From a8964a6d8a109573ee476536211ce989f8aaab54 Mon Sep 17 00:00:00 2001
From: Jeff Becker <jeff@i2p.rocks>
Date: Fri, 4 Jun 2021 07:15:00 -0400
Subject: [PATCH] add idempotent wake up for sending messages to the network
 and writing packets on interfaces

---
 llarp/handlers/tun.cpp | 11 +++++++++++
 llarp/handlers/tun.hpp |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/llarp/handlers/tun.cpp b/llarp/handlers/tun.cpp
index 0c00583ad..6feee9b1f 100644
--- a/llarp/handlers/tun.cpp
+++ b/llarp/handlers/tun.cpp
@@ -67,6 +67,8 @@ namespace llarp
         : service::Endpoint(r, parent)
         , m_UserToNetworkPktQueue("endpoint_sendq", r->loop(), r->loop())
     {
+      m_PacketSendWaker = r->loop()->make_waker([this]() { FlushWrite(); });
+      m_MessageSendWaker = r->loop()->make_waker([this]() { FlushSend(); });
       m_PacketRouter = std::make_unique<vpn::PacketRouter>(
           [this](net::IPPacket pkt) { HandleGotUserPacket(std::move(pkt)); });
 #ifdef ANDROID
@@ -224,6 +226,12 @@ namespace llarp
     {
       FlushSend();
       Pump(Now());
+      FlushWrite();
+    }
+
+    void
+    TunEndpoint::FlushWrite()
+    {
       // flush network to user
       while (not m_NetworkToUserPktQueue.empty())
       {
@@ -1144,6 +1152,8 @@ namespace llarp
         pkt.UpdateIPv6Address(src, dst);
       }
       m_NetworkToUserPktQueue.push(std::move(write));
+      // wake up packet flushing event so we ensure that all packets are written to user
+      m_PacketSendWaker->Trigger();
       return true;
     }
 
@@ -1252,6 +1262,7 @@ namespace llarp
     TunEndpoint::HandleGotUserPacket(net::IPPacket pkt)
     {
       m_UserToNetworkPktQueue.Emplace(std::move(pkt));
+      m_MessageSendWaker->Trigger();
     }
 
     TunEndpoint::~TunEndpoint() = default;
diff --git a/llarp/handlers/tun.hpp b/llarp/handlers/tun.hpp
index 2f0679485..0e614a8f6 100644
--- a/llarp/handlers/tun.hpp
+++ b/llarp/handlers/tun.hpp
@@ -209,6 +209,10 @@ namespace llarp
       virtual void
       FlushSend();
 
+      /// 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)
@@ -275,6 +279,11 @@ namespace llarp
       std::set<IPRange> m_OwnedRanges;
       /// how long to wait for path alignment
       llarp_time_t m_PathAlignmentTimeout;
+      /// idempotent wakeup for writing packets to user
+      std::shared_ptr<EventLoopWakeup> m_PacketSendWaker;
+
+      /// idempotent wakeup for writing messages to network
+      std::shared_ptr<EventLoopWakeup> m_MessageSendWaker;
     };
 
   }  // namespace handlers