From ef2670dfb479e3a2c73b9c03b19656c5024d2600 Mon Sep 17 00:00:00 2001
From: Stephen Shelton <stephen@stephenashelton.com>
Date: Tue, 19 Nov 2019 09:24:29 -0700
Subject: [PATCH] Drop new inbound IWP sessions when the first packet can't be
 handled

---
 llarp/iwp/linklayer.cpp | 12 ++++++++++--
 llarp/iwp/session.cpp   |  8 +++++++-
 llarp/iwp/session.hpp   |  2 +-
 llarp/link/session.hpp  |  3 ++-
 4 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/llarp/iwp/linklayer.cpp b/llarp/iwp/linklayer.cpp
index 30eee514b..907259b6b 100644
--- a/llarp/iwp/linklayer.cpp
+++ b/llarp/iwp/linklayer.cpp
@@ -78,7 +78,8 @@ namespace llarp
     LinkLayer::RecvFrom(const Addr& from, ILinkSession::Packet_t pkt)
     {
       std::shared_ptr< ILinkSession > session;
-      auto itr = m_AuthedAddrs.find(from);
+      auto itr          = m_AuthedAddrs.find(from);
+      bool isNewSession = false;
       if(itr == m_AuthedAddrs.end())
       {
         ACQUIRE_LOCK(Lock_t lock, m_PendingMutex);
@@ -86,6 +87,7 @@ namespace llarp
         {
           if(not permitInbound)
             return;
+          isNewSession = true;
           m_Pending.insert({from, std::make_shared< Session >(this, from)});
         }
         session = m_Pending.find(from)->second;
@@ -98,7 +100,13 @@ namespace llarp
       }
       if(session)
       {
-        session->Recv_LL(std::move(pkt));
+        bool success = session->Recv_LL(std::move(pkt));
+        if(!success and isNewSession)
+        {
+          LogWarn(
+              "Brand new session failed; removing from pending sessions list");
+          m_Pending.erase(m_Pending.find(from));
+        }
       }
     }
 
diff --git a/llarp/iwp/session.cpp b/llarp/iwp/session.cpp
index 7a7ccabef..7aafab65b 100644
--- a/llarp/iwp/session.cpp
+++ b/llarp/iwp/session.cpp
@@ -805,7 +805,7 @@ namespace llarp
       return m_State == State::Ready;
     }
 
-    void
+    bool
     Session::Recv_LL(ILinkSession::Packet_t data)
     {
       switch(m_State)
@@ -816,9 +816,14 @@ namespace llarp
             // initial data
             // enter introduction phase
             if(DecryptMessageInPlace(data))
+            {
               HandleGotIntro(std::move(data));
+            }
             else
+            {
               LogError("bad intro from ", m_RemoteAddr);
+              return false;
+            }
           }
           else
           {
@@ -844,6 +849,7 @@ namespace llarp
           HandleSessionData(std::move(data));
           break;
       }
+      return true;
     }
   }  // namespace iwp
 }  // namespace llarp
diff --git a/llarp/iwp/session.hpp b/llarp/iwp/session.hpp
index 657b153b9..7e19d43d5 100644
--- a/llarp/iwp/session.hpp
+++ b/llarp/iwp/session.hpp
@@ -72,7 +72,7 @@ namespace llarp
       void
       Close() override;
 
-      void Recv_LL(ILinkSession::Packet_t) override;
+      bool Recv_LL(ILinkSession::Packet_t) override;
 
       bool
       SendKeepAlive() override;
diff --git a/llarp/link/session.hpp b/llarp/link/session.hpp
index 572ac9b0b..8c81a5a1f 100644
--- a/llarp/link/session.hpp
+++ b/llarp/link/session.hpp
@@ -61,8 +61,9 @@ namespace llarp
 
     /// recv packet on low layer
     /// not used by utp
-    virtual void Recv_LL(Packet_t)
+    virtual bool Recv_LL(Packet_t)
     {
+      return true;
     }
 
     /// send a keepalive to the remote endpoint