// Matrix Construct // // Copyright (C) Matrix Construct Developers, Authors & Contributors // Copyright (C) 2016-2018 Jason Volk // // Permission to use, copy, modify, and/or distribute this software for any // purpose with or without fee is hereby granted, provided that the above // copyright notice and this permission notice is present in all copies. The // full license for this software is available in the LICENSE file. #include "s_dns.h" decltype(ircd::net::dns::resolver) ircd::net::dns::resolver; decltype(ircd::net::dns::resolver::servers) ircd::net::dns::resolver::servers { { { "name", "ircd.net.dns.resolver.servers" }, { "default", "4.2.2.1 4.2.2.2 4.2.2.3 4.2.2.4 4.2.2.5 4.2.2.6" }, }, [] { if(bool(ircd::net::dns::resolver)) ircd::net::dns::resolver->set_servers(); } }; decltype(ircd::net::dns::resolver::timeout) ircd::net::dns::resolver::timeout { { "name", "ircd.net.dns.resolver.timeout" }, { "default", 10000L }, }; decltype(ircd::net::dns::resolver::send_rate) ircd::net::dns::resolver::send_rate { { "name", "ircd.net.dns.resolver.send_rate" }, { "default", 60L }, }; decltype(ircd::net::dns::resolver::send_burst) ircd::net::dns::resolver::send_burst { { "name", "ircd.net.dns.resolver.send_burst" }, { "default", 8L }, }; decltype(ircd::net::dns::resolver::retry_max) ircd::net::dns::resolver::retry_max { { "name", "ircd.net.dns.resolver.retry_max" }, { "default", 4L }, }; // // interface // void ircd::net::dns::resolver_init(answers_callback callback) { assert(!ircd::net::dns::resolver); ircd::net::dns::resolver = new typename ircd::net::dns::resolver { std::move(callback) }; } void ircd::net::dns::resolver_fini() { delete ircd::net::dns::resolver; ircd::net::dns::resolver = nullptr; } uint16_t ircd::net::dns::resolver_call(const hostport &hp, const opts &opts) { if(unlikely(!resolver)) throw error { "Cannot resolve '%s': resolver unavailable.", host(hp) }; auto &resolver{*dns::resolver}; if(unlikely(!resolver.ns.is_open())) throw error { "Cannot resolve '%s': resolver is closed.", host(hp) }; return resolver(hp, opts); } // // resolver::resolver // ircd::net::dns::resolver::resolver(answers_callback callback) :callback { std::move(callback) } ,ns { ios::get() } ,recv_context { "dnsres R", 1_MiB, std::bind(&resolver::recv_worker, this), context::POST } ,timeout_context { "dnsres T", 64_KiB, std::bind(&resolver::timeout_worker, this), context::POST } ,sendq_context { "dnsres S", 64_KiB, std::bind(&resolver::sendq_worker, this), context::POST } { ns.open(ip::udp::v4()); ns.non_blocking(true); set_servers(); } ircd::net::dns::resolver::~resolver() noexcept { if(ns.is_open()) ns.close(); timeout_context.terminate(); sendq_context.terminate(); recv_context.terminate(); done.wait([this] { const bool ret(tags.empty()); if(!ret) log::warning { log, "Waiting for %zu unfinished DNS resolutions", tags.size() }; return ret; }); assert(tags.empty()); } /// Internal resolver entry interface. uint16_t ircd::net::dns::resolver::operator()(const hostport &hp, const opts &opts) { auto &tag(set_tag(hp, opts)); try { tag.question = make_query(tag.qbuf, tag); submit(tag); } catch(...) { remove(tag); throw; } return tag.id; } ircd::const_buffer ircd::net::dns::resolver::make_query(const mutable_buffer &buf, tag &tag) { thread_local char hostbuf[rfc1035::NAME_BUF_SIZE * 2]; string_view hoststr; switch(tag.opts.qtype) { case 0: throw error { "A query type is required to form a question." }; case 33: // SRV hoststr = make_SRV_key(hostbuf, host(tag.hp), tag.opts); break; default: hoststr = host(tag.hp); break; } assert(hoststr); assert(tag.opts.qtype); const rfc1035::question question { hoststr, tag.opts.qtype }; return rfc1035::make_query(buf, tag.id, question); } template ircd::net::dns::tag & ircd::net::dns::resolver::set_tag(A&&... args) { while(tags.size() < 65535) { auto id { ircd::rand::integer(1, 65535) }; auto it{tags.lower_bound(id)}; if(it != end(tags) && it->first == id) continue; it = tags.emplace_hint(it, std::piecewise_construct, std::forward_as_tuple(id), std::forward_as_tuple(std::forward(args)...)); it->second.id = id; dock.notify_one(); return it->second; } throw panic { "Too many DNS queries" }; } void __attribute__((noreturn)) ircd::net::dns::resolver::sendq_worker() { while(1) { dock.wait([this] { assert(sendq.empty() || !tags.empty()); return !sendq.empty() && !server.empty(); }); if(tags.size() > size_t(send_burst)) ctx::sleep(milliseconds(send_rate)); sendq_work(); } } void ircd::net::dns::resolver::sendq_work() { const std::lock_guard lock { mutex }; assert(!sendq.empty()); assert(sendq.size() < 65535); assert(sendq.size() <= tags.size()); const uint16_t next(sendq.front()); sendq.pop_front(); flush(next); } void ircd::net::dns::resolver::flush(const uint16_t &next) try { auto &tag { tags.at(next) }; submit(tag); } catch(const std::out_of_range &e) { log::error { log, "Queued tag id[%u] is no longer mapped", next }; } void ircd::net::dns::resolver::timeout_worker() try { while(1) { dock.wait([this] { return !tags.empty(); }); ctx::sleep(milliseconds(timeout)); check_timeouts(milliseconds(timeout)); } } catch(const ctx::terminated &) { const ctx::exception_handler eh; cancel_all(); } void ircd::net::dns::resolver::check_timeouts(const milliseconds &timeout) { const std::lock_guard lock { mutex }; const auto cutoff { now() - timeout }; auto it(begin(tags)); while(it != end(tags)) { const auto &id(it->first); auto &tag(it->second); if(check_timeout(id, tag, cutoff)) it = remove(tag, it); else ++it; } } bool ircd::net::dns::resolver::check_timeout(const uint16_t &id, tag &tag, const steady_point &cutoff) { if(tag.last == steady_point::min()) return false; if(tag.last > cutoff) return false; log::warning { log, "DNS timeout id:%u on attempt %u of %u '%s'", id, tag.tries, size_t(retry_max), host(tag.hp) }; tag.last = steady_point::min(); if(tag.tries < size_t(retry_max)) { submit(tag); return false; } static const std::system_error ec { make_error_code(std::errc::timed_out) }; error_one(tag, ec); return true; } // // submit // void ircd::net::dns::resolver::submit(tag &tag) { if(!ns.is_open() || server.empty()) { log::warning { log, "dns tag:%u submit queued because no nameserver is available.", tag.id }; queue_query(tag); return; } assert(!server.empty()); const auto rate(milliseconds(send_rate) / server.size()); const auto elapsed(now() - send_last); if(elapsed >= rate || tags.size() <= size_t(send_burst)) send_query(tag); else queue_query(tag); } void ircd::net::dns::resolver::send_query(tag &tag) try { assert(!server.empty()); ++server_next %= server.size(); const auto &ep { server.at(server_next) }; send_query(ep, tag); #ifdef RB_DEBUG thread_local char buf[128]; log::debug { log, "dns %s send tag:%u t:%u qtype:%u `%s'", string(buf, make_ipport(ep)), tag.id, tag.tries, tag.opts.qtype, host(tag.hp) }; #endif } catch(const std::out_of_range &) { throw error { "No DNS servers available for query" }; } void ircd::net::dns::resolver::queue_query(tag &tag) { assert(sendq.size() <= tags.size()); if(std::find(begin(sendq), end(sendq), tag.id) != end(sendq)) return; sendq.emplace_back(tag.id); dock.notify_one(); log::debug { log, "dns tag:%u t:%u qtype:%u added to sendq (tags:%zu sendq:%zu)", tag.id, tag.tries, tag.opts.qtype, tags.size(), sendq.size() }; } void ircd::net::dns::resolver::send_query(const ip::udp::endpoint &ep, tag &tag) { assert(ns.is_open()); assert(ns.non_blocking()); assert(!empty(tag.question)); const const_buffer &buf{tag.question}; const auto sent { ns.send_to(asio::const_buffers_1(buf), ep) }; send_last = now(); tag.last = send_last; tag.server = make_ipport(ep); tag.tries++; } // // recv // void ircd::net::dns::resolver::recv_worker() try { const unique_buffer buf { 64_KiB }; const auto interruption{[this] (ctx::ctx *const &) { if(this->ns.is_open()) this->ns.cancel(); }}; const asio::mutable_buffers_1 bufs{buf}; ip::udp::endpoint ep; while(ns.is_open()) try { size_t recv; continuation { continuation::asio_predicate, interruption, [this, &bufs, &recv, &ep] (auto &yield) { recv = ns.async_receive_from(bufs, ep, yield); } }; const mutable_buffer &reply { data(buf), recv }; const net::ipport &from { make_ipport(ep) }; handle(from, reply); } catch(const boost::system::system_error &e) { switch(make_error_code(e).value()) { case int(std::errc::operation_canceled): break; default: throw; } } } catch(const std::exception &e) { log::critical { log, "%s", e.what() }; } void ircd::net::dns::resolver::handle(const ipport &from, const mutable_buffer &buf) try { if(unlikely(size(buf) < sizeof(rfc1035::header))) throw rfc1035::error { "Got back %zu bytes < rfc1035 %zu byte header", size(buf), sizeof(rfc1035::header) }; rfc1035::header &header { *reinterpret_cast(data(buf)) }; bswap(&header.qdcount); bswap(&header.ancount); bswap(&header.nscount); bswap(&header.arcount); const const_buffer body { data(buf) + sizeof(header), size(buf) - sizeof(header) }; handle_reply(from, header, body); } catch(const std::exception &e) { log::error { log, "%s", e.what() }; } void ircd::net::dns::resolver::handle_reply(const ipport &from, const header &header, const const_buffer &body) { thread_local char addr_strbuf[2][128]; const std::lock_guard lock { // The primary mutex is locked here while this result is // processed. This locks out the sendq and timeout worker. mutex }; const auto it { tags.find(header.id) }; if(it == end(tags)) throw error { "DNS reply from %s for unrecognized tag id:%u", string(addr_strbuf[0], from), header.id }; auto &tag{it->second}; if(from != tag.server) throw error { "DNS reply from %s for tag:%u which we sent to %s", string(addr_strbuf[0], from), header.id, string(addr_strbuf[1], tag.server) }; log::debug { log, "dns %s recv tag:%u t:%u qtype:%u qd:%u an:%u ns:%u ar:%u", string(addr_strbuf[0], from), tag.id, tag.tries, tag.opts.qtype, header.qdcount, header.ancount, header.nscount, header.arcount, }; // Handle ServFail as a special case here. We can try again without // handling this tag or propagating this error any further yet. if(header.rcode == 2 && tag.tries < size_t(retry_max)) { log::error { log, "dns %s recv tag:%u t:%u qtype:%u protocol error #%u :%s", string(addr_strbuf[0], from), tag.id, tag.tries, tag.opts.qtype, header.rcode, rfc1035::rcode.at(header.rcode) }; assert(tag.tries > 0); tag.last = steady_point::min(); submit(tag); return; } // The tag is committed to being handled after this point. It will be // removed from the tags map and any retry must c const unwind untag{[this, &tag, &it] { remove(tag, it); }}; assert(tag.tries > 0); tag.last = steady_point::min(); tag.rcode = header.rcode; handle_reply(header, body, tag); } void ircd::net::dns::resolver::handle_reply(const header &header, const const_buffer &body, tag &tag) try { if(unlikely(header.qr != 1)) throw rfc1035::error { "Response header is marked as 'Query' and not 'Response'" }; if(header.qdcount > MAX_COUNT || header.ancount > MAX_COUNT) throw error { "Response contains too many sections..." }; if(header.qdcount < 1) throw error { "Response does not contain the question." }; if(!handle_error(header, tag)) throw rfc1035::error { "protocol error #%u :%s", header.rcode, rfc1035::rcode.at(header.rcode) }; const_buffer buffer { body }; // Questions are regurgitated back to us so they must be parsed first thread_local std::array qd; for(size_t i(0); i < header.qdcount; ++i) consume(buffer, size(qd.at(i).parse(buffer))); // Answers are parsed into this buffer thread_local std::array an; for(size_t i(0); i < header.ancount; ++i) consume(buffer, size(an.at(i).parse(buffer))); const vector_view answers { an.data(), header.ancount }; callback({}, tag, answers); } catch(const std::exception &e) { // There's no need to flash red to the log for NXDOMAIN which is // common in this system when probing SRV. const auto level { header.rcode != 3? log::ERROR : log::DERROR }; log::logf { log, level, "resolver tag:%u: %s", tag.id, e.what() }; assert(header.rcode != 3 || tag.opts.nxdomain_exceptions); const auto eptr(std::current_exception()); const ctx::exception_handler eh; callback(eptr, tag, answers{}); } bool ircd::net::dns::resolver::handle_error(const header &header, tag &tag) { switch(header.rcode) { case 0: // NoError; continue return true; case 3: // NXDomain; exception if(!tag.opts.nxdomain_exceptions) return true; return false; default: // Unhandled error; exception return false; } } // // removal // // This whole stack must be called under lock // void ircd::net::dns::resolver::cancel_all() { static const std::error_code &ec { make_error_code(std::errc::operation_canceled) }; error_all(ec); } void ircd::net::dns::resolver::error_all(const std::error_code &ec) { if(tags.empty()) return; log::dwarning { log, "Attempting to cancel all %zu pending tags.", tags.size() }; const auto eptr { make_system_eptr(ec) }; for(auto &p : tags) error_one(p.second, eptr); } void ircd::net::dns::resolver::error_one(tag &tag, const std::system_error &se) { error_one(tag, std::make_exception_ptr(se)); } void ircd::net::dns::resolver::error_one(tag &tag, const std::exception_ptr &eptr) { thread_local char hpbuf[128]; log::error { log, "DNS error id:%u for '%s' :%s", tag.id, string(hpbuf, tag.hp), what(eptr) }; static const answers empty; callback(eptr, tag, empty); remove(tag); } void ircd::net::dns::resolver::remove(tag &tag) { remove(tag, tags.find(tag.id)); } decltype(ircd::net::dns::resolver::tags)::iterator ircd::net::dns::resolver::remove(tag &tag, const decltype(tags)::iterator &it) { log::debug { log, "dns tag:%u t:%u qtype:%u removing (tags:%zu sendq:%zu)", tag.id, tag.tries, tag.opts.qtype, tags.size(), sendq.size() }; unqueue(tag); done.notify_all(); return it != end(tags)? tags.erase(it) : it; } void ircd::net::dns::resolver::unqueue(tag &tag) { const auto it { std::find(begin(sendq), end(sendq), tag.id) }; if(it != end(sendq)) sendq.erase(it); } // // util // void ircd::net::dns::resolver::set_servers() try { const std::string &list(resolver::servers); set_servers(list); dock.notify_all(); } catch(const std::exception &e) { log::error { log, "Erroneous configuration; falling back to defaults :%s", e.what() }; resolver::servers.fault(); if(!ircd::net::dns::resolver) set_servers(); } void ircd::net::dns::resolver::set_servers(const string_view &list) { server.clear(); server_next = 0; tokens(list, ' ', [this] (const string_view &hp) { add_server(hp); }); if(!empty(list) && server.empty()) throw error { "Failed to set any valid DNS servers from a non-empty list." }; } void ircd::net::dns::resolver::add_server(const string_view &str) try { const hostport hp { str }; const auto &port { net::port(hp) != canon_port? net::port(hp) : uint16_t(53) }; const ipport ipp { host(hp), port }; add_server(ipp); } catch(const std::exception &e) { log::error { log, "Failed to add server '%s' :%s", str, e.what() }; } void ircd::net::dns::resolver::add_server(const ipport &ipp) { server.emplace_back(make_endpoint_udp(ipp)); log::debug { log, "Adding [%s] as DNS server #%zu", string(ipp), server.size() }; }