From c736a9838b5523608cb0c0120fb3d3f9c463e4a7 Mon Sep 17 00:00:00 2001
From: Baptiste Wicht <baptiste.wicht@gmail.com>
Date: Sun, 10 Jul 2016 17:27:12 +0200
Subject: [PATCH] Basic IP decoding

---
 kernel/include/ip_layer.hpp   | 22 ++++++++++++++
 kernel/src/ethernet_layer.cpp |  3 +-
 kernel/src/ip_layer.cpp       | 54 +++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 kernel/src/ip_layer.cpp

diff --git a/kernel/include/ip_layer.hpp b/kernel/include/ip_layer.hpp
index 171a637a..70d635c6 100644
--- a/kernel/include/ip_layer.hpp
+++ b/kernel/include/ip_layer.hpp
@@ -10,6 +10,8 @@
 
 #include <types.hpp>
 
+#include "network.hpp"
+
 namespace network {
 
 namespace ip {
@@ -19,6 +21,9 @@ namespace ip {
 struct address {
     uint32_t raw_address = 0;
 
+    address(){}
+    address(uint32_t raw) : raw_address(raw) {}
+
     uint8_t operator()(size_t index) const {
         return (raw_address >> ((3 - index) * 8)) & 0xFF;
     }
@@ -41,6 +46,23 @@ inline address make_address(uint8_t a, uint8_t b, uint8_t c, uint8_t d){
     return addr;
 }
 
+struct header {
+    uint8_t version_ihl;
+    uint8_t dscp_ecn;
+    uint16_t total_len;
+    uint16_t identification;
+    uint16_t flags_offset;
+    uint8_t ttl;
+    uint8_t protocol;
+    uint16_t header_checksum;
+    uint32_t source_ip;
+    uint32_t target_ip;
+} __attribute__((packed));
+
+static_assert(sizeof(header) == 20, "The size of an IPv4 header must be 20 bytes");
+
+void decode(network::interface_descriptor& interface, network::ethernet::packet& packet);
+
 } // end of ip namespace
 
 } // end of network namespace
diff --git a/kernel/src/ethernet_layer.cpp b/kernel/src/ethernet_layer.cpp
index a90b92b3..b38076c0 100644
--- a/kernel/src/ethernet_layer.cpp
+++ b/kernel/src/ethernet_layer.cpp
@@ -12,6 +12,7 @@
 #include "logging.hpp"
 #include "kernel_utils.hpp"
 #include "arp_layer.hpp"
+#include "ip_layer.hpp"
 
 namespace {
 
@@ -70,7 +71,7 @@ void network::ethernet::decode(network::interface_descriptor& interface, packet&
 
     switch(packet.type){
         case ether_type::IPV4:
-            logging::logf(logging::log_level::TRACE, "ethernet: IPV4 Packet (unsupported)\n");
+            network::ip::decode(interface, packet);
             break;
         case ether_type::IPV6:
             logging::logf(logging::log_level::TRACE, "ethernet: IPV6 Packet (unsupported)\n");
diff --git a/kernel/src/ip_layer.cpp b/kernel/src/ip_layer.cpp
new file mode 100644
index 00000000..b458a5cb
--- /dev/null
+++ b/kernel/src/ip_layer.cpp
@@ -0,0 +1,54 @@
+//=======================================================================
+// Copyright Baptiste Wicht 2013-2016.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//=======================================================================
+
+#include <vector.hpp>
+#include <string.hpp>
+
+#include "ip_layer.hpp"
+#include "logging.hpp"
+#include "kernel_utils.hpp"
+
+void network::ip::decode(network::interface_descriptor& interface, network::ethernet::packet& packet){
+    header* arp_header = reinterpret_cast<header*>(packet.payload + packet.index);
+
+    logging::logf(logging::log_level::TRACE, "ip: Start IPv4 packet handling\n");
+
+    auto version = arp_header->version_ihl >> 4;
+
+    if(version != 4){
+        logging::logf(logging::log_level::ERROR, "ip: IPv6 Packet received instead of IPv4\n");
+
+        return;
+    }
+
+    auto ihl = arp_header->version_ihl & 0xF;
+    auto length = switch_endian_16(arp_header->total_len);
+    auto data_length = length - ihl * 4;
+
+    logging::logf(logging::log_level::TRACE, "ip: Data Length: %u\n", size_t(data_length));
+    logging::logf(logging::log_level::TRACE, "ip: Time To Live: %u\n", size_t(arp_header->ttl));
+
+    network::ip::address source(switch_endian_32(arp_header->source_ip));
+    network::ip::address target(switch_endian_32(arp_header->target_ip));
+
+    logging::logf(logging::log_level::TRACE, "ip: Source Protocol Address %u.%u.%u.%u \n",
+        uint64_t(source(0)), uint64_t(source(1)), uint64_t(source(2)), uint64_t(source(3)));
+    logging::logf(logging::log_level::TRACE, "ip: Target Protocol Address %u.%u.%u.%u \n",
+        uint64_t(target(0)), uint64_t(target(1)), uint64_t(target(2)), uint64_t(target(3)));
+
+    auto protocol = arp_header->protocol;
+
+    if(protocol == 0x01){
+        logging::logf(logging::log_level::DEBUG, "ip: ICMP packet detected\n");
+    } else if(protocol == 0x06){
+        logging::logf(logging::log_level::ERROR, "ip: TCP packet detected (unsupported)\n");
+    } else if(protocol == 0x11){
+        logging::logf(logging::log_level::ERROR, "ip: UDP packet detected (unsupported)\n");
+    } else {
+        logging::logf(logging::log_level::ERROR, "ip: Packet of unknown protocol detected (%h)\n", size_t(protocol));
+    }
+}