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547130584c
The ad-hoc IPC we were doing with LookupServer was kinda gross. With this, LookupServer is a regular IPC server. In the future, we want to add more APIs for LookupServer to talk to its clients (such as DHCPClient telling LookupServer about the DNS server discovered via DHCP, and DNS-SD client browsing for services), which calls for a more expressive IPC format; this is what LibIPC is perfect for. While the LookupServer side is using the regular LibIPC mechanics and patterns, the LibC side has to hand-roll LibIPC format serialization without actually using LibIPC. We might be able to get rid of this in the future, but for now it has to be like that. The good news is the format is not that bad at all.
264 lines
9 KiB
C++
264 lines
9 KiB
C++
/*
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* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "LookupServer.h"
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#include "ClientConnection.h"
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#include "DNSRequest.h"
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#include "DNSResponse.h"
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#include <AK/ByteBuffer.h>
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#include <AK/Debug.h>
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#include <AK/HashMap.h>
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#include <AK/String.h>
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#include <AK/StringBuilder.h>
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#include <LibCore/ConfigFile.h>
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#include <LibCore/File.h>
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#include <LibCore/LocalServer.h>
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#include <LibCore/LocalSocket.h>
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#include <LibCore/UDPSocket.h>
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#include <stdio.h>
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#include <sys/time.h>
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#include <unistd.h>
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namespace LookupServer {
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static LookupServer* s_the;
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LookupServer& LookupServer::the()
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{
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ASSERT(s_the);
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return *s_the;
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}
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LookupServer::LookupServer()
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{
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ASSERT(s_the == nullptr);
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s_the = this;
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auto config = Core::ConfigFile::get_for_system("LookupServer");
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dbgln("Using network config file at {}", config->file_name());
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m_nameservers = config->read_entry("DNS", "Nameservers", "1.1.1.1,1.0.0.1").split(',');
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load_etc_hosts();
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m_local_server = Core::LocalServer::construct(this);
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m_local_server->on_ready_to_accept = [this]() {
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auto socket = m_local_server->accept();
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if (!socket) {
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dbgln("Failed to accept a client connection");
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return;
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}
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static int s_next_client_id = 0;
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int client_id = ++s_next_client_id;
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IPC::new_client_connection<ClientConnection>(socket.release_nonnull(), client_id);
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};
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bool ok = m_local_server->take_over_from_system_server();
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ASSERT(ok);
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}
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void LookupServer::load_etc_hosts()
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{
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auto file = Core::File::construct("/etc/hosts");
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if (!file->open(Core::IODevice::ReadOnly))
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return;
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while (!file->eof()) {
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auto line = file->read_line(1024);
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if (line.is_empty())
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break;
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auto fields = line.split('\t');
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auto sections = fields[0].split('.');
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IPv4Address addr {
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(u8)atoi(sections[0].characters()),
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(u8)atoi(sections[1].characters()),
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(u8)atoi(sections[2].characters()),
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(u8)atoi(sections[3].characters()),
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};
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auto name = fields[1];
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m_etc_hosts.set(name, addr.to_string());
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IPv4Address reverse_addr {
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(u8)atoi(sections[3].characters()),
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(u8)atoi(sections[2].characters()),
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(u8)atoi(sections[1].characters()),
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(u8)atoi(sections[0].characters()),
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};
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StringBuilder builder;
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builder.append(reverse_addr.to_string());
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builder.append(".in-addr.arpa");
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m_etc_hosts.set(builder.to_string(), name);
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}
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}
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Vector<String> LookupServer::lookup(const String& name, unsigned short record_type)
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{
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#if LOOKUPSERVER_DEBUG
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dbgln("Got request for '{}'", name);
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#endif
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Vector<String> responses;
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if (auto known_host = m_etc_hosts.get(name); known_host.has_value()) {
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responses.append(known_host.value());
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} else if (!name.is_empty()) {
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for (auto& nameserver : m_nameservers) {
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#if LOOKUPSERVER_DEBUG
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dbgln("Doing lookup using nameserver '{}'", nameserver);
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#endif
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bool did_get_response = false;
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int retries = 3;
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do {
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responses = lookup(name, nameserver, did_get_response, record_type);
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if (did_get_response)
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break;
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} while (--retries);
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if (!responses.is_empty()) {
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break;
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} else {
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if (!did_get_response)
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dbgln("Never got a response from '{}', trying next nameserver", nameserver);
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else
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dbgln("Received response from '{}' but no result(s), trying next nameserver", nameserver);
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}
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}
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if (responses.is_empty()) {
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fprintf(stderr, "LookupServer: Tried all nameservers but never got a response :(\n");
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return {};
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}
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}
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return move(responses);
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}
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Vector<String> LookupServer::lookup(const String& hostname, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
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{
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if (auto it = m_lookup_cache.find(hostname); it != m_lookup_cache.end()) {
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auto& cached_lookup = it->value;
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if (cached_lookup.question.record_type() == record_type) {
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Vector<String> responses;
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for (auto& cached_answer : cached_lookup.answers) {
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#if LOOKUPSERVER_DEBUG
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dbgln("Cache hit: {} -> {}, expired: {}", hostname, cached_answer.record_data(), cached_answer.has_expired());
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#endif
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if (!cached_answer.has_expired())
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responses.append(cached_answer.record_data());
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}
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if (!responses.is_empty())
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return responses;
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}
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m_lookup_cache.remove(it);
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}
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DNSRequest request;
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request.add_question(hostname, record_type, should_randomize_case);
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auto buffer = request.to_byte_buffer();
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auto udp_socket = Core::UDPSocket::construct();
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udp_socket->set_blocking(true);
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struct timeval timeout {
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1, 0
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};
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int rc = setsockopt(udp_socket->fd(), SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
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if (rc < 0) {
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perror("setsockopt(SOL_SOCKET, SO_RCVTIMEO)");
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return {};
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}
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if (!udp_socket->connect(nameserver, 53))
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return {};
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if (!udp_socket->write(buffer))
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return {};
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u8 response_buffer[4096];
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int nrecv = udp_socket->read(response_buffer, sizeof(response_buffer));
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if (nrecv == 0)
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return {};
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did_get_response = true;
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auto o_response = DNSResponse::from_raw_response(response_buffer, nrecv);
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if (!o_response.has_value())
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return {};
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auto& response = o_response.value();
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if (response.id() != request.id()) {
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dbgln("LookupServer: ID mismatch ({} vs {}) :(", response.id(), request.id());
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return {};
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}
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if (response.code() == DNSResponse::Code::REFUSED) {
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if (should_randomize_case == ShouldRandomizeCase::Yes) {
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// Retry with 0x20 case randomization turned off.
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return lookup(hostname, nameserver, did_get_response, record_type, ShouldRandomizeCase::No);
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}
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return {};
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}
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if (response.question_count() != request.question_count()) {
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dbgln("LookupServer: Question count ({} vs {}) :(", response.question_count(), request.question_count());
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return {};
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}
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for (size_t i = 0; i < request.question_count(); ++i) {
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auto& request_question = request.questions()[i];
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auto& response_question = response.questions()[i];
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if (request_question != response_question) {
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dbgln("Request and response questions do not match");
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dbgln(" Request: name=_{}_, type={}, class={}", request_question.name(), response_question.record_type(), response_question.class_code());
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dbgln(" Response: name=_{}_, type={}, class={}", response_question.name(), response_question.record_type(), response_question.class_code());
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return {};
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}
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}
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if (response.answer_count() < 1) {
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dbgln("LookupServer: Not enough answers ({}) :(", response.answer_count());
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return {};
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}
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Vector<String, 8> responses;
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Vector<DNSAnswer, 8> cacheable_answers;
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for (auto& answer : response.answers()) {
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if (answer.type() != record_type)
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continue;
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responses.append(answer.record_data());
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if (!answer.has_expired())
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cacheable_answers.append(answer);
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}
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if (!cacheable_answers.is_empty()) {
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if (m_lookup_cache.size() >= 256)
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m_lookup_cache.remove(m_lookup_cache.begin());
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m_lookup_cache.set(hostname, { request.questions()[0], move(cacheable_answers) });
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}
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return responses;
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}
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}
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