// 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. namespace ircd::net::dns { template static rfc1035::record *new_record(mutable_buffer &, const rfc1035::answer &); static void handle_resolved(std::exception_ptr, const tag &, const answers &); static void handle_resolve_A_ipport(const hostport &, const json::object &rr, opts, callback_ipport); static void handle_resolve_SRV_ipport(const hostport &, const json::object &rr, opts, callback_ipport); static void handle_resolve_one(const hostport &, const json::array &rr, callback_one); } decltype(ircd::net::dns::log) ircd::net::dns::log { "net.dns" }; decltype(ircd::net::dns::opts_default) ircd::net::dns::opts_default; // // init // ircd::net::dns::init::init() { #ifdef HAVE_NETDB_H static const int stay_open {true}; ::setservent(stay_open); #endif assert(!resolver_instance); resolver_instance = new resolver { handle_resolved }; } ircd::net::dns::init::~init() noexcept { delete resolver_instance; resolver_instance = nullptr; #ifdef HAVE_NETDB_H ::endservent(); #endif } // // net/dns.h // void ircd::net::dns::resolve(const hostport &hp, const opts &opts_, callback_ipport callback) { if(unlikely(!port(hp) && !hp.service)) throw error { "Port or service is required for this query" }; dns::opts opts(opts_); opts.qtype = opts_.qtype?: 33; // default to SRV if(opts.qtype == 33) { opts.nxdomain_exceptions = false; net::dns::callback_one handler { std::bind(&handle_resolve_SRV_ipport, ph::_1, ph::_2, opts, std::move(callback)) }; resolve(hp, opts, std::move(handler)); } else if(opts.qtype == 1 || opts.qtype == 28) { net::dns::callback_one handler { std::bind(&handle_resolve_A_ipport, ph::_1, ph::_2, opts, std::move(callback)) }; resolve(hp, opts, std::move(handler)); } else throw error { "Query type:%u not valid for ipport result callback.", opts.qtype }; } void ircd::net::dns::resolve(const hostport &hp, const opts &opts, callback_one callback) { if(unlikely(!opts.qtype)) throw error { "Query type is required; not specified; cannot be deduced here." }; dns::callback handler { std::bind(&handle_resolve_one, ph::_1, ph::_2, std::move(callback)) }; resolve(hp, opts, std::move(handler)); } void ircd::net::dns::resolve(const hostport &hp_, const opts &opts, callback cb) { hostport hp(hp_); if(unlikely(!opts.qtype)) throw error { "Query type is required; not specified; cannot be deduced here." }; // Make any necessary attempt to translate a service name into a portnum. if(likely(opts.service_port)) if(!port(hp) && service(hp)) port(hp) = service_port(service(hp), opts.proto); // Try to satisfy from the cache first. This requires a ctx. if(likely(ctx::current && opts.cache_check)) if(cache::get(hp, opts, cb)) return; // Remote query will be made; register this callback as waiting for reply assert(cb); cache::waiting.emplace_back(hp, opts, std::move(cb)); // Check if there is already someone else waiting on the same query const auto count { std::count_if(begin(cache::waiting), end(cache::waiting), [] (const auto &a) { return a == cache::waiting.back(); }) }; // When nobody else is already waiting on this query we have to submit it. assert(count >= 1); if(count == 1) resolver_call(hp, opts); } /// Really assumptional and hacky right now. We're just assuming the SRV /// key is the first two elements of a dot-delimited string which start /// with underscores. If that isn't good enough in the future this will rot /// and become a regression hazard. ircd::string_view ircd::net::dns::unmake_SRV_key(const string_view &key) { if(token_count(key, '.') < 3) return key; if(!startswith(token(key, '.', 0), '_')) return key; if(!startswith(token(key, '.', 1), '_')) return key; return tokens_after(key, '.', 1); } ircd::string_view ircd::net::dns::make_SRV_key(const mutable_buffer &out, const hostport &hp, const opts &opts) { thread_local char tlbuf[2][rfc1035::NAME_BUFSIZE]; if(unlikely(!service(hp) && !opts.srv)) throw error { "Service name or query string option is required for SRV lookup." }; assert(host(hp)); if(!service(hp)) { assert(opts.srv); return fmt::sprintf { out, "%s%s", opts.srv, tolower(tlbuf[1], host(hp)) }; } assert(service(hp)); return fmt::sprintf { out, "_%s._%s.%s", tolower(tlbuf[0], service(hp)), opts.proto, tolower(tlbuf[1], host(hp)), }; } ircd::json::object ircd::net::dns::random_choice(const json::array &rrs) { const size_t &count { rrs.size() }; if(!count) return json::object{}; const auto choice { rand::integer(0, count - 1) }; assert(choice < count); const json::object &rr { rrs[choice] }; return rr; } bool ircd::net::dns::expired(const json::object &rr, const time_t &rr_ts) { const seconds &min_seconds { cache::min_ttl }; const seconds &err_seconds { cache::error_ttl }; const time_t &min { is_error(rr)? err_seconds.count(): min_seconds.count() }; return expired(rr, rr_ts, min); } bool ircd::net::dns::expired(const json::object &rr, const time_t &rr_ts, const time_t &min_ttl) { const auto &ttl { get_ttl(rr) }; return rr_ts + std::max(ttl, min_ttl) < ircd::time(); } time_t ircd::net::dns::get_ttl(const json::object &rr) { return rr.get("ttl", 0L); } bool ircd::net::dns::is_empty(const json::array &rrs) { return std::all_of(begin(rrs), end(rrs), [] (const json::object &rr) { return is_empty(rr); }); } bool ircd::net::dns::is_empty(const json::object &rr) { return empty(rr) || (rr.has("ttl") && size(rr) == 1); } bool ircd::net::dns::is_error(const json::array &rrs) { return !std::none_of(begin(rrs), end(rrs), [] (const json::object &rr) { return is_error(rr); }); } bool ircd::net::dns::is_error(const json::object &rr) { return rr.has("error"); } // // internal // void ircd::net::dns::handle_resolve_one(const hostport &hp, const json::array &rrs, callback_one callback) { const json::object &rr { random_choice(rrs) }; callback(hp, rr); } void ircd::net::dns::handle_resolve_SRV_ipport(const hostport &hp, const json::object &rr, opts opts, callback_ipport callback) { const json::string &error { rr.get("error") }; const hostport &target { rr.has("tgt")? rstrip(unquote(rr.at("tgt")), '.'): host(hp), rr.has("port")? rr.get("port"): !error? port(hp): uint16_t(0) }; if(error) { static const ipport empty; const auto eptr { make_exception_ptr(exception::hide_name, "%s", error) }; return callback(eptr, target, empty); } opts.qtype = 1; opts.nxdomain_exceptions = true; net::dns::callback_one handler { std::bind(&handle_resolve_A_ipport, ph::_1, ph::_2, opts, std::move(callback)) }; resolve(target, opts, std::move(handler)); } void ircd::net::dns::handle_resolve_A_ipport(const hostport &hp, const json::object &rr, const opts opts, const callback_ipport callback) { const json::string &error { rr.get("error") }; const json::string &ip { opts.qtype == 28? rr.get("ip", ":::0"_sv): rr.get("ip", "0.0.0.0"_sv) }; const ipport &ipport { ip, port(hp) }; const auto eptr { !empty(error)? make_exception_ptr(exception::hide_name, "%s", error): !ipport? make_exception_ptr("Host has no A record."): std::exception_ptr{} }; callback(eptr, hp, ipport); } /// Called back from the dns::resolver with a vector of answers to the /// question (we get the whole tag here). /// /// This is being invoked on the dns::resolver's receiver context stack /// under lock preventing any other activity with the resolver. /// /// We process these results and insert them into our cache. The cache /// insertion involves sending a message to the DNS room. Matrix hooks /// on that room will catch this message for the user(s) which initiated /// this query; we don't callback or deal with said users here. /// void ircd::net::dns::handle_resolved(std::exception_ptr eptr, const tag &tag, const answers &an) try { static const size_t recsz(1024); thread_local char recbuf[recsz * MAX_COUNT]; thread_local std::array record; size_t i(0); mutable_buffer buf{recbuf}; for(; i < an.size(); ++i) switch(an.at(i).qtype) { case 1: record.at(i) = new_record(buf, an.at(i)); continue; case 5: record.at(i) = new_record(buf, an.at(i)); continue; case 28: record.at(i) = new_record(buf, an.at(i)); continue; case 33: record.at(i) = new_record(buf, an.at(i)); continue; default: record.at(i) = new_record(buf, an.at(i)); continue; } // Sort the records by type so we can create smaller vectors to send to the // cache. nulls from running out of space should be pushed to the back. std::sort(begin(record), begin(record) + an.size(), [] (const auto *const &a, const auto *const &b) { if(!a) return false; if(!b) return true; return a->type < b->type; }); //TODO: don't send cache ephemeral rcodes // Bail on error here; send the cache the message if(eptr) { cache::put(tag.hp, tag.opts, tag.rcode, what(eptr)); return; } // Branch on no records with no error if(!i) { static const records empty; cache::put(tag.hp, tag.opts, empty); return; } // Iterate the record vector which was sorted by type; // send the cache an individual view of each type since // the cache is organized by record type. size_t s(0), e(0); auto last(record.at(e)->type); for(++e; e <= i; ++e) { if(e < i && record.at(e)->type == last) continue; const vector_view records { record.data() + s, record.data() + e }; assert(!empty(records)); cache::put(tag.hp, tag.opts, records); s = e; if(e < i) last = record.at(e)->type; } // We have to send something to the cache with the same type // as the query, otherwise our user will never get a response // to what they're waiting for. bool has_tag_qtype{false}; for(size_t i(0); i < an.size() && !has_tag_qtype; ++i) has_tag_qtype = an.at(i).qtype == tag.opts.qtype; if(!has_tag_qtype) { static const records empty; cache::put(tag.hp, tag.opts, empty); } } catch(const std::exception &e) { log::error { log, "handle resolved: tag[%u] :%s", tag.id, e.what() }; throw; } template ircd::rfc1035::record * ircd::net::dns::new_record(mutable_buffer &buf, const rfc1035::answer &answer) { if(unlikely(sizeof(type) > size(buf))) return nullptr; void *const pos(data(buf)); consume(buf, sizeof(type)); return new (pos) type(answer); }