ircd::net: Integrate SRV query composition; RFC1035 records to the user interface.

include/ircd/net/dns.h

@@ -23,29 +23,50 @@ namespace ircd::net
 ///
 struct ircd::net::dns
 {
+	struct opts;
 	struct resolver;
 
 	struct resolver static *resolver;
+	struct opts static const opts_default;
 
   public:
-	enum flag :uint;
+	using callback = std::function<void (std::exception_ptr, vector_view<const rfc1035::record *>)>;
-
+	using callback_A_one = std::function<void (std::exception_ptr, const rfc1035::record::A &)>;
-	using callback_one = std::function<void (std::exception_ptr, const ipport &)>;
+	using callback_SRV_one = std::function<void (std::exception_ptr, const rfc1035::record::SRV &)>;
-	using callback_many = std::function<void (std::exception_ptr, vector_view<const ipport>)>;
+	using callback_ipport_one = std::function<void (std::exception_ptr, const ipport &)>;
-	using callback_reverse = std::function<void (std::exception_ptr, const string_view &)>;
 
 	// Callback-based interface
-	void operator()(const ipport &, callback_reverse);
+	void operator()(const hostport &, const opts &, callback);
-	void operator()(const hostport &, callback_many);
+	void operator()(const hostport &, const opts &, callback_A_one);
-	void operator()(const hostport &, callback_one);
+	void operator()(const hostport &, const opts &, callback_SRV_one);
+	void operator()(const hostport &, const opts &, callback_ipport_one);
 
-	// Future-based interface
+	// Callback-based interface (default options)
-	ctx::future<ipport> operator()(const hostport &);
+	template<class Callback> void operator()(const hostport &, Callback&&);
-	ctx::future<std::string> operator()(const ipport &);
 };
 
-enum ircd::net::dns::flag
+/// DNS resolution options
-:uint
+struct ircd::net::dns::opts
 {
+	/// Overrides the SRV query to make for this resolution. If empty an
+	/// SRV query may still be made from other deductions. This string is
+	/// copied at the start of the resolution. It must be a fully qualified
+	/// SRV query string: Example: "_matrix._tcp."
+	string_view srv;
 
+	/// Specifies the SRV protocol part when deducing the SRV query to be
+	/// made. This is used when the net::hostport.service string is just
+	/// the name of the service like "matrix" so we then use this value
+	/// to build the protocol part of the SRV query string. It is ignored
+	/// if `srv` is set or if no service is specified (thus no SRV query is
+	/// made in the first place).
+	string_view proto{"tcp"};
 };
+
+template<class Callback>
+void
+ircd::net::dns::operator()(const hostport &hostport,
+                           Callback&& callback)
+{
+	operator()(hostport, opts_default, std::forward<Callback>(callback));
+}

include/ircd/net/resolver.h

@@ -30,8 +30,8 @@ struct ircd::net::dns::resolver
 	std::map<uint16_t, tag> tags;                // The active requests
 
 	ip::udp::socket ns;                          // A pollable activity object
-	ip::udp::endpoint reply_from;
+	ip::udp::endpoint reply_from;                // Remote addr of recv
-	char reply[64_KiB] alignas(16);
+	char reply[64_KiB] alignas(16);              // Buffer for recv
 
 	bool handle_error(const error_code &ec) const;
 	void handle_reply(const header &, const const_buffer &body, tag &);
@@ -42,8 +42,9 @@ struct ircd::net::dns::resolver
 	void send_query(const ip::udp::endpoint &, const const_buffer &);
 	void send_query(const const_buffer &);
 
-	void operator()(const hostport &, const flag &, callback_many);
+	tag &set_tag(tag &&);
-	void operator()(const ipport &, const flag &, callback_reverse);
+	const_buffer make_query(const mutable_buffer &buf, const tag &) const;
+	void operator()(const hostport &, const opts &, callback);
 
 	bool check_timeout(const uint16_t &id, tag &, const steady_point &now);
 	void check_timeouts();
@@ -56,25 +57,21 @@ struct ircd::net::dns::resolver
 
 struct ircd::net::dns::resolver::tag
 {
+	uint16_t id {0};
 	hostport hp;
-	ipport ipp;
+	dns::opts opts;
-	flag flags;
+	callback cb;
-	callback_many cb_many;
-	callback_reverse cb_reverse;
 	steady_point last {ircd::now<steady_point>()};
 	uint8_t tries {0};
 
-	void set_exception(std::exception_ptr &&);
+	tag(const hostport &, const dns::opts &, callback);
-
-	tag(const hostport &hp, const flag &flags, callback_many cb_many)
-	:hp{hp}
-	,flags{flags}
-	,cb_many{std::move(cb_many)}
-	{}
-
-	tag(const ipport &ipp, const flag &flags, callback_reverse cb_reverse)
-	:ipp{ipp}
-	,flags{flags}
-	,cb_reverse{std::move(cb_reverse)}
-	{}
 };
+
+inline
+ircd::net::dns::resolver::tag::tag(const hostport &hp,
+                                   const dns::opts &opts,
+                                   callback cb)
+:hp{hp}
+,opts{opts}
+,cb{std::move(cb)}
+{}

ircd/net.cc

@@ -2147,86 +2147,97 @@ decltype(ircd::net::dns::resolver)
 ircd::net::dns::resolver
 {};
 
-/// Resolve a numerical address to a hostname string. This is a PTR record
+/// Linkage for default opts
-/// query or 'reverse DNS' lookup.
+decltype(ircd::net::dns::opts_default)
-ircd::ctx::future<std::string>
+ircd::net::dns::opts_default
-ircd::net::dns::operator()(const ipport &ipport)
+{};
-{
-	ctx::promise<std::string> p;
-	ctx::future<std::string> ret{p};
-	operator()(ipport, [p(std::move(p))]
-	(std::exception_ptr eptr, const string_view &ptr)
-	mutable
-	{
-		if(eptr)
-			p.set_exception(std::move(eptr));
-		else
-			p.set_value(std::string{ptr});
-	});
 
-	return ret;
+/// Convenience composition with a single ipport callback. This is the result of
-}
+/// an automatic chain of queries such as SRV and A/AAAA based on the input and
-
+/// intermediate results.
-/// Resolve a hostname (with service name/portnum) to a numerical address. This
-/// is an A or AAAA query (with automatic SRV query) returning a single result.
-ircd::ctx::future<ircd::net::ipport>
-ircd::net::dns::operator()(const hostport &hostport)
-{
-	ctx::promise<ipport> p;
-	ctx::future<ipport> ret{p};
-	operator()(hostport, [p(std::move(p))]
-	(std::exception_ptr eptr, const ipport &ip)
-	mutable
-	{
-		if(eptr)
-			p.set_exception(std::move(eptr));
-		else
-			p.set_value(ip);
-	});
-
-	return ret;
-}
-
-/// Lower-level A or AAAA query (with automatic SRV query) with asynchronous
-/// callback interface. This returns only one result.
 void
 ircd::net::dns::operator()(const hostport &hostport,
-                           callback_one callback)
+                           const opts &opts,
+                           callback_ipport_one callback)
 {
-	assert(bool(ircd::net::dns::resolver));
+	operator()(hostport, opts, [this, hostport(hostport), opts(opts), callback(std::move(callback))]
-	operator()(hostport, [callback(std::move(callback))]
+	(std::exception_ptr eptr, const rfc1035::record::SRV &record)
-	(std::exception_ptr eptr, const vector_view<const ipport> &results)
+	mutable
 	{
 		if(eptr)
 			return callback(std::move(eptr), {});
 
-		if(results.empty())
+		if(!record.tgt.empty())
-			return callback(std::make_exception_ptr(nxdomain{}), {});
+			host(hostport) = record.tgt;
 
-		callback(std::move(eptr), results.at(0));
+		if(record.port != 0)
+			port(hostport) = record.port;
+
+		// Have to kill the service name to not run another SRV query now.
+		hostport.service = {};
+		opts.srv = {};
+		this->operator()(hostport, opts, [hostport, callback(std::move(callback))]
+		(std::exception_ptr eptr, const rfc1035::record::A &record)
+		{
+			if(eptr)
+				return callback(std::move(eptr), {});
+
+			const ipport ipport{record.ip4, port(hostport)};
+			callback(std::move(eptr), ipport);
+		});
 	});
 }
 
-/// Lower-level A+AAAA query (with automatic SRV query). This returns a vector
+/// Convenience callback with a single SRV record which was selected from
-/// of all results in the callback.
+/// the vector with stochastic respect for weighting and priority.
 void
 ircd::net::dns::operator()(const hostport &hostport,
-                           callback_many callback)
+                           const opts &opts,
+                           callback_SRV_one callback)
 {
-	static const flag flags{};
 	assert(bool(ircd::net::dns::resolver));
-	(*resolver)(hostport, flags, std::move(callback));
+	operator()(hostport, opts, [callback(std::move(callback))]
+	(std::exception_ptr eptr, const vector_view<const rfc1035::record *> rrs)
+	{
+		if(eptr || rrs.empty())
+			return callback(std::move(eptr), {});
+
+		//TODO: prng on weight / prio plz
+		const auto &rr{*rrs.at(0)};
+		const auto &record(rr.as<const rfc1035::record::SRV>());
+		callback(std::move(eptr), record);
+	});
 }
 
-/// Lower-level PTR query (i.e "reverse DNS") with asynchronous callback
+/// Convenience callback with a single A record which was selected from
-/// interface.
+/// the vector randomly.
 void
-ircd::net::dns::operator()(const ipport &ipport,
+ircd::net::dns::operator()(const hostport &hostport,
-                           callback_reverse callback)
+                           const opts &opts,
+                           callback_A_one callback)
 {
-	static const flag flags{};
 	assert(bool(ircd::net::dns::resolver));
-	(*resolver)(ipport, flags, std::move(callback));
+	operator()(hostport, opts, [callback(std::move(callback))]
+	(std::exception_ptr eptr, const vector_view<const rfc1035::record *> rrs)
+	{
+		if(eptr || rrs.empty())
+			return callback(std::move(eptr), {});
+
+		//TODO: prng plz
+		const auto &rr{*rrs.at(0)};
+		const auto &record(rr.as<const rfc1035::record::A>());
+		callback(std::move(eptr), record);
+	});
+}
+
+/// Fundamental callback with a vector of abstract resource records.
+void
+ircd::net::dns::operator()(const hostport &hostport,
+                           const opts &opts,
+                           callback cb)
+{
+	assert(bool(ircd::net::dns::resolver));
+	(*resolver)(hostport, opts, std::move(cb));
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -2309,71 +2320,83 @@ ircd::net::dns::resolver::check_timeout(const uint16_t &id,
 		boost::system::errc::timed_out, boost::system::system_category()
 	};
 
-	tag.set_exception(make_eptr(ec));
+	if(tag.cb)
+		tag.cb(make_eptr(ec), {});
+
 	return false;
 }
 
-/// Internal A/AAAA record resolver function
+/// Internal resolver entry interface.
 void
 ircd::net::dns::resolver::operator()(const hostport &hostport,
-                                     const flag &flags,
+                                     const opts &opts,
-                                     callback_many callback)
+                                     callback callback)
 {
-	uint16_t id; do
+	const auto &tag
 	{
-		id = ircd::rand::integer(1, 65535);
+		set_tag(resolver::tag
-		assert(tags.size() < 65535);
+		{
-		const auto it{tags.lower_bound(id)};
+			hostport, opts, std::move(callback)
-		if(it != end(tags) && it->first == id)
+		})
-			continue;
+	};
-
-		tags.emplace_hint(it, id, tag{hostport, flags, std::move(callback)});
-		dock.notify_one();
-		break;
-	}
-	while(1);
 
 	// Escape trunk
-	const unwind::exceptional untag{[this, &id]
+	const unwind::exceptional untag{[this, &tag]
 	{
-		tags.erase(id);
+		tags.erase(tag.id);
 	}};
 
-	// Trivial host string
-	const string_view &host
-	{
-		hostport.host
-	};
-
-	// Determine if the port is a string or requires a lex_cast to one.
-	char portbuf[8];
-	const string_view &port
-	{
-		hostport.portnum? lex_cast(hostport.portnum, portbuf) : hostport.port
-	};
-
-	// Generate the question
-	const rfc1035::question question
-	{
-		host, "A"
-	};
-
 	thread_local char buf[64_KiB];
-	const auto query
+	send_query(make_query(buf, tag));
-	{
-		rfc1035::make_query(buf, id, question)
-	};
-
-	send_query(query);
 }
 
-/// Internal PTR record resolver function
+ircd::const_buffer
-void
+ircd::net::dns::resolver::make_query(const mutable_buffer &buf,
-ircd::net::dns::resolver::operator()(const ipport &ipport,
+                                     const tag &tag)
-                                     const flag &flags,
+const
-                                     callback_reverse callback)
 {
-	throw not_implemented{};
+	if(tag.hp.service || tag.opts.srv)
+	{
+		thread_local char srvbuf[512];
+		string_view srvhost;
+		if(!tag.opts.srv)
+			srvhost = fmt::sprintf
+			{
+				srvbuf, "_%s._%s.%s", service(tag.hp), tag.opts.proto, host(tag.hp)
+			};
+		else
+			srvhost = fmt::sprintf
+			{
+				srvbuf, "%s%s", tag.opts.srv, host(tag.hp)
+			};
+
+		const rfc1035::question question{srvhost, "SRV"};
+		return rfc1035::make_query(buf, tag.id, question);
+	}
+
+	const rfc1035::question question{host(tag.hp), "A"};
+	return rfc1035::make_query(buf, tag.id, question);
+}
+
+ircd::net::dns::resolver::tag &
+ircd::net::dns::resolver::set_tag(tag &&tag)
+{
+	while(tags.size() < 65535)
+	{
+		tag.id = ircd::rand::integer(1, 65535);
+		auto it{tags.lower_bound(tag.id)};
+		if(it != end(tags) && it->first == tag.id)
+			continue;
+
+		it = tags.emplace_hint(it, tag.id, std::move(tag));
+		dock.notify_one();
+		return it->second;
+	}
+
+	throw assertive
+	{
+		"Too many DNS queries"
+	};
 }
 
 void
@@ -2512,60 +2535,84 @@ try
 			"protocol error: %s", rfc1035::rcode.at(header.rcode)
 		};
 
-	if(header.qdcount > 8 || header.ancount > 8)
+	// The maximum number of records we're accepting for a section
+	static const size_t MAX_COUNT
+	{
+		64
+	};
+
+	if(header.qdcount > MAX_COUNT || header.ancount > MAX_COUNT)
 		throw error
 		{
 			"Response contains too many sections..."
 		};
 
-	if(!header.ancount)
+	const_buffer buffer
 	{
-		tag.cb_many({}, {});
+		body
-		return;
+	};
-	}
 
-	const_buffer buf{body};
+	// Questions are regurgitated back to us so they must be parsed first
-	rfc1035::question qd[header.qdcount];
+	thread_local rfc1035::question qd[MAX_COUNT];
 	for(size_t i(0); i < header.qdcount; ++i)
-		consume(buf, size(qd[i].parse(buf)));
+		consume(buffer, size(qd[i].parse(buffer)));
 
-	rfc1035::answer an[header.ancount];
+	// Answers are parsed into this buffer
+	thread_local rfc1035::answer an[MAX_COUNT];
 	for(size_t i(0); i < header.ancount; ++i)
-		consume(buf, size(an[i].parse(buf)));
+		consume(buffer, size(an[i].parse(buffer)));
 
-	size_t ippi(0);
+	// This will be where we place the record instances which are dynamically
-	net::ipport ipp[header.ancount];
+	// laid out and sized types; this is an alternative to new'ing them
-	for(size_t i(0); i < header.ancount; ++i)
+	// without placement. 512 bytes is assumed as a soft maximum for each RR.
+	thread_local uint8_t recbuf[MAX_COUNT * 512];
+	thread_local const rfc1035::record *record[MAX_COUNT];
+
+	size_t i(0);
+	uint8_t *pos{recbuf};
+	for(; i < header.ancount; ++i) switch(an[i].qtype)
 	{
-		switch(an[i].qtype)
+		case 1:
 		{
-			case 0x01:
+			record[i] = new (pos) rfc1035::record::A(an[i]);
-			{
+			pos += sizeof(rfc1035::record::A);
-				const rfc1035::record::A rr(an[i].rdata);
-				ipp[ippi++] = { rr.ip4, port(tag.hp) };
 			continue;
 		}
 
-			case 0x21:
+		case 5:
 		{
-				const rfc1035::record::SRV rr(an[i].rdata);
+			record[i] = new (pos) rfc1035::record::CNAME(an[i]);
+			pos += sizeof(rfc1035::record::CNAME);
 			continue;
 		}
 
-			case 0x05:
+		case 33:
 		{
-				const rfc1035::record::CNAME rr(an[i].rdata);
+			record[i] = new (pos) rfc1035::record::SRV(an[i]);
+			pos += sizeof(rfc1035::record::SRV);
+			continue;
+		}
+
+		default:
+		{
+			record[i] = new (pos) rfc1035::record(an[i]);
+			pos += sizeof(rfc1035::record);
 			continue;
 		}
 	}
-	}
 
-	if(tag.cb_many)
+	if(tag.cb)
-		tag.cb_many({}, vector_view<const ipport>(ipp, header.ancount));
+		tag.cb({}, vector_view<const rfc1035::record *>(record, i));
 }
-catch(...)
+catch(const std::exception &e)
 {
-	tag.set_exception(std::current_exception());
+	log.error("resolver tag:%u [%s]: %s",
+	          tag.id,
+	          string(tag.hp),
+	          e.what());
+
+	if(tag.cb)
+		tag.cb(std::current_exception(), {});
 }
 
 bool
@@ -2609,15 +2656,6 @@ ircd::net::dns::resolver::init_servers()
 	});
 }
 
-void
-ircd::net::dns::resolver::tag::set_exception(std::exception_ptr &&eptr)
-{
-	if(cb_many)
-		cb_many(std::move(eptr), {});
-	else if(cb_reverse)
-		cb_reverse(std::move(eptr), {});
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 //
 // net/remote.h