Services: Renamed from Servers

It didn't feel right to have a "DHCPClient" in a "Servers" directory.
Rename this to Services to better reflect the type of programs we'll
be putting in there.

1 files changed, 259 insertions, 0 deletions

diff --git a/Services/LookupServer/LookupServer.cpp b/Services/LookupServer/LookupServer.cpp
new file mode 100644
index 0000000000..fe89bd97fc
--- /dev/null
+++ b/Services/LookupServer/LookupServer.cpp
@@ -0,0 +1,259 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "LookupServer.h"
+#include "DNSRequest.h"
+#include "DNSResponse.h"
+#include <AK/HashMap.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/ConfigFile.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/File.h>
+#include <LibCore/LocalServer.h>
+#include <LibCore/LocalSocket.h>
+#include <LibCore/UDPSocket.h>
+#include <stdio.h>
+#include <unistd.h>
+
+LookupServer::LookupServer()
+{
+    auto config = Core::ConfigFile::get_for_system("LookupServer");
+    dbg() << "Using network config file at " << config->file_name();
+    m_nameserver = config->read_entry("DNS", "Nameserver", "1.1.1.1");
+
+    load_etc_hosts();
+
+    m_local_server = Core::LocalServer::construct(this);
+    m_local_server->on_ready_to_accept = [this]() {
+        auto socket = m_local_server->accept();
+        socket->on_ready_to_read = [this, socket]() {
+            service_client(socket);
+            RefPtr<Core::LocalSocket> keeper = socket;
+            const_cast<Core::LocalSocket&>(*socket).on_ready_to_read = [] {};
+        };
+    };
+    bool ok = m_local_server->take_over_from_system_server();
+    ASSERT(ok);
+}
+
+void LookupServer::load_etc_hosts()
+{
+    auto file = Core::File::construct("/etc/hosts");
+    if (!file->open(Core::IODevice::ReadOnly))
+        return;
+    while (!file->eof()) {
+        auto line = file->read_line(1024);
+        if (line.is_empty())
+            break;
+        auto str_line = String((const char*)line.data(), line.size() - 1, Chomp);
+        auto fields = str_line.split('\t');
+
+        auto sections = fields[0].split('.');
+        IPv4Address addr {
+            (u8)atoi(sections[0].characters()),
+            (u8)atoi(sections[1].characters()),
+            (u8)atoi(sections[2].characters()),
+            (u8)atoi(sections[3].characters()),
+        };
+
+        auto name = fields[1];
+        m_etc_hosts.set(name, addr.to_string());
+
+        IPv4Address reverse_addr {
+            (u8)atoi(sections[3].characters()),
+            (u8)atoi(sections[2].characters()),
+            (u8)atoi(sections[1].characters()),
+            (u8)atoi(sections[0].characters()),
+        };
+        StringBuilder builder;
+        builder.append(reverse_addr.to_string());
+        builder.append(".in-addr.arpa");
+        m_etc_hosts.set(builder.to_string(), name);
+    }
+}
+
+void LookupServer::service_client(RefPtr<Core::LocalSocket> socket)
+{
+    u8 client_buffer[1024];
+    int nrecv = socket->read(client_buffer, sizeof(client_buffer) - 1);
+    if (nrecv < 0) {
+        perror("read");
+        return;
+    }
+
+    client_buffer[nrecv] = '\0';
+
+    char lookup_type = client_buffer[0];
+    if (lookup_type != 'L' && lookup_type != 'R') {
+        dbg() << "Invalid lookup_type " << lookup_type;
+        return;
+    }
+    auto hostname = String((const char*)client_buffer + 1, nrecv - 1, Chomp);
+    dbg() << "Got request for '" << hostname << "' (using IP " << m_nameserver << ")";
+
+    Vector<String> responses;
+
+    if (auto known_host = m_etc_hosts.get(hostname); known_host.has_value()) {
+        responses.append(known_host.value());
+    } else if (!hostname.is_empty()) {
+        bool did_timeout;
+        int retries = 3;
+        do {
+            did_timeout = false;
+            if (lookup_type == 'L')
+                responses = lookup(hostname, did_timeout, T_A);
+            else if (lookup_type == 'R')
+                responses = lookup(hostname, did_timeout, T_PTR);
+            if (!did_timeout)
+                break;
+        } while (--retries);
+        if (did_timeout) {
+            fprintf(stderr, "LookupServer: Out of retries :(\n");
+            return;
+        }
+    }
+
+    if (responses.is_empty()) {
+        int nsent = socket->write("Not found.\n");
+        if (nsent < 0)
+            perror("write");
+        return;
+    }
+    for (auto& response : responses) {
+        auto line = String::format("%s\n", response.characters());
+        int nsent = socket->write(line);
+        if (nsent < 0) {
+            perror("write");
+            break;
+        }
+    }
+}
+
+Vector<String> LookupServer::lookup(const String& hostname, bool& did_timeout, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
+{
+    if (auto it = m_lookup_cache.find(hostname); it != m_lookup_cache.end()) {
+        auto& cached_lookup = it->value;
+        if (cached_lookup.question.record_type() == record_type) {
+            Vector<String> responses;
+            for (auto& cached_answer : cached_lookup.answers) {
+                dbg() << "Cache hit: " << hostname << " -> " << cached_answer.record_data() << ", expired: " << cached_answer.has_expired();
+                if (!cached_answer.has_expired()) {
+                    responses.append(cached_answer.record_data());
+                }
+            }
+            if (!responses.is_empty())
+                return responses;
+        }
+        m_lookup_cache.remove(it);
+    }
+
+    DNSRequest request;
+    request.add_question(hostname, record_type, should_randomize_case);
+
+    auto buffer = request.to_byte_buffer();
+
+    auto udp_socket = Core::UDPSocket::construct();
+    udp_socket->set_blocking(true);
+
+    struct timeval timeout {
+        1, 0
+    };
+
+    int rc = setsockopt(udp_socket->fd(), SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
+    if (rc < 0) {
+        perror("setsockopt(SOL_SOCKET, SO_RCVTIMEO)");
+        return {};
+    }
+
+    if (!udp_socket->connect(m_nameserver, 53))
+        return {};
+
+    if (!udp_socket->write(buffer))
+        return {};
+
+    u8 response_buffer[4096];
+    int nrecv = udp_socket->read(response_buffer, sizeof(response_buffer));
+    if (nrecv == 0)
+        return {};
+
+    auto o_response = DNSResponse::from_raw_response(response_buffer, nrecv);
+    if (!o_response.has_value())
+        return {};
+
+    auto& response = o_response.value();
+
+    if (response.id() != request.id()) {
+        dbgprintf("LookupServer: ID mismatch (%u vs %u) :(\n", response.id(), request.id());
+        return {};
+    }
+
+    if (response.code() == DNSResponse::Code::REFUSED) {
+        if (should_randomize_case == ShouldRandomizeCase::Yes) {
+            // Retry with 0x20 case randomization turned off.
+            return lookup(hostname, did_timeout, record_type, ShouldRandomizeCase::No);
+        }
+        return {};
+    }
+
+    if (response.question_count() != request.question_count()) {
+        dbgprintf("LookupServer: Question count (%u vs %u) :(\n", response.question_count(), request.question_count());
+        return {};
+    }
+
+    for (size_t i = 0; i < request.question_count(); ++i) {
+        auto& request_question = request.questions()[i];
+        auto& response_question = response.questions()[i];
+        if (request_question != response_question) {
+            dbg() << "Request and response questions do not match";
+            dbg() << "   Request: {_" << request_question.name() << "_, " << request_question.record_type() << ", " << request_question.class_code() << "}";
+            dbg() << "  Response: {_" << response_question.name() << "_, " << response_question.record_type() << ", " << response_question.class_code() << "}";
+            return {};
+        }
+    }
+
+    if (response.answer_count() < 1) {
+        dbgprintf("LookupServer: Not enough answers (%u) :(\n", response.answer_count());
+        return {};
+    }
+
+    Vector<String, 8> responses;
+    Vector<DNSAnswer, 8> cacheable_answers;
+    for (auto& answer : response.answers()) {
+        if (answer.type() != T_A)
+            continue;
+        responses.append(answer.record_data());
+        if (!answer.has_expired())
+            cacheable_answers.append(answer);
+    }
+
+    if (!cacheable_answers.is_empty()) {
+        if (m_lookup_cache.size() >= 256)
+            m_lookup_cache.remove(m_lookup_cache.begin());
+        m_lookup_cache.set(hostname, { request.questions()[0], move(cacheable_answers) });
+    }
+    return responses;
+}