From 3eef5e0699f60db7fbdb0fd439305142c21167e7 Mon Sep 17 00:00:00 2001
From: Baptiste Wicht <baptiste.wicht@gmail.com>
Date: Sun, 11 Sep 2016 11:05:46 +0200
Subject: [PATCH] Prepare DNS decoding

---
 kernel/include/net/dns_layer.hpp | 49 ++++++++++++++++++++++++++++++++
 kernel/src/net/dns_layer.cpp     | 41 ++++++++++++++++++++++++++
 kernel/src/net/udp_layer.cpp     |  7 +++--
 3 files changed, 95 insertions(+), 2 deletions(-)
 create mode 100644 kernel/include/net/dns_layer.hpp
 create mode 100644 kernel/src/net/dns_layer.cpp

diff --git a/kernel/include/net/dns_layer.hpp b/kernel/include/net/dns_layer.hpp
new file mode 100644
index 00000000..0b2f2f3a
--- /dev/null
+++ b/kernel/include/net/dns_layer.hpp
@@ -0,0 +1,49 @@
+//=======================================================================
+// Copyright Baptiste Wicht 2013-2016.
+// Distributed under the terms of the MIT License.
+// (See accompanying file LICENSE or copy at
+//  http://www.opensource.org/licenses/MIT)
+//=======================================================================
+
+#ifndef NET_DNS_LAYER_H
+#define NET_DNS_LAYER_H
+
+#include <types.hpp>
+
+#include "net/ethernet_layer.hpp"
+#include "net/ip_layer.hpp"
+#include "net/network.hpp"
+
+namespace network {
+
+namespace dns {
+
+struct flags_t {
+    uint8_t qr : 1;
+    uint8_t opcode : 4;
+    uint8_t aa : 1;
+    uint8_t tc : 1;
+    uint8_t rd : 1;
+    uint8_t ra : 1;
+    uint8_t zeroes : 3;
+    uint8_t rcode : 4;
+} __attribute__((packed));
+
+static_assert(sizeof(flags_t) == 2, "DNS flags must be 16 bits");
+
+struct header {
+    uint16_t identification;
+    flags_t flags;
+    uint16_t questions;
+    uint16_t answers;
+    uint16_t authority_rrs;
+    uint16_t additional_rrs;
+} __attribute__((packed));
+
+void decode(network::interface_descriptor& interface, network::ethernet::packet& packet);
+
+} // end of dns namespace
+
+} // end of network namespace
+
+#endif
diff --git a/kernel/src/net/dns_layer.cpp b/kernel/src/net/dns_layer.cpp
new file mode 100644
index 00000000..7044a582
--- /dev/null
+++ b/kernel/src/net/dns_layer.cpp
@@ -0,0 +1,41 @@
+//=======================================================================
+// Copyright Baptiste Wicht 2013-2016.
+// Distributed under the terms of the MIT License.
+// (See accompanying file LICENSE or copy at
+//  http://www.opensource.org/licenses/MIT)
+//=======================================================================
+
+#include "net/dns_layer.hpp"
+
+#include "kernel_utils.hpp"
+
+namespace {
+
+
+} //end of anonymous namespace
+
+void network::dns::decode(network::interface_descriptor& /*interface*/, network::ethernet::packet& packet){
+    packet.tag(3, packet.index);
+
+    auto* dns_header = reinterpret_cast<header*>(packet.payload + packet.index);
+
+    logging::logf(logging::log_level::TRACE, "dns: Start DNS packet handling\n");
+
+    auto identification = switch_endian_16(dns_header->identification);
+    auto questions      = switch_endian_16(dns_header->questions);
+    auto answers        = switch_endian_16(dns_header->answers);
+
+    logging::logf(logging::log_level::TRACE, "dns: Identification %h \n", size_t(identification));
+    logging::logf(logging::log_level::TRACE, "dns: Questions %h \n", size_t(questions));
+    logging::logf(logging::log_level::TRACE, "dns: Answers %h \n", size_t(answers));
+
+    auto flags = dns_header->flags;
+
+    if(flags.qr){
+        logging::logf(logging::log_level::TRACE, "dns: Query\n");
+    } else {
+        logging::logf(logging::log_level::TRACE, "dns: Response\n");
+    }
+
+    //TODO
+}
diff --git a/kernel/src/net/udp_layer.cpp b/kernel/src/net/udp_layer.cpp
index 714a85ed..8106c065 100644
--- a/kernel/src/net/udp_layer.cpp
+++ b/kernel/src/net/udp_layer.cpp
@@ -6,6 +6,7 @@
 //=======================================================================
 
 #include "net/udp_layer.hpp"
+#include "net/dns_layer.hpp"
 
 #include "kernel_utils.hpp"
 
@@ -69,7 +70,7 @@ void prepare_packet(network::ethernet::packet& packet, size_t source, size_t tar
 
 } //end of anonymous namespace
 
-void network::udp::decode(network::interface_descriptor& /*interface*/, network::ethernet::packet& packet){
+void network::udp::decode(network::interface_descriptor& interface, network::ethernet::packet& packet){
     packet.tag(2, packet.index);
 
     auto* udp_header = reinterpret_cast<header*>(packet.payload + packet.index);
@@ -84,8 +85,10 @@ void network::udp::decode(network::interface_descriptor& /*interface*/, network:
     logging::logf(logging::log_level::TRACE, "udp: Target Port %h \n", target_port);
     logging::logf(logging::log_level::TRACE, "udp: Length %h \n", length);
 
+    packet.index += sizeof(header);
+
     if(target_port == 53){
-        //TODO DNS decoding
+        network::dns::decode(interface, packet);
     }
 }