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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Sergey Bugaev <bugaevc@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "DNSPacket.h"
#include "DNSName.h"
#include "DNSPacketHeader.h"
#include <AK/Debug.h>
#include <AK/MemoryStream.h>
#include <AK/StringBuilder.h>
#include <arpa/inet.h>
#include <stdlib.h>
namespace LookupServer {
void DNSPacket::add_question(DNSQuestion const& question)
{
m_questions.empend(question);
VERIFY(m_questions.size() <= UINT16_MAX);
}
void DNSPacket::add_answer(DNSAnswer const& answer)
{
m_answers.empend(answer);
VERIFY(m_answers.size() <= UINT16_MAX);
}
ByteBuffer DNSPacket::to_byte_buffer() const
{
DNSPacketHeader header;
header.set_id(m_id);
if (is_query())
header.set_is_query();
else
header.set_is_response();
header.set_authoritative_answer(m_authoritative_answer);
// FIXME: What should this be?
header.set_opcode(0);
header.set_response_code(m_code);
header.set_truncated(false); // hopefully...
header.set_recursion_desired(m_recursion_desired);
// FIXME: what should the be for requests?
header.set_recursion_available(m_recursion_available);
header.set_question_count(m_questions.size());
header.set_answer_count(m_answers.size());
DuplexMemoryStream stream;
stream << ReadonlyBytes { &header, sizeof(header) };
for (auto& question : m_questions) {
stream << question.name();
stream << htons((u16)question.record_type());
stream << htons(question.raw_class_code());
}
for (auto& answer : m_answers) {
stream << answer.name();
stream << htons((u16)answer.type());
stream << htons(answer.raw_class_code());
stream << htonl(answer.ttl());
if (answer.type() == DNSRecordType::PTR) {
DNSName name { answer.record_data() };
stream << htons(name.serialized_size());
stream << name;
} else {
stream << htons(answer.record_data().length());
stream << answer.record_data().bytes();
}
}
return stream.copy_into_contiguous_buffer();
}
class [[gnu::packed]] DNSRecordWithoutName {
public:
DNSRecordWithoutName() = default;
u16 type() const { return m_type; }
u16 record_class() const { return m_class; }
u32 ttl() const { return m_ttl; }
u16 data_length() const { return m_data_length; }
void* data() { return this + 1; }
void const* data() const { return this + 1; }
private:
NetworkOrdered<u16> m_type;
NetworkOrdered<u16> m_class;
NetworkOrdered<u32> m_ttl;
NetworkOrdered<u16> m_data_length;
};
static_assert(sizeof(DNSRecordWithoutName) == 10);
Optional<DNSPacket> DNSPacket::from_raw_packet(u8 const* raw_data, size_t raw_size)
{
if (raw_size < sizeof(DNSPacketHeader)) {
dbgln("DNS response not large enough ({} out of {}) to be a DNS packet.", raw_size, sizeof(DNSPacketHeader));
return {};
}
auto& header = *(DNSPacketHeader const*)(raw_data);
dbgln_if(LOOKUPSERVER_DEBUG, "Got packet (ID: {})", header.id());
dbgln_if(LOOKUPSERVER_DEBUG, " Question count: {}", header.question_count());
dbgln_if(LOOKUPSERVER_DEBUG, " Answer count: {}", header.answer_count());
dbgln_if(LOOKUPSERVER_DEBUG, " Authority count: {}", header.authority_count());
dbgln_if(LOOKUPSERVER_DEBUG, "Additional count: {}", header.additional_count());
DNSPacket packet;
packet.m_id = header.id();
packet.m_query_or_response = header.is_response();
packet.m_code = header.response_code();
// FIXME: Should we parse further in this case?
if (packet.code() != Code::NOERROR)
return packet;
size_t offset = sizeof(DNSPacketHeader);
for (u16 i = 0; i < header.question_count(); i++) {
auto name = DNSName::parse(raw_data, offset, raw_size);
struct RawDNSAnswerQuestion {
NetworkOrdered<u16> record_type;
NetworkOrdered<u16> class_code;
};
auto& record_and_class = *(RawDNSAnswerQuestion const*)&raw_data[offset];
u16 class_code = record_and_class.class_code & ~MDNS_WANTS_UNICAST_RESPONSE;
bool mdns_wants_unicast_response = record_and_class.class_code & MDNS_WANTS_UNICAST_RESPONSE;
packet.m_questions.empend(name, (DNSRecordType)(u16)record_and_class.record_type, (DNSRecordClass)class_code, mdns_wants_unicast_response);
offset += 4;
auto& question = packet.m_questions.last();
dbgln_if(LOOKUPSERVER_DEBUG, "Question #{}: name=_{}_, type={}, class={}", i, question.name(), question.record_type(), question.class_code());
}
for (u16 i = 0; i < header.answer_count(); ++i) {
auto name = DNSName::parse(raw_data, offset, raw_size);
auto& record = *(DNSRecordWithoutName const*)(&raw_data[offset]);
String data;
offset += sizeof(DNSRecordWithoutName);
switch ((DNSRecordType)record.type()) {
case DNSRecordType::PTR: {
size_t dummy_offset = offset;
data = DNSName::parse(raw_data, dummy_offset, raw_size).as_string();
break;
}
case DNSRecordType::CNAME:
// Fall through
case DNSRecordType::A:
// Fall through
case DNSRecordType::TXT:
// Fall through
case DNSRecordType::AAAA:
// Fall through
case DNSRecordType::SRV:
data = { record.data(), record.data_length() };
break;
default:
// FIXME: Parse some other record types perhaps?
dbgln("data=(unimplemented record type {})", (u16)record.type());
}
dbgln_if(LOOKUPSERVER_DEBUG, "Answer #{}: name=_{}_, type={}, ttl={}, length={}, data=_{}_", i, name, record.type(), record.ttl(), record.data_length(), data);
u16 class_code = record.record_class() & ~MDNS_CACHE_FLUSH;
bool mdns_cache_flush = record.record_class() & MDNS_CACHE_FLUSH;
packet.m_answers.empend(name, (DNSRecordType)record.type(), (DNSRecordClass)class_code, record.ttl(), data, mdns_cache_flush);
offset += record.data_length();
}
return packet;
}
}
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