mirror of
https://github.com/zerotier/ZeroTierOne.git
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111 lines
3.2 KiB
C++
111 lines
3.2 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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#define ZT_ANTIRECURSION_TAIL_LEN 256
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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 N
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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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* NOTE: this is applied to low-level packets before they are sent to
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* SocketManager and/or sockets, not to fully assembled packets before
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* (possible) fragmentation.
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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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throw()
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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 *data,unsigned int len)
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throw()
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{
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ArItem *i = &(_history[_ptr++ % ZT_ANTIRECURSION_HISTORY_SIZE]);
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const unsigned int tl = (len > ZT_ANTIRECURSION_TAIL_LEN) ? ZT_ANTIRECURSION_TAIL_LEN : len;
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memcpy(i->tail,((const unsigned char *)data) + (len - tl),tl);
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i->len = tl;
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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 *data,unsigned int len)
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throw()
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{
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for(unsigned int h=0;h<ZT_ANTIRECURSION_HISTORY_SIZE;++h) {
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ArItem *i = &(_history[h]);
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if ((i->len > 0)&&(len >= i->len)&&(!memcmp(((const unsigned char *)data) + (len - i->len),i->tail,i->len)))
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return false;
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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
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{
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unsigned char tail[ZT_ANTIRECURSION_TAIL_LEN];
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unsigned int len;
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};
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ArItem _history[ZT_ANTIRECURSION_HISTORY_SIZE];
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volatile unsigned int _ptr;
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};
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} // namespace ZeroTier
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#endif
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