From 4f691b8974c64bd8dca04772638a5ed2923f3988 Mon Sep 17 00:00:00 2001
From: Jeff Becker <jeff@i2p.rocks>
Date: Sun, 16 Sep 2018 08:06:19 -0400
Subject: [PATCH] make tun write correct number of bytes

try doing correct ip checksum and for upper layers that need it too

supported right now are icmp, tcp, and udp. more will come later
probably.
---
 llarp/handlers/tun.cpp     |  5 ++--
 llarp/ip.cpp               | 47 ++++++++++++++++++++++++++------------
 llarp/service/endpoint.cpp | 13 +++++++----
 llarp/service/protocol.cpp |  2 +-
 4 files changed, 44 insertions(+), 23 deletions(-)

diff --git a/llarp/handlers/tun.cpp b/llarp/handlers/tun.cpp
index ae6d57e6f..7d296d348 100644
--- a/llarp/handlers/tun.cpp
+++ b/llarp/handlers/tun.cpp
@@ -209,14 +209,15 @@ namespace llarp
       uint32_t usIP   = m_OurIP;
       auto buf        = llarp::Buffer(msg->payload);
       net::IPv4Packet pkt;
-      memcpy(pkt.buf, buf.base, std::min(buf.sz, sizeof(pkt.buf)));
+      pkt.sz = std::min(buf.sz, sizeof(pkt.buf));
+      memcpy(pkt.buf, buf.base, pkt.sz);
       pkt.src(themIP);
       pkt.dst(usIP);
       pkt.UpdateChecksum();
       llarp::LogInfo(Name(), " handle data message ", msg->payload.size(),
                      " bytes from ", inet_ntoa({htonl(themIP)}));
-
       llarp_ev_tun_async_write(&tunif, pkt.buf, pkt.sz);
+
       /*
       if(!m_NetworkToUserPktQueue.EmplaceIf(
              [buf, themIP, usIP](net::IPv4Packet &pkt) -> bool {
diff --git a/llarp/ip.cpp b/llarp/ip.cpp
index b83e7b3a5..2ec9023f1 100644
--- a/llarp/ip.cpp
+++ b/llarp/ip.cpp
@@ -3,6 +3,8 @@
 #include <llarp/ip.hpp>
 #include "llarp/buffer.hpp"
 #include "mem.hpp"
+#include <netinet/in.h>
+#include <map>
 
 namespace llarp
 {
@@ -26,29 +28,44 @@ namespace llarp
       return llarp::InitBuffer(buf, sz);
     }
 
-    void
-    IPv4Packet::UpdateChecksum()
-    {
-      auto hdr   = Header();
-      hdr->check = 0;
+    /// bytes offset to checksum relative to end of ip header for each protocol
+    static std::map< byte_t, uint16_t > protoChecksumOffsets = {
+        {IPPROTO_TCP, 16}, {IPPROTO_ICMP, 2}, {IPPROTO_UDP, 6}};
 
-      size_t count = hdr->ihl;
+    static uint16_t
+    ipchksum(const byte_t *buf, size_t sz)
+    {
       uint32_t sum = 0;
-      byte_t *addr = buf;
-
-      while(count > 1)
+      while(sz > 1)
       {
-        sum += *(uint16_t *)addr;
-        count -= sizeof(uint16_t);
-        addr += sizeof(uint16_t);
+        sum += *(const uint16_t *)buf;
+        sz -= sizeof(uint16_t);
+        buf += sizeof(uint16_t);
       }
-      if(count > 0)
-        sum += *(byte_t *)addr;
+      if(sz > 0)
+        sum += *(const byte_t *)buf;
 
       while(sum >> 16)
         sum = (sum & 0xffff) + (sum >> 16);
 
-      hdr->check = ~sum;
+      return ~sum;
+    }
+
+    void
+    IPv4Packet::UpdateChecksum()
+    {
+      auto hdr   = Header();
+      hdr->check = 0;
+      auto len   = hdr->ihl * 4;
+      hdr->check = ipchksum(buf, len);
+
+      auto itr = protoChecksumOffsets.find(hdr->protocol);
+      if(itr != protoChecksumOffsets.end())
+      {
+        uint16_t *check = (uint16_t *)(buf + len + itr->second);
+        *check          = 0;
+        *check          = ipchksum(buf, sz);
+      }
     }
 
   }  // namespace net
diff --git a/llarp/service/endpoint.cpp b/llarp/service/endpoint.cpp
index 434fcb25a..88471e93f 100644
--- a/llarp/service/endpoint.cpp
+++ b/llarp/service/endpoint.cpp
@@ -820,7 +820,7 @@ namespace llarp
     Endpoint::OutboundContext::OnIntroSetUpdate(const Address& addr,
                                                 const IntroSet* i)
     {
-      if(i && addr == i->A.Addr() && currentIntroSet.OtherIsNewer(*i))
+      if(i)
       {
         currentIntroSet = *i;
         ShiftIntroduction();
@@ -837,8 +837,9 @@ namespace llarp
         auto itr = m_AddressToService.find(remote);
         if(itr != m_AddressToService.end())
         {
-          ProtocolFrame f;
-          path::Path* p = nullptr;
+          routing::PathTransferMessage transfer;
+          ProtocolFrame& f = transfer.T;
+          path::Path* p    = nullptr;
           std::set< ConvoTag > tags;
           if(!GetConvoTagsForService(itr->second, tags))
           {
@@ -869,18 +870,20 @@ namespace llarp
             return false;
           }
           ProtocolMessage m(f.T);
-          m.PutBuffer(data);
           m.proto      = t;
           m.introReply = p->intro;
           m.sender     = m_Identity.pub;
+          m.PutBuffer(data);
           f.N.Randomize();
+          f.S = GetSeqNoForConvo(f.T);
           f.C.Zero();
+          transfer.Y.Randomize();
+          transfer.P = intro.pathID;
           if(!f.EncryptAndSign(&Router()->crypto, m, K, m_Identity))
           {
             llarp::LogError("failed to encrypt and sign");
             return false;
           }
-          routing::PathTransferMessage transfer(f, intro.pathID);
           return p->SendRoutingMessage(&transfer, Router());
         }
       }
diff --git a/llarp/service/protocol.cpp b/llarp/service/protocol.cpp
index a4fb75434..dcf5fe1c4 100644
--- a/llarp/service/protocol.cpp
+++ b/llarp/service/protocol.cpp
@@ -248,7 +248,7 @@ namespace llarp
         if(!self->frame->Verify(crypto, self->msg->sender))
         {
           llarp::LogError("intro frame has invalid signature Z=",
-                          self->frame->Z, " from ", self->msg->sender);
+                          self->frame->Z, " from ", self->msg->sender.Addr());
           delete self->msg;
           delete self;
           return;