Deferred decode for HELLO to prevent HELLOcalypse under high load of new peers.

node/DeferredPackets.cpp

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+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2015  ZeroTier, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * --
+ *
+ * ZeroTier may be used and distributed under the terms of the GPLv3, which
+ * are available at: http://www.gnu.org/licenses/gpl-3.0.html
+ *
+ * If you would like to embed ZeroTier into a commercial application or
+ * redistribute it in a modified binary form, please contact ZeroTier Networks
+ * LLC. Start here: http://www.zerotier.com/
+ */
+
+#include "Constants.hpp"
+#include "DeferredPackets.hpp"
+#include "IncomingPacket.hpp"
+#include "RuntimeEnvironment.hpp"
+#include "Node.hpp"
+
+namespace ZeroTier {
+
+DeferredPackets::DeferredPackets(const RuntimeEnvironment *renv) :
+	RR(renv),
+	_readPtr(0),
+	_writePtr(0),
+	_die(false)
+{
+}
+
+DeferredPackets::~DeferredPackets()
+{
+	_q_m.lock();
+	_die = true;
+	_q_m.unlock();
+	_q_s.post();
+}
+
+bool DeferredPackets::enqueue(IncomingPacket *pkt)
+{
+	_q_m.lock();
+	const unsigned long p = _writePtr % ZT_DEFFEREDPACKETS_MAX;
+	if (_q[p]) {
+		_q_m.unlock();
+		return false;
+	} else {
+		_q[p].setToUnsafe(pkt);
+		++_writePtr;
+		_q_m.unlock();
+		_q_s.post();
+		return true;
+	}
+}
+
+int DeferredPackets::process()
+{
+	SharedPtr<IncomingPacket> pkt;
+
+	_q_m.lock();
+	if (_die) {
+		_q_m.unlock();
+		_q_s.post();
+		return -1;
+	}
+	while (_readPtr == _writePtr) {
+		_q_m.unlock();
+		_q_s.wait();
+		_q_m.lock();
+		if (_die) {
+			_q_m.unlock();
+			_q_s.post();
+			return -1;
+		}
+	}
+	pkt.swap(_q[_readPtr++ % ZT_DEFFEREDPACKETS_MAX]);
+	_q_m.unlock();
+
+	pkt->tryDecode(RR,true);
+	return 1;
+}
+
+} // namespace ZeroTier