From 477fe01e400b04a4c57dac6d04d3c2eeb8bad1f0 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Tue, 8 May 2018 15:03:24 -0700
Subject: [PATCH] ircd::net::dns: Write question into tag buffer; add
 send_burst conf item.

---
 include/ircd/net/resolver.h | 16 +++++-----
 ircd/net.cc                 | 62 ++++++++++++++++++-------------------
 2 files changed, 40 insertions(+), 38 deletions(-)

diff --git a/include/ircd/net/resolver.h b/include/ircd/net/resolver.h
index 4debe0d8c..70e6ccc7a 100644
--- a/include/ircd/net/resolver.h
+++ b/include/ircd/net/resolver.h
@@ -25,6 +25,7 @@ struct ircd::net::dns::resolver
 	static constexpr const size_t &MAX_COUNT{64};
 	static conf::item<milliseconds> timeout;
 	static conf::item<milliseconds> send_rate;
+	static conf::item<size_t> send_burst;
 
 	std::vector<ip::udp::endpoint> server;       // The list of active servers
 	size_t server_next{0};                       // Round-robin state to hit servers
@@ -33,8 +34,7 @@ struct ircd::net::dns::resolver
 	ctx::dock dock;
 	std::map<uint16_t, tag> tags;                // The active requests
 	steady_point send_last;                      // Time of last send
-	using queued = std::pair<uint16_t, std::string>;
-	std::deque<queued> sendq;                    // Queue of frames for rate-limiting
+	std::deque<uint16_t> sendq;                  // Queue of frames for rate-limiting
 
 	ip::udp::socket ns;                          // A pollable activity object
 	ip::udp::endpoint reply_from;                // Remote addr of recv
@@ -47,10 +47,10 @@ struct ircd::net::dns::resolver
 	void handle(const error_code &ec, const size_t &) noexcept;
 	void set_handle();
 
-	void queue_query(const const_buffer &, tag &);
-	void send_query(const ip::udp::endpoint &, const const_buffer &, tag &);
-	void send_query(const const_buffer &, tag &);
-	void submit(const const_buffer &, tag &);
+	void send_query(const ip::udp::endpoint &, tag &);
+	void queue_query(tag &);
+	void send_query(tag &);
+	void submit(tag &);
 
 	template<class... A> tag &set_tag(A&&...);
 	const_buffer make_query(const mutable_buffer &buf, const tag &) const;
@@ -61,7 +61,7 @@ struct ircd::net::dns::resolver
 	void timeout_worker();
 	ctx::context timeout_context;
 
-	void flush(const queued &);
+	void flush(const uint16_t &);
 	void sendq_worker();
 	ctx::context sendq_context;
 
@@ -74,10 +74,12 @@ struct ircd::net::dns::resolver::tag
 	uint16_t id {0};
 	hostport hp;
 	dns::opts opts;       // note: invalid after query sent
+	const_buffer question;
 	callback cb;
 	steady_point last;
 	uint8_t tries {0};
 	char hostbuf[256];
+	char qbuf[384];
 
 	tag(const hostport &, const dns::opts &, callback &&);
 };
diff --git a/ircd/net.cc b/ircd/net.cc
index 209a5e1a9..b03064469 100644
--- a/ircd/net.cc
+++ b/ircd/net.cc
@@ -2817,6 +2817,13 @@ 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                                },
+};
+
 ircd::net::dns::resolver::resolver()
 :ns{*ircd::ios}
 ,reply
@@ -2871,26 +2878,21 @@ ircd::net::dns::resolver::sendq_worker()
 }
 
 void
-ircd::net::dns::resolver::flush(const queued &next)
+ircd::net::dns::resolver::flush(const uint16_t &next)
 try
 {
 	auto &tag
 	{
-		tags.at(next.first)
+		tags.at(next)
 	};
 
-	const const_buffer buf
-	{
-		data(next.second), size(next.second)
-	};
-
-	send_query(buf, tag);
+	send_query(tag);
 }
 catch(const std::out_of_range &e)
 {
 	log::error
 	{
-		"Queued tag id[%u] is no longer mapped", next.first
+		"Queued tag id[%u] is no longer mapped", next
 	};
 }
 
@@ -2978,8 +2980,8 @@ ircd::net::dns::resolver::operator()(const hostport &hp,
 		tags.erase(tag.id);
 	}};
 
-	thread_local char buf[64_KiB];
-	submit(make_query(buf, tag), tag);
+	tag.question = make_query(tag.qbuf, tag);
+	submit(tag);
 }
 
 ircd::const_buffer
@@ -3031,28 +3033,25 @@ ircd::net::dns::resolver::set_tag(A&&... args)
 }
 
 void
-ircd::net::dns::resolver::submit(const const_buffer &buf,
-                                 tag &tag)
+ircd::net::dns::resolver::queue_query(tag &tag)
 {
-	const auto rate(milliseconds(send_rate) / server.size());
-	const auto elapsed(now<steady_point>() - send_last);
-	if(elapsed >= rate)
-		send_query(buf, tag);
-	else
-		queue_query(buf, tag);
-}
-
-void
-ircd::net::dns::resolver::queue_query(const const_buffer &buf,
-                                      tag &tag)
-{
-	sendq.emplace_back(tag.id, std::string(data(buf), size(buf)));
+	sendq.emplace_back(tag.id);
 	dock.notify_one();
 }
 
 void
-ircd::net::dns::resolver::send_query(const const_buffer &buf,
-                                     tag &tag)
+ircd::net::dns::resolver::submit(tag &tag)
+{
+	const auto rate(milliseconds(send_rate) / server.size());
+	const auto elapsed(now<steady_point>() - 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());
@@ -3062,7 +3061,7 @@ try
 		server.at(server_next)
 	};
 
-	send_query(ep, buf, tag);
+	send_query(ep, tag);
 }
 catch(const std::out_of_range &)
 {
@@ -3074,14 +3073,15 @@ catch(const std::out_of_range &)
 
 void
 ircd::net::dns::resolver::send_query(const ip::udp::endpoint &ep,
-                                     const const_buffer &buf,
                                      tag &tag)
 {
-	assert(!empty(buf));
 	assert(ns.non_blocking());
+	assert(!empty(tag.question));
+	const const_buffer &buf{tag.question};
 	ns.send_to(asio::const_buffers_1(buf), ep);
 	send_last = now<steady_point>();
 	tag.last = send_last;
+	tag.tries++;
 }
 
 void