastActive > timeout;
+      return true;
+    }
+
     bool
     Endpoint::SendOutboundTraffic(llarp_buffer_t buf)
     {
@@ -83,6 +93,7 @@ namespace llarp
         return false;
       }
       m_TxRate += buf.sz;
+      m_LastActive = m_Parent->Now();
       return true;
     }
 
diff --git a/llarp/handlers/exit.cpp b/llarp/handlers/exit.cpp
index ff42293c4..b9a2dec8f 100644
--- a/llarp/handlers/exit.cpp
+++ b/llarp/handlers/exit.cpp
@@ -37,10 +37,16 @@ namespace llarp
     {
     }
 
+    llarp_time_t 
+    ExitEndpoint::Now() const
+    {
+      return m_Router->Now();
+    }
+
     void
     ExitEndpoint::FlushInbound()
     {
-      auto now = Router()->Now();
+      auto now = Now();
       m_InetToNetwork.Process([&](Pkt_t &pkt) {
         llarp::PubKey pk;
         {
@@ -58,23 +64,27 @@ namespace llarp
         auto range                = m_ActiveExits.equal_range(pk);
         auto itr                  = range.first;
         uint64_t min              = std::numeric_limits< uint64_t >::max();
-        /// pick path with lowest rx rate
+        /// pick non dead looking path with lowest tx rate
         while(itr != range.second)
         {
-          if(ep == nullptr)
-            ep = itr->second.get();
-          else if(itr->second->RxRate() < min && !itr->second->ExpiresSoon(now))
+          if(itr->second->TxRate() < min && !itr->second->LooksDead(now))
           {
-            min = ep->RxRate();
             ep  = itr->second.get();
+            min = ep->TxRate();
           }
           ++itr;
         }
-        if(ep)
+        
+        if(ep == nullptr)
+        {
+          // we may have all dead sessions, wtf now?
+          llarp::LogWarn(Name(), " dropped inbound traffic for session ", pk, " as we have no working endpoints");
+        }
+        else
         {
           if(!ep->SendInboundTraffic(pkt.Buffer()))
           {
-            llarp::LogWarn(Name(), " dropped inbound traffic for session ", pk);
+            llarp::LogWarn(Name(), " dropped inbound traffic for session ", pk, " as we are overloaded (probably)");
           }
         }
       });