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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/
*/
#ifndef ZT_ANTIRECURSION_HPP
#define ZT_ANTIRECURSION_HPP
#include <string.h>
#include <stdlib.h>
#include "Constants.hpp"
namespace ZeroTier {
/**
* Size of anti-recursion history
*/
#define ZT_ANTIRECURSION_HISTORY_SIZE 16
/**
* Filter to prevent recursion (ZeroTier-over-ZeroTier)
*
* This works by logging ZeroTier packets that we send. It's then invoked
* again against packets read from local Ethernet taps. If the last 32
* bytes representing the ZeroTier packet match in the tap frame, then
* the frame is a re-injection of a frame that we sent and is rejected.
*
* This means that ZeroTier packets simply will not traverse ZeroTier
* networks, which would cause all sorts of weird problems.
*
* This is highly optimized code since it's checked for every packet.
*/
class AntiRecursion
{
public:
AntiRecursion()
{
for(int i=0;i<ZT_ANTIRECURSION_HISTORY_SIZE;++i) {
_history[i].tail[0] = 0;
_history[i].tail[1] = 0;
_history[i].tail[2] = 0;
_history[i].tail[3] = 0;
}
_ptr = 0;
}
/**
* Add an outgoing ZeroTier packet to the circular log
*
* @param data ZT packet data
* @param len Length of packet
*/
inline void logOutgoingZT(const void *const data,const unsigned int len)
{
if (len < 32)
return;
#ifdef ZT_NO_TYPE_PUNNING
memcpy(_history[++_ptr % ZT_ANTIRECURSION_HISTORY_SIZE].tail,reinterpret_cast<const uint8_t *>(data) + (len - 32),32);
#else
uint64_t *t = _history[++_ptr % ZT_ANTIRECURSION_HISTORY_SIZE].tail;
const uint64_t *p = reinterpret_cast<const uint64_t *>(reinterpret_cast<const uint8_t *>(data) + (len - 32));
*(t++) = *(p++);
*(t++) = *(p++);
*(t++) = *(p++);
*t = *p;
#endif
}
/**
* Check an ethernet frame from a local tap against anti-recursion history
*
* @param data Raw frame data
* @param len Length of frame
* @return True if frame is OK to be passed, false if it's a ZT frame that we sent
*/
inline bool checkEthernetFrame(const void *const data,const unsigned int len) const
{
if (len < 32)
return true;
const uint8_t *const pp = reinterpret_cast<const uint8_t *>(data) + (len - 32);
const _ArItem *i = _history;
const _ArItem *const end = i + ZT_ANTIRECURSION_HISTORY_SIZE;
while (i != end) {
#ifdef ZT_NO_TYPE_PUNNING
if (!memcmp(pp,i->tail,32))
return false;
#else
const uint64_t *t = i->tail;
const uint64_t *p = reinterpret_cast<const uint64_t *>(pp);
uint64_t bits = *(t++) ^ *(p++);
bits |= *(t++) ^ *(p++);
bits |= *(t++) ^ *(p++);
bits |= *t ^ *p;
if (!bits)
return false;
#endif
++i;
}
return true;
}
private:
struct _ArItem { uint64_t tail[4]; };
_ArItem _history[ZT_ANTIRECURSION_HISTORY_SIZE];
volatile unsigned long _ptr;
};
} // namespace ZeroTier
#endif
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