mirror of
https://github.com/zerotier/ZeroTierOne.git
synced 2024-12-28 08:48:52 +00:00
129 lines
3.6 KiB
C++
129 lines
3.6 KiB
C++
/*
|
|
* 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()
|
|
{
|
|
memset(_history,0,sizeof(_history));
|
|
_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
|