From 4dfa4d70ebb3214c3b404912f7752845ae6a564f Mon Sep 17 00:00:00 2001
From: Matias Fontanini <matias.fontanini@gmail.com>
Date: Wed, 17 Aug 2011 15:12:29 -0300
Subject: [PATCH] DHCP is working. Fixed ip checksum problem.

---
 src/ip.cpp  | 12 ++++--------
 src/tcp.cpp |  6 +++---
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/src/ip.cpp b/src/ip.cpp
index a1d00e5..491e53b 100644
--- a/src/ip.cpp
+++ b/src/ip.cpp
@@ -28,7 +28,6 @@
 #include "rawpdu.h"
 #include "utils.h"
 
-#include <iostream>
 
 using namespace std;
 
@@ -200,16 +199,13 @@ void Tins::IP::write_serialization(uint8_t *buffer, uint32_t total_sz, const PDU
     _ip.protocol = new_flag;
     _ip.tot_len = Utils::net_to_host_s(total_sz);
     _ip.ihl = my_sz / sizeof(uint32_t);
-    if (parent && (_ip.check == 0)) {
-        uint32_t checksum = PDU::do_checksum((uint8_t*)&_ip, ((uint8_t*)&_ip) + sizeof(iphdr));
-        checksum += PDU::do_checksum(buffer + sizeof(iphdr), buffer + total_sz);
+    memcpy(buffer, &_ip, sizeof(iphdr));
+    if (parent && !_ip.check) {
+        uint32_t checksum = PDU::do_checksum(buffer, buffer + sizeof(iphdr));
         while (checksum >> 16)
             checksum = (checksum & 0xffff) + (checksum >> 16);
-        _ip.check = Utils::net_to_host_s(~checksum);
+        ((iphdr*)buffer)->check = Utils::net_to_host_s(~checksum);
     }
-
-    memcpy(buffer, &_ip, sizeof(iphdr));
-
     /* IP Options here... */
     buffer += sizeof(iphdr);
     for (uint32_t i = 0; i < _ip_options.size(); ++i)
diff --git a/src/tcp.cpp b/src/tcp.cpp
index d0a2f46..fea0d5e 100644
--- a/src/tcp.cpp
+++ b/src/tcp.cpp
@@ -151,14 +151,14 @@ void Tins::TCP::write_serialization(uint8_t *buffer, uint32_t total_sz, const PD
     }
 
     const Tins::IP *ip_packet = dynamic_cast<const Tins::IP*>(parent);
+    memcpy(tcp_start, &_tcp, sizeof(tcphdr));
     if(!_tcp.check && ip_packet) {
         uint32_t checksum = PDU::pseudoheader_checksum(ip_packet->source_address(), ip_packet->dest_address(), size(), IPPROTO_TCP) +
-                            PDU::do_checksum(tcp_start + sizeof(tcphdr), tcp_start + total_sz) + PDU::do_checksum((uint8_t*)&_tcp, ((uint8_t*)&_tcp) + sizeof(tcphdr));
+                            PDU::do_checksum(tcp_start, tcp_start + total_sz);
         while (checksum >> 16)
             checksum = (checksum & 0xffff) + (checksum >> 16);
-        _tcp.check = Utils::net_to_host_s(~checksum);
+        ((tcphdr*)tcp_start)->check = Utils::net_to_host_s(~checksum);
     }
-    memcpy(tcp_start, &_tcp, sizeof(tcphdr));
     _tcp.check = 0;
 }