Martin Michelsen
132 lines
3.2 KiB
C++
132 lines
3.2 KiB
C++
#include "DNSServer.hh"
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#include <stdio.h>
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#include <unistd.h>
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#include <poll.h>
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#include <netinet/in.h>
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#include <phosg/Network.hh>
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#include <phosg/Strings.hh>
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#include <vector>
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#include <string>
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#include "NetworkAddresses.hh"
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using namespace std;
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DNSServer::DNSServer(uint32_t local_connect_address,
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uint32_t external_connect_address) :
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should_exit(false), local_connect_address(local_connect_address),
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external_connect_address(external_connect_address) { }
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DNSServer::~DNSServer() {
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for (int fd : this->fds) {
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close(fd);
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}
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}
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void DNSServer::listen(const std::string& socket_path) {
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this->add_socket(::listen(socket_path, 0, 0));
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}
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void DNSServer::listen(const std::string& addr, int port) {
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this->add_socket(::listen(addr, port, 0));
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}
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void DNSServer::listen(int port) {
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this->add_socket(::listen("", port, 0));
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}
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void DNSServer::add_socket(int fd) {
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this->fds.emplace(fd);
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}
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void DNSServer::start() {
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this->t = thread(&DNSServer::run_thread, this);
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}
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void DNSServer::schedule_stop() {
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this->should_exit = true;
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}
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void DNSServer::wait_for_stop() {
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this->t.join();
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}
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void DNSServer::run_thread() {
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vector<pollfd> poll_fds;
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for (int fd : this->fds) {
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poll_fds.emplace_back();
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auto& pfd = poll_fds.back();
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pfd.fd = fd;
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pfd.events = POLLIN;
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pfd.revents = 0;
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}
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while (!this->should_exit) {
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sockaddr_in remote;
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socklen_t remote_size = sizeof(sockaddr_in);
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memset(&remote, 0, remote_size);
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// 10 second timeout
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int num_fds = poll(poll_fds.data(), poll_fds.size(), 10000);
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if (num_fds < 0) {
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auto s = string_for_error(errno);
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log(ERROR, "DNS server terminating due to error: %s", s.c_str());
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break;
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}
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if (num_fds == 0) {
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continue;
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}
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for (const auto& pfd : poll_fds) {
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if (!(pfd.revents & POLLIN)) {
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continue;
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}
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string input(2048, 0);
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ssize_t bytes = recvfrom(pfd.fd, const_cast<char*>(input.data()),
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input.size(), 0, reinterpret_cast<sockaddr*>(&remote), &remote_size);
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if (bytes > 0) {
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input.resize(bytes);
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uint32_t connect_address;
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if (is_local_address(remote.sin_addr.s_addr)) {
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connect_address = this->local_connect_address;
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} else {
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connect_address = this->external_connect_address;
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}
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string output = this->build_response(input, connect_address);
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if (!output.empty()) {
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sendto(pfd.fd, output.data(), output.size(), 0,
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reinterpret_cast<sockaddr*>(&remote), remote_size);
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}
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}
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}
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}
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}
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string DNSServer::build_response(const std::string& input,
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uint32_t connect_address) {
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if (input.size() < 0x0C) {
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return "";
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}
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string ret;
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size_t name_len = strlen(input.data() + 0x0C) + 1;
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ret.append(input.substr(0, 2));
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ret.append("\x81\x80\x00\x01\x00\x01\x00\x00\x00\x00", 10);
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ret.append(input.substr(12, name_len));
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ret.append("\x00\x01\x00\x01\xC0\x0C\x00\x01\x00\x01\x00\x00\x00\x3C\x00\x04", 16);
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ret.append(reinterpret_cast<const char*>(&connect_address), 4);
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return ret;
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}
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