mirror of
https://github.com/zerotier/ZeroTierOne.git
synced 2024-12-24 07:06:39 +00:00
129 lines
3.6 KiB
C++
129 lines
3.6 KiB
C++
/*
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* ZeroTier One - Network Virtualization Everywhere
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* Copyright (C) 2011-2015 ZeroTier, Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* --
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*
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* ZeroTier may be used and distributed under the terms of the GPLv3, which
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* are available at: http://www.gnu.org/licenses/gpl-3.0.html
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*
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* If you would like to embed ZeroTier into a commercial application or
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* redistribute it in a modified binary form, please contact ZeroTier Networks
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* LLC. Start here: http://www.zerotier.com/
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*/
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#ifndef ZT_ANTIRECURSION_HPP
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#define ZT_ANTIRECURSION_HPP
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#include <string.h>
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#include <stdlib.h>
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#include "Constants.hpp"
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namespace ZeroTier {
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/**
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* Size of anti-recursion history
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*/
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#define ZT_ANTIRECURSION_HISTORY_SIZE 16
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/**
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* Filter to prevent recursion (ZeroTier-over-ZeroTier)
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*
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* This works by logging ZeroTier packets that we send. It's then invoked
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* again against packets read from local Ethernet taps. If the last 32
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* bytes representing the ZeroTier packet match in the tap frame, then
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* the frame is a re-injection of a frame that we sent and is rejected.
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*
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* This means that ZeroTier packets simply will not traverse ZeroTier
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* networks, which would cause all sorts of weird problems.
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*
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* This is highly optimized code since it's checked for every packet.
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*/
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class AntiRecursion
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{
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public:
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AntiRecursion()
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{
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memset(_history,0,sizeof(_history));
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_ptr = 0;
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}
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/**
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* Add an outgoing ZeroTier packet to the circular log
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*
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* @param data ZT packet data
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* @param len Length of packet
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*/
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inline void logOutgoingZT(const void *const data,const unsigned int len)
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{
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if (len < 32)
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return;
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#ifdef ZT_NO_TYPE_PUNNING
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memcpy(_history[++_ptr % ZT_ANTIRECURSION_HISTORY_SIZE].tail,reinterpret_cast<const uint8_t *>(data) + (len - 32),32);
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#else
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uint64_t *t = _history[++_ptr % ZT_ANTIRECURSION_HISTORY_SIZE].tail;
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const uint64_t *p = reinterpret_cast<const uint64_t *>(reinterpret_cast<const uint8_t *>(data) + (len - 32));
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*(t++) = *(p++);
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*(t++) = *(p++);
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*(t++) = *(p++);
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*t = *p;
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#endif
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}
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/**
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* Check an ethernet frame from a local tap against anti-recursion history
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*
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* @param data Raw frame data
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* @param len Length of frame
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* @return True if frame is OK to be passed, false if it's a ZT frame that we sent
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*/
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inline bool checkEthernetFrame(const void *const data,const unsigned int len) const
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{
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if (len < 32)
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return true;
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const uint8_t *const pp = reinterpret_cast<const uint8_t *>(data) + (len - 32);
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const _ArItem *i = _history;
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const _ArItem *const end = i + ZT_ANTIRECURSION_HISTORY_SIZE;
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while (i != end) {
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#ifdef ZT_NO_TYPE_PUNNING
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if (!memcmp(pp,i->tail,32))
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return false;
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#else
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const uint64_t *t = i->tail;
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const uint64_t *p = reinterpret_cast<const uint64_t *>(pp);
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uint64_t bits = *(t++) ^ *(p++);
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bits |= *(t++) ^ *(p++);
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bits |= *(t++) ^ *(p++);
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bits |= *t ^ *p;
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if (!bits)
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return false;
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#endif
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++i;
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}
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return true;
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}
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private:
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struct _ArItem { uint64_t tail[4]; };
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_ArItem _history[ZT_ANTIRECURSION_HISTORY_SIZE];
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volatile unsigned long _ptr;
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};
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} // namespace ZeroTier
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#endif
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